WO2018064347A1 - Tuning electrode surface electronics with thin layers - Google Patents

Tuning electrode surface electronics with thin layers Download PDF

Info

Publication number
WO2018064347A1
WO2018064347A1 PCT/US2017/054040 US2017054040W WO2018064347A1 WO 2018064347 A1 WO2018064347 A1 WO 2018064347A1 US 2017054040 W US2017054040 W US 2017054040W WO 2018064347 A1 WO2018064347 A1 WO 2018064347A1
Authority
WO
WIPO (PCT)
Prior art keywords
bis
cycles
conductive
cyclopentadienyl
heterogeneous
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2017/054040
Other languages
French (fr)
Inventor
Cody E. FINKE
Michael R. Hoffmann
Justin JASPER
Laleh Majari KASMAEE
Stefan OMELCHENKO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
California Institute of Technology
Original Assignee
California Institute of Technology
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by California Institute of Technology filed Critical California Institute of Technology
Publication of WO2018064347A1 publication Critical patent/WO2018064347A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/467—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction
    • C02F1/4672—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation
    • C02F1/4674—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis by electrochemical disinfection; by electrooxydation or by electroreduction by electrooxydation with halogen or compound of halogens, e.g. chlorine, bromine
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
    • C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
    • C23C16/40—Oxides
    • C23C16/405—Oxides of refractory metals or yttrium
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
    • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
    • C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
    • C23C16/45523—Pulsed gas flow or change of composition over time
    • C23C16/45525—Atomic layer deposition [ALD]
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/02—Hydrogen or oxygen
    • C25B1/04—Hydrogen or oxygen by electrolysis of water
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/24—Halogens or compounds thereof
    • C25B1/26—Chlorine; Compounds thereof
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/055—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material
    • C25B11/057—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the substrate or carrier material consisting of a single element or compound
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/075—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound
    • C25B11/077—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of a single catalytic element or catalytic compound the compound being a non-noble metal oxide
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/461—Treatment of water, waste water, or sewage by electrochemical methods by electrolysis
    • C02F1/46104—Devices therefor; Their operating or servicing
    • C02F1/46109—Electrodes
    • C02F2001/46133—Electrodes characterised by the material
    • C02F2001/46138—Electrodes comprising a substrate and a coating
    • C02F2001/46142—Catalytic coating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Definitions

  • the disclosure provides for thin films that can be used to tune the catalytic characteristics of heterogeneous
  • Catalysts act by reducing the activation energy to perform a chemical reaction by destabilizing intermediates and stabilizing transition states.
  • the Sabatier principle states that an effective catalyst must bind a precursor just right. Too tight binding of a precursor or too loose binding of
  • All catalysts (including biological and heterogeneous) contain an active site or sites which provide the specific requirements for the "just right” binding of a precursor. In general, the two ways to tune an active site for "just right” binding are through either altering charge distribution
  • the disclosure provides for creating heterogeneous electrocatalysts by layering one or more thin films of one or more electrocatalytic materials onto the surface of a different
  • heterogeneous electrocatalysts can be tuned based upon the composition and/or thickness of the applied film.
  • the performance of the chlorine evolution reaction (CER) and oxygen evolution reaction (OER) catalysts, IrC> 2 , RUO 2 , and FTO can be tuned by depositing thin films of T1O 2 using atomic layer deposition (ALD) .
  • the electrocatalytic performance of IrC> 2 and RUO 2 for the Oxygen Evolution Reaction can be greatly improved by depositing a thin film of T1O 2 on their surfaces, so much so that the specific catalytic activity (io) and overpotential of these catalysts were tuned to an order of magnitude better than any previously reported catalyst for the OER in 1 M H 2 SO 4 .
  • the improvement of electrocatalytic performance was attributed to a favorable change in the electrocatalysts ' surface species' charge density.
  • the surface species' charge density of all catalyst studied was found to be predictably tunable based upon the thickness of the T1O 2 layer. Accordingly, the methods of the disclosure are directed to a platform technology that in principle can be used to rationally design heterogeneous electrocatalysts that can be used in many types of reactions where reactants are
  • the methods of the disclosure provide for the use of multiple (2 or more) electrocatalytic materials and layering them in thin layers on top of the surface of a different electrocatalytic material or substrate.
  • the top or outermost electrocatalytic layer is less than 50 nm in thickness.
  • numerous heterogeneous electrocatalysts > 50 were created for 2 different industrially important reactions, the chlorine evolution reaction (CER) and the oxygen evolution reaction (OER) .
  • multiple different materials e.g., fluorine doped tin oxide (FTO), iridium oxide
  • electrocatalysts new heterogeneous electrocatalysts were created for OER which operated at lower or equal overpotentials (corrected for electrochemically active surface area) than any previously reported electrocatalyst using the industry standard OER conditions.
  • the current best electrocatalyst for the OER in 1 M H 2 SO 4 is RUO 2 which operates at a specific activity (normalized to electrochemically active surface area) of 0.42 mA/cm 2 at 350 mV overpotential .
  • electrocatalyst was made by layering 10 cycles of T1O 2 onto IrO x . This heterogeneous electrocatalyst was found to operate at a specific activity of 3.5 mA/cm 2 at 350 mV overpotential. Further, a new heterogeneous electrocatalyst made by layering 10 cycles of TiO x onto RUO 2 using the methods of the disclosure, yielded a
  • heterogeneous electrocatalyst that operated at of 2.8 mA/cm 2 at 350 mV overpotential for the OER.
  • the disclosure provides a method to manufacture a heterogeneous electrocatalyst that has improved electrocatalytic activity for an electrochemical reaction, comprising: layering or depositing one or more thin films of one or more conductive and/or semiconductive catalytic materials onto a surface of a conductive electrocatalytic substrate by using 1 to 100 cycles of an atomic layer deposition process, wherein the
  • composition of the one of more thin films is different from the composition of the conductive electrocatalytic substrate, wherein the number of cycles of the atomic layer deposition process is used to tune the electrocatalytic activity of the heterogeneous
  • one or more thin films disclosed herein comprise, consist essentially of, or consists of metals, alloys, metal oxides, metal nitrides, metal sulfides, metal fluorides, or a combination thereof.
  • one or more thin films disclosed herein comprise, consist essentially of, or consists of metal oxides.
  • one or more thin films disclosed herein comprise, consist essentially of, or consists of metal oxides selected from A1 2 0 3 , NH 4 OSbW, Sb 2 0 5 , BaO, BaTi0 3 , BaZr0 3 , Al 6 BeOi 0 , BeO, Bi 2 0 3 , Bi 2 0 5 , B2O3, CdO, CaO, Ce 2 0 3 , Ce0 2 , CrO, Cr 2 0 3 , Cr0 2 , Cr0 3 , CoO, Co 2 0 3 ,
  • one or more thin films disclosed herein comprise, consist essentially of, or consists of Ti0 2 .
  • a method disclosed herein uses 1 to 50 cycles of an atomic layer deposition process to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate.
  • a method disclosed herein uses 1 to 25 cycles of an atomic layer deposition process to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate.
  • a method disclosed herein uses 1 to 15 cycles of an atomic layer deposition process to deposit or layer a thin film of Ti0 2 onto a surface of the conductive electrocatalytic substrate.
  • a method disclosed herein uses one or more thin films that are made from one or more precursors used in the atomic layer deposition process comprising, consisting essentially of, or consisting of aluminum tris (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , triisobutylaluminum, trimethylaluminum, tris (dimethylamido) aluminum (III) ,
  • triphenylantimony (III) tris (dimethylamido) antimony (III) , triphenylarsine, Triphenylarsine oxide, barium bis (2,2, 6,6- tetramethyl-3, 5-heptanedionate) hydrate, barium nitrate,
  • bromopentacarbonylmanganese (I) cyclopentadienylmanganese (I) tricarbonyl, ethylcyclopentadienylmanganese ( I ) tricarbonyl, manganese(O) carbonyl, (bicyclo [ 2.2.1 ] hepta-2 , 5- diene ) tetracarbonylmolybdenum ( 0 ) , bis (cyclopentadienyl ) molybdenum ( IV) dichloride,
  • hexaphenylditin (IV) , tetraallyltin, tetrakis (diethylamido) tin (IV) , tetramethyltin, tetravinyltin, tin (II) acetylacetonate ,
  • cyclopentadienyltungsten ( I I ) tricarbonyl hydride, tetracarbonyl ( 1 , 5- cyclooctadiene ) tungsten ( 0 ) , triamminetungsten ( IV) tricarbonyl, tungsten hexacarbonyl , bis (cyclopentadienyl) vanadium (II) ,
  • a method disclosed herein uses one or more thin films that are made from one or more precursors used in the atomic layer deposition process comprising, consisting essentially of, or consisting of tetrakis (dimethylamido) titanium ( IV) .
  • precursors used in the atomic layer deposition process comprising, consisting essentially of, or consisting of tetrakis (dimethylamido) titanium ( IV) .
  • the conductive electrocatalytic substrate is at least 100 nm in thickness. In an embodiment disclosed herein or as an alternate or further embodiment, the conductive electrocatalytic substrate is at least 10 ⁇ in thickness. In an embodiment disclosed herein or as an alternate or further embodiment, the conductive electrocatalytic substrate is at least 100 nm in thickness. In an embodiment disclosed herein or as an alternate or further
  • the conductive electrocatalytic substrate comprises, consists essentially of, or consists of a of a conductive material, semiconductive material and/or superconductive material. In an embodiment disclosed herein or as an alternate or further
  • the conductive electrocatalytic substrate comprises, consists essentially of, or consists of a metal oxide. In an embodiment disclosed herein or as an alternate or further
  • the conductive electrocatalytic substrate comprises, consists essentially of, or consists of a metal oxide selected fromAl 2 0 3 , NH 4 OSbW, Sb 2 0 5 , BaO, BaTi0 3 , BaZr0 3 , Al 6 BeOi 0 , BeO, Bi 2 0 3 , Bi 2 0 5 , B 2 0 3 , CdO, CaO, Ce 2 0 3 , Ce0 2 , CrO, Cr 2 0 3 , Cr0 2 , Cr0 3 , CoO, Co 2 0 3 , Cu 2 0 5 Yb 2 , Cu 2 0, CuFe 2 0 4 , CuO, GaO, Ga 2 0 3 , GeO, Ge0 2 , Au 2 0, Au 2 0 3 , Hf0 2 , ln 2 0, InO, ln 2 0 3 , lr 2 0 3 , Ir0 2 , Fe 3 0 4 , FeO, Fe 2 0
  • the electrochemical reaction is selected from the group comprising, consisting essentially of, or consisting of the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction and the oxygen reduction reaction.
  • the electrochemical reaction is the oxygen evolution reaction or the chlorine evolution reaction.
  • the electrochemical reaction the heterogeneous electrocatalyst exhibits a lower overpotential or improved specific activity for the chemical reaction than the conductive electrocatalytic substrate.
  • the heterogeneous electrocatalyst exhibits has a more favorable surface charge distribution for the chemical reaction than the conductive
  • the disclosure provides for a heterogeneous electrocatalyst made by a method disclosed herein. In an embodiment disclosed herein or as an alternate or further embodiment, the disclosure provides for a heterogeneous
  • electrocatalyst that comprises, consists essentially of, or consists of a conductive electrocatalytic substrate of IrC> 2 , FTO, or RUO 2 .
  • the disclosure provides for a heterogeneous
  • electrocatalyst that comprises, consists essentially of, or consists of a thin film of T1O 2 .
  • the disclosure provides for a heterogeneous electrocatalyst that comprises, consists essentially of, or consists of a thin film of T1O 2 is less than 1 nm in
  • the disclosure provides for an electrode comprising, consisting essentially of, or consisting of a heterogeneous electrocatalyst disclosed herein.
  • the electrode is used to generate reactive chlorine species in a wastewater treatment system.
  • Figure 1 demonstrates that a heterogeneous
  • Figure 2 presents a schematic representation of the
  • Heterogeneous electrocatalysts act by forming bonds with reactants that stabilize transition states and destabilize intermediates.
  • the perfect bond strength between the electrocatalyst and reactant will yield the optimal reactivity.
  • a too strong or too weak bond will yield subpar reactivity.
  • This concept i.e., Sabatier principle, is demonstrated by the "volcano plot" where the x-axis is a measure of bonding and the y axis is a measure of catalytic activity.
  • Figure 3 shows an example of a homogenous electrocatalyst system, where it is reasonably straightforward to tune the catalyst- reactant bond strength, by swapping and modifying ligands to be either more electron withdrawing or donating. Unfortunately, for heterogeneous electrocatalysts the tools to modify the
  • electrocatalysts are not similarly available.
  • Figure 4 provides a schematic of an atomic layer deposition process used herein for generating heterogeneous electrocatalysts. Also shown is the structure of tetrakis
  • Figure 5A-B presents (A) polarization curves for IrC> 2 electrodes with various numbers of ALD cycles of T1O 2 . Polarization was conducted in 5M NaCl, pH 2 under a chlorine atmosphere to ensure no significant oxygen evolution. (B) Example Tafel lines obtained by taking the logarithm of the current data in (A) .
  • Figure 6 demonstrates the average overpotentials at 0.1 mA/cm 2 as measured and calculated from at least 3 replicates of each IrC> 2 electrode coated with various numbers of ALD cycles of T1O 2 .
  • Figure 7A-B provides impedance spectroscopy of RUO 2 as well as Ir02 with various ALD cycle numbers of T1O2.
  • the resulting semi-circle was modeled as an Rs (CPE-Rp) .
  • the CPE-P term was between 0.9 and 1.0, indicating that the CPE-T term could reasonably be approximated as capacitance.
  • Each dot represents the capacitance measurement.
  • the low point along the lines of dots represents the E PZC .
  • E PZC from points presented in plot (A) were utilized and graphed vs ALD cycles of T1O 2 .
  • Figure 8 presents representative polarization curves for
  • Polarization was conducted in 5 M NaCl at pH 2 to ensure no significant oxygen evolution.
  • example Tafel curves obtained from taking the logarithm of current density and extracting the linear portion of the resulting curve.
  • Figure 9A-B presents the average exchange current densities (io) (A) and average overpotentials (B) of each IrC> 2 based electrode coated with T1O 2 via cycles of ALD. Bare RUO 2 is shown as a red square for comparison. As thickness of T1O 2 increased beyond reasonably thick layers, the overpotential continued to increase considerably (see FIG. 11) , likely due to the high resistivity of TiC> 2 . Overpotentials and exchange current densities are the average of at least 3 polarization curve replicates. Exchange current densities are obtained by fitting the polarization curve data to the Tafel equation and solving for the current density at the
  • FIG. 10 shows E PZC of Ir02 anodes coated with various
  • E PZC was calculated from electrochemical impedance spectroscopy (see FIG. 13) .
  • E PZC values represent the potential in any given solution at which an electrode has zero charge. E PZC is therefore a measure of the charge density of the surface species.
  • Epzc has a negative correlation with electronegativity of the metal.
  • E PZC is obtained by extracting the capacitance term from the circuit fit of the electrochemical impedance spectroscopy data for an electrode at several different applied potentials. The minimum capacitance value represents the E PZC (see FIG. 12) .
  • Figure 11A-B presents the average exchange current densities (io) (A) and average overpotential at zero io (B) of each IrC> 2 based electrode coated with T1O 2 via cycles of ALD. Bare RUO 2 is shown as a red square for comparison. As thickness of T1O 2 increased beyond reasonably thick layers, the overpotential continued to increase, likely due to high resistivity.
  • Overpotentials and exchange current densities are the average of at least 3 polarization curve replicates. These figures present the same data as FIG. 9, but are extended to 1000 ALD cycles.
  • Figure 12 shows the electrochemical impedance
  • Figure 13 presents E PZC of IrC> 2 anodes coated with various
  • FIG. 12 This figure is the same as FIG. 10, except bulk T1O 2 (1000 ALD cycles) is also shown.
  • Figure 14 shows the overpotential at 1 mA/cm 2 for the CER of T1O 2 deposited on RUO 2 using ever-increasing cycles.
  • Standard CER conditions were 5M NaCl, pH 1 (HC1) , 1 atm Cl 2 , with 100% Faradaic Efficiency.
  • Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O 2 on RUO 2 substrate.
  • ALD cycles can be thought of as single atomic layers of TiO x .
  • Figure 15 provides representative polarization curves for
  • Figure 16 presents the specific activity (current density normalized to electrochemically active surface area) at a 350 mV overpotential in 1M H 2 SO 4 under an oxygen atmosphere for the OER of T1O 2 deposited on RUO 2 using ever-increasing cycles.
  • Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of TiC> 2 .
  • ALD cycles can be thought of as single atomic layers of TiO x .
  • Figure 17 provides representative polarization curves for
  • Figure 18 shows the overpotential at 1 mA/cm 2 for the CER of T1O 2 deposited on IrC> 2 using ever-increasing cycles.
  • Standard CER conditions were 5M NaCl, pH 2 (HC1) , 1 atm Cl 2 , with 100% Faradaic Efficiency.
  • Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O 2 on I r0 2 substrate.
  • ALD cycles can be thought of as single atomic layers of TiO x .
  • Figure 19 provides representative polarization curves for
  • Figure 20 presents the specific activity at a 350 mV overpotential in 1M H 2 SO 4 under 1 atm of oxygen for the OER of T1O 2 deposited on I r0 2 using ever-increasing cycles. Each dot represents a new catalyst that has a different number of atomic layer
  • ALD cycles can be thought of as single atomic layers of TiO x .
  • Figure 21 shows the overpotential at 1 mA/cm 2 for the CER of T1O 2 deposited on FTO using ever-increasing cycles.
  • Standard CER conditions were 5M NaCl, pH 1 (HC1) , 1 atm Cl 2 , with 100% Faradaic Efficiency.
  • Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O 2 on FTO substrate.
  • ALD cycles can be thought of as single atomic layers of TiO x .
  • Figure 22 provides representative polarization curves for
  • Figure 23 presents the specific activity at a 350 mV overpotential in 1M H 2 S0 4 for the OER of Ti0 2 deposited on FTO under an oxygen atmosphere using ever-increasing cycles.
  • Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O 2 .
  • ALD cycles can be thought of as single atomic layers of TiO x .
  • a "conductive material” as used herein refers to a material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electrical conductors. Electrical current is generated by the flow of
  • Examples of conductive materials include but are not limited to, metals, alloys, metal containing compounds, graphite, and conductive polymers.
  • Examples of good conducting metals include but are not limited to, silver, copper, gold, aluminum, molybdenum, zinc, lithium, tungsten, brass, nickel, iron, palladium, platinum, and tin.
  • a "semiconductive material” as used herein refers to material has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass.
  • the resistance of a semiconductive material decreases as the temperature of the semiconductive material increases, which is behavior opposite to that of a metal.
  • the conducting properties of semiconductive material may be altered in useful ways by the deliberate, controlled introduction of impurities ("doping") into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Semiconductor devices can display a range of useful properties such as passing current more easily in one direction than the other, showing variable resistance, and
  • semiconductive materials include, but are not limited to, group 14 elements (e.g., C, Si, Ge) ; binary compounds between group 13 and 15 elements (e.g., AlSb, GaAs, GaN, GaP, InN, InP) ; binary compounds between groups 12 and 16 elements (e.g., CdS, ZnO, ZnS, ZnTe) ; binary compounds between group 14 and 16 elements (e.g., PbSe, PbS, SnS, SnTe) ; and binary compounds between different group 14 elements (e.g., SiC) ternary
  • semiconductor alloys e.g., Al/Ga/As, In/Ga/As, In/Ga/P, Ga/As/N, Ga/As/P, In/Ga/N
  • semiconductive oxides e.g., T1O 2 , CU 2 O, CuO, Bi 2 0 3 , ZnO, Sn0 2 , BaTi0 3 , SrTi0 3 .
  • superconductive materials include, but are not limited to, type II alloys (e.g., Hg/Ba/Ca/Cu/O, Hg/Ti/Ba/Ca/Cu/O, Hg/Ba/Ca/Cu/O, Ti/Ba/Ca/Cu/O, Bi/Sr/Ca/Cu/O) .
  • type II alloys e.g., Hg/Ba/Ca/Cu/O, Hg/Ti/Ba/Ca/Cu/O, Hg/Ba/Ca/Cu/O, Ti/Ba/Ca/Cu/O, Bi/Sr/Ca/Cu/O
  • An "electrocatalyst” as used herein refers to a catalyst that participates in an electrochemical reaction, and which modifies or increases the rate of the electrochemical reaction without being consumed in the process.
  • An electrocatalyst can be heterogeneous such as a metal oxide surface, or homogeneous like a coordination complex. The electrocatalyst assists in transferring electrons between the electrode and reactants, and/or facilitates an
  • a “heterogeneous electrocatalyst” as used herein refers to a catalyst that participates in electrochemical reactions and which is in a separate phase from the reactants and/or products.
  • the reactants and products may be in a fluid phase, while the heterogeneous electrocatalyst is in a solid phase.
  • a “homogenous electrocatalyst” as used herein refers to a catalyst that participates in electrochemical reactions and which is in the same phase as the reactants and/or products.
  • An "electrochemical reaction” as used herein refers to a process either caused or accompanied by the passage of an electrons or an electric current and involving in most cases the transfer of electrons between two substances. The energy of an electric current can then be used to bring about many chemical reactions that do not occur spontaneously.
  • electrochemical reactions include the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction, and the oxygen reduction reaction.
  • a "thin film” as used herein refers to one or more layers of a conductive material and/or semiconductive material as defined herein that has been applied or deposited onto the surface of another conductive material, semiconductive and/or superconductive material.
  • the composition of the thin film is different from the composition of the conductive material
  • semiconductive and/or superconductive material that thin film is in direct contact with.
  • the "thin film” is applied, deposited, or layered on top of the surface of another conductive material, semiconductive material and/or superconductive material.
  • a chemical vapor deposition (CVD) -based process or an atomic layer deposition (ALD) -based process is used to apply, or deposit a thin film on top of the surface of another conductive material, semiconductive material, or superconductive material.
  • a "thin film” as used herein refers to a layer of conductive and/or semiconductive material which has a thickness of ⁇ 50 nm, ⁇ 25 nm, ⁇ 10 nm, ⁇ 5 nm, ⁇ 1 nm, ⁇ 9 A, ⁇ 8 A, ⁇ 7 A, ⁇ 6 A, ⁇ 5 A, ⁇ 4 A, ⁇ 3 A, ⁇ 2 A, ⁇ 1 A, or ⁇ 0.5 A.
  • the 'thin film' is a layer of conductive material that has a thickness of 0.1 A, 0.2 A, 0.3 A, 0.4 A, 0.5 A, 0.6 A, 0.7 A, 0.8 A, 0.9 A, 1 A, 1.1 A, 1.2 A, 1.3 A, 1.4 A, 1.5 A, 1.6 A, 1.7 A, 1.8 A, 1.9 A, 2 A, 2.1 A, 2.2 A, 2.3 A, 2.4 A, 2.5 A, 2.6 A, 2.7 A, 2.8 A, 2.9 A, 3 A, 3.1 A, 3.2 A, 3.3 A, 3.4 A, 3.5 A, 3.6 A, 3.7 A, 3.8 A, 3 9 A, 4 A, 4.1 A, 4.2 A, 4.3 A, 4.4 A, 4.5 A,
  • a 'thin film' as used herein refers to a layer of conductive material and/or semiconductive material which has a thickness resulting from using an ALD process with 1 to 1000 cycles, 1 to 500 cycles, 1 to 100 cycles, 1 to 90 cycles, 1 to 80 cycles, 1 to 70 cycles, 1 to 60 cycles, 1 to 55 cycles, 1 to 50 cycles, 1 to 45 cycles, 1 to 40 cycles, 1 to 35 cycles, 1 to 30 cycles, 1 to 25 cycles, 1 to 24 cycles, 1 to 23 cycles, 1 to 22 cycles, 1 to 21 cycles, 1 to 20 cycles, 1 to 19 cycles, 1 to 18, cycles, 1 to 17 cycles, 1 to 16 cycles, 1 to 15 cycles, 1 to 14 cycles, 1 to 13 cycles, 1 to 12 cycles, 1 to 11 cycles, 1 to 10 cycles, 1 to 9 cycles, 1 to 7 cycles, 1 to 6 cycles or 1 to 5 cycles.
  • a 'thin film' as used herein refers to a layer of conductive material and/or
  • semiconductive material which has a thickness resulting from using an ALD process with 1 cycle, 2 cycles, 3 cycles, 4 cycles, 5 cycles, 6 cycles, 7 cycles, 8 cycles, 9 cycles, 10 cycles, 11 cycles, 12 cycles, 13 cycles, 14 cycles, 15 cycles, 16 cycles, 17 cycles, 18 cycles, 19 cycles, 20 cycles, 21 cycles, 22 cycles, 23 cycles, 24 cycles, 25 cycles, 30 cycles, 35 cycles, 40 cycles, 45 cycles, 50 cycles, 55 cycles, 60 cycles, 70 cycles, 80 cycles, 90 cycles, 100 cycles, 500 cycles, 1000 cycles, or any range between any two of the foregoing cycle numbers.
  • a "conductive electrocatalytic substrate” as used herein refers to substrate that is comprised of one or more conductive materials, semiconductive materials and/or superconductive materials as defined herein that can be used as a catalyst in an electrochemical reaction.
  • the conductive electrocatalytic substrate is not limited to having any specific shape or having any specific dimension (e.g., thickness). Accordingly, the conductive
  • the electrocatalytic substrate can have any shape and any suitable dimension.
  • the substrate is ⁇ 100 nm, ⁇ 1 ⁇ , ⁇ 10 ⁇ , ⁇ 100 ⁇ or ⁇ 1 mm in thickness.
  • the conductive electrocatalytic substrate is a component of an electrode.
  • an electrode comprises the conductive electrocatalytic substrate.
  • Electrocatalysts are used both to speed up electrode reactions and to enable them to occur close to their
  • thermodynamically predicted potentials In electrochemical power supplies such as fuel cells, the incorporation of electrocatalysts into the electrode structure enables the fuel cell to operate near its theoretically expected potential even when appreciable current is drawn from the cell.
  • the electrocatalyst is said to reduce the overvoltage for the electrode reaction.
  • a related example is the water electrolysis cell; electrocatalysts are important here to lower the minimum voltage necessary for electrolysis to occur, and to keep it low as the rate of electrolysis at the electrodes is increased -- this will permit high efficiency of operation.
  • donating/withdrawing or sterically hindering ligands can be used to define a perfect catalytic active site, progress in the field of heterogeneous electrocatalysis has been relatively attenuated due to limited tools for crafting active sites.
  • optimizing bond strength to a precursor is a difficult task.
  • Previous studies have used dopants, vacancies, mixed oxides, topography induced strain, and ligand addition to alter electronics, mainly by sterics. Full tunability, however, has proven very difficult. In order to design optimal active sites, more tools are needed. The methods described herein have been shown to be useful for tuning surface electronics. In particular, to tune the surface electronics and corresponding activity of heterogeneous
  • electrocatalysts for the industrially and environmentally important electrochemical reactions (e.g., Chlorine Evolution Reaction (CER) and the Oxygen Evolution Reaction (OER) ) .
  • CER Chlorine Evolution Reaction
  • OER Oxygen Evolution Reaction
  • Catalysts act to reduce a chemical reaction's activation energy requirements by destabilizing intermediates and stabilizing transition states.
  • reactant binding sites active sites
  • the methods of the disclosure provide a step of layering or applying one or more materials (e.g., electrocatalytic materials) to another different material (e.g., a different electrocatalytic material) using atomic layer deposition, wherein the thickness of the layered or applied material can be tunably controlled based upon the number of ALD cycles.
  • materials e.g., electrocatalytic materials
  • another different material e.g., a different electrocatalytic material
  • the general principal of this catalyst tuning process is that it is possible to create surfaces with designer and predictable properties for catalysis. This is achieved by layering multiple conductive materials that are sufficiently thin such that the overlying film can electronically "feel" the underlying film. When a very thin layer is stacked on top of another layer, the surface becomes an electronic average of the two materials. That average can be tuned by tuning the thickness of the overlying materials. For example, a single atomic layer of an overlying materials will look a lot more like the underlying material than 100 atomic layers of the overlying material will look.
  • the methods provided herein provide a new means by which heterogeneous electrocatalysts could be designed and developed.
  • the methods disclosed herein allow for the deposition of one or more thin layers of a conductive material on top of another conductive material or substrate so as to afford a new material that has electronic properties that are intermediate between the two (or more) conductive materials. While not beholden to the specific examples presented herein, it is clear that methods of disclosure can be used to design heterogeneous electrocatalysts that have improved catalytic activities for the oxygen evolution reaction, and the chlorine evolution reaction. Additionally, the methods of the disclosure are directed to a platform technology, whereby the methods can be similarly applied to improve the catalytic activities of electrocatalysts in other types of
  • the methods disclosed herein it is now possible to evaluate materials based upon their associated electronic properties, properties such as electronic structure, polarity in forming bonds, bond strength, and electronegativities of the elements making up the material, and then layering another material which has complementary or different properties in thin layers on top of the first material to afford a new material that has electronic properties that are somewhere between the two materials, which can be adjusted if desired, based upon the number of cycles in the layering process.
  • the methods of the disclosure now make it possible to create custom electrocatalytic materials that have more desirable electronic properties based upon combining the electronic properties of known materials to make new electrocatalytic materials.
  • the data presented herein indicate that adding various layers of a metal oxide with a more electron poor metal and more electron rich oxygen on top of a metal oxide with a less electron poor metal and less electron rich oxygen can tune the surface charge density and the catalytic parameters. Furthermore, the data show that when the charge density is matched to that of a better catalyst, the catalytic parameters also match as predicted by the Sabatier principal. Therefore, the methods of the disclosure represent a new means for improving the performance of heterogeneous electrocatalysts by tuning an active surface species' charge density by overcoating with an appropriate material or mix of materials. Furthermore, the methods of the disclosure provide a pathway to enhance the catalytic activity of earth abundant electrocatalysts for important reactions that was not previously available due to a dearth of means to tune the activity of heterogeneous
  • electrocatalysts By looking at parameters that dictate the electron concentration of the surface (i.e., heat of formation, electron affinity, potential of zero charge, etc.) of the best-known catalyst (RUO2) , a series of new catalysts for the chlorine and the oxygen evolution reactions were generated. Based up testing, some of these newly created catalysts exhibited catalytic properties which exceeded that of the 'best' known catalysts for the OER and CER reactions.
  • conductive materials were chosen such that the surface charge concentration properties of the composite material were similar to that of RUO 2 (i.e., Ti has an electron affinity of -8 eV while Ir has an electron affinity of -150 eV and Ru has an electron affinity of -101 eV) .
  • T1O 2 on top of IrC> 2 provided for a composite material that had similar surface charge properties to RUO 2 . It should be noted, however, that RUO 2 while having favorable surface charge properties for the OER, suffers from low stability. Thus, the above composite material of T1O 2 and IrC> 2 exhibits favorable surface charge
  • heterogeneous electrocatalyst systems such as designing and fabricating new heterogeneous electrocatalysts for all types of reactions from energy storage in batteries or fuels to industrial commodity chemical production and more.
  • the disclosure provides for applying a thin film of a conductive material using one or more cycles of atomic layer deposition to a surface of another different conductive material or substrate.
  • Atomic layer deposition is a thin film deposition technique that is based on the sequential use of a gas phase chemical process (see FIG . 4 ) .
  • ALD is considered a subclass of chemical vapor deposition.
  • precursors typically called precursors. These precursors react with the surface of a material one at a time in a sequential, self-limiting, manner. Through the repeated exposure to separate precursors, a thin film is slowly deposited.
  • the precursors are never present simultaneously in the reactor, but they are inserted as a series of sequential, non-overlapping pulses. In each of these pulses the precursor molecules react with the surface in a self-limiting way, so that the reaction terminates once all the reactive sites on the surface are consumed. Consequently, the maximum amount of material deposited on the surface after a single exposure to all of the precursors (a so-called ALD cycle) is determined by the nature of the precursor-surface interaction. By varying the number of cycles, it is possible to grow materials uniformly and with high precision on arbitrarily complex and large substrates. ALD produces very thin, conformal films with control of the thickness and composition of the films possible at the atomic level.
  • each reactant reacts with the surface in a self-limited way: the reactant molecules can react only with a finite number of reactive sites on the surface. Once all those sites have been consumed in the reactor, the growth stops. The remaining reactant molecules are flushed away and only then reactant B is inserted into the reactor. By alternating exposures of A and B, a thin film is deposited.
  • ALD process when describing an ALD process one refers to both dose times (the time a surface is being exposed to a precursor) and purge times (the time left in between doses for the precursor to evacuate the chamber) for each precursor.
  • dose times the time a surface is being exposed to a precursor
  • purge times the time left in between doses for the precursor to evacuate the chamber.
  • the dose-purge-dose-purge sequence of a binary ALD process constitutes an ALD cycle.
  • ALD processes are described in terms of their growth per cycle.
  • ALD precursors have self-limiting reactivity with the substrate and the film surface. For most precursors, only one element is contributed to the deposited film, with the rest of the molecules vaporized during the process.
  • Certain compounds can contribute more than one element and bring down the number of reactants needed for a specific process.
  • Precursors for ALD are commercially available from a variety of vendors (e.g., Sigma Aldrich Co., St. Louis MO; and Strem Chemicals Inc., Newburyport, MA) .
  • Examples of ALD precursors include, but are not limited to, aluminum tris (2 , 2 , 6, 6-tetramethyl-3, 5- heptanedionate ) , triisobutylaluminum, trimethylaluminum,
  • bromopentacarbonylmanganese (I) cyclopentadienylmanganese (I) tricarbonyl, ethylcyclopentadienylmanganese ( I ) tricarbonyl, manganese(O) carbonyl, (bicyclo [ 2.2.1 ] hepta-2 , 5- diene ) tetracarbonylmolybdenum ( 0 ) ,
  • hexaphenylditin (IV) , tetraallyltin, tetrakis (diethylamido) tin (IV) , tetramethyltin, tetravinyltin, tin (II) acetylacetonate ,
  • cyclopentadienyltungsten ( I I ) tricarbonyl hydride, tetracarbonyl ( 1 , 5- cyclooctadiene ) tungsten ( 0 ) , triamminetungsten ( IV) tricarbonyl, tungsten hexacarbonyl , bis (cyclopentadienyl) vanadium (II) ,
  • the conductive catalytic materials or electrocatalysts of the disclosure comprises metals, metal sufides, metal nitrides, metal fluorides, metal oxides, alloys, or any combination of the foregoing.
  • any of the foregoing may further comprise dopants, e.g., iridium doped iron oxide, molybdenum doped iron oxide, niobium doped iron oxide, and fluorine doped tin oxide.
  • the metal oxide comprises the oxide of a single metal selected from, but not limited to,
  • transition metals e.g., iron, cobalt, nickel, vanadium, copper, zinc, zirconium, tungsten, ruthenium, platinum, palladium,
  • molybdenum osmium, manganese, chromium, titanium, rhodium, ruthenium, iridium
  • alkaline earth metals e.g., magnesium, calcium, strontium, and barium
  • poor metals /metalloids e.g., zinc, gallium, aluminum, germanium, tin, and bismuth
  • metal oxides include, but are not limited to, AI 2 O 3 , NH 4 OSbW, Sb 2 0 5 , BaO, BaTi0 3 , BaZr0 3 , Al 6 BeOi 0 , BeO, Bi 2 0 3 , Bi 2 0 5 , B 2 0 3 , CdO, CaO, Ce 2 0 3 , Ce0 2 , CrO, Cr 2 0 3 , Cr0 2 , Cr0 3 , CoO, Co 2 0 3 , Cu 2 0 5 Yb 2 , Cu 2 0, CuFe 2 0 4 , CuO, GaO, Ga 2 0 3 , GeO, Ge0 2 , Au 2 0, Au 2 0 3 , Hf0 2 , ln 2 0, InO, ln 2 0 3 , lr 2 0 3 , Ir0 2 , Fe 3 0 4 , FeO, Fe 2 0 3 , PbO, Pb0 2 , Li 2
  • the alloy may be a mixture of a metal and another element, or a mixture of metals. If there is a mixture of only two types of atoms (not counting impurities) then it is a binary alloy.
  • binary alloys include, but are not limited to, iron/cobalt, iron/nickel, cobalt/nickel, cobalt/aluminum, nickel/aluminum, iron/aluminum, iron/cerium, iron/molybdenum, iron/copper, iron/iridium,
  • iron/manganese iron/tin, and iron/niobium. If there is a mixture of three types of atoms (not counting impurities) then it is a ternary alloy.
  • ternary alloys include, but are not limited to, iron/cobalt/nickel, iron/aluminum/nickel,
  • electrocatalysts which comprise a conductive electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or
  • heterogeneous electrocatalysts comprise a conductive
  • the heterogeneous electrocatalysts comprise a conductive electrocatalytic substrate made of a conductive material and thin layer (s) that are comprised of conductive materials.
  • the heterogeneous electrocatalysts comprise a conductive electrocatalytic substrate made of a conductive material and thin layer (s) that are comprised of conductive materials.
  • heterogeneous electrocatalysts comprise a conductive
  • electrocatalytic substrate that is comprised of a semiconductive material and thin layer (s) that are comprised of semiconductive materials.
  • electrocatalysts comprise a conductive electrocatalytic substrate that is comprised of a semiconductive material and thin layer (s) that are comprised of conductive materials.
  • a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive or semiconductive materials that has a thickness of ⁇ 50 nm, ⁇ 25 nm, ⁇ 10 nm, ⁇ 5 nm, ⁇ 1 nm, ⁇ 9 A, ⁇ 8 A, ⁇ 7 A, ⁇ 6 A, ⁇ 5 A, ⁇ 4 A, ⁇ 3 A, ⁇ 2 A, ⁇ 1 A, or ⁇ 0.5 A.
  • a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive and/or semiconductive materials that have a thickness of 0 .1 A, 0 .2 A, 0.3
  • a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive and/or semiconductive materials that has a thickness resulting from using an ALD process with 1 to 1000 cycles, 1 to 500 cycles, 1 to 100 cycles, 1 to 90 cycles, 1 to 80 cycles, 1 to 70 cycles, 1 to 60 cycles, 1 to 55 cycles, 1 to 50 cycles, 1 to 45 cycles, 1 to 40 cycles, 1 to 35 cycles, 1 to 30 cycles, 1 to 25 cycles, 1 to 24 cycles, 1 to 23 cycles, 1 to 22 cycles, 1 to 21 cycles, 1 to 20 cycles, 1 to 19 cycles, 1 to 18, cycles, 1 to 17 cycles, 1 to 16 cycles, 1 to 15 cycles, 1 to 14 cycles, 1 to 13 cycles, 1 to 12 cycles, 1 to 11 cycles, 1 to 10 cycles, 1 to 9 cycles, 1 to 7 cycles, 1 to 6 cycles or 1 to 5 cycles.
  • a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive and/or semiconductive materials that has a thickness resulting from using an ALD process with 1 cycle, 2 cycles, 3 cycles, 4 cycles, 5 cycles, 6 cycles, 7 cycles, 8 cycles, 9 cycles, 10 cycles, 11 cycles, 12 cycles, 13 cycles, 14 cycles, 15 cycles, 16 cycles, 17 cycles, 18 cycles, 19 cycles, 20 cycles, 21 cycles, 22 cycles, 23 cycles, 24 cycles, 25 cycles, 30 cycles, 35 cycles, 40 cycles, 45 cycles, 50 cycles, 55 cycles, 60 cycles, 70 cycles, 80 cycles, 90 cycles, 100 cycles, 500 cycles, 1000 cycles, or any range between any two of the foregoing cycle numbers.
  • a heterogeneous electrocatalyst disclosed herein comprises a conductive electrocatalytic substrate that is ⁇ 100 nm, ⁇ 1 ⁇ , ⁇ 10 ⁇ , ⁇ 100 ⁇ or ⁇ 1 mm in thickness.
  • the disclosure provides for a heterogeneous electrocatalyst that is suitable for the Oxygen
  • a conductive electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or
  • the substrate and thin films are selected from the following materials: Ni0 2 and WO 3 , Ni0 2 and W0 3 , Ni0 2 and A1 2 0 3 , Ni0 2 and Mn0 2 , Ru0 2 and Ti0 2 , Ru0 2 and W0 3 , Ru0 2 and A1 2 0 3 , Ru0 2 and Mn0 2 , Cu0 2 and Ti0 2 , Cu0 2 and W0 3 , Cu0 2 and A1 2 0 3 , Cu0 2 and Mn0 2 , Ir0 2 and Ti0 2 , Ir0 2 and W0 3 , Ir0 2 and A1 2 0 3 , Ir0 2 and Mn0 2 , Sn0 2 /FTO and Ti0 2 , Sn0 2 /FTO and W0 3 , Sn0 2 /FTO and A1 2 0 3 , and Sn0 2 /FTO and Mn0 2 .
  • the disclosure provides for a heterogeneous electrocatalyst that is suitable for the Nitrogen Reduction Reaction which comprises a conductive electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or
  • the substrate and thin films are selected from the following materials: Ni and Ti, Cu and Ti, Nb and Ti, Mo and Ti, Tc and Ti, Ru and Ti, Rh and Ti, Ag and Ti, Sn and Ti, Os and Ti, Ir and Ti, Ni and Mn, Cu and Mn, Nb and Mn, Mo and Mn, Tc and Mn, Ru and Mn, Rh and Mn, Ag and Mn, Sn and Mn, Os and Mn, Ir and Mn, Ni and Zn, Cu and Zn, Nb and Zn, Mo and Zn, Tc and Zn, Ru and Zn, Rh and Zn, Ag and Zn, Sn and Zn, Os and Zn, and Ir and Zn.
  • the disclosure provides for a heterogeneous electrocatalyst that is suitable for the CO2 Reduction Reaction which comprises a conductive
  • electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or semiconductive materials, and wherein the substrate and thin films are selected from the following materials: Ni and Ti, Ni and W, Ni and Al, Ni and Mn, Ru and Ti, Ru and W, Ru and Al, Ru and Mn, Cu and Ti, Cu and W, Cu and Al, Cu and Mn, Ir and Ti, Ir and W, Ir and Al, Ir and Mn, Sn and Ti, Sn and W, Sn and Al, and Sn and Mn.
  • an anode comprises one or more heterogeneous electrocatalysts disclosed herein.
  • a cathode comprises one or more heterogeneous electrocatalysts disclosed herein.
  • a cathode and an anode comprises one or more heterogeneous electrocatalysts disclosed herein.
  • an electrode which comprises one or more heterogeneous electrocatalysts disclosed herein is used in an electrochemical reaction. Examples of electrochemical reactions, include but are not limited to, the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction, and the oxygen reduction reaction .
  • the disclosure provides a method to manufacture a heterogeneous electrocatalyst that has improved electrocatalytic activity for an electrochemical reaction, comprising: layering or depositing one or more thin films of one or more conductive catalytic materials onto a surface of a conductive electrocatalytic substrate by using 1 to 100 cycles of an atomic layer deposition process, wherein the number of cycles of the atomic layer deposition process is used to tune the electrocatalytic activity of the heterogeneous electrocatalysts for the
  • the one or more thin films are comprised of metals, alloys, metal oxides, metal nitrides, metal sulfides, metal fluorides, or a combination thereof,
  • the one or more thin films are comprised of metal oxides
  • the one or more thin films are comprised of metal oxides selected from AI 2 O 3 , NH 4 OSbW, Sb 2 Os, BaO, BaTi0 3 , BaZr0 3 , Al 6 BeOi 0 , BeO, Bi 2 0 3 , Bi 2 0 5 , B 2 0 3 , CdO, CaO, Ce 2 0 3 , Ce0 2 , CrO, Cr 2 0 3 , Cr0 2 , Cr0 3 , CoO, Co 2 0 3 , Cu 2 0 5 Yb 2 , Cu 2 0, CuFe 2 0 4 , CuO, GaO, Ga 2 0 3 , GeO, Ge0 2 , Au 2 0, Au 2 0 3 , Hf0 2 , ln 2 0, InO, ln 2 0 3 , lr 2 0 3 , Ir0 2 , Fe 3 0 4 ,
  • the one or more thin films comprise Ti0 2 .
  • a method disclosed herein comprises 1 to 50 cycles of an atomic layer deposition process used to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate, preferably wherein 1 to 25 cycles of an atomic layer deposition process are used to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate, more
  • a method disclosed herein comprises one or more thin films are made from one or more precursors used in the atomic layer deposition process selected from aluminum tris (2, 2, 6, 6-tetramethyl-3, 5-heptanedionate) , triisobutylaluminum, trimethy1aluminum,
  • bromopentacarbonylmanganese (I) cyclopentadienylmanganese (I) tricarbonyl, ethylcyclopentadienylmanganese ( I ) tricarbonyl, manganese(O) carbonyl, (bicyclo [ 2.2.1 ] hepta-2 , 5- diene ) tetracarbonylmolybdenum ( 0 ) ,
  • hexaphenylditin IV
  • tetraallyltin tetrakis (diethylamido) tin
  • IV tetramethyltin, tetravinyltin, tin (II) acetylacetonate , trimethyl (phenylethynyl ) tin, trimethyl (phenyl ) tin, tetrakis
  • cyclopentadienyltungsten ( I I ) tricarbonyl hydride, tetracarbonyl ( 1 , 5- cyclooctadiene ) tungsten ( 0 ) , triamminetungsten ( IV) tricarbonyl, tungsten hexacarbonyl , bis (cyclopentadienyl) vanadium (II) ,
  • the one or more thin films are made from a precursor of tetrakis (dimethylamido) titanium ( IV) used in the atomic layer deposition process.
  • a method disclosed herein comprises a conductive electrocatalytic substrate is at least 100 nm in thickness, preferably wherein the conductive electrocatalytic substrate is at least 10 ⁇ in thickness.
  • a method disclosed herein comprises a conductive electrocatalytic substrate that is comprised of a conductive material, semiconductive material and/or superconductive material (e.g., a metal, alloy, metal oxide, metal nitride, metal sulfide, metal fluoride, or a combination thereof) , preferably wherein the conductive electrocatalytic substrate is comprised of a metal oxide, more preferably wherein the conductive electrocatalytic substrate is comprised of a metal oxide selected from AI 2 O 3 , NH 4 OSbW, Sb 2 0s, BaO, BaTi0 3 , BaZr0 3 , Al 6 BeOi 0 , BeO, Bi 2 0 3 , Bi 2 0
  • a method disclosed herein comprises a conductive electrocatalytic substrate that is comprised of Ir0 2 or Ru0 2 .
  • a method disclosed herein comprises an electrochemical reaction that is selected from the group consisting of the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, and the oxygen reduction reaction, preferably wherein the electrochemical reaction is the oxygen evolution reaction or the chlorine evolution reaction.
  • a method disclosed herein comprises a heterogeneous electrocatalyst exhibits a lower overpotential or improved specific activity for the chemical reaction than the conductive electrocatalytic substrate.
  • a method disclosed herein comprises a heterogeneous electrocatalyst exhibits has a more favorable surface charge distribution for the chemical reaction than the conductive electrocatalytic substrate.
  • the conductive electrocatalytic substrate In an embodiment disclosed herein or as a further embodiment, the
  • a heterogeneous electrocatalyst made by a method of the disclosure.
  • a heterogeneous electrocatalyst disclosed herein comprises a conductive electrocatalytic substrate of Ir0 2 , FTO, or Ru0 2 .
  • a heterogeneous electrocatalyst disclosed herein comprises a thin film of Ti0 2 , preferably wherein the thin film of Ti0 2 is made from 1 to 15 cycles of an ALD process.
  • an electrode comprises a heterogeneous electrocatalyst disclosed herein, preferably wherein the electrode is used to generate reactive chloride species in a wastewater treatment system.
  • each ALD cycle consisted of a 0.25 s pulse of tetrakis (dimethylamido) titanium (TDMAT, Sigma-Aldrich, 99.999%, used as received), followed by a 0.06 s pulse of 3 ⁇ 40 (18 ⁇ -cm, Millipore) .
  • TDMAT tetrakis (dimethylamido) titanium
  • 0.06 s pulse 3 ⁇ 40 (18 ⁇ -cm, Millipore) .
  • a 15 s purge under a constant 0.13 L min "1 flow of research-grade Ar (g) was performed between each precursor pulse.
  • the base pressure during the T1O 2 growth was kept at -0.1 torr.
  • T1O 2 Growth rate of T1O 2 was -0.05 nm/cycle. Bare IrC> 2 samples were subjected to only one pulse of 0.06 s 3 ⁇ 40.
  • the pH was adjusted to a pH of 1 using 37% reagent grade HC1 ( Sigma-Aldrich) , and then diluted to 1 L with water (18 ⁇ -cm, Millipore) . Constant stirring was used during CVs, and a coiled 0.5 mm Pt wire counter electrode was used (Sigma- Aldrich, 99.99%) . At least three different samples for each T1O 2 thickness were compared for at least 10 cycles from 0.9 to 1.4 V vs Ag/AgCl. Peak current was similar for the 10 cycles of any given sample, and surface area did not significantly change before and after cyclic voltammetry and, surface area as measured by
  • CV current data was converted to mA/cm 2 units and then logged to perform Tafel analysis. Overpotentials and exchange current densities were averaged from at least three different samples. Overpotential calculations were conducted using the Nernst equation and activities of CI " and CI 2 .
  • CI 2 is a gas so fugacity was used while CI " activities were estimated from ionic strength.
  • Thermodynamic potential was calculated to be 1094 mV vs an Ag/AgCl reference electrode.
  • Electrochemical Impedance Spectroscopy 5M NaN03 at pH 1 was prepared by dissolving NaN03 (J.T. Baker, 99.6%) in 900 mL of water (18 ⁇ -cm, Millipore), adjusting the pH to 1 using HNO 3 (Sigma Aldrich, > 60%) and diluting with water (18 ⁇ ⁇ cm, Millipore) to 1 L. Electrodes were prepared as previously described and placed in sealed custom glass reaction containers with a 1M KC1 Ag/AgCl reference electrode (CH instruments) , 2 x 2 cm stainless steel counter electrode and enough NaN03 solution to cover the exposed 2 mm diameter anode. The reaction container was then purged with N 2 for > 30 minutes. Impedance measurements were carried out using Bio-Logic potentiostat/galvanostat model VSP-300 with EIS
  • E PZC relative potentials of zero charge
  • T1O 2 was also chosen because it conveys high stability to IrC> 2 catalysts, and can be conveniently deposited by ALD.
  • IrC> 2 was deposited on atomically flat p+ [100] silicon wafers by reactive sputtering for a nearly flat surface. ALD was then used to chemically bond 0-1000 ALD cycles of T1O 2 to the IrC> 2 surface (thick films of T1O 2 are nearly inert for the chlorine evolution reaction at reasonable overpotentials ) . Polarization curves for T1O 2 coated IrC> 2 and bare IrC> 2 were measured and Tafel analysis was conducted
  • FIG . 7A and B indicate that the E PZC follows the
  • samples of Ir0 2 were prepared with different numbers of atomic layer deposition (ALD) cycles of T1O 2 deposited on top the Ir0 2 substrate in order to tune the charge density of the catalyst's surface.
  • ALD atomic layer deposition
  • the layer thickness using ALD can be controlled down to a single monolayer.
  • ALD is a mature technology that has been used extensively in the microelectronics industry to vary the surface charge density of semiconductors by depositing thin layers of gate oxides.
  • Ir0 2 was coated with between 1 and 60 ALD cycles of T1O 2 .
  • the catalytic performance of these samples for the CER was measured under conditions similar to industrial CER (i.e., 5 M CI " , pH 1) in order to eliminate competition with OER.
  • Metal oxide charge densities were evaluated by measuring the correlated potential of zero charge (E PZ c) , the potential for a given electrode in a given solution where the net surface charge is zero (i.e., a metal oxide with a more electron rich oxygen and more electron poor metal has a higher E PZ c) ⁇
  • CI may coordinate either to vacancies on the surface metal or surface bound oxygens, therefore the electron density of the surface oxygen and metal are important parameters governing the activity of CER catalysts.
  • the correlated potential at zero charge is a means of quantifying the surface oxygen and metal charge densities for metal oxides, where higher EPZC values indicate higher electron densities on surface oxygen atoms and electron-poor metal atoms.
  • the active site for chlorine adsorption is proposed to be a surface oxygen atom which has adsorbed on a coordinately unsaturated (cus) Ir site.
  • chlorine adsorption is
  • any substrate could be tuned by combining two materials that have different electronic properties in thin layers. This tuning could allow the surface electronics to match the requisites of any chemical reaction of interest. Combinations of 2 or more metal - nonmetal materials may be deposited to achieve a perfect electronic state of the surface. It is further postulated that tuning could be performed with earth abundant or non-precious metal-nonmetal electrodes in order to fit a chemically active regime .
  • TiO x was deposited as atomically thin layers ((from a single atomic layer ( ⁇ 0.5 angstroms) to 1000 atomic layers (approximately 50 nm) ) on top of a FTO, IrO x , and RuO x substrate, where a new catalyst was created for each thickness of TiO x .
  • the electrocatalysts made by the methods disclosed herein had improved catalytic activity for the OER in comparison to the best industry catalysts.
  • the current best electrocatalyst for the OER in 1 M H 2 SO 4 is RUO 2 which operates at a specific activity (normalized to electrochemically active surface area) of 0.42 mA/cm 2 at 350 mV overpotential .
  • electrocatalyst was made by layering 10 cycles of T1O 2 onto IrO x was found to operate at a specific activity of 3.5 mA/cm 2 at 350 mV overpotential. Further, a new heterogeneous electrocatalyst made by layering 10 cycles of TiO x onto RUO 2 using the methods of the disclosure, yielded a heterogeneous electrocatalyst that operated at of 2.8 mA/cm 2 at 350 mV overpotential for the OER.
  • FIG. 15 and 16 polarization curves and specific activities for RUO 2 coated with increasing ALD cycles of Ti0 2 for OER are provided in FIG. 15 and 16, respectively.
  • the polarization curves and overpotential curves for Ir0 2 coated with increasing ALD cycles of T1O 2 for CER are provided in FIG. 17 and 18, respectively; while the polarization curves and specific activities for Ir0 2 coated with increasing ALD cycles of T1O 2 for CER are provided in FIG. 19 and 20, respectively.
  • the overpotentials of FTO coated with increasing ALD cycles of T1O 2 for CER are provided in FIG. 21; while the polarization curves and specific activities for FTO coated with increasing ALD cycles of T1O 2 for OER are provided in FIG. 22 and 23, respectively.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Metallurgy (AREA)
  • Materials Engineering (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Hydrology & Water Resources (AREA)
  • Water Supply & Treatment (AREA)
  • Environmental & Geological Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Catalysts (AREA)

Abstract

The disclosure provides for thin films that can be used to tune the catalytic characteristics of heterogeneous electrocatalysts.

Description

TUNING ELECTRODE SURFACE ELECTRONICS WITH THIN LAYERS
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority under 35 U.S.C. §119 from Provisional Application Serial No. 62/401,045 filed September 28, 2016, the disclosure of which is incorporated herein by reference .
TECHNICAL FIELD
[0002] The disclosure provides for thin films that can be used to tune the catalytic characteristics of heterogeneous
electrocatalysts .
BACKGROUND
[0003] Catalysts act by reducing the activation energy to perform a chemical reaction by destabilizing intermediates and stabilizing transition states. The Sabatier principle states that an effective catalyst must bind a precursor just right. Too tight binding of a precursor or too loose binding of
products /intermediates will prevent conversion to
product/intermediates while too tight binding of
product/intermediates or too loose binding of precursor will foul the catalyst preventing release of product or initiation of catalysis (see FIG. 2) . All catalysts (including biological and heterogeneous) contain an active site or sites which provide the specific requirements for the "just right" binding of a precursor. In general, the two ways to tune an active site for "just right" binding are through either altering charge distribution
(electronics) or steric hindrance (sterics) (see FIG. 3) . With heterogeneous electrocatalysts, the reactant-catalyst binding sites' charge density is important for catalytic activity, yet there is no known way to sufficiently tune this parameter.
SUMMARY
[0004] The disclosure provides for creating heterogeneous electrocatalysts by layering one or more thin films of one or more electrocatalytic materials onto the surface of a different
electrocatalytic material or substrate, whereby catalytic
characteristics of heterogeneous electrocatalysts can be tuned based upon the composition and/or thickness of the applied film. As evidenced herein, the performance of the chlorine evolution reaction (CER) and oxygen evolution reaction (OER) catalysts, IrC>2, RUO2, and FTO, can be tuned by depositing thin films of T1O2 using atomic layer deposition (ALD) . In particular, by using the methods of disclosure it was found that the electrocatalytic performance of IrC>2 and RUO2 for the Oxygen Evolution Reaction can be greatly improved by depositing a thin film of T1O2 on their surfaces, so much so that the specific catalytic activity (io) and overpotential of these catalysts were tuned to an order of magnitude better than any previously reported catalyst for the OER in 1 M H2SO4. The improvement of electrocatalytic performance was attributed to a favorable change in the electrocatalysts ' surface species' charge density. Moreover, the surface species' charge density of all catalyst studied was found to be predictably tunable based upon the thickness of the T1O2 layer. Accordingly, the methods of the disclosure are directed to a platform technology that in principle can be used to rationally design heterogeneous electrocatalysts that can be used in many types of reactions where reactants are
electrocatalytically converted into products. In other words, the results presented herein merely demonstrate an example of how the methods of disclosure can be used, not that the methods of the disclosure are limited to only creating chlorine evolution reaction (CER) electrocatalysts or oxygen evolution reaction (OER)
electrocatalysts .
[ 0005 ] In a particular embodiment, the methods of the disclosure provide for the use of multiple (2 or more) electrocatalytic materials and layering them in thin layers on top of the surface of a different electrocatalytic material or substrate. In a further embodiment, the top or outermost electrocatalytic layer is less than 50 nm in thickness. As demonstrated herein, numerous heterogeneous electrocatalysts (> 50) were created for 2 different industrially important reactions, the chlorine evolution reaction (CER) and the oxygen evolution reaction (OER) . In particular, multiple different materials (e.g., fluorine doped tin oxide (FTO), iridium oxide
(IrOx), ruthenium oxide (RuOx) , and titania (TiOx) ) were utilized in the methods disclosed herein to create new heterogeneous
electrocatalysts. By using the methods of the disclosure, new heterogeneous electrocatalysts were created for OER which operated at lower or equal overpotentials (corrected for electrochemically active surface area) than any previously reported electrocatalyst using the industry standard OER conditions. For example, the current best electrocatalyst for the OER in 1 M H2SO4 is RUO2 which operates at a specific activity (normalized to electrochemically active surface area) of 0.42 mA/cm2 at 350 mV overpotential . By using the methods presented herein, a new heterogeneous
electrocatalyst was made by layering 10 cycles of T1O2 onto IrOx. This heterogeneous electrocatalyst was found to operate at a specific activity of 3.5 mA/cm2 at 350 mV overpotential. Further, a new heterogeneous electrocatalyst made by layering 10 cycles of TiOx onto RUO2 using the methods of the disclosure, yielded a
heterogeneous electrocatalyst that operated at of 2.8 mA/cm2 at 350 mV overpotential for the OER.
[ 0006] In a particular embodiment, the disclosure provides a method to manufacture a heterogeneous electrocatalyst that has improved electrocatalytic activity for an electrochemical reaction, comprising: layering or depositing one or more thin films of one or more conductive and/or semiconductive catalytic materials onto a surface of a conductive electrocatalytic substrate by using 1 to 100 cycles of an atomic layer deposition process, wherein the
composition of the one of more thin films is different from the composition of the conductive electrocatalytic substrate, wherein the number of cycles of the atomic layer deposition process is used to tune the electrocatalytic activity of the heterogeneous
electrocatalysts for the electrochemical reaction, and wherein the electrocatalytic activity of the heterogeneous electrocatalyst for the electrochemical reaction is improved in comparison to the electrocatalytic activity of the conductive electrocatalytic substrate. In an embodiment disclosed herein or in a further embodiment, one or more thin films disclosed herein comprise, consist essentially of, or consists of metals, alloys, metal oxides, metal nitrides, metal sulfides, metal fluorides, or a combination thereof. In an embodiment disclosed herein or as an alternate or further embodiment, one or more thin films disclosed herein comprise, consist essentially of, or consists of metal oxides. In an embodiment disclosed herein or as an alternate or further embodiment, one or more thin films disclosed herein comprise, consist essentially of, or consists of metal oxides selected from A1203, NH4OSbW, Sb205, BaO, BaTi03, BaZr03, Al6BeOi0, BeO, Bi203, Bi205, B2O3, CdO, CaO, Ce203, Ce02, CrO, Cr203, Cr02, Cr03, CoO, Co203,
Cu205Yb2, Cu20, CuFe204, CuO, GaO, Ga203, GeO, Ge02, Au20, Au203, Hf02, ln20, InO, ln203, lr203, Ir02, Fe304, FeO, Fe203, PbO, Pb02, Li20, Al2Mg04, MgO, Mn304, MnO, Mn203, Mn02, Mn205, Mn207, Hg20, HgO, Mo02, Mo03, Mo205, NiFe204, NiO, Ni203, LiNb03, NaNb03, Nb203, Nb205, Os203, Os03, Os04, PdO, Pd02, (C6H5)AsO, Pt304, PtO, Pt203, K20, Re207, Re04, Rh203, Rb20, Ru02, Ru04, Sc203, Se304, Ag20, Na20, SrO, NaTa03, Ta203, Ta205, Si02, SnO, Sn02, SrTi03, TiO, Ti203, Ti02, WC1202, W203, W02, W03, W205, VOCl2, VO, V203, V02, V205, Yb203, YBa2Cu307, Y203, ZnO, Zr02, fluorine doped tin oxide, iron doped titanium oxide, W03 doped ZnO, Fe doped Ce02, tin doped Fe304, and indium tin oxide. In an embodiment disclosed herein or as an alternate or further
embodiment, one or more thin films disclosed herein comprise, consist essentially of, or consists of Ti02. In an embodiment disclosed herein or as an alternate or further embodiment, a method disclosed herein uses 1 to 50 cycles of an atomic layer deposition process to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate. In an embodiment disclosed herein or as an alternate or further embodiment, a method disclosed herein uses 1 to 25 cycles of an atomic layer deposition process to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate. In an embodiment disclosed herein or as an alternate or further embodiment, a method disclosed herein uses 1 to 15 cycles of an atomic layer deposition process to deposit or layer a thin film of Ti02 onto a surface of the conductive electrocatalytic substrate. In an embodiment disclosed herein or as an alternate or further embodiment, a method disclosed herein uses one or more thin films that are made from one or more precursors used in the atomic layer deposition process comprising, consisting essentially of, or consisting of aluminum tris (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , triisobutylaluminum, trimethylaluminum, tris (dimethylamido) aluminum (III) ,
triphenylantimony (III) , tris (dimethylamido) antimony (III) , triphenylarsine, Triphenylarsine oxide, barium bis (2,2, 6,6- tetramethyl-3, 5-heptanedionate) hydrate, barium nitrate,
Ba (C9H23N3) 2 [CxHyC (O) CHC (O) CxHy]2 (x=3-4, y=2x+l),
[Ba (C5 (CH3) 5) 2] -2 (C4H80) , [Ba (C5 (C3H7) 3H2) 2] -2 (C4H80) , bis (acetato- O) triphenylbismuth (V) , triphenylbismuth, tris (2- methoxyphenyl ) bismuthine , triisopropyl borate, triphenylborane , tris (pentafluorophenyl ) borane , cadmium acetylacetonate , calcium bis (6,6,7,7,8,8,8, -heptafluoro-2 , 2-dimethyl-3, 5-octanedionate) , calcium bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
bis (cyclopentadienyl ) chromium (II),
bis (pentamethylcyclopentadienyl ) chromium (II), chromium (III) tris (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
bis (cyclopentadienyl) cobalt (II) ,
bis (pentamethylcyclopentadienyl) cobalt (II) , copper
bis (6,6,7,7,8,8, 8-heptafluoro-2 , 2-dimethyl-3, 5-octanedionate) , copper bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
tris (dimethylamido) gallium (III) , germanium ( IV) fluoride, hexaethyldigermanium ( IV) , tetramethylgermanium, tributylgermanium hydride, triethylgermanium hydride, triphenylgermanium hydride, bis (tert-butylcyclopentadienyl ) dimethylhafnium ( IV) ,
bis (trimethylsilyl) amidohafnium (IV) chloride,
dimethylbis (cyclopentadienyl) hafnium (IV) ,
tetrakis (diethylamido) hafnium ( IV) ,
tetrakis (dimethylamido) hafnium ( IV) ,
tetrakis (ethylmethylamido) hafnium ( IV) , [1,1'- bis (diphenylphosphino) ferrocene ] tetracarbonylmolybdenum ( 0 ) , bis (pentamethylcyclopentadienyl ) iron ( I I ) , 1,1' -diethyl ferrocene , iron(0) pentacarbonyl , iron(III) tris (2, 2, 6, 6-tetramethyl-3, 5- heptanedionate ) , bis (cyclopentadienyl) magnesium (II) ,
bis (pentamethylcyclopentadienyl) magnesium,
Mg(C6Hi6N2) [CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis (pentamethylcyclopentadienyl ) manganese (II) ,
bis (tetramethylcyclopentadienyl ) manganese (II) ,
bromopentacarbonylmanganese (I) , cyclopentadienylmanganese (I) tricarbonyl, ethylcyclopentadienylmanganese ( I ) tricarbonyl, manganese(O) carbonyl, (bicyclo [ 2.2.1 ] hepta-2 , 5- diene ) tetracarbonylmolybdenum ( 0 ) , bis (cyclopentadienyl ) molybdenum ( IV) dichloride,
cyclopentadienylmolybdenum ( I I ) tricarbonyl dimer,
molybdenumhexacarbonyl , (propylcyclopentadienyl ) molybdenum ( I ) tricarbonyl dimer, allyl (cyclopentadienyl) nickel (II) ,
bis (cyclopentadienyl) nickel (II) ,
bis (ethylcyclopentadienyl ) nickel ( I I ) , nickel (II) bis (2, 2,6,6- tetramethyl-3 , 5-heptanedionate) , bis (cyclopentadienyl) niobium (IV) dichloride, trimethyl (methylcyclopentadienyl ) platinum ( IV) , dirhenium decacarbonyl , (acetylacetonato) ( 1 , 5-cyclooctadiene ) rhodium ( I ) , (acetylacetonato) (1, 5-cyclooctadiene) rhodium (I) ,
bis (cyclopentadienyl) ruthenium ( I I ) ,
bis (ethylcyclopentadienyl) ruthenium ( I I ) ,
bis (pentamethylcyclopentadienyl) ruthenium ( II ) , triruthenium dodecacarbonyl, Sr (C9H23N3) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l), pentakis (dimethylamino) tantalum (V) , tantalum (V) ethoxide,
tris (diethylamido) (tert-butylimido) tantalum (V) ,
tris (ethylmethylamido) (tert-butylimido) tantalum (V) ,
Ta(C2H50)4[CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis [bis (trimethylsilyl) amino] tin (II) , dibutyldiphenyltin,
hexaphenylditin (IV) , tetraallyltin, tetrakis (diethylamido) tin (IV) , tetramethyltin, tetravinyltin, tin (II) acetylacetonate ,
trimethyl (phenylethynyl ) tin, trimethyl (phenyl ) tin, tetrakis
(dimethylamido) titanium (IV) (TDMAT) ,
tetrakis (ethylmethylamido) titanium (IV) , titanium (IV)
diisopropoxidebis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , titanium tetrachloride, titanium (IV) isopropoxide ,
Ti (OC3H7) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l),
bis (butylcyclopentadienyl ) tungsten ( IV) diiodide, bis (tert- butylimino) bis (tert-butylamino) tungsten, bis (tert- butylimino) bis (dimethylamino) tungsten (VI ) ,
bis (cyclopentadienyl) tungsten (IV) dichloride,
bis (cyclopentadienyl) tungsten (IV) dihydride,
bis (isopropylcyclopentadienyl) tungsten (IV) dihydride,
cyclopentadienyltungsten ( I I ) tricarbonyl hydride, tetracarbonyl ( 1 , 5- cyclooctadiene ) tungsten ( 0 ) , triamminetungsten ( IV) tricarbonyl, tungsten hexacarbonyl , bis (cyclopentadienyl) vanadium (II) ,
bis (cyclopentadienyl ) vanadium (II), vanadium (V) oxytriisopropoxide , bis (pentafluorophenyl ) zinc, bis (2,2, 6, 6-tetramethyl-3 , 5- heptanedionato) zinc (II) , diethylzinc, and diphenylzinc . In an embodiment disclosed herein or as an alternate or further
embodiment, a method disclosed herein uses one or more thin films that are made from one or more precursors used in the atomic layer deposition process comprising, consisting essentially of, or consisting of tetrakis (dimethylamido) titanium ( IV) . In an
embodiment disclosed herein or as an alternate or further
embodiment, the conductive electrocatalytic substrate is at least 100 nm in thickness. In an embodiment disclosed herein or as an alternate or further embodiment, the conductive electrocatalytic substrate is at least 10 μπ\ in thickness. In an embodiment disclosed herein or as an alternate or further embodiment, the conductive electrocatalytic substrate is at least 100 nm in thickness. In an embodiment disclosed herein or as an alternate or further
embodiment, the conductive electrocatalytic substrate comprises, consists essentially of, or consists of a of a conductive material, semiconductive material and/or superconductive material. In an embodiment disclosed herein or as an alternate or further
embodiment, the conductive electrocatalytic substrate comprises, consists essentially of, or consists of a metal oxide. In an embodiment disclosed herein or as an alternate or further
embodiment, the conductive electrocatalytic substrate comprises, consists essentially of, or consists of a metal oxide selected fromAl203, NH4OSbW, Sb205, BaO, BaTi03, BaZr03, Al6BeOi0, BeO, Bi203, Bi205, B203, CdO, CaO, Ce203, Ce02, CrO, Cr203, Cr02, Cr03, CoO, Co203, Cu205Yb2, Cu20, CuFe204, CuO, GaO, Ga203, GeO, Ge02, Au20, Au203, Hf02, ln20, InO, ln203, lr203, Ir02, Fe304, FeO, Fe203, PbO, Pb02, Li20, Al2Mg04, MgO, Mn304, MnO, Mn203, Mn02, Mn205, Mn207, Hg20, HgO, Mo02, Mo03, Mo205, NiFe204, NiO, Ni203, LiNb03, NaNb03, Nb203, Nb205, Os203, Os03, Os04, PdO, Pd02, (C6H5)AsO, Pt304, PtO, Pt203, K20, Re207, Re04, Rh203, Rb20, Ru02, Ru04, Sc203, Se304, Ag20, Na20, SrO, NaTa03, Ta203, Ta205, Si02, SnO, Sn02, SrTi03, TiO, Ti203, Ti02, WC1202, W203, W02, W03, W205, V0C12, VO, V203, V02, V205, Yb203, YBa2Cu307, Y203, ZnO, Zr02, fluorine doped tin oxide, iron doped titanium oxide, W03 doped ZnO, Fe doped Ce02, tin doped Fe304, and indium tin oxide. In an embodiment disclosed herein or as an alternate or further embodiment, the conductive electrocatalytic substrate comprises, consists essentially of, or consists of IrC>2 or RUO2. In an embodiment disclosed herein or as an alternate or further
embodiment, the electrochemical reaction is selected from the group comprising, consisting essentially of, or consisting of the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction and the oxygen reduction reaction. In an embodiment disclosed herein or as an alternate or further embodiment, the electrochemical reaction is the oxygen evolution reaction or the chlorine evolution reaction. In an embodiment disclosed herein or as an alternate or further embodiment, the electrochemical reaction the heterogeneous electrocatalyst exhibits a lower overpotential or improved specific activity for the chemical reaction than the conductive electrocatalytic substrate. In an embodiment disclosed herein or as an alternate or further embodiment, the heterogeneous electrocatalyst exhibits has a more favorable surface charge distribution for the chemical reaction than the conductive
electrocatalytic substrate. In an embodiment disclosed herein or as an alternate or further embodiment, the disclosure provides for a heterogeneous electrocatalyst made by a method disclosed herein. In an embodiment disclosed herein or as an alternate or further embodiment, the disclosure provides for a heterogeneous
electrocatalyst that comprises, consists essentially of, or consists of a conductive electrocatalytic substrate of IrC>2, FTO, or RUO2. In an embodiment disclosed herein or as an alternate or further embodiment, the disclosure provides for a heterogeneous
electrocatalyst that comprises, consists essentially of, or consists of a thin film of T1O2. In an embodiment disclosed herein or as an alternate or further embodiment, the disclosure provides for a heterogeneous electrocatalyst that comprises, consists essentially of, or consists of a thin film of T1O2 is less than 1 nm in
thickness (e.g., the thin film is made from 1 to 15 cycles of an atomic layer deposition process) . In an embodiment disclosed herein or as an alternate or further embodiment, the disclosure provides for an electrode comprising, consisting essentially of, or consisting of a heterogeneous electrocatalyst disclosed herein. In an embodiment disclosed herein or as an alternate or further embodiment, the electrode is used to generate reactive chlorine species in a wastewater treatment system.
DESCRIPTION OF DRAWINGS
[0007] Figure 1 demonstrates that a heterogeneous
electrocatalyst made by layering T1O2 onto IrC>2 using atomic layer deposition (ALD) resulted in a reduction in overpotential for the chlorine evolution reactions (CER) and oxygen evolution reactions
(OER) . The following overpotential reductions for CER and OER correlated with a change in catalyst surface charge density:
Δ/ι 'CER, l mA„/,cm 2 2 = 97.4 mV ,' Αη ' O„ER, 10 mA Λ IΙ cm 2 = 217.8 mV .
[0008] Figure 2 presents a schematic representation of the
Sabatier principle for heterogeneous electrocatalysts .
Heterogeneous electrocatalysts act by forming bonds with reactants that stabilize transition states and destabilize intermediates. The perfect bond strength between the electrocatalyst and reactant will yield the optimal reactivity. A too strong or too weak bond will yield subpar reactivity. This concept, i.e., Sabatier principle, is demonstrated by the "volcano plot" where the x-axis is a measure of bonding and the y axis is a measure of catalytic activity.
[0009] Figure 3 shows an example of a homogenous electrocatalyst system, where it is reasonably straightforward to tune the catalyst- reactant bond strength, by swapping and modifying ligands to be either more electron withdrawing or donating. Unfortunately, for heterogeneous electrocatalysts the tools to modify the
electrocatalysts are not similarly available.
[0010] Figure 4 provides a schematic of an atomic layer deposition process used herein for generating heterogeneous electrocatalysts. Also shown is the structure of tetrakis
(dimethylamido) titanium ( IV) (TDMAT) , a titanium-based precursor used in the ALD process.
[0011] Figure 5A-B presents (A) polarization curves for IrC>2 electrodes with various numbers of ALD cycles of T1O2. Polarization was conducted in 5M NaCl, pH 2 under a chlorine atmosphere to ensure no significant oxygen evolution. (B) Example Tafel lines obtained by taking the logarithm of the current data in (A) .
[0012] Figure 6 demonstrates the average overpotentials at 0.1 mA/cm2 as measured and calculated from at least 3 replicates of each IrC>2 electrode coated with various numbers of ALD cycles of T1O2.
[0013] Figure 7A-B provides impedance spectroscopy of RUO2 as well as Ir02 with various ALD cycle numbers of T1O2. The resulting semi-circle was modeled as an Rs (CPE-Rp) . The CPE-P term was between 0.9 and 1.0, indicating that the CPE-T term could reasonably be approximated as capacitance. (A) Each dot represents the capacitance measurement. The low point along the lines of dots represents the EPZC. (B) EPZC from points presented in plot (A) were utilized and graphed vs ALD cycles of T1O2.
[0014] Figure 8 presents representative polarization curves for
IrC>2 electrodes coated with various numbers of ALD cycles of TiC>2. Polarization was conducted in 5 M NaCl at pH 2 to ensure no significant oxygen evolution. (Inset) example Tafel curves obtained from taking the logarithm of current density and extracting the linear portion of the resulting curve.
[0015] Figure 9A-B presents the average exchange current densities (io) (A) and average overpotentials (B) of each IrC>2 based electrode coated with T1O2 via cycles of ALD. Bare RUO2 is shown as a red square for comparison. As thickness of T1O2 increased beyond reasonably thick layers, the overpotential continued to increase considerably (see FIG. 11) , likely due to the high resistivity of TiC>2. Overpotentials and exchange current densities are the average of at least 3 polarization curve replicates. Exchange current densities are obtained by fitting the polarization curve data to the Tafel equation and solving for the current density at the
intersection between the log (current density) axis and the data fit line. Overpotentials are obtained by fitting the polarization curve data to the Tafel equation and solving for the applied potential less the Nernstian thermodynamic potential at zero current density.
[0016] Figure 10 shows EPZC of Ir02 anodes coated with various
ALD cycles of T1O2. The red square denotes the EPZC of RUO2. EPZC was calculated from electrochemical impedance spectroscopy (see FIG. 13) . EPZC values represent the potential in any given solution at which an electrode has zero charge. EPZC is therefore a measure of the charge density of the surface species. In regards to metal oxides, Epzc has a negative correlation with electronegativity of the metal. EPZC is obtained by extracting the capacitance term from the circuit fit of the electrochemical impedance spectroscopy data for an electrode at several different applied potentials. The minimum capacitance value represents the EPZC (see FIG. 12) .
[0017] Figure 11A-B presents the average exchange current densities (io) (A) and average overpotential at zero io (B) of each IrC>2 based electrode coated with T1O2 via cycles of ALD. Bare RUO2 is shown as a red square for comparison. As thickness of T1O2 increased beyond reasonably thick layers, the overpotential continued to increase, likely due to high resistivity.
Overpotentials and exchange current densities are the average of at least 3 polarization curve replicates. These figures present the same data as FIG. 9, but are extended to 1000 ALD cycles.
[0018] Figure 12 shows the electrochemical impedance
spectroscopy of RUO2 and IrC>2 coated with various ALD cycles of T1O2 at 25 mV intervals. The resulting semi circles were modeled as Rs (CPE-Rp) circuits. The calculated capacitance values (dots) for each sample (set of dots) are shown. The minimum value of each curve represents the EPZC. The magnitude of the capacitance values represents the surface area of the sample.
[0019] Figure 13 presents EPZC of IrC>2 anodes coated with various
ALD cycles of T1O2. EPZC was calculated from electrochemical
impedance spectroscopy (FIG. 12) . This figure is the same as FIG. 10, except bulk T1O2 (1000 ALD cycles) is also shown.
[0020] Figure 14 shows the overpotential at 1 mA/cm2 for the CER of T1O2 deposited on RUO2 using ever-increasing cycles. Standard CER conditions were 5M NaCl, pH 1 (HC1) , 1 atm Cl2, with 100% Faradaic Efficiency. Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O2 on RUO2 substrate. ALD cycles can be thought of as single atomic layers of TiOx.
[0021] Figure 15 provides representative polarization curves for
RUO2 electrodes coated with various numbers of ALD cycles of T1O2 for the OER. [0022] Figure 16 presents the specific activity (current density normalized to electrochemically active surface area) at a 350 mV overpotential in 1M H2SO4 under an oxygen atmosphere for the OER of T1O2 deposited on RUO2 using ever-increasing cycles. Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of TiC>2 . ALD cycles can be thought of as single atomic layers of TiOx.
[0023] Figure 17 provides representative polarization curves for
IrC>2 electrodes coated with various numbers of ALD cycles of T1O2 for the CER. Polarization was conducted in 5 M NaCl at pH 2 under a chlorine gas atmosphere to ensure no significant oxygen evolution.
[0024] Figure 18 shows the overpotential at 1 mA/cm2 for the CER of T1O2 deposited on IrC>2 using ever-increasing cycles. Standard CER conditions were 5M NaCl, pH 2 (HC1) , 1 atm Cl2, with 100% Faradaic Efficiency. Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O2 on I r02 substrate. ALD cycles can be thought of as single atomic layers of TiOx.
Deposition of T1O2 on I r02 lead to a -30 mV reduction in
overpotential for the CER at 1 mA/cm2. For the best overpotenial rllrOxITi02,CER ~ WlV .
[0025] Figure 19 provides representative polarization curves for
I r02 electrodes coated with various numbers of ALD cycles of T1O2 for the OER.
[0026] Figure 20 presents the specific activity at a 350 mV overpotential in 1M H2 SO4 under 1 atm of oxygen for the OER of T1O2 deposited on I r02 using ever-increasing cycles. Each dot represents a new catalyst that has a different number of atomic layer
deposition cycles of T1O2 . ALD cycles can be thought of as single atomic layers of TiOx.
[0027] Figure 21 shows the overpotential at 1 mA/cm2 for the CER of T1O2 deposited on FTO using ever-increasing cycles. Standard CER conditions were 5M NaCl, pH 1 (HC1) , 1 atm Cl2, with 100% Faradaic Efficiency. Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O2 on FTO substrate. ALD cycles can be thought of as single atomic layers of TiOx.
Deposition of T1O2 on FTO lead to a -140 mV reduction in overpotential for the CER at 1 mA/cm2. The best overpotential for this catalyst is reduced to
Figure imgf000014_0001
[0028] Figure 22 provides representative polarization curves for
FTO electrodes coated with various numbers of ALD cycles of T1O2 for the OER.
[0029] Figure 23 presents the specific activity at a 350 mV overpotential in 1M H2S04 for the OER of Ti02 deposited on FTO under an oxygen atmosphere using ever-increasing cycles. Each dot represents a new catalyst that has a different number of atomic layer deposition cycles of T1O2. ALD cycles can be thought of as single atomic layers of TiOx.
DETAILED DESCRIPTION
[0030] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a heterogeneous electrocatalyst" includes a plurality of such heterogeneous electrocatalysts and reference to "the thin film" includes reference to one or more thin films and equivalents thereof known to those skilled in the art, and so forth.
[0031] Also, the use of "or" means "and/or" unless stated otherwise. Similarly, "comprise," "comprises," "comprising"
"include," "includes," and "including" are interchangeable and not intended to be limiting.
[0032] It is to be further understood that where descriptions of various embodiments use the term "comprising," those skilled in the art would understand that in some specific instances, an embodiment can be alternatively described using language "consisting
essentially of" or "consisting of."
[0033] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this disclosure belongs. Although many methods and reagents are similar or equivalent to those described herein, the exemplary methods and materials are disclosed herein.
[0034] All publications mentioned herein are incorporated herein by reference in full for the purpose of describing and disclosing the methodologies, which might be used in connection with the description herein. Moreover, for terms expressly defined in this disclosure, the definition of the term as expressly provided in this disclosure will control in all respects, even if the term has been given a different meaning in a publication, dictionary, treatise, and the like.
[ 0035 ] A "conductive material" as used herein refers to a material that allows the flow of an electrical current in one or more directions. Materials made of metal are common electrical conductors. Electrical current is generated by the flow of
negatively charged electrons, positively charged holes, and positive or negative ions in some cases. Examples of conductive materials, include but are not limited to, metals, alloys, metal containing compounds, graphite, and conductive polymers. Examples of good conducting metals include but are not limited to, silver, copper, gold, aluminum, molybdenum, zinc, lithium, tungsten, brass, nickel, iron, palladium, platinum, and tin.
[ 0036] A "semiconductive material" as used herein refers to material has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. The resistance of a semiconductive material decreases as the temperature of the semiconductive material increases, which is behavior opposite to that of a metal. The conducting properties of semiconductive material may be altered in useful ways by the deliberate, controlled introduction of impurities ("doping") into the crystal structure. Where two differently-doped regions exist in the same crystal, a semiconductor junction is created. The behavior of charge carriers which include electrons, ions and electron holes at these junctions is the basis of diodes, transistors and all modern electronics. Semiconductor devices can display a range of useful properties such as passing current more easily in one direction than the other, showing variable resistance, and
sensitivity to light or heat. Because the electrical properties of a semiconductor material can be modified by doping, or by the application of electrical fields or light, devices made from semiconductors can be used for amplification, switching, and energy conversion. Examples of semiconductive materials include, but are not limited to, group 14 elements (e.g., C, Si, Ge) ; binary compounds between group 13 and 15 elements (e.g., AlSb, GaAs, GaN, GaP, InN, InP) ; binary compounds between groups 12 and 16 elements (e.g., CdS, ZnO, ZnS, ZnTe) ; binary compounds between group 14 and 16 elements (e.g., PbSe, PbS, SnS, SnTe) ; and binary compounds between different group 14 elements (e.g., SiC) ternary
semiconductor alloys (e.g., Al/Ga/As, In/Ga/As, In/Ga/P, Ga/As/N, Ga/As/P, In/Ga/N) ; and semiconductive oxides (e.g., T1O2, CU2O, CuO, Bi203, ZnO, Sn02, BaTi03, SrTi03) .
[ 0037 ] A "superconductive material" as used herein refers to metals, ceramics, organic materials, or heavily doped semiconductors that conduct electricity without resistance. Superconducting materials can transport electrons with no resistance, and hence release no heat, sound, or other energy forms. Superconductivity occurs at a specific material's critical temperature (Tc) . As temperature decreases, a superconducting material's resistance gradually decreases until it reaches critical temperature. At this point resistance drops off, often to zero. Examples of
superconductive materials include, but are not limited to, type II alloys (e.g., Hg/Ba/Ca/Cu/O, Hg/Ti/Ba/Ca/Cu/O, Hg/Ba/Ca/Cu/O, Ti/Ba/Ca/Cu/O, Bi/Sr/Ca/Cu/O) .
[ 0038 ] An "electrocatalyst" as used herein refers to a catalyst that participates in an electrochemical reaction, and which modifies or increases the rate of the electrochemical reaction without being consumed in the process. An electrocatalyst can be heterogeneous such as a metal oxide surface, or homogeneous like a coordination complex. The electrocatalyst assists in transferring electrons between the electrode and reactants, and/or facilitates an
intermediate chemical transformation described by an overall half- reaction .
[ 0039] A "heterogeneous electrocatalyst" as used herein refers to a catalyst that participates in electrochemical reactions and which is in a separate phase from the reactants and/or products. For example, the reactants and products may be in a fluid phase, while the heterogeneous electrocatalyst is in a solid phase. [ 0040 ] A "homogenous electrocatalyst" as used herein refers to a catalyst that participates in electrochemical reactions and which is in the same phase as the reactants and/or products.
[ 0041 ] An "electrochemical reaction" as used herein refers to a process either caused or accompanied by the passage of an electrons or an electric current and involving in most cases the transfer of electrons between two substances. The energy of an electric current can then be used to bring about many chemical reactions that do not occur spontaneously. Examples of "electrochemical reactions" include the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction, and the oxygen reduction reaction.
[ 0042 ] A "thin film" as used herein refers to one or more layers of a conductive material and/or semiconductive material as defined herein that has been applied or deposited onto the surface of another conductive material, semiconductive and/or superconductive material. For purposes herein, the composition of the thin film is different from the composition of the conductive material,
semiconductive and/or superconductive material that thin film is in direct contact with. For example, a thin film of T1O2 deposited or applied to an IrC>2 substrate. Universally, the "thin film" is applied, deposited, or layered on top of the surface of another conductive material, semiconductive material and/or superconductive material. Typically, a chemical vapor deposition (CVD) -based process or an atomic layer deposition (ALD) -based process is used to apply, or deposit a thin film on top of the surface of another conductive material, semiconductive material, or superconductive material. In a certain embodiment, a "thin film" as used herein refers to a layer of conductive and/or semiconductive material which has a thickness of < 50 nm, < 25 nm, < 10 nm, < 5 nm, < 1 nm, < 9 A, < 8 A, < 7 A, < 6 A, < 5 A, < 4 A, < 3 A, < 2 A, < 1 A, or < 0.5 A. In a particular embodiment, the 'thin film' is a layer of conductive material that has a thickness of 0.1 A, 0.2 A, 0.3 A, 0.4 A, 0.5 A, 0.6 A, 0.7 A, 0.8 A, 0.9 A, 1 A, 1.1 A, 1.2 A, 1.3 A, 1.4 A, 1.5 A, 1.6 A, 1.7 A, 1.8 A, 1.9 A, 2 A, 2.1 A, 2.2 A, 2.3 A, 2.4 A, 2.5 A, 2.6 A, 2.7 A, 2.8 A, 2.9 A, 3 A, 3.1 A, 3.2 A, 3.3 A, 3.4 A, 3.5 A, 3.6 A, 3.7 A, 3.8 A, 3 9 A, 4 A, 4.1 A, 4.2 A, 4.3 A, 4.4 A, 4.5 A,
4.6 A, 4. 7 A, 4. 8 A, 4 9 A, 5 A, 5.1 A, 5. 2 A, 5 .3 A, 5. 4 A, 5.5 A,
5.6 A, 5. 7 A, 5. 8 A, 5 9 A, 6 A, 6.1 A, 6. 2 A, 6 .3 A, 6. 4 A, 6.5 A,
6.6 A, 6. 7 A, 6. 8 A, 6 9 A, 7 A, 7.1 A, 7. 2 A, 7 .3 A, 7. 4 A, 7.5 A,
7.6 A, 7. 7 A, 7. 8 A, 7 9 A, 8 A, 8.1 A, 8. 2 A, 8 .3 A, 8. 4 A, 8.5 A,
8.6 A, 8. 7 A, 8. 8 A, 8 9 A, 9 A, 9.1 A, 9. 2 A, 9 .3 A, 9. 4 A, 9.5 A,
9.6 A, 9. 7 A, 9. 8 A, 9 9 A, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 12 nm, 14 nm, 15 nm, 16 nm, 18 nm 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or a range including or between any two of the foregoing numbers. In regards to an ALD- based process, the thickness of the 'thin film' is directly controlled based upon the number of cycles used in the ALD-based process. Thus, in another embodiment, a 'thin film' as used herein refers to a layer of conductive material and/or semiconductive material which has a thickness resulting from using an ALD process with 1 to 1000 cycles, 1 to 500 cycles, 1 to 100 cycles, 1 to 90 cycles, 1 to 80 cycles, 1 to 70 cycles, 1 to 60 cycles, 1 to 55 cycles, 1 to 50 cycles, 1 to 45 cycles, 1 to 40 cycles, 1 to 35 cycles, 1 to 30 cycles, 1 to 25 cycles, 1 to 24 cycles, 1 to 23 cycles, 1 to 22 cycles, 1 to 21 cycles, 1 to 20 cycles, 1 to 19 cycles, 1 to 18, cycles, 1 to 17 cycles, 1 to 16 cycles, 1 to 15 cycles, 1 to 14 cycles, 1 to 13 cycles, 1 to 12 cycles, 1 to 11 cycles, 1 to 10 cycles, 1 to 9 cycles, 1 to 7 cycles, 1 to 6 cycles or 1 to 5 cycles. In yet another embodiment, a 'thin film' as used herein refers to a layer of conductive material and/or
semiconductive material which has a thickness resulting from using an ALD process with 1 cycle, 2 cycles, 3 cycles, 4 cycles, 5 cycles, 6 cycles, 7 cycles, 8 cycles, 9 cycles, 10 cycles, 11 cycles, 12 cycles, 13 cycles, 14 cycles, 15 cycles, 16 cycles, 17 cycles, 18 cycles, 19 cycles, 20 cycles, 21 cycles, 22 cycles, 23 cycles, 24 cycles, 25 cycles, 30 cycles, 35 cycles, 40 cycles, 45 cycles, 50 cycles, 55 cycles, 60 cycles, 70 cycles, 80 cycles, 90 cycles, 100 cycles, 500 cycles, 1000 cycles, or any range between any two of the foregoing cycle numbers.
[ 0043 ] A "conductive electrocatalytic substrate" as used herein refers to substrate that is comprised of one or more conductive materials, semiconductive materials and/or superconductive materials as defined herein that can be used as a catalyst in an electrochemical reaction. The conductive electrocatalytic substrate is not limited to having any specific shape or having any specific dimension (e.g., thickness). Accordingly, the conductive
electrocatalytic substrate can have any shape and any suitable dimension. In a particular embodiment, the substrate is ≥ 100 nm, ≥ 1 μπι, ≥ 10 μπι, ≥ 100 μπ\ or ≥ 1 mm in thickness. In a particular embodiment, the conductive electrocatalytic substrate is a component of an electrode. In an alternate embodiment, an electrode comprises the conductive electrocatalytic substrate.
[ 0044 ] Electrocatalysts are used both to speed up electrode reactions and to enable them to occur close to their
thermodynamically predicted potentials. In electrochemical power supplies such as fuel cells, the incorporation of electrocatalysts into the electrode structure enables the fuel cell to operate near its theoretically expected potential even when appreciable current is drawn from the cell. The electrocatalyst is said to reduce the overvoltage for the electrode reaction. A related example is the water electrolysis cell; electrocatalysts are important here to lower the minimum voltage necessary for electrolysis to occur, and to keep it low as the rate of electrolysis at the electrodes is increased -- this will permit high efficiency of operation.
[ 0045 ] Unlike in homogenous catalysis where electron
donating/withdrawing or sterically hindering ligands can be used to define a perfect catalytic active site, progress in the field of heterogeneous electrocatalysis has been relatively attenuated due to limited tools for crafting active sites. For heterogeneous catalysts, optimizing bond strength to a precursor is a difficult task. Previous studies have used dopants, vacancies, mixed oxides, topography induced strain, and ligand addition to alter electronics, mainly by sterics. Full tunability, however, has proven very difficult. In order to design optimal active sites, more tools are needed. The methods described herein have been shown to be useful for tuning surface electronics. In particular, to tune the surface electronics and corresponding activity of heterogeneous
electrocatalysts for the industrially and environmentally important electrochemical reactions (e.g., Chlorine Evolution Reaction (CER) and the Oxygen Evolution Reaction (OER) ) .
[ 0046] The CER is fundamentally important for a myriad of industrial processes. Global chlorine production is currently an 88.5-billion-dollar industry, with 40-50% of the production cost being due to the cost for electricity. Additionally, chlorine evolution electrocatalysts have shown great promise for treating and recycling wastewater in the developing world.
[ 0047 ] The most active known catalyst for the CER is Ru02 which operates at near zero overpotential in concentrated brine for 1 mA/cm2, however, RUO2 is seldom used industrially due to low stability. Instead, I r02 and Ru02/ I r02 mixed metal oxide catalysts are preferred even though they have diminished activity
(overpotentials > 50 mV in concentrated brine for 1 mA2) but much better stability. In highly corrosive environments like wastewater treatment, I r02 is occasionally coated with T1O2 to enhance stability (overpotential >>50 mV in concentrated brine for 1 mA/cm2) .
[ 0048 ] Development of catalysts is important for storing energy and creating commodity chemicals. Catalysts act to reduce a chemical reaction's activation energy requirements by destabilizing intermediates and stabilizing transition states. On catalysts, reactant binding sites (active sites) provide the specific
requirements for optimal binding of reactants—neither too tightly, preventing release of products or initiation of catalysis, nor too loosely, preventing conversion to products. Altering the activity of an electrocatalyst is therefore possible by tailoring the active site charge density, which alters how well the catalyst binds to reaction intermediates. In homogenous electrocatalysis , designer electron donating/withdrawing ligands or sterically hindering ligands can be used to tune catalytic activity by optimizing the charge density of active sites on metal centers.
[ 0049] The strategies employed in homogenous catalysis for controlling the charge density at the active site often fail for heterogeneous catalysts, however. For example, ligands tend to be unstable on the surface of heterogeneous catalysts, and may block already coordinately saturated active sites. Unlike in homogenous catalysis where the binding environment primarily controls the active site charge density, in heterogeneous electrocatalysis the applied potential also affects the charge density at the binding site, further complicating one's ability to predictably alter the active site charge density. Previous studies have used dopants, vacancies, mixed oxides, topographically induced strain, and in special cases ligand addition to alter the charge density of surface species on heterogeneous catalysts with some success. However, complete tunability of surface charge density on heterogeneous catalysts has not been shown and additional tools are therefore needed to improve electrocatalytic efficiencies.
[ 0050 ] Reported herein are methods that have been demonstrated as providing an effective means for tuning the catalytic parameters on heterogeneous electrocatalysts in a way similar to ligand addition in homogenous electrocatalysts (e.g., using an electron rich ligand on an electron poor metal to form an intermediate electron density at the binding site) . In a particular embodiment, the methods of the disclosure provide a step of layering or applying one or more materials (e.g., electrocatalytic materials) to another different material (e.g., a different electrocatalytic material) using atomic layer deposition, wherein the thickness of the layered or applied material can be tunably controlled based upon the number of ALD cycles. The general principal of this catalyst tuning process is that it is possible to create surfaces with designer and predictable properties for catalysis. This is achieved by layering multiple conductive materials that are sufficiently thin such that the overlying film can electronically "feel" the underlying film. When a very thin layer is stacked on top of another layer, the surface becomes an electronic average of the two materials. That average can be tuned by tuning the thickness of the overlying materials. For example, a single atomic layer of an overlying materials will look a lot more like the underlying material than 100 atomic layers of the overlying material will look.
[ 0051 ] As shown herein, the methods of the disclosure were utilized to produce a T1O2 coated IrC>2 electrocatalyst that exhibited improved catalytic properties for the chlorine evolution reaction (CER) . The CER accounts for greater than 2% of global energy demand and further has shown promise for treating and recycling wastewater, especially in the non-developed world where a sewer system is generally lacking.
[ 0052 ] The methods provided herein, provide a new means by which heterogeneous electrocatalysts could be designed and developed. In a particular embodiment, the methods disclosed herein allow for the deposition of one or more thin layers of a conductive material on top of another conductive material or substrate so as to afford a new material that has electronic properties that are intermediate between the two (or more) conductive materials. While not beholden to the specific examples presented herein, it is clear that methods of disclosure can be used to design heterogeneous electrocatalysts that have improved catalytic activities for the oxygen evolution reaction, and the chlorine evolution reaction. Additionally, the methods of the disclosure are directed to a platform technology, whereby the methods can be similarly applied to improve the catalytic activities of electrocatalysts in other types of
reactions, including but not limited to, the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction and the oxygen reduction reaction. Thus, it is possible to improve the electrocatalytic activities of common non-precious metals by tuning these metals using the methods disclosed herein to have electronic properties similar to that of precious or rare earth metals. The methods of the disclosure, therefore, could realize substantial cost savings for industry in regards of cost for mineral resources, production, and energy.
[ 0053 ] Previous technologies exist for tuning electrocatalyst electronic properties, for example doping, creating vacancies, mixing oxides, and adding ligands . These technologies, however, are not sufficient to fully tune catalyst electronics. For example, heretofore there was no good way to tune IrC>2 to a sufficient level to improve the operating overpotential of the material in the chlorine evolution reaction. Additionally, the methods disclosed herein allow for rational designing catalytic systems for particular reactions. Previous technologies, like doping, heavily relied on trial and error to tune the surface electronics. Using the methods disclosed herein, it is now possible to evaluate materials based upon their associated electronic properties, properties such as electronic structure, polarity in forming bonds, bond strength, and electronegativities of the elements making up the material, and then layering another material which has complementary or different properties in thin layers on top of the first material to afford a new material that has electronic properties that are somewhere between the two materials, which can be adjusted if desired, based upon the number of cycles in the layering process. Thus, the methods of the disclosure now make it possible to create custom electrocatalytic materials that have more desirable electronic properties based upon combining the electronic properties of known materials to make new electrocatalytic materials.
[ 0054 ] The data presented herein indicate that adding various layers of a metal oxide with a more electron poor metal and more electron rich oxygen on top of a metal oxide with a less electron poor metal and less electron rich oxygen can tune the surface charge density and the catalytic parameters. Furthermore, the data show that when the charge density is matched to that of a better catalyst, the catalytic parameters also match as predicted by the Sabatier principal. Therefore, the methods of the disclosure represent a new means for improving the performance of heterogeneous electrocatalysts by tuning an active surface species' charge density by overcoating with an appropriate material or mix of materials. Furthermore, the methods of the disclosure provide a pathway to enhance the catalytic activity of earth abundant electrocatalysts for important reactions that was not previously available due to a dearth of means to tune the activity of heterogeneous
electrocatalysts. By looking at parameters that dictate the electron concentration of the surface (i.e., heat of formation, electron affinity, potential of zero charge, etc.) of the best-known catalyst (RUO2) , a series of new catalysts for the chlorine and the oxygen evolution reactions were generated. Based up testing, some of these newly created catalysts exhibited catalytic properties which exceeded that of the 'best' known catalysts for the OER and CER reactions. In particular, conductive materials were chosen such that the surface charge concentration properties of the composite material were similar to that of RUO2 (i.e., Ti has an electron affinity of -8 eV while Ir has an electron affinity of -150 eV and Ru has an electron affinity of -101 eV) . It was found that layering T1O2 on top of IrC>2 provided for a composite material that had similar surface charge properties to RUO2. It should be noted, however, that RUO2 while having favorable surface charge properties for the OER, suffers from low stability. Thus, the above composite material of T1O2 and IrC>2 exhibits favorable surface charge
properties as RUO2, but without the stabilities concerns. Using the methods disclosed herein, FTO, IrC>2, and RUO2 were coated with a thin layer of T1O2 so as to improve the specific catalytic activities of each catalyst. In particular, the methods disclosed herein allowed for the manufacture of a catalyst that exhibited the highest intrinsic activity for the OER known in the art. Moreover, all three under layers showed order of magnitude increases in specific activity for both the chlorine evolution reaction and the oxygen evolution reaction for a given overlying thickness of TiC>2. These materials showed a predictable "volcano" trend where activities initially increased with T1O2 layers then peaked and decreased again. Accordingly, the methods of the disclosure represent a platform technology that can be broadly applied to many
heterogeneous electrocatalyst systems, such as designing and fabricating new heterogeneous electrocatalysts for all types of reactions from energy storage in batteries or fuels to industrial commodity chemical production and more.
[ 0055 ] In a particular embodiment, the disclosure provides for applying a thin film of a conductive material using one or more cycles of atomic layer deposition to a surface of another different conductive material or substrate. Atomic layer deposition (ALD) is a thin film deposition technique that is based on the sequential use of a gas phase chemical process (see FIG . 4 ) . ALD is considered a subclass of chemical vapor deposition. The majority of ALD reactions use two chemicals, typically called precursors. These precursors react with the surface of a material one at a time in a sequential, self-limiting, manner. Through the repeated exposure to separate precursors, a thin film is slowly deposited. In contrast to chemical vapor deposition, the precursors are never present simultaneously in the reactor, but they are inserted as a series of sequential, non-overlapping pulses. In each of these pulses the precursor molecules react with the surface in a self-limiting way, so that the reaction terminates once all the reactive sites on the surface are consumed. Consequently, the maximum amount of material deposited on the surface after a single exposure to all of the precursors (a so-called ALD cycle) is determined by the nature of the precursor-surface interaction. By varying the number of cycles, it is possible to grow materials uniformly and with high precision on arbitrarily complex and large substrates. ALD produces very thin, conformal films with control of the thickness and composition of the films possible at the atomic level.
[ 0056] In a prototypical ALD process, a substrate is exposed to two reactants A and B in a sequential, non-overlapping way. In contrast to other techniques such as chemical vapor deposition
(CVD) , where thin film growth proceeds on a steady-state fashion, in ALD each reactant reacts with the surface in a self-limited way: the reactant molecules can react only with a finite number of reactive sites on the surface. Once all those sites have been consumed in the reactor, the growth stops. The remaining reactant molecules are flushed away and only then reactant B is inserted into the reactor. By alternating exposures of A and B, a thin film is deposited.
Consequently, when describing an ALD process one refers to both dose times (the time a surface is being exposed to a precursor) and purge times (the time left in between doses for the precursor to evacuate the chamber) for each precursor. The dose-purge-dose-purge sequence of a binary ALD process constitutes an ALD cycle. Also, rather than using the concept of growth rate, ALD processes are described in terms of their growth per cycle.
[ 0057 ] In ALD, enough time must be allowed in each reaction step so that a full adsorption density can be achieved. When this happens, the process has reached saturation. This time will depend on two key factors: the precursor pressure, and the sticking probability. Therefore, the rate of adsorption per unit of surface area can be expressed as: Where R is the rate of adsorption, S is the sticking probability, and F is the incident molar flux. However, a key characteristic of ALD is the S will change with time, as more molecules have reacted with the surface this sticking probability will become smaller until reaching a value of zero once saturation is reached.
[ 0058 ] While the reaction mechanisms are strongly dependent on the particular ALD process, there are hundreds of ALD processes described in the literature to deposit oxide, metals, nitrides, sulfides, chalcogenides , and fluoride materials. The right selection of precursors is very important in order to obtain the desired material. Initially CVD precursors include metal hydrides and halides but today a large array of metal organic compounds are used that include metal alkoxides, metal alkyls, metal diketonites, metal amidinates, metal carbonyls and others. It is important that precursors are volatile but thermally stable so that they do not decompose during vaporization, and are preferably soluble in an inert solvent or liquid at room temperature. Furthermore, they must have preferential reactivity towards the substrate and the growing film. It is also important that ALD precursors have self-limiting reactivity with the substrate and the film surface. For most precursors, only one element is contributed to the deposited film, with the rest of the molecules vaporized during the process.
Certain compounds can contribute more than one element and bring down the number of reactants needed for a specific process.
Precursors for ALD are commercially available from a variety of vendors (e.g., Sigma Aldrich Co., St. Louis MO; and Strem Chemicals Inc., Newburyport, MA) . Examples of ALD precursors include, but are not limited to, aluminum tris (2 , 2 , 6, 6-tetramethyl-3, 5- heptanedionate ) , triisobutylaluminum, trimethylaluminum,
tris (dimethylamido) aluminum (III) , triphenylantimony (III) ,
tris (dimethylamido) antimony (III) , triphenylarsine, Triphenylarsine oxide, barium bis (2, 2, 6, 6-tetramethyl-3, 5-heptanedionate) hydrate, barium nitrate, Ba (C9H23N3) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l),
[Ba (C5 (CH3) 5) 2] -2 (C4H80) , [Ba (C5 (C3H7) 3¾) 2] -2 (C4H80) , bis (acetato- O) triphenylbismuth (V) , triphenylbismuth, tris (2- methoxyphenyl ) bismuthine , triisopropyl borate, triphenylborane , tris (pentafluorophenyl ) borane , cadmium acetylacetonate , calcium bis (6,6,7,7,8,8,8, -heptafluoro-2 , 2-dimethyl-3, 5-octanedionate) , calcium bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate ) ,
bis (cyclopentadienyl ) chromium (II),
bis (pentamethy1cyclopentadienyl ) chromium (II), chromium (III) tris (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
bis (cyclopentadienyl) cobalt (II) ,
bis (pentamethylcyclopentadienyl ) cobalt (II) , copper
bis (6,6,7,7,8,8, 8-heptafluoro-2 , 2-dimethyl-3, 5-octanedionate) , copper bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
tris (dimethylamido) gallium (III) , germanium ( IV) fluoride, hexaethyldigermanium ( IV) , tetramethylgermanium, tributylgermanium hydride, triethylgermanium hydride, triphenylgermanium hydride, bis (tert-butylcyclopentadienyl ) dimethylhafnium ( IV) ,
bis (trimethylsilyl) amidohafnium (IV) chloride,
dimethylbis (cyclopentadienyl) hafnium (IV) ,
tetrakis (diethylamido) hafnium ( IV) ,
tetrakis (dimethylamido) hafnium ( IV) ,
tetrakis (ethylmethylamido) hafnium ( IV) , [1,1'- bis (diphenylphosphino) ferrocene ] tetracarbonylmolybdenum ( 0 ) , bis (pentamethylcyclopentadienyl ) iron ( I I ) , 1,1' -diethyl ferrocene , iron(0) pentacarbonyl , iron(III) tris (2, 2, 6, 6-tetramethyl-3, 5- heptanedionate ) , bis (cyclopentadienyl) magnesium (II) ,
bis (pentamethylcyclopentadienyl) magnesium,
Mg(C6Hi6N2) [CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis (pentamethylcyclopentadienyl ) manganese (II) ,
bis (tetramethylcyclopentadienyl ) manganese (II) ,
bromopentacarbonylmanganese (I) , cyclopentadienylmanganese (I) tricarbonyl, ethylcyclopentadienylmanganese ( I ) tricarbonyl, manganese(O) carbonyl, (bicyclo [ 2.2.1 ] hepta-2 , 5- diene ) tetracarbonylmolybdenum ( 0 ) ,
bis (cyclopentadienyl ) molybdenum ( IV) dichloride,
cyclopentadienylmolybdenum ( I I ) tricarbonyl dimer,
molybdenumhexacarbonyl , (propylcyclopentadienyl ) molybdenum ( I ) tricarbonyl dimer, allyl (cyclopentadienyl) nickel (II) ,
bis (cyclopentadienyl) nickel (II) ,
bis (ethylcyclopentadienyl ) nickel ( I I ) , nickel (II) bis (2, 2,6,6- tetramethyl-3 , 5-heptanedionate) , bis (cyclopentadienyl) niobium (IV) dichloride, trimethyl (methylcyclopentadienyl ) platinum ( IV) , dirhenium decacarbonyl , (acetylacetonato) ( 1 , 5-cyclooctadiene ) rhodium ( I ) , (acetylacetonato) (1, 5-cyclooctadiene) rhodium (I) ,
bis (cyclopentadienyl ) ruthenium ( I I ) ,
bis (ethylcyclopentadienyl ) ruthenium ( I I ) ,
bis (pentamethylcyclopentadienyl) ruthenium ( II ) , triruthenium dodecacarbonyl, Sr (C9H23N3) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l), pentakis (dimethylamino) tantalum (V) , tantalum (V) ethoxide,
tris (diethylamido) (tert-butylimido) tantalum (V) ,
tris (ethylmethylamido) (tert-butylimido) tantalum (V) ,
Ta(C2H50)4[CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis [bis (trimethylsilyl) amino] tin (II) , dibutyldiphenyltin,
hexaphenylditin (IV) , tetraallyltin, tetrakis (diethylamido) tin (IV) , tetramethyltin, tetravinyltin, tin (II) acetylacetonate ,
trimethyl (phenylethynyl ) tin, trimethyl (phenyl ) tin, tetrakis
(dimethylamido) titanium (IV) (TDMAT) ,
tetrakis (ethylmethylamido) titanium (IV) , titanium (IV)
diisopropoxidebis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , titanium tetrachloride, titanium (IV) isopropoxide ,
Ti (OC3H7) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l),
bis (butylcyclopentadienyl ) tungsten ( IV) diiodide, bis (tert- butylimino) bis (tert-butylamino) tungsten, bis (tert- butylimino) bis (dimethylamino) tungsten (VI ) ,
bis (cyclopentadienyl) tungsten (IV) dichloride,
bis (cyclopentadienyl) tungsten (IV) dihydride,
bis (isopropylcyclopentadienyl) tungsten (IV) dihydride,
cyclopentadienyltungsten ( I I ) tricarbonyl hydride, tetracarbonyl ( 1 , 5- cyclooctadiene ) tungsten ( 0 ) , triamminetungsten ( IV) tricarbonyl, tungsten hexacarbonyl , bis (cyclopentadienyl) vanadium (II) ,
bis (cyclopentadienyl ) vanadium (II), vanadium (V) oxytriisopropoxide , bis (pentafluorophenyl ) zinc, bis (2,2, 6, 6-tetramethyl-3 , 5- heptanedionato) zinc (II) , diethylzinc, and diphenylzinc .
[ 0059] In a certain embodiment, the conductive catalytic materials or electrocatalysts of the disclosure comprises metals, metal sufides, metal nitrides, metal fluorides, metal oxides, alloys, or any combination of the foregoing. Moreover, any of the foregoing may further comprise dopants, e.g., iridium doped iron oxide, molybdenum doped iron oxide, niobium doped iron oxide, and fluorine doped tin oxide. Typically, the metal oxide comprises the oxide of a single metal selected from, but not limited to,
transition metals (e.g., iron, cobalt, nickel, vanadium, copper, zinc, zirconium, tungsten, ruthenium, platinum, palladium,
molybdenum, osmium, manganese, chromium, titanium, rhodium, ruthenium, iridium), alkaline earth metals (e.g., magnesium, calcium, strontium, and barium), and poor metals /metalloids (e.g., zinc, gallium, aluminum, germanium, tin, and bismuth) . Specific examples of metal oxides include, but are not limited to, AI2O3, NH4OSbW, Sb205, BaO, BaTi03, BaZr03, Al6BeOi0, BeO, Bi203, Bi205, B203, CdO, CaO, Ce203, Ce02, CrO, Cr203, Cr02, Cr03, CoO, Co203, Cu205Yb2, Cu20, CuFe204, CuO, GaO, Ga203, GeO, Ge02, Au20, Au203, Hf02, ln20, InO, ln203, lr203, Ir02, Fe304, FeO, Fe203, PbO, Pb02, Li20, Al2Mg04, MgO, Mn304, MnO, Mn203, Mn02, Mn205, Mn207, Hg20, HgO, Mo02, Mo03, Mo205, NiFe204, NiO, Ni203, LiNb03, NaNb03, Nb203, Nb205, Os203, Os03, Os04, PdO, Pd02, (C6H5)AsO, Pt304, PtO, Pt203, K20, Re207, Re04, Rh203, Rb20, Ru02, Ru04, Sc203, Se304, Ag20, Na20, SrO, NaTa03, Ta203, Ta205, Si02, SnO, Sn02, SrTi03, TiO, Ti203, Ti02, WC1202, W203, W02, W03, W205, V0C12, VO, V203, V02, V205, Yb203, YBa2Cu307, Y203, ZnO, Zr02, fluorine doped tin oxide, iron doped titanium oxide, W03 doped ZnO, Fe doped Ce02, tin doped Fe304, and indium tin oxide. In regards to alloys, the alloy may be a mixture of a metal and another element, or a mixture of metals. If there is a mixture of only two types of atoms (not counting impurities) then it is a binary alloy. Examples of binary alloys include, but are not limited to, iron/cobalt, iron/nickel, cobalt/nickel, cobalt/aluminum, nickel/aluminum, iron/aluminum, iron/cerium, iron/molybdenum, iron/copper, iron/iridium,
iron/manganese, iron/tin, and iron/niobium. If there is a mixture of three types of atoms (not counting impurities) then it is a ternary alloy. Examples of ternary alloys include, but are not limited to, iron/cobalt/nickel, iron/aluminum/nickel,
aluminum/cobalt/nickel, and aluminum/cobalt/iron.
[ 0060 ] The disclosure also provides for heterogeneous
electrocatalysts which comprise a conductive electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or
semiconductive materials. In a particular embodiment, the
heterogeneous electrocatalysts comprise a conductive
electrocatalytic substrate and thin layer (s) that are comprised of different materials. In another embodiment, the heterogeneous electrocatalysts comprise a conductive electrocatalytic substrate made of a conductive material and thin layer (s) that are comprised of conductive materials. In yet another embodiment, the
heterogeneous electrocatalysts comprise a conductive
electrocatalytic substrate that is comprised of a semiconductive material and thin layer (s) that are comprised of semiconductive materials. In a further embodiment, the heterogeneous
electrocatalysts comprise a conductive electrocatalytic substrate that is comprised of a semiconductive material and thin layer (s) that are comprised of conductive materials. In another embodiment, a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive or semiconductive materials that has a thickness of < 50 nm, < 25 nm, < 10 nm, < 5 nm, < 1 nm, < 9 A, < 8 A, < 7 A, < 6 A, < 5 A, < 4 A, < 3 A, < 2 A, < 1 A, or < 0.5 A. In yet another embodiment, a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive and/or semiconductive materials that have a thickness of 0 .1 A, 0 .2 A, 0.3
A, 0. 4 A, 0 5 A, 0 6 A, 0 .7 A, 0.8 A, 0.9 A, 1 A, 1 .1 A, 1 .2 A, 1.3
A, 1. 4 A, 1 5 A, 1 6 A, 1 .7 A, 1.8 A, 1.9 A, 2 A, 2 .1 A, 2 .2 A, 2.3
A, 2. 4 A, 2 5 A, 2 6 A, 2 .7 A, 2.8 A, 2.9 A, 3 A, 3 .1 A, 3 .2 A, 3.3
A, 3. 4 A, 3 5 A, 3 6 A, 3 .7 A, 3.8 A, 3.9 A, 4 A, 4 .1 A, 4 .2 A, 4.3
A, 4. 4 A, 4 5 A, 4 6 A, 4 .7 A, 4.8 A, 4.9 A, 5 A, 5 .1 A, 5 .2 A, 5.3
A, 5. 4 A, 5 5 A, 5 6 A, 5 .7 A, 5.8 A, 5.9 A, 6 A, 6 .1 A, 6 .2 A, 6.3
A, 6. 4 A, 6 5 A, 6 6 A, 6 .7 A, 6.8 A, 6.9 A, 7 A, 7 .1 A, 7 .2 A, 7.3
A, 7. 4 A, 7 5 A, 7 6 A, 7 .7 A, 7.8 A, 7.9 A, 8 A, 8 .1 A, 8 .2 A, 8.3
A, 8. 4 A, 8 5 A, 8 6 A, 8 .7 A, 8.8 A, 8.9 A, 9 A, 9 .1 A, 9 .2 A, 9.3
A, 9. 4 A, 9 5 A, 9 6 A, 9 .7 A, 9.8 A, 9.9 A, 1 nm, 2 nm, 3 nm, 4 nm,
5 nm, 6 nm, 7 nm, ί 3 nm, 9 nm, 10 nm, 12 nm, 14 nm, 15 nm, 16 nm , 18 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, or a range including or between any two of the foregoing numbers. In a certain embodiment, a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive and/or semiconductive materials that has a thickness resulting from using an ALD process with 1 to 1000 cycles, 1 to 500 cycles, 1 to 100 cycles, 1 to 90 cycles, 1 to 80 cycles, 1 to 70 cycles, 1 to 60 cycles, 1 to 55 cycles, 1 to 50 cycles, 1 to 45 cycles, 1 to 40 cycles, 1 to 35 cycles, 1 to 30 cycles, 1 to 25 cycles, 1 to 24 cycles, 1 to 23 cycles, 1 to 22 cycles, 1 to 21 cycles, 1 to 20 cycles, 1 to 19 cycles, 1 to 18, cycles, 1 to 17 cycles, 1 to 16 cycles, 1 to 15 cycles, 1 to 14 cycles, 1 to 13 cycles, 1 to 12 cycles, 1 to 11 cycles, 1 to 10 cycles, 1 to 9 cycles, 1 to 7 cycles, 1 to 6 cycles or 1 to 5 cycles. In yet another embodiment, a heterogeneous electrocatalyst disclosed herein comprises a thin layer (s) of one or more conductive and/or semiconductive materials that has a thickness resulting from using an ALD process with 1 cycle, 2 cycles, 3 cycles, 4 cycles, 5 cycles, 6 cycles, 7 cycles, 8 cycles, 9 cycles, 10 cycles, 11 cycles, 12 cycles, 13 cycles, 14 cycles, 15 cycles, 16 cycles, 17 cycles, 18 cycles, 19 cycles, 20 cycles, 21 cycles, 22 cycles, 23 cycles, 24 cycles, 25 cycles, 30 cycles, 35 cycles, 40 cycles, 45 cycles, 50 cycles, 55 cycles, 60 cycles, 70 cycles, 80 cycles, 90 cycles, 100 cycles, 500 cycles, 1000 cycles, or any range between any two of the foregoing cycle numbers. In yet another embodiment, a heterogeneous electrocatalyst disclosed herein comprises a conductive electrocatalytic substrate that is ≥ 100 nm, ≥ 1 μπι, ≥ 10 μπι, ≥ 100 μπ\ or ≥ 1 mm in thickness.
[ 0061 ] In a certain embodiment, the disclosure provides for a heterogeneous electrocatalyst that is suitable for the Oxygen
Evolution Reaction which comprises a conductive electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or
semiconductive materials, and wherein the substrate and thin films are selected from the following materials: Ni02 and WO3, Ni02 and W03, Ni02 and A1203, Ni02 and Mn02, Ru02 and Ti02, Ru02 and W03, Ru02 and A1203, Ru02 and Mn02, Cu02 and Ti02, Cu02 and W03, Cu02 and A1203, Cu02 and Mn02, Ir02 and Ti02, Ir02 and W03, Ir02 and A1203, Ir02 and Mn02, Sn02/FTO and Ti02, Sn02/FTO and W03, Sn02/FTO and A1203, and Sn02/FTO and Mn02. [ 0062 ] In an alternate embodiment, the disclosure provides for a heterogeneous electrocatalyst that is suitable for the Nitrogen Reduction Reaction which comprises a conductive electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or
semiconductive materials, and wherein the substrate and thin films are selected from the following materials: Ni and Ti, Cu and Ti, Nb and Ti, Mo and Ti, Tc and Ti, Ru and Ti, Rh and Ti, Ag and Ti, Sn and Ti, Os and Ti, Ir and Ti, Ni and Mn, Cu and Mn, Nb and Mn, Mo and Mn, Tc and Mn, Ru and Mn, Rh and Mn, Ag and Mn, Sn and Mn, Os and Mn, Ir and Mn, Ni and Zn, Cu and Zn, Nb and Zn, Mo and Zn, Tc and Zn, Ru and Zn, Rh and Zn, Ag and Zn, Sn and Zn, Os and Zn, and Ir and Zn.
[ 0063 ] In a further alternate embodiment, the disclosure provides for a heterogeneous electrocatalyst that is suitable for the CO2 Reduction Reaction which comprises a conductive
electrocatalytic substrate comprised of one or more conductive, semiconductive and/or superconductive materials that has been coated on one or more surfaces with a thin layer (s) of one or more conductive or semiconductive materials, and wherein the substrate and thin films are selected from the following materials: Ni and Ti, Ni and W, Ni and Al, Ni and Mn, Ru and Ti, Ru and W, Ru and Al, Ru and Mn, Cu and Ti, Cu and W, Cu and Al, Cu and Mn, Ir and Ti, Ir and W, Ir and Al, Ir and Mn, Sn and Ti, Sn and W, Sn and Al, and Sn and Mn.
[ 0064 ] The disclosure further provides for one or more
electrodes which comprises one or more heterogeneous
electrocatalysts disclosed herein. In a particular embodiment, an anode comprises one or more heterogeneous electrocatalysts disclosed herein. In an alternate embodiment, a cathode comprises one or more heterogeneous electrocatalysts disclosed herein. In a further alternate embodiment, a cathode and an anode comprises one or more heterogeneous electrocatalysts disclosed herein. In further embodiment, an electrode which comprises one or more heterogeneous electrocatalysts disclosed herein is used in an electrochemical reaction. Examples of electrochemical reactions, include but are not limited to, the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction, and the oxygen reduction reaction .
[ 0065 ] In a particular embodiment, the disclosure provides a method to manufacture a heterogeneous electrocatalyst that has improved electrocatalytic activity for an electrochemical reaction, comprising: layering or depositing one or more thin films of one or more conductive catalytic materials onto a surface of a conductive electrocatalytic substrate by using 1 to 100 cycles of an atomic layer deposition process, wherein the number of cycles of the atomic layer deposition process is used to tune the electrocatalytic activity of the heterogeneous electrocatalysts for the
electrochemical reaction, and wherein the electrocatalytic activity of the heterogeneous electrocatalyst for the electrochemical reaction is improved in comparison to the electrocatalytic activity of the conductive electrocatalytic substrate. In an embodiment disclosed herein or as a further embodiment, the one or more thin films are comprised of metals, alloys, metal oxides, metal nitrides, metal sulfides, metal fluorides, or a combination thereof,
preferably wherein the one or more thin films are comprised of metal oxides, more preferably wherein the one or more thin films are comprised of metal oxides selected from AI2O3, NH4OSbW, Sb2Os, BaO, BaTi03, BaZr03, Al6BeOi0 , BeO, Bi203, Bi205, B203, CdO, CaO, Ce203, Ce02, CrO, Cr203, Cr02, Cr03, CoO, Co203, Cu205Yb2, Cu20, CuFe204, CuO, GaO, Ga203, GeO, Ge02, Au20, Au203, Hf02, ln20, InO, ln203, lr203, Ir02, Fe304, FeO, Fe203, PbO, Pb02, Li20, Al2Mg04, MgO, Mn304, MnO, Mn203, Mn02, Mn205, Mn207, Hg20, HgO, Mo02, Mo03, Mo205, NiFe204, NiO, Ni203, LiNb03, NaNb03, Nb203, Nb205, Os203, Os03, Os04, PdO, Pd02, (C6H5)AsO, Pt304, PtO, Pt203, K20, Re207, Re04, Rh203, Rb20, Ru02, Ru04, Sc203, Se304, Ag20, Na20, SrO, NaTa03, Ta203, Ta205, Si02, SnO, Sn02, SrTi03, TiO, Ti203, Ti02, WC1202, W203, W02, W03, W205, V0C12, vo, V203, vo2, V2C>5, Yb203, YBa2Cu307, Y203, ZnO, Zr02, fluorine doped tin oxide, iron doped titanium oxide, W03 doped ZnO, Fe doped Ce02, tin doped Fe304, and indium tin oxide. In an embodiment disclosed herein or as a further embodiment, the one or more thin films comprise Ti02. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises 1 to 50 cycles of an atomic layer deposition process used to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate, preferably wherein 1 to 25 cycles of an atomic layer deposition process are used to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate, more
preferably wherein 1 to 15 cycles of an atomic layer deposition process are used to deposit or layer a thin film of T1O2 onto a surface of the conductive electrocatalytic substrate. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises one or more thin films are made from one or more precursors used in the atomic layer deposition process selected from aluminum tris (2, 2, 6, 6-tetramethyl-3, 5-heptanedionate) , triisobutylaluminum, trimethy1aluminum,
tris (dimethylamido) aluminum (III) , triphenylantimony (III) ,
tris (dimethylamido) antimony (III) , triphenylarsine, Triphenylarsine oxide, barium bis (2, 2, 6, 6-tetramethyl-3, 5-heptanedionate) hydrate, barium nitrate, Ba (C9H23N3) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l),
[Ba (C5 (CH3) 5) 2] -2 (C4H80) , [Ba (C5 (C3H7) 3¾) 2] -2 (C4H80) , bis (acetato- O) triphenylbismuth (V) , triphenylbismuth, tris (2- methoxyphenyl ) bismuthine , triisopropyl borate, triphenylborane , tris (pentafluorophenyl ) borane , cadmium acetylacetonate , calcium bis (6,6,7,7,8,8,8, -heptafluoro-2 , 2-dimethyl-3, 5-octanedionate) , calcium bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
bis (eyelopentadienyl ) chromium (II),
bis (pentamethyleyelopentadienyl ) chromium (II), chromium (III) tris (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
bis (cyclopentadienyl ) cobalt (II) ,
bis (pentamethyleyelopentadienyl) cobalt (II) , copper
bis (6,6,7,7,8,8, 8-heptafluoro-2 , 2-dimethyl-3, 5-octanedionate) , copper bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
tris (dimethylamido) gallium (III) , germanium ( IV) fluoride,
hexaethyldigermanium ( IV) , tetramethylgermanium, tributylgermanium hydride, triethylgermanium hydride, triphenylgermanium hydride, bis (tert-butylcyclopentadienyl ) dimethylhafnium ( IV) ,
bis (trimethylsilyl) amidohafnium (IV) chloride, dimethylbis (cyclopentadienyl) hafnium (IV) ,
tetrakis (diethylamido) hafnium ( IV) ,
tetrakis (dimethylamido) hafnium ( IV) ,
tetrakis (ethylmethylamido) hafnium ( IV) , [1,1'- bis (diphenylphosphino) ferrocene ] tetracarbonylmolybdenum ( 0 ) , bis (pentamethy1cyclopentadienyl ) iron ( I I ) , 1,1' -diethyl ferrocene , iron(0) pentacarbonyl , iron(III) tris (2, 2, 6, 6-tetramethyl-3, 5- heptanedionate ) , bis (cyclopentadienyl) magnesium (II) ,
bis (pentamethylcyclopentadienyl ) magnesium,
Mg(C6Hi6N2) [CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis (pentamethylcyclopentadienyl ) manganese (II) ,
bis (tetramethylcyclopentadienyl ) manganese (II) ,
bromopentacarbonylmanganese (I) , cyclopentadienylmanganese (I) tricarbonyl, ethylcyclopentadienylmanganese ( I ) tricarbonyl, manganese(O) carbonyl, (bicyclo [ 2.2.1 ] hepta-2 , 5- diene ) tetracarbonylmolybdenum ( 0 ) ,
bis (cyclopentadienyl ) molybdenum ( IV) dichloride,
cyclopentadienylmolybdenum ( I I ) tricarbonyl dimer,
molybdenumhexacarbonyl , (propylcyclopentadienyl ) molybdenum ( I ) tricarbonyl dimer, allyl (cyclopentadienyl) nickel (II) ,
bis (cyclopentadienyl) nickel (II) ,
bis (ethylcyclopentadienyl ) nickel ( I I ) , nickel (II) bis (2, 2,6,6- tetramethyl-3 , 5-heptanedionate) , bis (cyclopentadienyl) niobium (IV) dichloride, trimethyl (methylcyclopentadienyl ) platinum ( IV) , dirhenium decacarbonyl , (acetylacetonato) ( 1 , 5-cyclooctadiene ) rhodium ( I ) , (acetylacetonato) (1, 5-cyclooctadiene) rhodium (I) ,
bis (cyclopentadienyl) ruthenium ( I I ) ,
bis (ethylcyclopentadienyl) ruthenium ( I I ) ,
bis (pentamethylcyclopentadienyl) ruthenium ( II ) , triruthenium dodecacarbonyl, Sr (C9H23N3) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l), pentakis (dimethylamino) tantalum (V) , tantalum (V) ethoxide,
tris (diethylamido) (tert-butylimido) tantalum (V) ,
tris (ethylmethylamido) (tert-butylimido) tantalum (V) ,
Ta(C2H50)4[CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis [bis (trimethylsilyl) amino] tin (II) , dibutyldiphenyltin,
hexaphenylditin (IV) , tetraallyltin, tetrakis (diethylamido) tin (IV) , tetramethyltin, tetravinyltin, tin (II) acetylacetonate , trimethyl (phenylethynyl ) tin, trimethyl (phenyl ) tin, tetrakis
(dimethylamido) titanium (IV) (TDMAT) ,
tetrakis (ethylmethylamido) titanium (IV) , titanium (IV)
diisopropoxidebis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , titanium tetrachloride, titanium (IV) isopropoxide ,
Ti (OC3H7) 2 [CxHyC (O) CHC (O) CxHyk (x=3-4, y=2x+l),
bis (butylcyclopentadienyl ) tungsten ( IV) diiodide, bis (tert- butylimino) bis (tert-butylamino) tungsten, bis (tert- butylimino) bis (dimethylamino) tungsten (VI ) ,
bis (cyclopentadienyl ) tungsten (IV) dichloride,
bis (cyclopentadienyl) tungsten (IV) dihydride,
bis (isopropylcyclopentadienyl) tungsten (IV) dihydride,
cyclopentadienyltungsten ( I I ) tricarbonyl hydride, tetracarbonyl ( 1 , 5- cyclooctadiene ) tungsten ( 0 ) , triamminetungsten ( IV) tricarbonyl, tungsten hexacarbonyl , bis (cyclopentadienyl) vanadium (II) ,
bis (cyclopentadienyl ) vanadium (II), vanadium (V) oxytriisopropoxide , bis (pentafluorophenyl ) zinc, bis (2,2, 6, 6-tetramethyl-3 , 5- heptanedionato) zinc (II) , diethylzinc, and diphenylzinc, preferably wherein the one or more thin films are made from a precursor of tetrakis (dimethylamido) titanium ( IV) used in the atomic layer deposition process. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises a conductive electrocatalytic substrate is at least 100 nm in thickness, preferably wherein the conductive electrocatalytic substrate is at least 10 μπ\ in thickness. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises a conductive electrocatalytic substrate that is comprised of a conductive material, semiconductive material and/or superconductive material (e.g., a metal, alloy, metal oxide, metal nitride, metal sulfide, metal fluoride, or a combination thereof) , preferably wherein the conductive electrocatalytic substrate is comprised of a metal oxide, more preferably wherein the conductive electrocatalytic substrate is comprised of a metal oxide selected from AI2O3, NH4OSbW, Sb20s, BaO, BaTi03, BaZr03, Al6BeOi0, BeO, Bi203, Bi205, B203, CdO, CaO, Ce203, Ce02, CrO, Cr203, Cr02, Cr03, CoO, Co203, Cu205Yb2, Cu20, CuFe204, CuO, GaO, Ga203, GeO, Ge02, Au20, Au203, Hf02, ln20, InO, ln203, lr203, Ir02, Fe304, FeO, Fe203, PbO, Pb02, Li20, Al2Mg04, MgO, Mn304, MnO, Mn203, Mn02, Mn205, Mn207, Hg20, HgO, Mo02, M0O3, Mo205, NiFe204, NiO, Ni203, LiNb03, NaNb03, Nb203, Nb205, Os203, Os03, Os04, PdO, Pd02, (C6H5)AsO, Pt304, PtO, Pt203, K20, Re207, Re04, Rh203, Rb20, Ru02, Ru04, Sc203, Se304, Ag20, Na20, SrO, NaTa03, Ta203, Ta205, Si02, SnO, Sn02, SrTi03, TiO, Ti203, Ti02, WC1202, W203, W02, W03, W205, VOCl2, vo, V203, vo2, V205, Yb203, YBa2Cu3C>7, Y203, ZnO, Zr02, fluorine doped tin oxide, iron doped titanium oxide, W03 doped ZnO, Fe doped Ce02, tin doped Fe304, and indium tin oxide. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises a conductive electrocatalytic substrate that is comprised of Ir02 or Ru02. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises an electrochemical reaction that is selected from the group consisting of the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, and the oxygen reduction reaction, preferably wherein the electrochemical reaction is the oxygen evolution reaction or the chlorine evolution reaction. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises a heterogeneous electrocatalyst exhibits a lower overpotential or improved specific activity for the chemical reaction than the conductive electrocatalytic substrate. In an embodiment disclosed herein or as a further embodiment, a method disclosed herein comprises a heterogeneous electrocatalyst exhibits has a more favorable surface charge distribution for the chemical reaction than the conductive electrocatalytic substrate. In an embodiment disclosed herein or as a further embodiment, the
disclosure provides for a heterogeneous electrocatalyst made by a method of the disclosure. In an embodiment disclosed herein or as a further embodiment, a heterogeneous electrocatalyst disclosed herein comprises a conductive electrocatalytic substrate of Ir02, FTO, or Ru02. In an embodiment disclosed herein or as a further embodiment, a heterogeneous electrocatalyst disclosed herein comprises a thin film of Ti02, preferably wherein the thin film of Ti02 is made from 1 to 15 cycles of an ALD process. In an embodiment disclosed herein or as a further embodiment, an electrode comprises a heterogeneous electrocatalyst disclosed herein, preferably wherein the electrode is used to generate reactive chloride species in a wastewater treatment system.
[ 0066] The following examples are intended to illustrate but not limit the disclosure. While they are typical of those that might be used, other procedures known to those skilled in the art may alternatively be used.
EXAMPLES
[ 0067 ] Sample Preparation: [100] boron doped p+, < 0.01 Ω-cm,
525 +/- 25 μπ\ thick silicon wafers were obtained from Addison
Engineering. Wafers were cleaned for 1 minute in buffered HF
(Transene, used as received) , and then immediately put under vacuum of at least 7 x 10"6 torr. Ru02 or IrC>2 were deposited on the wafer using a AJA International Inc. Orion sputter deposition system equipped with Phase II-J software. For sputtering, samples were heated to 400 °C and sputtered with Ir or Ru plasma with a pressure of 20 torr argon and 3 torr oxygen for 22 minutes 25 seconds for Ir and a pressure of 15 torr argon and 5 torr oxygen for 18 minutes for Ru. 0-1000 T1O2 ALD cycles were deposited on the exposed Si wafer/IrC>2 at 150 °C using an Ultratech Fiji 200 Plasma Atomic Layer Deposition System. Prior to the ALD, one pulse of 0.06s ¾0 was applied onto the sample. Each ALD cycle consisted of a 0.25 s pulse of tetrakis (dimethylamido) titanium (TDMAT, Sigma-Aldrich, 99.999%, used as received), followed by a 0.06 s pulse of ¾0 (18 ΜΩ-cm, Millipore) . A 15 s purge under a constant 0.13 L min"1 flow of research-grade Ar (g) was performed between each precursor pulse. The base pressure during the T1O2 growth was kept at -0.1 torr.
Growth rate of T1O2 was -0.05 nm/cycle. Bare IrC>2 samples were subjected to only one pulse of 0.06 s ¾0.
[ 0068 ] Tafel Analysis : Galium-Indium eutectic (Alfa-Aesar,
99.99%) was scribed into the backside of the Si wafer electrode using a tungsten carbide scribe (VWR) . A copper wire was then stuck to the Ga-In and secured with one sided copper foil tape (3M) to provide the electrode contact. Samples were then covered in 470 electroplating tape (3M) which had a 2, 3, or 4 mm diameter punched circle in it to expose a constant electrode area. CVs were then performed on a Bio-Logic VSP 300 potentiostat using a 1M KC1 Ag/AgCl reference electrode (CH instruments) . 5M NaCl at pH 1 was prepared by dissolving 5 mol of reagent grade NaCl (Macron) into 900 mL of water (18 ΜΩ-cm, Millipore) . The pH was adjusted to a pH of 1 using 37% reagent grade HC1 ( Sigma-Aldrich) , and then diluted to 1 L with water (18 ΜΩ-cm, Millipore) . Constant stirring was used during CVs, and a coiled 0.5 mm Pt wire counter electrode was used (Sigma- Aldrich, 99.99%) . At least three different samples for each T1O2 thickness were compared for at least 10 cycles from 0.9 to 1.4 V vs Ag/AgCl. Peak current was similar for the 10 cycles of any given sample, and surface area did not significantly change before and after cyclic voltammetry and, surface area as measured by
integrating the non-faradaic current on the CVs was similar between samples. CV current data was converted to mA/cm2 units and then logged to perform Tafel analysis. Overpotentials and exchange current densities were averaged from at least three different samples. Overpotential calculations were conducted using the Nernst equation and activities of CI" and CI2. CI2 is a gas so fugacity was used while CI" activities were estimated from ionic strength.
Thermodynamic potential was calculated to be 1094 mV vs an Ag/AgCl reference electrode.
[ 0069] Electrochemical Impedance Spectroscopy: 5M NaN03 at pH 1 was prepared by dissolving NaN03 (J.T. Baker, 99.6%) in 900 mL of water (18 ΜΩ-cm, Millipore), adjusting the pH to 1 using HNO3 (Sigma Aldrich, > 60%) and diluting with water (18 ΜΩ · cm, Millipore) to 1 L. Electrodes were prepared as previously described and placed in sealed custom glass reaction containers with a 1M KC1 Ag/AgCl reference electrode (CH instruments) , 2 x 2 cm stainless steel counter electrode and enough NaN03 solution to cover the exposed 2 mm diameter anode. The reaction container was then purged with N2 for > 30 minutes. Impedance measurements were carried out using Bio-Logic potentiostat/galvanostat model VSP-300 with EIS
capability. All studies were performed at 298 ± 2 K. Impedance spectra were recorded in the frequency range of 1 MHz to 10 mHz, and the modulation amplitude of 5 mV. Potential range was 1.1 V to 0V versus a Ag/AgCl reference electrode at a step size of 25 mV.
[ 0070 ] EIS data were fitted, using ZView software, to a Rs- (Rp-
CPE) circuit, where Rs is solution resistance in high frequencies, CPE is a Constance Phase Element that represents double layer capacitance in mid-range frequencies, and Rp is charge transfer resistance at low frequencies. Spectroscopy was then redone on new samples in the range of the EPZE to confirm accuracy.
[ 0071 ] Initial Electrocatalytic Studies with Ti02 Coated Ir02 in the Chlorine Evolution Reaction: The most active electrocatalyst (stability not withstanding) for the chlorine evolution reaction is RUO2 and the second most active is IrC>2. While IrC>2 operates at a higher overpotential for a given surface area (-50 mV or higher) than RUO2, RUO2 use is limited by its instability. Measurements of the metal-oxygen bond strength and electron density of the surface metal and oxygen by x-ray photoelectron spectroscopy in RUO2 and IrC>2 indicate that the surface oxygen on RUO2 is more electron rich and the metal is more electron poor than the surface oxygen and metal on IrC>2. It is likely that this disparity accounts for the difference in the activity between the two catalysts.
[ 0072 ] The important surface electronic state of the two catalysts can be experimentally characterized by the relative potentials of zero charge (EPZC) , heat of formation, electron affinity measurements and others. Here we used EPZC to approximate electronic states. Absolute EPZE can vary considerably with
electrolyte conditions (reported values for T1O2 are between -790 to 570 mV vs Ag/AgCl) , however trends within a given electrolyte are consistent across electrolytes and are also negatively linearly correlated with the isoelectric point (IEP) (which also varies considerably with electrolyte) . The reported IEP trend in a 1M NaNC>3 electrolyte is an IEP of 5.3-5.5 for IrC>2, which is less than the RUO2 that has an IEP of 4. Based on the established trend, these values predict that RUO2 should have a -20 mV higher EPZC than IrC>2. This trend agrees well with the measured values of EPZC in 5M NaNC>3, pH 1, where Ir02 has an EPZc of 100 mV vs Ag/AgCl; and Ru02 has an EPZC of 125 mV vs Ag/AgCl.
[ 0073 ] It was hypothesized that by overlaying IrC>2 with a very thin coat of a metal-oxide that has a much more oxidative EPZC than IrC>2, it would be possible to tune the electronics of the underlying IrC>2 such that the surface had electronics similar to RUO2. For this purpose, T1O2 was used, which has a measured EPZC of 475 mV vs
Ag/AgCl in 5M NaNC>3, pH 1 (within the range of reported values) . Aside from having the desirable Epzc, T1O2 was also chosen because it conveys high stability to IrC>2 catalysts, and can be conveniently deposited by ALD.
[ 0074 ] To measure catalytic change in IrC>2 by ALD, IrC>2 was deposited on atomically flat p+ [100] silicon wafers by reactive sputtering for a nearly flat surface. ALD was then used to chemically bond 0-1000 ALD cycles of T1O2 to the IrC>2 surface (thick films of T1O2 are nearly inert for the chlorine evolution reaction at reasonable overpotentials ) . Polarization curves for T1O2 coated IrC>2 and bare IrC>2 were measured and Tafel analysis was conducted
(see FIG . 5A and B) . All polarization curves were performed in 5 M NaCl, pH 2 to ensure no significant oxygen evolution in the potential range tested.
[ 0075 ] It was found that the reaction operated under a constant mechanism with Tafel slopes varying between 72 and 78 mV/decade . The traditionally measured catalytic parameter is activation energy. However, overpotential was measured herein. The Y intercept marks the onset potential for chlorine evolution. These potentials were graphed in FIG . 6 with RUO2 , the optimal catalyst, which is shown for comparison.
[ 0076 ] These data indicate that increasing the number of ALD cycles of Ti02 can alter the onset potential of the catalyst. This effect follows a Sabatier principle type volcano plot (see FIG . 2 ) , where the T1O2 ALD cycles appear to be most beneficial at 3 ALD cycles of T1O2 , and less beneficial when less than three ALD cycles was used. Interestingly, the onset potential for the CER for IrC>2 coated with 3 ALD cycles of Ti02 is not significantly different from the fully optimized onset potential of Ru02 (~1 mV in concentrated brine) .
[ 0077 ] To investigate the role of surface electronics, impedance spectroscopy was preformed to determine the EPZC for these
electrodes. In these experiments, the capacitance of an electrode was measured in an inert ionic solution. The capacitance will be lowest at the EPZC as an uncharged surface attracts the smallest double layer. These experiments were conducted at the same ionic strength and pH as the polarization curve experiments except that NaCl was replaced with the oxidatively inert salt, NaN03. The EPZC is a measure of the surface electronics, the more negative charge character a surface has, the higher the EPZC, and the less negative charge character a surface has the lower the EPZC.
[ 0078 ] FIG . 7A and B indicate that the EPZC follows the
established trend and was in good agreement with predicted values. It was found that the surface EPZC varies incrementally with added T1O2 up until the curve flattens somewhat for thick (> 20 ALD cycles, ~lnm) , highly resistive films of T1O2 (1000 ALD cycles of T1O2 yield an EPZC of 475 mV vs Ag/AgCl) and chracterisitc inert CER activity due to poor conductivity. These data show that the surface electronics of the Ir02/Ti02 system can be altered by applying very thin films of the highly oxidative EPZC T1O2 on top of the less oxidative EPZC IrC>2.
[ 0079 ] Additional Electrocatalytic Studies with Ti02 Coated Ir02 in the Chlorine Evolution Reaction: Computational studies show that the CI" is most likely to coordinate onto the oxygen on the M-0 surface, this means that the electronics of that oxygen are likely very important for the CER. XPS measured electron configurations and electronegativities imply that Ir02 has a less electron dense terminal O atom than RUO2 and both Ir02 and RUO2 have a much less electron rich O atom than T1O2. Therefore, adding one ALD cycle of T1O2 could significantly alter the electronic state of the surface Oxygen and could account for the observed altered electronics and the fully optimized (~0 mV) overpoentenial for CER in concentrated brine .
[ 0080 ] To this end, samples of Ir02 were prepared with different numbers of atomic layer deposition (ALD) cycles of T1O2 deposited on top the Ir02 substrate in order to tune the charge density of the catalyst's surface. The layer thickness using ALD can be controlled down to a single monolayer. ALD is a mature technology that has been used extensively in the microelectronics industry to vary the surface charge density of semiconductors by depositing thin layers of gate oxides. Here, Ir02 was coated with between 1 and 60 ALD cycles of T1O2. The catalytic performance of these samples for the CER was measured under conditions similar to industrial CER (i.e., 5 M CI", pH 1) in order to eliminate competition with OER. Metal oxide charge densities were evaluated by measuring the correlated potential of zero charge (EPZc) , the potential for a given electrode in a given solution where the net surface charge is zero (i.e., a metal oxide with a more electron rich oxygen and more electron poor metal has a higher EPZc) ·
[ 0081 ] The catalytic performance of IrC>2 electrocatalysts with varying ALD cycles of Ti02 is shown in FIG. 8. The additional deposition of T1O2 on the surface of IrC>2 did not change the CER reaction mechanism as evidenced by the Tafel slopes (72 and 76 mV per decade) in the inset in FIG. 8, which are consistent with the range of values reported in literature for CER. The fundamental measures of an electrocatalyst' s activity are the exchange current density (i0) , a measure of the one-way rate of a reaction at equilibrium which is determined by fitting the current-voltage data to the Tafel equation and the overpotential ( η) , which is a measure of the electrochemical activation energy. While the CER mechanism for all thicknesses of T1O2 was unchanged, deposition of T1O2 significantly altered the exchange current density and
overpotential, resulting in volcano-shaped plots with optimal performance occurring at 3 ALD cycles, as seen in FIG. 9A and 9B, respectively. These volcano relations are indicative of the
Sabatier principle, which states that the ideal catalytic surface is one that provides "just right" biding of reaction intermediates. Deposition of 3 cycles of T1O2 resulted in an over fivefold increase in the exchange current density, from 0.14 to 0.77 mA/cm2, and a decrease in overpotential by 60 mV, compared to the bare I r02 sample. This performance is commensurate with the performance of the best known CER catalyst, RUO2 (the red square in FIG. 9A and 9B) . Deposition of T1O2 at thicknesses greater than 60 ALD cycles increased the CER overpotential dramatically, as expected for highly resistive bulk Ti02 (see Fig. 11A and B) .
[ 0082 ] CI" may coordinate either to vacancies on the surface metal or surface bound oxygens, therefore the electron density of the surface oxygen and metal are important parameters governing the activity of CER catalysts. The correlated potential at zero charge is a means of quantifying the surface oxygen and metal charge densities for metal oxides, where higher EPZC values indicate higher electron densities on surface oxygen atoms and electron-poor metal atoms. Previously measured electron configurations,
electronegativities, and EPZC values imply that the electron density of the oxygen in the metal oxide bond follows the pattern IrC>2 < RUO2 << T1O2. However, the Epzc of IrC>2 anodes overcoated with Ti02 increased approximately linearly with increasing T1O2 thickness, up to 20 ALD cycles, after which increasing the T1O2 layer thickness resulted in Epzc values that approached those of bulk T1O2 (see FIG . 10 and FIG . 13 ) . This suggests that deposition of a thin layer of T1O2 on IrC>2 does not result in the bulk T1O2 surface species charge densities but rather charge densities that were intermediate to those of IrC>2 and T1O2. At the optimal T1O2 thickness for CER catalysis (3 ALD cycles) the Epzc of the I r02/TiC>2 sample was virtually indistinguishable from that of RUO2, indicating that the surface oxygen and surface metal charge densities can be tuned to produce an ideal binding environment for catalysis.
[ 0083 ] In order to further investigate the effect of thin layers of T1O2 on the catalytic performance of IrC>2, density functional theory (DFT) was used to calculate how the free energy of chlorine adsorption to the IrC>2 surface is altered by adding layers of T1O2. The CER proceeds through the Volmer-Heyvrosky mechanism,
* + CI" = CI* + e~ (1) CI* + CI" = Cl2 + e" (2) where * stands for an active adsorption site. On the rutile I r02
(110) surface, the active site for chlorine adsorption is proposed to be a surface oxygen atom which has adsorbed on a coordinately unsaturated (cus) Ir site. However, chlorine adsorption is
activated directly on the cus Ti site on the T1O2 covered I r02
surfaces, because the adsorption energies of oxygen on cus Ti site are prohibitively large. According to the Volmer-Heyvrosky
mechanism, the sign of free energy of binding CI" to the active site
(AG(C1*)) dictates whether the Volmer step (1) or the Heyvrosky step
(2) is rate-determining, while the magnitude of AG (CI*) determines the overpotential for CER. Thus, AG (CI*) for the bare I r02 (110) surface and with one, two, and three layers (1L, 2L, 3L) of T1O2, was calculated using DFT. As the number of simulated T1O2 layers increases from 1 to 3, the |AG(C1*) | decreases from 0.28 eV to 0.07 eV, indicating a reduction in overpotential and increase in catalytic activity with the incorporation of T1O2. The sign of AG (CI*) changes from 2L to 3L, such that further increasing the number of T1O2 layers beyond 3 leads to an increase in |AG(C1*) |, and therefore an increase in the overpotential for CER. These computational results support the experimental findings that adding a very thin layer of T1O2 to IrC>2 improves the catalytic performance for the CER.
[ 0084 ] These data indicate that adding various layers of a metal oxide with a more electron poor metal and more electron rich oxygen on top of a metal oxide with a less electron poor metal and less electron rich oxygen can tune the surface charge density and the catalytic parameters. Furthermore, these data show that when the charge density is matched to that of a better catalyst, the catalytic parameters also match as predicted by the Sabatier principal. Therefore, the methods of the disclosure represent a new tool for improving the performance of heterogeneous electrocatalysts by tuning an active surface species' charge density by overcoating with an appropriate material or mix of materials. Furthermore, this technique may provide a pathway to enhance the catalytic activity of earth abundant electrocatalysts for critical reactions that was not previously available due to a dearth of tools to tune the activity of heterogeneous electrocatalysts.
[ 0085 ] The foregoing additionally demonstrates that the surface electronics of any substrate could be tuned by combining two materials that have different electronic properties in thin layers. This tuning could allow the surface electronics to match the requisites of any chemical reaction of interest. Combinations of 2 or more metal - nonmetal materials may be deposited to achieve a perfect electronic state of the surface. It is further postulated that tuning could be performed with earth abundant or non-precious metal-nonmetal electrodes in order to fit a chemically active regime .
[ 0086] Additional Electrocatalytic Studies with four different materials coated with TiOx in the Chlorine and Oxygen Evolution Reaction: Additional catalysts were created (> 50) for the study of two industrially important electrochemical reactions (the chlorine evolution reaction (CER) and the oxygen evolution reaction (OER) ) . In the studies, 4 different materials (fluorine doped tin oxide (FTO) , iridium oxide (IrOx), ruthenium oxide (RuOx) , and titania (TiOx) ) were utilized. TiOx was deposited as atomically thin layers ((from a single atomic layer (<0.5 angstroms) to 1000 atomic layers (approximately 50 nm) ) on top of a FTO, IrOx, and RuOx substrate, where a new catalyst was created for each thickness of TiOx.
[0087] In was found that the electrocatalysts made by the methods disclosed herein had improved catalytic activity for the OER in comparison to the best industry catalysts. For example, the current best electrocatalyst for the OER in 1 M H2SO4 is RUO2 which operates at a specific activity (normalized to electrochemically active surface area) of 0.42 mA/cm2 at 350 mV overpotential . By using the methods presented herein, a new heterogeneous
electrocatalyst was made by layering 10 cycles of T1O2 onto IrOx was found to operate at a specific activity of 3.5 mA/cm2 at 350 mV overpotential. Further, a new heterogeneous electrocatalyst made by layering 10 cycles of TiOx onto RUO2 using the methods of the disclosure, yielded a heterogeneous electrocatalyst that operated at of 2.8 mA/cm2 at 350 mV overpotential for the OER.
[0088] The overpotentials of RUO2 coated with increasing ALD cycles of T1O2 for CER are provided in FIG. 14; while the
polarization curves and specific activities for RUO2 coated with increasing ALD cycles of Ti02 for OER are provided in FIG. 15 and 16, respectively. The polarization curves and overpotential curves for Ir02 coated with increasing ALD cycles of T1O2 for CER are provided in FIG. 17 and 18, respectively; while the polarization curves and specific activities for Ir02 coated with increasing ALD cycles of T1O2 for CER are provided in FIG. 19 and 20, respectively. The overpotentials of FTO coated with increasing ALD cycles of T1O2 for CER are provided in FIG. 21; while the polarization curves and specific activities for FTO coated with increasing ALD cycles of T1O2 for OER are provided in FIG. 22 and 23, respectively.
[0089] It will be understood that various modifications may be made without departing from the spirit and scope of this disclosure. Accordingly, other embodiments are within the scope of the following claims .

Claims

WHAT IS CLAIMED IS:
1. A method to manufacture a heterogeneous electrocatalyst that has improved electrocatalytic activity for an electrochemical reaction, comprising:
layering or depositing one or more thin films of one or more conductive and/or semiconductive catalytic materials onto a surface of a conductive electrocatalytic substrate by using 1 to 100 cycles of an atomic layer deposition process,
wherein the composition of the one of more thin films is different from the composition of the conductive electrocatalytic substrate ,
wherein the number of cycles of the atomic layer deposition process is used to tune the electrocatalytic activity of the heterogeneous electrocatalysts for the electrochemical reaction, and wherein the electrocatalytic activity of the
heterogeneous electrocatalyst for the electrochemical reaction is improved in comparison to the electrocatalytic activity of the conductive electrocatalytic substrate.
2. The method of claim 1, wherein the one or more thin films are comprised of metals, alloys, metal oxides, metal nitrides, metal sulfides, metal fluorides, or a combination thereof.
3. The method of claim 1 or claim 2, wherein the one or more thin films are comprised of metal oxides.
4. The method of any one of the preceding claims, wherein the one of more thin films comprise one or more oxides selected from A1203, NH4OSbW, Sb205, BaO, BaTi03, BaZr03, Al6BeOi0, BeO, Bi203, Bi205, B2O3, CdO, CaO, Ce203, Ce02, CrO, Cr203, Cr02, Cr03, CoO, Co203, Cu205Yb2, Cu20, CuFe204, CuO, GaO, Ga203, GeO, Ge02, Au20, Au203, Hf02, ln20, InO, ln203, lr203, Ir02, Fe304, FeO, Fe203, PbO, Pb02, Li20, Al2Mg04, MgO, Mn304, MnO, Mn203, Mn02, Mn205, Mn207, Hg20, HgO, Mo02, Mo03, Mo205, NiFe204, NiO, Ni203, LiNb03, NaNb03, Nb203, Nb205, Os203, Os03, Os04, PdO, Pd02, (C6H5)AsO, Pt304, PtO, Pt203, K20, Re207, Re04, Rh203, Rb20, Ru02, Ru04, Sc203, Se304, Ag20, Na20, SrO, NaTa03, Ta203, Ta205, Si02, SnO, Sn02, SrTi03, TiO, Ti203, Ti02, WC1202, W203, W02, W03, W205, VOCl2, VO, V203, V02, V205, Yb203, YBa2Cu307, Y203, ZnO, Zr02, fluorine doped tin oxide, iron doped titanium oxide, W03 doped ZnO, Fe doped Ce02, tin doped Fe3C>4, and indium tin oxide.
5. The method of any one of the preceding claims, wherein the one or more thin films comprise Ti02.
6. The method of any one of the preceding claims, wherein 1 to
50 cycles of an atomic layer deposition process are used to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate.
7. The method of any one of the preceding claims, wherein 1 to 25 cycles of an atomic layer deposition process are used to deposit or layer one or more thin films onto a surface of the conductive electrocatalytic substrate.
8. The method of any one of the preceding claims, wherein 1 to
15 cycles of an atomic layer deposition process are used to deposit or layer a thin film of Ti02 onto a surface of the conductive electrocatalytic substrate.
9. The method of any one of the preceding claims, wherein the one or more thin films are made from one or more precursors used in the atomic layer deposition process selected from aluminum tris (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , triisobutylaluminum, trimethylaluminum, tris (dimethylamido) aluminum ( I I I ) ,
triphenylantimony (III) , tris (dimethylamido) antimony (III) ,
triphenylarsine, Triphenylarsine oxide, barium bis (2,2, 6,6- tetramethyl-3, 5-heptanedionate) hydrate, barium nitrate,
Ba(C9H23N3)2[CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
[Ba (C5 (CH3) 5) 2] -2 (C4H80) , [Ba (C5 (C3H7) 3H2) 2] -2 (C4H80) , bis (acetato- O) triphenylbismuth (V) , triphenylbismuth, tris (2- methoxyphenyl) bismuthine, triisopropyl borate, triphenylborane , tris (pentafluorophenyl) borane, cadmium acetylacetonate , calcium bis(6,6,7,7,8,8,8, -heptafluoro-2 , 2-dimethyl-3, 5-octanedionate ) , calcium bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , bis (cyclopentadienyl ) chromium (II),
bis (pentamethy1cyclopentadienyl ) chromium (II), chromium (III) tris (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
bis (cyclopentadienyl) cobalt (II) ,
bis (pentamethylcyclopentadienyl ) cobalt (II) , copper
bis(6,6,7,7,8,8, 8-heptafluoro-2 , 2 -dimethyl-3 , 5-octanedionate) , copper bis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) ,
tris (dimethylamido) gallium (III) , germanium ( IV) fluoride, hexaethyldigermanium ( IV) , tetramethylgermanium, tributylgermanium hydride, triethylgermanium hydride, triphenylgermanium hydride, bis (tert-butylcyclopentadienyl) dimethylhafnium (IV) ,
bis (trimethylsilyl) amidohafnium (IV) chloride,
dimethylbis (cyclopentadienyl) hafnium (IV) ,
tetrakis (diethylamido) hafnium ( IV) ,
tetrakis (dimethylamido) hafnium ( IV) ,
tetrakis (ethylmethylamido) hafnium ( IV) , [1,1'- bis (diphenylphosphino) ferrocene ] tetracarbonylmolybdenum ( 0 ) , bis (pentamethylcyclopentadienyl ) iron ( I I ) , 1,1' -diethyl ferrocene , iron(0) pentacarbonyl, iron(III) tris (2, 2, 6, 6-tetramethyl-3, 5- heptanedionate ) , bis (cyclopentadienyl) magnesium (II) ,
bis (pentamethylcyclopentadienyl) magnesium,
Mg(C6Hi6N2) [CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis (pentamethylcyclopentadienyl ) manganese (II) ,
bis (tetramethylcyclopentadienyl) manganese (II) ,
bromopentacarbonylmanganese (I) , cyclopentadienylmanganese (I) tricarbonyl, ethylcyclopentadienylmanganese ( I ) tricarbonyl, manganese(O) carbonyl, (bicyclo [ 2.2.1 ] hepta-2 , 5- diene) tetracarbonylmolybdenum ( 0 ) ,
bis (cyclopentadienyl ) molybdenum ( IV) dichloride,
cyclopentadienylmolybdenum ( I I ) tricarbonyl dimer,
molybdenumhexacarbonyl , (propylcyclopentadienyl ) molybdenum ( I ) tricarbonyl dimer, allyl (cyclopentadienyl) nickel (II) ,
bis (cyclopentadienyl) nickel (II) ,
bis (ethylcyclopentadienyl) nickel (II) , nickel (II) bis (2,2, 6,6- tetramethyl-3, 5-heptanedionate) , bis (cyclopentadienyl) niobium (IV) dichloride, trimethyl (methylcyclopentadienyl ) platinum ( IV) , dirhenium decacarbonyl , (acetylacetonato) (1,5- cyclooctadiene ) rhodium ( I ) , (acetylacetonato) (1,5- cyclooctadiene ) rhodium (I) , bis (cyclopentadienyl) ruthenium ( II ) , bis (ethylcyclopentadienyl) ruthenium ( II ) ,
bis (pentamethylcyclopentadienyl) ruthenium ( 11 ) , triruthenium dodecacarbonyl, Sr (C9H23N3) 2 [CxHyC (O) CHC (O) CxHy] 2 (x=3-4, y=2x+l), pentakis (dimethylamino) tantalum (V) , tantalum (V) ethoxide,
tris (diethylamido) (tert-butylimido) tantalum (V) ,
tris (ethylmethylamido) (tert-butylimido) tantalum (V) ,
Ta(C2H50)4[CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis [bis (trimethylsilyl) amino] tin (II) , dibutyldiphenyltin,
hexaphenylditin (IV) , tetraallyltin, tetrakis (diethylamido) tin (IV) , tetramethyltin, tetravinyltin, tin (II) acetylacetonate ,
trimethyl (phenylethynyl ) tin, trimethyl (phenyl) tin, tetrakis
(dimethylamido) titanium (IV) (TDMAT) ,
tetrakis (ethylmethylamido) titanium ( IV) , titanium ( IV)
diisopropoxidebis (2,2, 6, 6-tetramethyl-3 , 5-heptanedionate) , titanium tetrachloride, titanium (IV) isopropoxide ,
Ti(OC3H7)2[CxHyC(0)CHC(0)CxHy]2 (x=3-4, y=2x+l),
bis (butylcyclopentadienyl ) tungsten ( IV) diiodide, bis (tert- butylimino) bis (tert-butylamino) tungsten, bis (tert- butylimino) bis (dimethylamino) tungsten (VI) ,
bis (cyclopentadienyl) tungsten (IV) dichloride,
bis (cyclopentadienyl) tungsten (IV) dihydride,
bis (isopropylcyclopentadienyl) tungsten (IV) dihydride,
cyclopentadienyltungsten ( I I ) tricarbonyl hydride,
tetracarbonyl (1, 5-cyclooctadiene) tungsten (0) , triamminetungsten (IV) tricarbonyl, tungsten hexacarbonyl ,
bis (cyclopentadienyl ) vanadium ( 11 ) ,
bis (cyclopentadienyl ) vanadium ( I I ) , vanadium (V) oxytriisopropoxide , bis (pentafluorophenyl) zinc, bis (2,2, 6, 6-tetramethyl-3 , 5- heptanedionato) zinc ( II ) , diethylzinc, and diphenylzinc .
10. The method of any one of the preceding claims, wherein the one or more thin films are made from a precursor of tetrakis
(dimethylamido) titanium ( IV) used in the atomic layer deposition process .
11. The method of any one of the preceding claims, wherein the conductive electrocatalytic substrate is at least 100 nm in thickness .
12. The method of any one of the preceding claims, wherein the conductive electrocatalytic substrate is at least 10 μπ\ in
thickness .
13. The method of any one of the preceding claims, wherein the conductive electrocatalytic substrate is comprised of a conductive material, semiconductive material and/or superconductive material.
14. The method of any one of the preceding claims, wherein the conductive electrocatalytic substrate is comprised of a metal oxide .
15. The method of any one of the preceding claims, wherein the conductive electrocatalytic substrate is comprised of a metal oxide selected from A1203, NH4OSbW, Sb205, BaO, BaTi03, BaZr03, Al6BeOi0, BeO, Bi203, Bi205, B203, CdO, CaO, Ce203, Ce02, CrO, Cr203, Cr02, Cr03, CoO, Co203, Cu205Yb2, Cu20, CuFe204, CuO, GaO, Ga203, GeO, Ge02, Au20, Au203, Hf02, ln20, InO, ln203, lr203, Ir02, Fe304, FeO, Fe203, PbO, Pb02, Li20, Al2Mg04, MgO, Mn304, MnO, Mn203, Mn02, Mn205, Mn207, Hg20, HgO, Mo02, Mo03, Mo205, NiFe204, NiO, Ni203, LiNb03, NaNb03, Nb203, Nb205, Os203, Os03, Os04, PdO, Pd02, (C6H5)AsO, Pt304, PtO, Pt203, K20, Re207, Re04, Rh203, Rb20, Ru02, Ru04, Sc203, Se304, Ag20, Na20, SrO, NaTa03, Ta203, Ta205, Si02, SnO, Sn02, SrTi03, TiO, Ti203, Ti02, WC1202, W203, W02, W03, W205, V0C12, VO, V203, V02, V205, Yb203, YBa2Cu307, Y203, ZnO, Zr02, fluorine doped tin oxide, iron doped titanium oxide, W03 doped ZnO, Fe doped Ce02, tin doped Fe304, and indium tin oxide.
16. The method of any one of the preceding claims, wherein the conductive electrocatalytic substrate is comprised of Ir02 or Ru02.
17. The method of any one of the preceding claims, wherein the electrochemical reaction is selected from the group consisting of the chlorine evolution reaction, the oxygen evolution reaction, the hydrogen evolution reaction, the carbon dioxide reduction reaction, the electrochemical water splitting reaction, the nitrogen reduction reaction and the oxygen reduction reaction.
18. The method of any one of the preceding claims, wherein the electrochemical reaction is the oxygen evolution reaction or the chlorine evolution reaction.
19. The method of any one of the preceding claims, wherein the heterogeneous electrocatalyst exhibits a lower overpotential or improved specific activity for the chemical reaction than the conductive electrocatalytic substrate.
20. The method of any one of the preceding claims, wherein the heterogeneous electrocatalyst exhibits has a more favorable surface charge distribution for the chemical reaction than the conductive electrocatalytic substrate.
21. A heterogeneous electrocatalyst made by the method of any one of the preceding claims.
22. The heterogeneous electrocatalyst of claim 21, wherein the heterogeneous electrocatalyst comprises a conductive
electrocatalytic substrate of IrC>2, FTO, or Ru02.
23. The heterogeneous electrocatalyst of claim 21 or claim 22, wherein the heterogeneous electrocatalyst comprises a thin film of Ti02.
24. The heterogeneous electrocatalyst of any one of claims 21 to 23, wherein the thin film of T1O2 is less than 1 nm in thickness.
25. An electrode comprising the heterogeneous electrocatalyst of any one of claims 21 to 24.
26. The electrode of claim 25, wherein the electrode is used generate reactive chloride species in a wastewater treatment system.
PCT/US2017/054040 2016-09-28 2017-09-28 Tuning electrode surface electronics with thin layers Ceased WO2018064347A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201662401045P 2016-09-28 2016-09-28
US62/401,045 2016-09-28

Publications (1)

Publication Number Publication Date
WO2018064347A1 true WO2018064347A1 (en) 2018-04-05

Family

ID=61687205

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2017/054040 Ceased WO2018064347A1 (en) 2016-09-28 2017-09-28 Tuning electrode surface electronics with thin layers

Country Status (2)

Country Link
US (1) US20180087164A1 (en)
WO (1) WO2018064347A1 (en)

Families Citing this family (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3679177B1 (en) * 2017-09-07 2024-11-06 The Trustees of Princeton University Binary alloys and oxides thereof for electrocatalytic reduction of carbon dioxide
US20210147987A1 (en) * 2018-04-11 2021-05-20 Haskoli Islands Electroreduction of carbon dioxide on transition metal oxide catalysts
CN108840369B (en) * 2018-06-15 2020-05-05 湖南工业大学 α -manganese dioxide, preparation method thereof and electrocatalyst
US10981819B2 (en) * 2018-06-28 2021-04-20 Fluent Technologies, Llc Variable pulsed ionic waste stream reclamation system and method
KR20210113234A (en) * 2018-12-17 2021-09-15 캘리포니아 인스티튜트 오브 테크놀로지 Antimonate electrocatalyst for electrochemical reactions
US11702756B2 (en) 2019-02-26 2023-07-18 King Fahd University Of Petroleum And Minerals Cobalt oxide film upon electron sink
CN110148763B (en) * 2019-04-24 2021-06-11 南京师范大学 Preparation method and application of Fe-doped Mn3O4 carbon-nitrogen material with hollow nano-framework structure
US11473193B2 (en) 2019-04-30 2022-10-18 King Fahd University Of Petroleum And Minerals Fabrication, characterization and photoelectrochemical properties of CeO2-TiO2 thin film electrodes
CN111029564B (en) * 2019-12-10 2022-11-29 河南创力新能源科技股份有限公司 Preparation method of iron negative electrode material of iron-nickel secondary battery
CN114377682B (en) * 2020-10-22 2023-06-30 陕西科技大学 Self-supporting electrocatalytic material and preparation method thereof
CN113235105B (en) * 2021-02-07 2022-03-25 中国船舶重工集团公司第七一八研究所 Modification optimization method of iridium dioxide catalyst
JP7733242B2 (en) * 2021-11-29 2025-09-02 インテグリス・インコーポレーテッド Organometallic compounds and methods for preparing same
US12577122B2 (en) 2022-08-05 2026-03-17 Imam Abdulrahman Bin Faisal University Superconducting material and method of preparation thereof
CN118271372A (en) * 2022-12-30 2024-07-02 华为技术有限公司 Precursor material, precursor composition and method for depositing film layer
CN116516394B (en) * 2023-03-24 2026-03-31 浙江大学 A two-dimensional ferroelectric electrocatalyst supported on single-atom Ag
CN117326761B (en) * 2023-11-22 2026-03-31 山东默同生态有限公司 An electrocatalytic oxidation device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110009679A1 (en) * 2006-08-07 2011-01-13 Rappe Andrew M Tunable ferroelectric supported catalysts and method and uses thereof
US20110045969A1 (en) * 2003-09-17 2011-02-24 Uchicago Argonne, Llc Subnanometer and nanometer catalysts, method for preparing size-selected catalysts
WO2013144631A1 (en) * 2012-03-30 2013-10-03 Johnson Matthey Fuel Cells Limited Thin film catalytic material for use in fuel
US20150247258A1 (en) * 2014-02-28 2015-09-03 The Board Of Trustees Of The Leland Stanford Junior University Functionalized Graphene-Pt composites for fuel cells and photoelectrochemical cells

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070243452A1 (en) * 2006-04-14 2007-10-18 Applied Materials, Inc. Reliable fuel cell electrode design
US20110053020A1 (en) * 2007-11-09 2011-03-03 Washington State University Research Foundation Catalysts and related methods
US8319208B2 (en) * 2008-10-02 2012-11-27 Zettacore Ip, Inc. Methods of forming thin films for molecular based devices
JP5686988B2 (en) * 2009-05-04 2015-03-18 シャープ株式会社 Catalyst layer used for membrane electrode assembly for fuel cell, membrane electrode assembly for fuel cell using the same, fuel cell, and production method thereof

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110045969A1 (en) * 2003-09-17 2011-02-24 Uchicago Argonne, Llc Subnanometer and nanometer catalysts, method for preparing size-selected catalysts
US20110009679A1 (en) * 2006-08-07 2011-01-13 Rappe Andrew M Tunable ferroelectric supported catalysts and method and uses thereof
WO2013144631A1 (en) * 2012-03-30 2013-10-03 Johnson Matthey Fuel Cells Limited Thin film catalytic material for use in fuel
US20150086902A1 (en) * 2012-03-30 2015-03-26 Johnson Matthey Fuel Cells Limited Thin film catalytic material for use in fuel
US20150247258A1 (en) * 2014-02-28 2015-09-03 The Board Of Trustees Of The Leland Stanford Junior University Functionalized Graphene-Pt composites for fuel cells and photoelectrochemical cells

Also Published As

Publication number Publication date
US20180087164A1 (en) 2018-03-29

Similar Documents

Publication Publication Date Title
US20180087164A1 (en) Tuning electrode surface electronics with thin layers
Akbashev et al. Activation of ultrathin SrTiO 3 with subsurface SrRuO 3 for the oxygen evolution reaction
US11230775B2 (en) Non-noble metal based electro-catalyst compositions for proton exchange membrane based water electrolysis and methods of making
Moriau et al. Supported iridium‐based oxygen evolution reaction electrocatalysts‐recent developments
Zhao et al. Regulation of perovskite surface stability on the electrocatalysis of oxygen evolution reaction
Schipper et al. Effects of catalyst phase on the hydrogen evolution reaction of water splitting: preparation of phase-pure films of FeP, Fe2P, and Fe3P and their relative catalytic activities
Kreider et al. Nitride or oxynitride? Elucidating the composition–activity relationships in molybdenum nitride electrocatalysts for the oxygen reduction reaction
Gayen et al. Pyrochlores for advanced oxygen electrocatalysis
Plate et al. On the origin of the OER activity of ultrathin manganese oxide films
Qin et al. Manganese as electron reservoir stabilized RuMnO x@ RuO x with enhanced activity and robust durability for acidic water oxidation
Kim et al. Low-temperature atomic layer deposition of cobalt oxide as an effective catalyst for photoelectrochemical water-splitting devices
Dong et al. Noble-metal-free metal oxides for catalyzing acidic oxygen and hydrogen evolution reactions: recent developments and future perspectives
Strotkötter et al. Discovery of high-entropy oxide electrocatalysts: from thin-film material libraries to particles
Wei et al. Controlling the cation exsolution of perovskite to customize heterostructure active site for oxygen evolution reaction
Irshad et al. High catalytic activity of amorphous Ir-Pi for oxygen evolution reaction
Pickrahn et al. ALD of ultrathin ternary oxide electrocatalysts for water splitting
Siddiqi et al. Stable water oxidation in acid using manganese-modified TiO2 protective coatings
KR20080024988A (en) Electrolytic electrode, electrolytic method using same and electrolytic device using same
Yoshida et al. Photocatalytic CO2 reduction using a pristine Cu2ZnSnS4 film electrode under visible light irradiation
Arunachalam et al. Effective Corrosion‐Resistant Single‐Atom Alloy Catalyst on HfO2‐Passivated BiVO4 Photoanode for Durable (≈ 800 h) Solar Water Oxidation
Kim et al. Multimetallic nanostructures for electrocatalytic oxygen evolution reaction in acidic media
Park et al. Atomic layer deposition of iridium using a tricarbonyl cyclopropenyl precursor and oxygen
Palaniappan et al. Hydrogen evolution reaction kinetics on electrodeposited Pt-M (M= Ir, Ru, Rh, and Ni) cathodes for ammonia electrolysis
Chen et al. Hierarchical superhydrophilic/superaerophobic Ni (OH) 2@ NiFe-PBA nanoarray supported on nickel foam for boosting the oxygen evolution reaction
Wu et al. Efficient modulation of electrocatalyst interfaces by atomic layer deposition: Fundamentals to application

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 17857427

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 17857427

Country of ref document: EP

Kind code of ref document: A1