WO2019241717A1 - Réseaux de microfeuilles à base de ni5p4 pris en sandwich entre du phosphure métallique hiérarchique utilisés en tant qu'électrocatalyseurs robustes à ph universel destinés à une génération efficace d'hydrogène - Google Patents

Réseaux de microfeuilles à base de ni5p4 pris en sandwich entre du phosphure métallique hiérarchique utilisés en tant qu'électrocatalyseurs robustes à ph universel destinés à une génération efficace d'hydrogène Download PDF

Info

Publication number
WO2019241717A1
WO2019241717A1 PCT/US2019/037329 US2019037329W WO2019241717A1 WO 2019241717 A1 WO2019241717 A1 WO 2019241717A1 US 2019037329 W US2019037329 W US 2019037329W WO 2019241717 A1 WO2019241717 A1 WO 2019241717A1
Authority
WO
WIPO (PCT)
Prior art keywords
catalyst
cop
microsheet
current density
electrode
Prior art date
Application number
PCT/US2019/037329
Other languages
English (en)
Inventor
Zhifeng Ren
Haiqing Zhou
Ishwar Kumar MISHRA
Shuo Chen
Luo Yu
Original Assignee
University Of Houston System
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 University Of Houston System filed Critical University Of Houston System
Publication of WO2019241717A1 publication Critical patent/WO2019241717A1/fr

Links

Classifications

    • 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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • 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
    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
    • 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 herein is related to the field of HER electro-catalysts; and more particularly to hierarchical metal phosphide-sandwiched Ni 5 P 4 -based microsheet arrays as robust PH-universal electro-catalysts for efficient hydrogen generation, and methods of making the same.
  • Hydrogen produced by water electrolysis is a clean energy carrier, which can be regarded as a potential alternative to fossil fuels.
  • Water dissociation for hydrogen production via electrolysis requires highly active catalysts to minimize the overpotentials.
  • Platinum (Pt)-based materials are the most active electrocatalysts for hydrogen evolution reaction (HER).
  • the noble-metal based catalysts are not suitable for large-scale application due to their high cost and limited availability on the earth’s crust.
  • 5,6 For sustainable and clean hydrogen economy, highly active and affordable catalysts based on earth-abundant materials have to be developed.
  • Noble metal-free materials including metal sulfides, selenides, phosphides, etc., have been widely explored for catalyzing HER. 7 10 Among them, transition-metal phosphides (TMPs) have been receiving attention due to their promising catalytic activity for HER in water splitting.
  • TMPs transition-metal phosphides
  • an ideal electro- catalyst is expected to exhibit outstanding catalytic HER activity over a wide pH range (0-14) like Pt, considering the abundant sources of water on earth, and different water electrolysis technologies with different demands on the pH values of the electrolytes.
  • very few non-noble electro-catalysts can be simultaneously robust in catalyzing the HER in both acidic and alkaline media.
  • developing robust catalysts with pH universality or PH independence, and long-term durability at high current densities remains challenging.
  • Electro-catalysts are further prone to diminished catalytic performances with varying electrolytes and pH values, and many electro-catalysts require complicated preparation procedures, which are difficult to reproduce, and therefore unsuited to industrial application.
  • a new method of producing robust pH-universal HER catalysts is therefore disclosed herein, which are further suitable for commercial use.
  • the HER catalysts disclosed provide improved hydrogen generation in acid or base, and are stable at extremely large current densities such as above 500 mA cm 2 .
  • the disclosure herein relates in some embodiments to a three dimensional hydrogen evolution reaction (HER) catalyst as disclosed herein, and comprises a porous Ni foam support; a Ni 5 P 4 -Ni 2 P scaffold positioned on the support; a first layer of a metal phosphide (M X P) positioned on a first side of the Ni 5 P 4 -Ni 2 P scaffold; and a second layer of the metal phosphate (M X P) positioned on a second side of the Ni 5 P 4 - Ni 2 P scaffold to form a M x P/Ni 5 P 4 /M x P microsheet array.
  • HER three dimensional hydrogen evolution reaction
  • the metal phosphide (M X P) is selected from the group consisting of Co, Ni, and Fe or a combination thereof, and in a further embodiment x is equal to 1 , 2, or 1/2.
  • the microsheet array comprises CoP/Ni 5 P 4 /CoP, and in other embodiments the M x P/Ni 5 P 4 /M x P microsheet array comprises mesoporous pores; in further embodiments the mesoporous pores are between 0.001 nm and 50 nm in diameter; and in still further embodiments the M x P/Ni 5 P 4 /M x P microsheet array comprises surface active sites for HER.
  • the catalyst is pH independent for catalyzing hydrogen evolution reaction (HER) from water splitting; in other embodiments the catalyst comprises an overpotential of about 71 mv at a current density of about 10 mA cm 2 in an alkaline electrolyte; in a further embodiment the catalyst comprises an overpotential of about 33mv at a current density of about 10 mA cm 2 in an acid electrolyte; and in some embodiments, the catalyst has at least one of: a low onset potential, large cathode current density, small Tafel slopes, or large exchange current density.
  • HER hydrogen evolution reaction
  • the M x P/Ni 5 P 4 /M x P microsheet comprises a about to 7.43 c 10 7 mol/cm 2 active sites; and in another embodiment the catalyst comprises TOF values of between 0.453 and 1.220 s 1 at overpotentials of between 75 and 100 mV.
  • Some embodiments herein disclosed provide a method of making a three dimensional hydrogen evolution reaction (HER) catalyst, comprising: positioning a porous Ni foam support, phosphorizing said Ni foam support, and forming a Ni 5 P 4 - Ni 2 P scaffold; soaking said scaffold in a Mc-ink, phosphorizing said Mc-ink; and forming a M x P/Ni 5 P 4 /M x P microsheet array comprising the three dimensional hydrogen evolution reaction (HER) catalyst.
  • phosphorizing of the Ni foam support is in an Ar atmosphere, and in another embodiment phosphorizing the Ni foam support at about 500 °C.
  • the Mc-ink is Co-ink
  • the method further comprising dissolving cobalt nitrate hexahydrate [Co(N0 3 ) 2 -6H 2 0] in N,N dimethylformamide (DMF) to form said Co-ink.
  • an electrode comprising: a three dimensional Hydrogen Evolution Reaction (HER) catalyst, wherein said electrode comprises: a porous Ni foam support; a Ni 5 P 4 -Ni 2 P scaffold positioned on the support; a first layer of a metal phosphide (M X P) positioned on a first side of the Ni 5 P 4 -Ni 2 P scaffold; and a second layer of the metal phosphate (M X P) positioned on a second side of the Ni 5 P 4 -Ni 2 P scaffold to form a M x P/Ni 5 P 4 /M x P microsheet array, wherein said catalyst has at least one of: a low onset potential, a large cathode current density, a small Tafel slopes or a large exchange current density, at either of an alkaline or acidic pH.
  • HER Hydrogen Evolution Reaction
  • the a low onset potential is between -10 and 200 mV; a large cathode current density is between -10 mV at 10 mA/cm 2 to about -120 mV at 10 mA/cm 2 ; a small Tafel slopes is between 10 mV/dec to about 100 mV/dec; and a large exchange current density is between 10 to about 1000 pA/cm 2 .
  • the electrode comprises a large 3-D porous surface area.
  • Figure 1 depict a synthetic scheme of sandwich-like CoP/Ni 5 P 4 /CoP electrocatalyst
  • (a and e) show SEM images of Ni foam used as the starting electrode material.
  • (b,f) show SEM images of nickel phosphide nanosheet arrays after the first synthetic step
  • (c) Diagram showing nickel phosphide nanosheets on Ni foam that was soaked in cobalt precursor ink prepared by dissolving cobalt nitrate hexahydrate [Co(N0 3 ) 2 .6H 2 0] in DMF.
  • (d,g) show SEM images of hierarchical CoP/Ni 5 P 4 /CoP microsheet arrays after the third synthetic step;
  • Figure 2 depict the morphology and chemical composition of CoP/Ni 5 P 4 /CoP electro-catalyst
  • a-c show SEM images of CoP/Ni 5 P 4 /CoP electrode
  • HRTEM image shows crystalline Ni 5 P 4 at the inner structure of CoP/Ni 5 P 4 /CoP electrode.
  • the Fast Fourier Transform (FFT) in the inset demonstrates the crystal structure of Ni 5 P 4.
  • FFTs in the inset of (e) and (f) demonstrate the amorphous and crystalline structures of CoP, respectively;
  • Figure 3 depict the characterization of the CoP/Ni 5 P 4 /CoP microsheet arrays electrode
  • Figure 4 (a-f) depict Electro-catalytic measurements of different electrodes for hydrogen evolution in acid
  • Figure 5 depict Electrochemical performance of CoP/Ni 5 P 4 /CoP microsheet arrays electrode in 1.0 M KOH.
  • Figure 6 depicts SEM images of CoP/Ni 5 P 4 /CoP samples prepared with Co- ink concentrations of (a, d) 0.4 g/ml, (b, e) 0.25 g/ml, and (c, f) 0.1 g/ml;
  • Figure 7 depicts A typical SEM image showing the sandwich-like structures of CoP/Ni 5 P 4 /CoP when CoP particles are in-situ grown on the surfaces of nickel phosphide nanosheet arrays.
  • the dark and light arrows indicate the CoP and Ni 5 P 4 nanosheet parts, respectively;
  • Figure 8 depicts SEM images of samples prepared with annealing in the absence of phosphorus at the third step of synthesis (a, b) before electrochemical test; and (c) after electrochemical test in 0.5 M H 2 S0 4 ;
  • Figure 9 depicts at image (a) and (b) SEM images of a sample prepared at 600 °C at the third step of synthesis, showing a high resolution SEM image on the right side;
  • Figure 10 depicts a comparison of the SEM morphologies between original Ni 5 P 4 -Ni 2 P/Ni and CoP/Ni 5 P 4 /CoP catalysts
  • Figure 1 1 depicts the distribution of mesopore sizes of the sandwich-like CoP/Ni 5 P 4 /CoP electrocatalysts measured by the BJH method
  • Figure 12 depicts EDS elemental mapping images of the as-prepared CoP/Ni 5 P 4 /CoP.
  • (a) HAADF (b) Co
  • Figure 13 depicts a comparison of the XRD patterns of the nickel phosphide nanosheets after the 2 nd phosphorization or 1 st phosphorization at 500 °C without cobalt ink, and CoP/Ni 5 P 4 /CoP using cobalt ink;
  • Figure 14 depicts a comparison of XRD patterns between the samples prepared with and without phosphorus source at the third synthetic step
  • Figure 15 depicts a XPS survey spectra of as-prepared CoP/Ni 5 P 4 /CoP electrode
  • Figure 16 depicts SEM images of the as-prepared CoP/Ni 5 P 4 /CoP sample.
  • A- B showing protruded parts of nickel phosphide nanosheets after phosphorization at the third synthetic step, with a high resolution SEM image on the right side (B);
  • Figure 17 depicts an image of a three-electrode setup for electrochemical tests, wherein, in some embodiments a graphite rod or graphite paper was used as the counter electrode;
  • Figure 18 depicts plots of the electrochemical performance of CoP/Ni 5 P 4 /CoP samples prepared with different concentrations of Co-ink, showing (a) polarization curves, and (b) corresponding Tafel plots of the samples in (a).
  • Figure 19 depicts plots of the electrochemical performance comparison between samples prepared with annealing in the absence of phosphorus at the third step of synthesis and Ni 5 P 4 -NiP 2 /Ni support in 0.5 M H 2 S0 4, (a) shows polarization curves., and (b) shows the corresponding Tafel plots of the samples in (a);
  • Figure 20 depicts plots of the electrochemical performance comparison between samples prepared at 500 °C and 600 °C at the third step of synthesis (a) Polarization curves (b) Corresponding Tafel plots of the samples in (a);
  • Figure 21 depicts CV curves recorded on the CoP/Ni 5 P 4 /CoP electrode in the potential ranges between -0.2 V vs RHE and 0.6 V vs RHE in 1 M PBS, wherein the he scan rate was 50 mV s 1 ;
  • Figure 22 depicts TOF values of the CoP/Ni 5 P 4 /CoP electrode varied with the HER potentials
  • Figure 23 depicts a simplified Randles model used to fit the EIS data
  • Figure 24 depicts the electrochemical measurements of the double-layer capacitance of different electrodes, wherein (a) is Ni 5 P 4 -Ni 2 P/Ni., and (b) is CoP/Ni 5 P 4 /CoP; [0040]
  • Figure 25 depicts SEM images of as-prepared CoP/Ni 5 P 4 /CoP sample; (a, and b) are before electrochemical testing, and (c, and d) are after electrochemical test in 0.5 M H 2 S0 4 , b and d are high resolution SEM images;
  • Figure 26 depicts XRD patterns of the CoP/Ni 5 P 4 /CoP electrode before and after electrochemical test in 0.5 M H 2 S0 4 ;
  • Figure 27 depicts high resolution XPS spectra of as-prepared CoP/Ni 5 P 4 /CoP sample (a-c) are before electrochemical testing, and (d-f) are after electrochemical testing in 0.5 M H 2 S0 4 ;
  • Figure 28 depicts measuring the gas products and determining the corresponding Faradaic efficiency using a gas chromatography (GC) technique.
  • GC gas chromatography
  • Figure 29 (A-B) depicts a schematic illustration of (a) the fabrication procedure of the self-supported 3D Ni2(1-x)Mo2xP electrode, and (b) highly porous nanowire arrays for a hydrogen evolution reaction, as described herein;
  • Figure 30 depicts the morphology and chemical composition analyses of Ni2(1 -x)Mo2xP; and SEM images of (a) NiMo04 xH20 precursor, and (b, c) Ni2(1- x)Mo2xP at different magnifications, (d, e) TEM images of Ni2(1-x)Mo2xP. (f) XRD pattern of Ni2(1 -x)Mo2xP.
  • Figure 31 depicts (a) a XPS survey, and a high-resolution XPS spectra of (b) Ni 2p, (c) P 2p, and (d) Mo 3d of the Ni2(1-x)Mo2xP and a Ni2P electrode;
  • Figure 32 depicts a HER performance conducted in 1 M KOH, wherein (a) depicts polarization curves, (and b) depicts the current density at the overpotential of 300 mV, and (c) Tafel plots and calculated exchange current density (jO) of the electrodes (d) Polarization curves of the Ni 2(1-X) Mo 2x P/NF electrode before and after 5000 CV cycles (e) Time dependence of the current density for the Ni 2(1-X) Mo 2x P/NF electrode under constant potentials of -1 10, -170, and -220 mV;
  • Figure 33 depicts DFT calculations (a) Chemisorption models of H 2 0 adsorption, OH adsorption, and H adsorption for the calculated free energies.
  • TS represents a transition state of H 2 0 activation
  • Adsorption free energy of H 2 0 (DEH20)
  • Figure 34 (A-D) depicts the overall water splitting performance in 1 M KOH.
  • (a) is a schematic illustration of the electrolyzer using Ni 2(1-X) Mo 2x Pand Cu@NiFe LDH as cathode and anode, respectively. Polarization curves at (b) low, and (c) high current density. (The benchmark electrodes of lr02(+)/Pt(-) are tested the same way.)
  • the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean“including, but not limited to...
  • the term“couple” or“couples” is intended to mean either an indirect, direct, optical or wireless electrical connection.
  • a first device couples to a second device, that connection may be through a direct engagement of the devices, through an indirect connection via other intermediate devices and connections, through an optical electrical connection, or through a wireless electrical connection.
  • R R L +k * (Ru-R L ), wherein k is a variable ranging from 1 percent to 100 percent with a 1 percent increment, i.e., k is 1 percent, 2 percent, 3 percent, 4 percent, 5 percent, ... 50 percent, 51 percent, 52 percent, ... , 95 percent, 96 percent, 97 percent, 98 percent, 99 percent, or 100 percent.
  • any numerical range defined by two R numbers as defined in the above is also specifically disclosed.
  • Use of the term "optionally” with respect to any element of a claim is intended to mean that the subject element is required, or alternatively, is not required. Both alternatives are intended to be within the scope of the claim.
  • Use of broader terms such as comprises, includes, having, etc. should be understood to provide support for narrower terms such as consisting of, consisting essentially of, comprised substantially of, etc.
  • This catalyst is a sandwich-like construct where in some embodiments cobalt phosphide (CoP) nanoparticles serve as the thin skin covering both sides of nickel phosphide (Ni 5 P 4 ) nanosheet arrays, and forming self-supported sandwich-like CoP/Ni 5 P 4 /CoP microsheet arrays with lots of mesopores and macropores.
  • CoP cobalt phosphide
  • the as-prepared electro-catalyst requires an overpotential of 33 mV to achieve the benchmark 10 mA cm 2 with a very large exchange current density, and high turnover frequencies (TOFs) in acid media (which is superior to most electro- catalysts made of metal phosphides, well-known MoS 2 , and WS 2 catalysts, and performs comparably with the state-of-the-art Pt catalysts).
  • TOFs turnover frequencies
  • this electro- catalyst shows impressive operational stability at extremely large current densities of up to 1 A cm 2 , indicating its suitability for large-scale water electrolysis.
  • this electrocatalyst is very active in alkaline electrolyte (71 mV at 10 mA cm 2 ), which demonstrates its pH universality as a HER catalyst with outstanding catalytic activity. This method does not involve any solvothermal and hydrothermal process, paving a new avenue to design robust non-noble electro-catalysts for hydrogen production toward commercial water electrolysis.
  • the as-prepared electrocatalyst requires an overpotential of only 33 mV to achieve the benchmark 10 mA cm 2 with very large exchange current density, and high turnover frequencies (TOFs) in acid media, which is superior to most electrocatalysts made of metal phosphides, well-known MoS 2 , and WS 2 catalysts, and performs comparably with the state-of-the-art Pt catalysts.
  • this electrocatalyst shows impressive operational stability at extremely large current densities of 1 A cm 2 , indicating its possible application toward large- scale water electrolysis.
  • this electrocatalyst is very active in alkaline electrolyte (71 mV at 10 mA cm 2 ), which demonstrates its pH universality as a HER catalyst with outstanding catalytic activity.
  • This simple strategy does not involve any solvothermal and hydrothermal process, paving a new avenue to design robust non- noble electrocatalysts for hydrogen production toward commercial water electrolysis.
  • the electro-catalyst disclosed herein requires overpotentials of only 33 and 85 mV to achieve current densities of 10 and 100 mA cm 2 respectively, with a relatively small Tafel slope of 43 mV dec 1 and large exchange current density of 1.71 mA cm 2 , and exhibits large surface area and simultaneous large turnover frequencies (TOF) of 0.453 and 1.22 s 1 at 75 and 100 mV overpotentials respectively, outperforming most efficient non-noble-metal HER electrocatalysts.
  • TOF simultaneous large turnover frequencies
  • this robust catalyst shows excellent durability at high current density of 1 A cm 2 .
  • the as-prepared CoP/Ni 5 P 4 /CoP microsheet arrays electrode only requires 71 mV to deliver 10 mA cm 2 in 1 M KOH, and also exhibits good durability at 30 and 500 mA cm 2 , demonstrating its pH universality for efficient hydrogen production.
  • Ni fi P4-Ni ? P nanosheet array support on Ni foam The as-obtained commercial Ni foam was in some embodiments cut into 1 cm 2 regular pieces, one piece of 1 cm 2 Ni foam was placed in the tube furnace, which was heated to 500 °C quickly and kept at this temperature for around 1 hour for thermal phosphorization in argon atmosphere. The red phosphorus powder was used as the phosphorus source put in at the upstream. After material growth, shut down of the power of the tube furnace occurred and naturally cooled under argon protection.
  • CoP/N PVCoP microsheet arrays electro-catalyst The cobalt precursor ink was prepared by dissolving cobalt nitrate hexahydrate [CO(N0 3 ) 2 .6H 2 0] in N,N dimethylformamide (DMF), then the nickel phosphide nanosheet arrays on Ni foam (Ni 5 P 4 -Ni 2 P/Ni) was soaked in the Co-ink and dried at ambient condition. The dried sample was then thermally phosphorized at 500 °C in a tube furnace with the red phosphorus powder placed at upstream, which resulted in the formation of hierarchical CoP/Ni 5 P 4 /CoP microsheet arrays.
  • DMF N,N dimethylformamide
  • Nitrogen adsorption measurements The electro-catalyst microsheet array samples were firstly dried in vacuum at 373 K for 12 h before measurement. Nitrogen adsorption-desorption isotherms were tested at 77 K by a Quantachrome Autosorb-iQ BET surface analyzer. The specific surface area was evaluated from the BET method, and the distribution of pore sizes was analyzed by the BJH method.
  • Electrochemical measurements were carried out at room temperature via a three-electrode configuration using Gamry Instruments, Reference 600. An 82 ml_ 0.5 M H 2 S0 4 was added into the cell for HER as acidic electrolyte, and 100 ml of 1 .0 M KOH was used for HER as alkaline electrolyte. Saturated calomel electrode (SCE) and Hg/HgO electrode were used as the reference electrodes in acidic and alkaline electrolytes, respectively. Graphite foil (Alfa Aesar) was used as the counter electrode and the self-supported catalysts were directly connected with the working electrode.
  • SCE saturated calomel electrode
  • Hg/HgO electrode were used as the reference electrodes in acidic and alkaline electrolytes, respectively.
  • Graphite foil Alfa Aesar
  • the catalytic performance was studied by collecting the polarization curves under a sweep rate of 2 mV s 1 with the potentials ranging from 0.050 V to - 0.150 V vs RHE.
  • High-purity anhydrous N 2 gas (Matheson, 99.9999%) was used to purge the system for 30 minutes before any measurements.
  • the catalyst was continuously cycled for over 1000 cycles at a scan rate of 50 mV s 1 , so as to check its electrochemical stability.
  • Electrochemical tests were performed at room temperature and the curves were reported with iR compensation.
  • TOF turnover frequency
  • the physical variables F, n, and / represent the Faraday constant ( ⁇ 96485 C/mol), active site density (mol), and the current (A) during hydrogen evolution in 0.5 M H 2 S0 4 , respectively.
  • the factor 1/2 is because water electrolysis requires two electrons to evolve one hydrogen molecule from two protons.
  • F and Q correspond to the Faraday constant and the whole charge of CV curve, respectively.
  • the number of active sites for this sandwich-like catalyst CoP/Ni 5 P 4 /CoP is close to 7.43 c 10 7 mol/cm 2 .
  • the TOF values are calculated to be around 0.453 and 1.220 s 1 for the CoP/Ni 5 P 4 /CoP catalyst at overpotentials of 75 and 100 mV, respectively.
  • Faradaic efficiency determination A technique based on gas chromatography (GC) 1 was used to quantify the gas products and then the Faradaic efficiency under a constant current density of -50 mA cm 2 . Every 10 min, a glass syringe was used to carefully take 0.3 ml_ gas product from the sealed cell and injected it into the GC instrument (GOW-MAC 350 TCD) (Hamilton Gastight 1002). Based on this technique, H 2 gas was found to be the only product in experiment, and at nearly the same amount as that by theoretical calculations, supposing that each electron was utilized for H 2 generation.
  • GC gas chromatography
  • Ni foam was thermally phosphorized at 500 °C in a tube furnace using red phosphorous (P) to form nickel phosphide nanosheet arrays as demonstrated by the scanning electron microscopy (SEM) images in Figure 1 b and 1f.
  • SEM scanning electron microscopy
  • the nickel phosphide nanosheet arrays on Ni foam was soaked in the Co-ink and dried at ambient condition (Figure 1 (c)).
  • the cobalt (Co) precursor ink was prepared by dissolving cobalt nitrate hexahydrate [CO(N0 3 ) 2 .6H 2 0] in N,N-Dimethylformamide (DMF).
  • the firmly constructed structure ( Figure 1 b and 1f) as well as hydrophilic nature of the nickel phosphide nanosheets facilitated to develop a uniform coverage of the nanosheets by Co precursor ink.
  • the dried sample was thermally phosphorized again at 500 °C, leading to the formation of a unique structure of hierarchical CoP/Ni 5 P 4 /CoP microsheet arrays electrode, as revealed by the SEM images in Figure 1 d and 1 g.
  • Figure 1 shows: a synthetic scheme of sandwich-like Cop/Ni 5 P 4 /CoP electrocatalyst.
  • (a,e) show SEM images of Ni foam used as the starting electrode material
  • (b, f) show SEM images of nickel phosphide nanosheet arrays after the first synthetic step
  • (c) is a diagram showing nickel phosphide nanosheets on Ni foam that was soaked in cobalt precursor ink prepared by dissolving cobalt nitrate hexahydrate [Co(N0 3 ) 2 .6H 2 0] in DMF
  • (d,g) show an SEM images of hierarchical CoP/Ni 5 P 4 /CoP microsheet arrays after the third synthetic step.
  • the role of phosphorus was examined, wherein a sample was also prepared by annealing in the absence of phosphorus source at the third step for comparison.
  • a notably different morphology was observed in the absence of phosphorus source ( Figure 8 (a, b) ESI ⁇ ), which in some embodiments may be due to formation of a different chemical compound of cobalt.
  • the morphology variation with temperature was also investigated by phosphorization at 600 °C at the third step of synthesis.
  • Figure 2 Shows the morphology and chemical composition of CoP/Ni 5 P 4 /CoP electro-catalyst (a-c) depicts SEM images of CoP/Ni 5 P 4 /CoP electrode; (d) depicts an HRTEM image showing crystalline Ni 5 P 4 at the inner structure of CoP/Ni 5 P 4 /CoP electrode, and the Fast Fourier Transform (FFT) in the inset demonstrates the crystal structure of Ni 5 P 4. (e, f), HRTEM images showing amorphous as well as crystalline CoP at the outer structure of CoP/Ni 5 P 4 /CoP electrode. The FFTs in the inset of (e) and (f) demonstrate the amorphous and crystalline structures of CoP, respectively.
  • a-c depicts SEM images of CoP/Ni 5 P 4 /CoP electrode
  • (d) depicts an HRTEM image showing crystalline Ni 5 P 4 at the inner structure of CoP/Ni 5 P 4 /CoP electrode, and the Fast Four
  • the high-resolution transmission electron microscopy (HRTEM) image in Figure 2 (d) clearly demonstrates that the nickel phosphide nanosheets are highly crystallized with the lattice fringe spacings of 0.207 nm and 0.298 nm corresponding to the (224) and (020) planes of Ni 5 P 4 crystals, respectively. Accordingly, the outer coverage of the electrode indicates a mixed structure showing that a small fraction is crystallized corresponding to the (220) and ( ⁇ 2 ⁇ ) planes of CoP crystals, along with amorphous CoP as revealed by HRTEM images in Figure 2 (e) and 2 (f).
  • the energy dispersive spectroscopy (EDS) elemental mapping confirms the uniform distribution of Co and P along with a small fraction of Ni, with atomic ratio of Co:P to be 1 :0.93, which is very close to the 1 :1 ratio as CoP, indicating the formation of CoP in the as-prepared electrode ( Figure 12, ESI ⁇ ).
  • the small fraction of Ni in the EDS mapping could be either from Ni 5 P 4 that remained while peeling off the cobalt phosphide from the electrode during TEM sample preparation or from diffusion of Ni from inner support during synthesis.
  • Powder X-ray diffraction was employed to further characterize the phase composition of the samples and to determine the rough atomic ratio of different elements.
  • the XRD patterns from the as-prepared nanosheet arrays demonstrate a mixture of nickel phosphides: mainly Ni 5 P 4 and minor Ni 2 P and a small amount of metallic Ni ( Figure 3 (a)), suggesting that the original Ni foam was not fully transformed to nickel phosphide.
  • the XRD pattern of the electrode prepared with re-phosphorization after step 3 shows mostly Ni 5 P 4, along with a small shoulder around 48° of the 2-theta position corresponding to the CoP phase.
  • Ni 2 P and Ni after re- phosphorization may result from the diffusion of P source into the nickel and nickel phosphide converting them to Ni 5 P 4 phase.
  • a second phosphorization of nickel phosphide nanosheet samples in the same conditions as that of CoP growth was performed.
  • the XRD pattern ( Figure 13, ESI ⁇ ) is the same as that with Ni 5 P 4 crystals, confirming the conversion of mixed Ni 5 P 4 /Ni 2 P/Ni phases to a high-purity Ni 5 P 4 phase during CoP growth.
  • the small peak of CoP in XRD patterns indicates the presence of only a small fraction of CoP crystals and the rest in some embodiments may be amorphous CoP, or in some embodiments may be because of the very thin thickness of CoP on top of Ni 5 P 4 , further supporting the mixed composition of CoP in the as-prepared hierarchical CoP/Ni 5 P 4 /CoP electrode as revealed by HRTEM images.
  • similar phase composition was noticed on the sample prepared by annealing only at the third synthetic step ( Figure 14, ESI ⁇ ), which indicates no further phase change of the nickel rich phosphides in the absence of additional P source.
  • Table 1 Detailed analysis of XPS binding energies of different elements for CoP/Ni 5 P 4 /CoP catalyst.
  • X-ray photoelectron spectroscopy was utilized to study the surface chemical composition of the samples. According to the high-resolution XPS spectra of the hierarchical CoP/Ni 5 P 4 /CoP arrays electrode, therefore providing clear identification of the presence of Co, P, and Ni ( Figure 3 (b-d), Figure 15 and Table 1 , ESI ⁇ ).
  • the Co core level peaks appear at binding energies (BEs) of 779.6 eV and 794.6 eV, corresponding to Co 2p 3/2 and 2p 1/2 of cobalt phosphide, respectively.
  • Ni core level peaks are also observed at the BEs of 857.7 eV and 875.0 eV, originating from the Ni 2p 3/2 and 2p 1/2 of surface oxidized nickel phosphide, respectively, which is possibly from the protruded nickel phosphide nanosheets ( Figure 16, ESI ⁇ ).
  • the protruded part in some embodiments is resulted from the formation of P- rich nickel phosphide (Ni 5 P 4 ) phases by diffused P during re-phosphorization, and such feature is observed only in a few regions of the electrode. Furthermore, the BE of Co 2p centered at 779.6 eV is positively shifted from the position of elemental Co (778.1-778.2 eV), and that of P 2p centered at 129.6 eV is negatively shifted from the position of elemental P (129.9 eV), which imply that the Co carries a partial positive charge (d + ) and the P carries a partial negative charge (d ) in CoP.
  • This metal center Co (d + ) and pendant base P (d ) in CoP resembles with hydrogenases and other metal complex HER catalysts, indicating the similar catalytic mechanism of CoP with them.
  • FIG. 1 Characterization of the CoP/Ni 5 P 4 /CoP microsheet arrays electrode
  • the CoP/Ni 5 P 4 /CoP electrocatalyst shows a fast increase of cathodic current density with increasing overpotentials, suggesting CoP/Ni 5 P 4 /CoP as a high- performance 3D cathode for hydrogen generation from water splitting.
  • the as-prepared hierarchical CoP/Ni 5 P 4 /CoP 3D electrode requires an overpotential of only 33 mV, which is very close to that of Pt (31 mV), and much lower than 293 mV for pure Ni foam and 79 mV for the Ni 5 P 4 - Ni 2 P/Ni support.
  • the phosphorization temperature at step 3 of synthesis plays a role in the morphologies of the hierarchical CoP/Ni 5 P 4 /CoP, which accordingly has great effects on the electrocatalytic HER activity, confirming that in some embodiments that 500 °C is the optimal temperature for growing this sandwich-like CoP/Ni 5 P 4 /CoP electrocatalyst ( Figure 20), wherein in some further embodiments, the electro-catalytic performance of CoP/Ni 5 P 4 /CoP grown at 500 °C is improved as compared to many of the highly efficient HER electrocatalysts reported recently (Table 2), including nanostructured Ni 2 P (105 mV), Mo-W-P/carbon cloth (100 mV), WS 2(i -x) Se 2x /NiSe 2 (88 mV), MoS 2(1.
  • Table 2 tabulates the catalytic performance of the as-obtained HER catalyst in comparison with other available non-precious catalysts in the literatures.
  • h ⁇ , /7-I 00, and /7-1000 are denoted as the overpotentials at current density of 10, 100, and 1000 mA cm 2 , respectively, and j 0 is the exchange current density.
  • NA Not applicable since not reported.
  • the symbol“” means that the value is extracted on the basis of the Tafel slope and overpotential at 10 mA cm 2 .
  • a Tafel slope of 43 mV dec 1 ( Figure 4 (b), derived from the polarization curve, indicates that the HER process by this CoP/Ni 5 P 4 /CoP electrode proceeds through Volmer-Heyrovsky mechanism.
  • the exchange current density to be 1.708 mA cm 2 for the CoP/Ni 5 P 4 /CoP catalyst (Table 2, ESI ⁇ ), which is significantly larger than most of the reported active catalysts based on transition metal chalcogenides including CoSe 2 , WP 2 nanowire/CC, and transition metal phosphides including CoP, Ni 2 P, and MoP particles can be extracted.
  • Table 3 shows the comparison of the catalytic parameters among the catalyst and other robust non-precious catalysts of embodiments of the electro- catalysts disclosed herein.
  • C di, ECSA, TOF 75 , and TOF 10o represent double-layer capacitance, electrochemical surface area, and turnover frequencies at overpotentials of 75 and 100 mV, respectively.
  • the TOF value of the electro-catalysts disclosed herein increases to 4 H 2 s 1 at only 135 mV ( Figure 22, ESI ⁇ ).
  • this sandwich-like CoP/Ni 5 P 4 /CoP is found to have a very low overpotential (33 mV), small Tafel slope (43 mV dec 1 ), extremely large exchange current density (1 .708 mA cm 2 ), and very large TOF of 4 H 2 s 1 at 135 mV,_suggesting its exceptional H 2 -evolving efficiency.
  • Figure 4. depicts electro-catalytic measurements of different electrodes for hydrogen evolution in acid
  • Table 4 provides a summary of the catalytic activities from the Ni 5 P 4 -Ni 2 P/Ni and CoP/Ni 5 P 4 /CoP electrodes yo, normalized is the normalized current density by relative surface area.
  • the electro-catalyst there is a large electrochemical surface area and roughness factor due to the presence of mesopores, nanosheet arrays and macropores of the catalyst (Table 3, ESI ⁇ ). Then the exchange current density (/o , normalized ) is further normalized by the C di values, which is a useful parameter to compare the intrinsic catalytic activity.
  • the CoP/Ni 5 P 4 /CoP electrode has a much higher electrode kinetics toward hydrogen evolution, which could be related to the following factors: (1 ) the strong contact of CoP with inner Ni 5 P 4 support that enables good mechanical and electrical connection, providing an easy pathway for electrons to flow during cathodic polarization; (2) increased and improved electrical conductivity of CoP, facilitating fast charge transport; and (3) the 3D structure along with highly porous feature of the interconnected nanostructures that enables greater exposure of active sites for hydrogen adsorption as well as easy diffusion pathways for the electrolyte and gaseous products.
  • Figure 5 shows the HER performance of CoP/Ni 5 P 4 /CoP in 1.0 M KOH (pl-M4).
  • the hierarchical CoP/Ni 5 P 4 /CoP requires only 71 and 140 mV of overpotentials to obtain the current densities of 10 and 100 mA cm 2 , respectively, along with the Tafel slope of 58 mV dec 1 .
  • the catalytic activity of as-prepared CoP/Ni 5 P 4 /CoP at a benchmark current density of 10 mA cm 2 in alkaline media compares favorably to the recently reported efficient non-noble-metal based HER catalysts, including NiS 2 /MoS 2 (204 mV), CoMoP (81 mV), (Co 1-x Fe x ) 2 P (79 mV), transition metal phosphides (Table 5).
  • NA Not applicable since not reported.
  • the symbol“” means that the value is extracted on the basis of the Tafel slope and overpotential at 10 mA cm 2 .
  • metal phosphosulfides are promising electrocatalysts for hydrogen generation for water splitting in acid or base, however, the best of these prior art catalysts still require an overpotential of 48 mV to reach the benchmark current density 10 mA cm 2 in acid, which is not a efficient as the CoP/Ni 5 P 4 /CoP catalysts described herein (33 mV), and such catalysts have much lower Tafel slope, and faster increase of the geometric current density with the overpotential, lower overpotential (71 mV) to reach 10 mA cm 2 , for hydrogen generation at wide pH ranges.
  • a highly efficient HER electrocatalyst developed by a facile synthetic approach.
  • the as-prepared hierarchical CoP/Ni 5 P 4 /CoP microsheet arrays electrode is binder free, self-supported 3D architecture that can be directly used as a cathode for HER.
  • the CoP/Ni 5 P 4 /CoP microsheets arrays electrode shows Pt-like activity for HER catalysis with reasonable operational stability at high current density in acidic as well as alkaline electrolytes.
  • the outstanding HER catalytic activity of this electrode is related to the good mechanical and electrical connection between CoP catalyst and Ni 5 P 4 support, numerous active sites and high intrinsic catalytic activity of the sandwich-like CoP/Ni 5 P 4 /CoP electrode.
  • Herein disclosed is a new self-supported 3D robust HER catalysts for large-scale hydrogen production via water splitting.
  • an efficient HER catalyst functions in an alkaline environment under a large current density. It is of immense importance to accelerate gas releasing from the catalyst surface for large-current-density water splitting, which makes way for more active sites. This can be achieved by integrating 1 D nanorods or nanowires (NWs) into 3D hierarchical architectures on conductive substrates which not only enhances the gas releasing but also maximizes the surface area and accelerates the electron transfer. Meanwhile, it also avoids the use of polymer binders and ensures robust contacts. Furthermore, porous materials are extremely favorable for catalytic reactions due to their large surface area and rich active sites.
  • a novel 3D hierarchical catalyst consisting of highly porous Ni 2(i-x )Mo 2x P nanowire arrays on Ni foams for efficient HER under large-current-density in alkaline electrolyte are also disclosed herein.
  • the well-aligned nanowire arrays on the Ni foam make the ternary Ni 2(1 -x) Mo 2x P catalyst as an integrated 3D electrode, where the Ni foam works as an efficient current collector and the highly conductive Ni 2(1-x) Mo 2x P nanowires provides a continuous pathway for electron transfer.
  • the highly porous nanowires with a rough surface offer a large active surface area with numerous active sites and rapid release of H 2 . More importantly, density functional theory (DFT) calculations determine that the free energy of water activation and hydrogen adsorption is optimized for the Ni 2(1 -x) Mo 2x P catalyst.
  • DFT density functional theory
  • NiMo0 4 xH 2 0 nanowire arrays were grown on Ni foams (NF) via a hydrothermal method. Then the as-prepared NiMo0 4 xH 2 0 nanowire arrays were transformed to ternary Ni 2(1-x) Mo 2x P through a one-step phosphorization reaction.
  • the NF was treated in HCI solution (3 M) for several minutes, which generates a rough surface for strong adhesion of active materials, as the scanning electron microscopy (SEM) image shown in Figure 30 (a) which shows the SEM images of NiMo0 4 xH 2 0 precursor, revealing uniform coverage of vertical nanowire arrays on the entire NF.
  • SEM scanning electron microscopy
  • XRD X-ray diffraction
  • EDX energy dispersive X-ray
  • a series of Ni 2(1-x) Mo 2x P nanowire arrays were synthesized on the NF under different temperatures and phosphorus (P) amounts to optimize the phosphorization process.
  • Figure 30 (b and c) show the SEM images of N ⁇ 2(1-c) Mo 2c R sample prepared under 500 °C with 100 mg P at low and high magnifications, respectively. From Figure 30 (b), it can observe that the bimetallic phosphide maintains the vertically aligned nanowire morphology and integration feature of the precursor after phosphorization. The well aligned nanowire arrays grown on the NF will offer efficient diffusion pathways for electrolyte and open channels for gaseous products to be released. Figure 30 (c) reveals that the nanowires present a cuboid shape with a rough surface.
  • the cross-sectional SEM images further show that the nanowires are vertically grown on the Ni foam, and the thickness of the nanowire layer are ⁇ 10 pm.
  • Transmission electron microscopy (TEM) images in Figure 30 (d and e) further reveal that the nanowires are highly porous with many tiny pores inside.
  • Figure 30 (e) also exhibit the extremely rough surface of the nanowires. Such highly porous and rough nanostructures are beneficial to catalytic reactions by providing more exposed active sites.
  • Figure 30 (f) shows the XRD pattern of Ni2(1-x)Mo2xP, which is consistent with the standard Ni2P pattern (JCPDS No. 89-2742; the tiny peak around 53.8° was attributed to the NiMo04 precursor.)
  • High-resolution TEM (HRTEM) image in Figure 30 (g) reveals apparent lattice fringes with an inter-planar spacing of 0.225 nm, which is assigned to the (1 1 1 ) plane of Ni 2(i-x) Mo 2x P.
  • SAED selected- area electron diffraction
  • Figure 30 (h) further verifies the diffraction spots of different planes of the well crystallized Ni 2(i-x) Mo 2x P.
  • Figure 1 (i) shows the scanning TEM (STEM) image and corresponding EDX elemental mapping images of Ni, Mo, and P, confirming the existence and uniform distribution of the three elements in the whole nanowires.
  • the atomic ratio of Ni: Mo: P was determined to be 1 : 0.97: 0.91 by the inductively coupled plasma optical emission spectrometry (ICP- OES) (See: Luo et al.,“Ternary Ni 2(1 -x) Mo 2x P Nanowire Arrays toward Efficient and Stable Hydrogen Evolution Electrocatalysis under Large-Current-Density”, Nano Energy 53, 492-500 (2016) incorporated herein in its entirety by reference).
  • ICP- OES inductively coupled plasma optical emission spectrometry
  • Ni 2 P was also synthesized on the Ni foam via the same phosphorization method of Ni(OH)2 under 500 °C with 100 mg P.
  • X-ray photoelectron spectroscopy (XPS) measurements were then conducted to investigate the surface composition and chemical valence states of the Ni 2(1-x) Mo 2x P and Ni 2 P samples.
  • the XPS survey spectra confirm the presence of Ni, Mo, and P elements for Ni 2(1-x) Mo 2x P, while only Ni and P elements for Ni 2 P.
  • the high-resolution XPS spectra of Ni 2p show two spin- orbit doublets along with two shakeup satellites (identified as“Sat.”) for the two samples.
  • the two spin-orbit doublets are located at binding energies (BEs) of 854.6 and 872.4 eV, which are assigned to the Ni 2p3/2 and Ni 2p1/2 of Ni-P, respectively.
  • BEs binding energies
  • the two spin-orbit doublets slightly shift to the lower BEs at 854.1 and 871.9 eV for the Ni2(1-x)Mo2xP, suggesting an electronic structure change due to Mo substitution.
  • the two small peaks at BEs of 856.4 and 874.8 eV for the Ni2P correspond to the Ni-POx due to the surface oxidation of Ni 2 P in air.
  • the HER activity of as-prepared catalysts was evaluated in 1 M KOH in a typical three-electrode cell comprising a graphite foil as the counter electrode.
  • the activity of various Ni 2(1-x) Mo 2x P electrodes prepared under different temperatures and P amounts were first assessed.
  • the inset in Figure 3a displays the HER performance at current densities up to 100 mA cm 2 , showing that the ternary Ni 2(1-x) Mo 2x P catalyst at disclosed herein yields current densities of 10 and 100 mA cm 2 at overpotentials of 72 and 162 mV, respectively, exhibiting a much higher activity than that of NiMo04 (263 and 446 mV) and Ni2P (167 and 279 mV).
  • TMPs catalysts including MoP 2 (194 and 260 mV) [45], (Co1 -xFex)2P (79 and 178 mV) and CoMoP (81 and 165 mV), TMDs catalysts including MoS 2 /Ni 3 S 2 (98 and 191 mV), NixCo3-xS4/Ni3S2 (136 and 258 mV), Cu@CoS x (134 and 267 mV), and other non-noble metal catalysts for the alkaline HER.
  • Embodiments of the 3D Ni 2(i-x) Mo 2x P electrode presented herein exceeds the Pt wire when the current density is larger than 188 mA cm 2 , and it delivers current densities of 500 and 1000 mA cm-2 at overpotentials of 240 and 294 mV, respectively.
  • Figure 31 (b) presents a comparison of current density at overpotential of 300 mV for the electrodes.
  • the 3D Ni 2(1-x) Mo 2x P electrode achieves a current density of 1077 mA cm 2 at overpotential of 300 mV, which is about 58 and 7.7 times that of NiMo04 (18.5 mA cm 2 ) and Ni2P (140 mA cm 2 ), respectively, as well as 90% higher than that of commercial Pt wire (566 mA cm-2).
  • the Tafel plots of Figure 31 (c) shows that the 3D N ⁇ 2( ⁇ - c) Mo 2c R electrode has a Tafel slope of 46.4 mV dec-1 , which is close to that of the Pt wire (36.9 mV dec-1 ) and much smaller than that of NiMo0 4 (106 mV dec-1 ) and Ni2P(89.6 mV dec-1 ).
  • Stability is also a pivotal criterion in evaluating the performance of an electrocatalyst, especially for large-scale water electrolysis.
  • CV cyclic voltammetry
  • Ni 2(1-x) Mo 2x P electrode possesses a Cdl of 51.2 mF cm 2 , which is nearly 1 .3 times that of Ni 2 P (39.4 mF cm 2 ) and 3.22 times that of NiMo0 4 (16.2 mF cm 2 ), indicating a large ECSA with more exposure of active sites.
  • Electrochemical impedance spectroscopy was then used to study the catalytic kinetics of the catalysts.
  • Ni 2(1-x) Mo 2x P electrodes of embodiments herein exhibit a much smaller charge transfer resistance (Ret) of ⁇ 1 .5 W, in contrast to 3.1 W of Ni 2 P and 13.3 W of NiMo0 4 , revealing favorable electron transport and fast catalytic kinetics. Meanwhile, all the three electrodes possess small series resistances (Rs), suggesting good electrical contacts with the substrate.
  • the small Ret was closely related to the excellent conductivity of Ni 2(1 -x) Mo 2x P, which was further demonstrated by the electronic band structures calculated by the density function theory (DFT).
  • DFT density function theory
  • the adopted structure for the Ni 2(1-x) Mo 2x P and Ni 2 P was hexagonal in some embodiments, and in some embodiments both compounds show no band gap, indicating a metallic nature, thus beneficial for electron transfer.
  • the HER in alkaline media mainly involves two typical processes, namely, the Volmer step (equation 1 a) for H 2 0 adsorption and activation (cleavage of O-H bonds to form H atoms adsorbed on surface of catalysts, H * ), and the Heyrovsky step (equation 2a) for H * combination and H 2 release, which was called Volmer- Heyrovsky pathway:
  • Cat. refers to catalysts. Therefore, further DFT calculations were conducted to assess the free energies of H 2 0 adsorption, H 2 0 activation, OH adsorption, and H adsorption on the (0001 ) surface of Ni 2 P and Ni 2(1-x) Mo 2x P to deeply understand the nature of high HER activity of the Ni 2(1-x) Mo 2x P catalyst.
  • the atomic ratio of Ni, Mo, and P in the Ni 2(1 -x) Mo 2x P is around 1 :1 :1 , so a NiMoP hexagonal structure was used for calculation, and two possibilities with Ni exposure and Mo exposure were considered.
  • FIG 33 (a) further displays the chemisorption models of H 2 0 adsorption, OH adsorption and H adsorption on the (0001 ) surface of Ni 2 P and NiMoP.
  • Figure 33 (c) shows the H 2 0 activation energy for cleavage of O-H bonds on the (0001 ) surfaces of Ni 2 P and NiMoP. It is clear that the NiMoP catalyst, especially for the Mo exposed surface, has a much lower H 2 0 activation energy than that of Ni 2 P. Thus, the Volmer step of H 2 0 adsorption and activation is more favorable for the Ni 2(1-x) Mo 2x P catalyst, while relatively sluggish for the Ni 2 P.
  • Figure 4d shows the free energy diagram for H adsorption (AGH) on the (0001 ) surfaces of Ni 2 P and NiMoP.
  • the Mo exposed NiMoP has a lowest
  • Ni 2(1-x) Mo 2x P catalysts in 1 M KOH was found to deliver current densities of 50 and 100 mA cm 2 at overpotentials of 323 and 346 mV, respectively.
  • OER catalysts of Cu nanowires which support NiFe layered double hydroxide nanosheets (Cu@ NiFe LDH) however had an output current densities of 50 and 100 mA cm 2 at overpotentials of 244 and 281 mV, respectively. Therefore, some embodiments combined the disclosed 3D ternary Ni 2(i - X) MO 2x P electrode with an Cu@NiFe LDH catalyst to build an alkaline electrolyzer for overall water splitting (Figure 34 (a)).
  • the electrolyzer delivers a current density of 10 mA cm 2 at a small voltage of 1.51 V at room temperature, which is lower than the benchmark of Ir02/Pt.
  • embodiments of the HER catalyst Ni 2(1-x) Mo 2x P and OER catalyst Cu@NiFe LDH disclosed herein are very promising for large-scale water electrolysis.
  • embodiments of the 3D ternary Ni 2(1-x) Mo 2x P porous nanowire arrays supported on Ni foams as disclosed herein are highly efficient and stable electrocatalysts for HER in alkaline media.
  • the 3D porous nanowire structures endow the catalyst with abundant active sites and open channels for gas releasing, and the good electrical conductivity of the bimetallic phosphide ensures the fast electron transfer.
  • ternary Ni 2(1-x) Mo 2x P owns optimal free energy of water activation and hydrogen adsorption on the surface.
  • embodiments of the 3D ternary catalyst exhibits outstanding HER performance in alkaline electrolytes, especially at large-current-density, outperforms the commercial Pt wire and almost all the other alkaline HER catalysts. Pairing of the HER catalyst with OER catalyst of Cu@NiFe LDH, the electrolyzer also enables excellent performance for overall water splitting.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Catalysts (AREA)

Abstract

L'invention concerne un électrocatalyseur actif et durable à pH universel destiné à la catalyse de la réaction de dégagement d'hydrogène (HER) à partir de la dissociation de l'eau. Les catalyseurs formés par croissance de nanoparticules de phosphure métallique hiérarchiques en tant que revêtements minces recouvrant les deux côtés de réseaux de nanofeuilles de phosphure de nickel ((Ni5P4) en vue de former des réseaux de microfeuilles de type sandwich ΜχΡ/Νί5Ρ4/ΜχΡ autonomes sont constitués de mésopores et de macropores.
PCT/US2019/037329 2018-06-15 2019-06-14 Réseaux de microfeuilles à base de ni5p4 pris en sandwich entre du phosphure métallique hiérarchique utilisés en tant qu'électrocatalyseurs robustes à ph universel destinés à une génération efficace d'hydrogène WO2019241717A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US201862685660P 2018-06-15 2018-06-15
US62/685,660 2018-06-15

Publications (1)

Publication Number Publication Date
WO2019241717A1 true WO2019241717A1 (fr) 2019-12-19

Family

ID=68843228

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US2019/037329 WO2019241717A1 (fr) 2018-06-15 2019-06-14 Réseaux de microfeuilles à base de ni5p4 pris en sandwich entre du phosphure métallique hiérarchique utilisés en tant qu'électrocatalyseurs robustes à ph universel destinés à une génération efficace d'hydrogène

Country Status (1)

Country Link
WO (1) WO2019241717A1 (fr)

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111437847A (zh) * 2020-05-22 2020-07-24 北京化工大学 一种分层有序多孔镍钴双金属磷化物纳米材料的制备方法
CN111495399A (zh) * 2020-05-08 2020-08-07 桂林理工大学 一种s掺杂wp2纳米片阵列电催化剂及其制备方法
CN111575729A (zh) * 2020-04-22 2020-08-25 广东工业大学 一种具有多层级孔洞结构的磷化镍复合物及其制备方法和应用
CN111889111A (zh) * 2020-08-14 2020-11-06 北方民族大学 具有三维异质结构的整体式光催化剂及其制备方法和应用
CN112044458A (zh) * 2020-08-21 2020-12-08 广东工业大学 一种多层级金属磷化物及其制备方法和应用
CN112614994A (zh) * 2020-12-10 2021-04-06 三峡大学 一种水系锌钴电池叠层正极材料的制备方法
CN112746285A (zh) * 2021-01-15 2021-05-04 武汉科技大学 一种焦磷酸氧钒-磷化镍纳米复合催化剂及其制备方法和应用
CN112951613A (zh) * 2021-02-01 2021-06-11 中国科学技术大学 一种电极材料及其制备方法和应用
CN113005469A (zh) * 2021-01-27 2021-06-22 浙江大学衢州研究院 一种钌负载无定型的氢氧化镍/磷化镍复合电极及其制备方法和应用
CN113089014A (zh) * 2021-04-07 2021-07-09 西南石油大学 一种核壳结构超亲水超疏气高效析氢催化剂及其制备方法
WO2021184563A1 (fr) * 2020-03-19 2021-09-23 苏州楚捷新材料科技有限公司 Procédé de préparation d'un catalyseur à base de nickel expansé pour la production d'hydrogène par électrolyse de l'eau
CN113481529A (zh) * 2021-07-07 2021-10-08 华中师范大学 一种铁、钴修饰的磷化镍纳米片阵列及其制备方法
CN113684497A (zh) * 2021-08-19 2021-11-23 武汉工程大学 一种泡沫铜负载镍钼磷基复合材料及其制备方法与应用
CN113699552A (zh) * 2021-08-26 2021-11-26 中南大学 一种磷酸钴三氧化钼复合纳米棒阵列三维电极材料及其制备方法与应用
CN113789543A (zh) * 2021-10-11 2021-12-14 北京化工大学 一种三维分层纳米阵列结构铜基材料及其制备方法和应用
CN114086205A (zh) * 2021-11-17 2022-02-25 中南大学 一种泡沫金属基改性材料的制备方法
CN114289043A (zh) * 2020-09-22 2022-04-08 新疆大学 一种自支撑多孔纳米板钴镍磷化物催化剂制备方法及应用
CN114481213A (zh) * 2022-02-25 2022-05-13 同济大学 一种低温磷化铂镍纳米合金团簇/碳催化剂及制备与应用
CN114574891A (zh) * 2022-03-29 2022-06-03 宁波大学 一种双金属共掺杂磷化镍纳米片的制备方法及用途
CN114990626A (zh) * 2022-07-11 2022-09-02 河北工业大学 一种Se掺杂Ni5P4材料的制备方法及其在新能源领域中的应用
CN115672356A (zh) * 2021-07-28 2023-02-03 天津工业大学 一种CoP/MoS2复合光催化剂的制备方法及应用

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180087163A1 (en) * 2015-03-31 2018-03-29 INL-International Iberian Nanotechnology Laboratory Method for manufacturing of a porous electrode material

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180087163A1 (en) * 2015-03-31 2018-03-29 INL-International Iberian Nanotechnology Laboratory Method for manufacturing of a porous electrode material

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MISHRA ET AL.: "Hierarchical CoP/Ni5P4/CoP microsheet arrays as a robust pH-universal electrocatalyst for efficient hydrogen generation", ENERGY & ENVIRONMENTAL SCIENCE, 25 May 2018 (2018-05-25), XP055662765 *

Cited By (30)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2021184563A1 (fr) * 2020-03-19 2021-09-23 苏州楚捷新材料科技有限公司 Procédé de préparation d'un catalyseur à base de nickel expansé pour la production d'hydrogène par électrolyse de l'eau
CN111575729A (zh) * 2020-04-22 2020-08-25 广东工业大学 一种具有多层级孔洞结构的磷化镍复合物及其制备方法和应用
WO2021213338A1 (fr) * 2020-04-22 2021-10-28 广东工业大学 Composite de phosphure de nickel avec une structure de pores multiniveau, son procédé de préparation, et son utilisation
CN111495399A (zh) * 2020-05-08 2020-08-07 桂林理工大学 一种s掺杂wp2纳米片阵列电催化剂及其制备方法
CN111495399B (zh) * 2020-05-08 2023-04-07 桂林理工大学 一种s掺杂wp2纳米片阵列电催化剂及其制备方法
CN111437847A (zh) * 2020-05-22 2020-07-24 北京化工大学 一种分层有序多孔镍钴双金属磷化物纳米材料的制备方法
CN111889111A (zh) * 2020-08-14 2020-11-06 北方民族大学 具有三维异质结构的整体式光催化剂及其制备方法和应用
CN111889111B (zh) * 2020-08-14 2023-03-31 北方民族大学 具有三维异质结构的整体式光催化剂及其制备方法和应用
CN112044458A (zh) * 2020-08-21 2020-12-08 广东工业大学 一种多层级金属磷化物及其制备方法和应用
CN112044458B (zh) * 2020-08-21 2021-07-20 广东工业大学 一种多层级金属磷化物及其制备方法和应用
CN114289043A (zh) * 2020-09-22 2022-04-08 新疆大学 一种自支撑多孔纳米板钴镍磷化物催化剂制备方法及应用
CN112614994A (zh) * 2020-12-10 2021-04-06 三峡大学 一种水系锌钴电池叠层正极材料的制备方法
CN112746285B (zh) * 2021-01-15 2024-02-20 武汉科技大学 一种焦磷酸氧钒-磷化镍纳米复合催化剂及其制备方法和应用
CN112746285A (zh) * 2021-01-15 2021-05-04 武汉科技大学 一种焦磷酸氧钒-磷化镍纳米复合催化剂及其制备方法和应用
CN113005469A (zh) * 2021-01-27 2021-06-22 浙江大学衢州研究院 一种钌负载无定型的氢氧化镍/磷化镍复合电极及其制备方法和应用
CN113005469B (zh) * 2021-01-27 2022-04-08 浙江大学衢州研究院 一种钌负载无定型的氢氧化镍/磷化镍复合电极及其制备方法和应用
CN112951613A (zh) * 2021-02-01 2021-06-11 中国科学技术大学 一种电极材料及其制备方法和应用
CN113089014A (zh) * 2021-04-07 2021-07-09 西南石油大学 一种核壳结构超亲水超疏气高效析氢催化剂及其制备方法
CN113481529A (zh) * 2021-07-07 2021-10-08 华中师范大学 一种铁、钴修饰的磷化镍纳米片阵列及其制备方法
CN115672356A (zh) * 2021-07-28 2023-02-03 天津工业大学 一种CoP/MoS2复合光催化剂的制备方法及应用
CN113684497A (zh) * 2021-08-19 2021-11-23 武汉工程大学 一种泡沫铜负载镍钼磷基复合材料及其制备方法与应用
CN113699552B (zh) * 2021-08-26 2022-07-29 中南大学 一种磷酸钴三氧化钼复合纳米棒阵列三维电极材料及其制备方法与应用
CN113699552A (zh) * 2021-08-26 2021-11-26 中南大学 一种磷酸钴三氧化钼复合纳米棒阵列三维电极材料及其制备方法与应用
CN113789543B (zh) * 2021-10-11 2022-08-02 北京化工大学 一种三维分层纳米阵列结构铜基材料及其制备方法和应用
CN113789543A (zh) * 2021-10-11 2021-12-14 北京化工大学 一种三维分层纳米阵列结构铜基材料及其制备方法和应用
CN114086205A (zh) * 2021-11-17 2022-02-25 中南大学 一种泡沫金属基改性材料的制备方法
CN114481213A (zh) * 2022-02-25 2022-05-13 同济大学 一种低温磷化铂镍纳米合金团簇/碳催化剂及制备与应用
CN114481213B (zh) * 2022-02-25 2023-08-29 同济大学 一种低温磷化铂镍纳米合金团簇/碳催化剂及制备与应用
CN114574891A (zh) * 2022-03-29 2022-06-03 宁波大学 一种双金属共掺杂磷化镍纳米片的制备方法及用途
CN114990626A (zh) * 2022-07-11 2022-09-02 河北工业大学 一种Se掺杂Ni5P4材料的制备方法及其在新能源领域中的应用

Similar Documents

Publication Publication Date Title
WO2019241717A1 (fr) Réseaux de microfeuilles à base de ni5p4 pris en sandwich entre du phosphure métallique hiérarchique utilisés en tant qu'électrocatalyseurs robustes à ph universel destinés à une génération efficace d'hydrogène
Liu et al. Metal–organic framework-derived hierarchical ultrathin CoP nanosheets for overall water splitting
Xu et al. A branch-like Mo-doped Ni 3 S 2 nanoforest as a high-efficiency and durable catalyst for overall urea electrolysis
Wang et al. Engineering NiF3/Ni2P heterojunction as efficient electrocatalysts for urea oxidation and splitting
Ramakrishnan et al. Rational design of multifunctional electrocatalyst: An approach towards efficient overall water splitting and rechargeable flexible solid-state zinc–air battery
Yuan et al. A universal synthesis strategy for single atom dispersed cobalt/metal clusters heterostructure boosting hydrogen evolution catalysis at all pH values
Liu et al. Highly conductive and metallic cobalt–nickel selenide nanorods supported on Ni foam as an efficient electrocatalyst for alkaline water splitting
Eisa et al. Nickel nanorods over nickel foam as standalone anode for direct alkaline methanol and ethanol fuel cell
Singh et al. Multi-walled carbon nanotube supported manganese selenide as a highly active bifunctional OER and ORR electrocatalyst
Yin et al. In-situ transformation obtained defect-rich porous hollow CuO@ CoZn-LDH nanoarrays as self-supported electrode for highly efficient overall water splitting
Hou et al. Promoting active sites in core–shell nanowire array as Mott–Schottky electrocatalysts for efficient and stable overall water splitting
Yu et al. Ternary nickel–iron sulfide microflowers as a robust electrocatalyst for bifunctional water splitting
Sidhureddy et al. Shape-controlled synthesis of Co 3 O 4 for enhanced electrocatalysis of the oxygen evolution reaction
Meng et al. In situ coupling of Co 0.85 Se and N-doped carbon via one-step selenization of metal–organic frameworks as a trifunctional catalyst for overall water splitting and Zn–air batteries
Yu et al. Hierarchical NiFeP microflowers directly grown on Ni foam for efficient electrocatalytic oxygen evolution
Zhang et al. Highly defective porous CoP nanowire as electrocatalyst for full water splitting
Liu et al. Cobalt phosphide supported by two-dimensional molybdenum carbide (MXene) for the hydrogen evolution reaction, oxygen evolution reaction, and overall water splitting
Zhu et al. Carbon-coated hollow mesoporous FeP microcubes: an efficient and stable electrocatalyst for hydrogen evolution
To et al. High-performance oxygen reduction and evolution carbon catalysis: From mechanistic studies to device integration
Zhu et al. Co 3 O 4 nanobelt arrays assembled with ultrathin nanosheets as highly efficient and stable electrocatalysts for the chlorine evolution reaction
Bian et al. Nickel iron phosphide ultrathin nanosheets anchored on nitrogen-doped carbon nanoflake arrays as a bifunctional catalyst for efficient overall water splitting
Yan et al. Oxygen defect-rich double-layer hierarchical porous Co3O4 arrays as high-efficient oxygen evolution catalyst for overall water splitting
Chang et al. A 3D hierarchical network derived from 2D Fe-doped NiSe nanosheets/carbon nanotubes with enhanced OER performance for overall water splitting
Zhao et al. Nanostructured NiMoO4 as active electrocatalyst for oxygen evolution
Peng et al. Zn doped ZIF67-derived porous carbon framework as efficient bifunctional electrocatalyst for water splitting

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: 19820367

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: 19820367

Country of ref document: EP

Kind code of ref document: A1