EP3775321A1 - Électroréduction de dioxyde de carbone sur des catalyseurs à base d'oxyde de métal de transition - Google Patents

Électroréduction de dioxyde de carbone sur des catalyseurs à base d'oxyde de métal de transition

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Publication number
EP3775321A1
EP3775321A1 EP19720060.3A EP19720060A EP3775321A1 EP 3775321 A1 EP3775321 A1 EP 3775321A1 EP 19720060 A EP19720060 A EP 19720060A EP 3775321 A1 EP3775321 A1 EP 3775321A1
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EP
European Patent Office
Prior art keywords
transition metal
cathode
metal oxide
crc
mnc
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EP19720060.3A
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German (de)
English (en)
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Egill SKULASON
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Haskoli Islands
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Haskoli Islands
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Publication of EP3775321A1 publication Critical patent/EP3775321A1/fr
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    • 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
    • C25B3/00—Electrolytic production of organic compounds
    • C25B3/20—Processes
    • C25B3/25—Reduction
    • 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
    • C25B11/0775—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 of the rutile type

Definitions

  • the invention is within the field of process chemistry, and specifically relating to the reduction of carbon dioxide with electrolytic methods, and new transition metal oxide catalysts therefor.
  • Cu electrode produces methane (40%), methanol (0.1 %), ethylene (25%), ethanol (10%) and propanol (4%). This shows that the Cu electrode is more efficient towards producing hydrocarbons than alcohols, and only insignificant amount of methanol is produced, which would be the most attractive product as transportation fuel.
  • TCM approach has been successfully applied on a number of electrochemical systems; including the water oxidation reaction on transition metal oxides (TMOs), the N2 electroreduction reaction on the surfaces of transition metals, transition metal nitrides, as well as transition metal oxides, hydrogen evolution reaction (HER) on transition metal nitrides and CO2RR on transition metals and TMOs.
  • TMOs transition metal oxides
  • HER hydrogen evolution reaction
  • the effect of the applied potential can be included implicitly using the computational hydrogen electrode (CHE; Norskov et al. J Phys Chem B (2004) 108, 17886-92).
  • CHE Norskov et al. J Phys Chem B (2004) 108, 17886-92
  • TMOs are used as catalysts for CO2RR than when the pure metal electrodes are used.
  • Experimental works have shown that some particular TMOs, especially RUO2, and RUO2 in combination with other transition metal oxides such as Ir0 2 , are active for CO2RR and more selective towards methanol formation than any of the pure metals tested so far.
  • metal oxide catalysts are more selective towards methanol, while pure metals are more selective towards methane and ethylene since there the oxygen atoms are reduced to water molecules. Therefore, metal oxides might open up new avenues for efficient liquid fuel production from CO2.
  • the present invention is based on the discovery that certain transition metal oxides are useful catalysts for CO2 reduction.
  • transition metal oxide catalysts may be employed in the electrochemical reduction of carbon dioxide. This has lead to the present invention, that makes possible to produce high-value products from carbon dioxide under various conditions, including at ambient room temperature and atmospheric pressure.
  • the invention provides a method for the electrolytic reduction of CO2, the method comprising steps of: (i) providing an electrolytic cell comprising at least one reaction chamber that comprises at least one anode and at least one cathode, wherein the at least one cathode comprises at least one catalyst surface comprising at least one transition metal oxide; (2) placing at least one electrolyte solution between the at least one anode and the at least one cathode, so that the at least one anode and the at least cathode come into contact with the electrolyte solution; (iii) providing CO2 in the electrolyte solution; and (iv) applying electrical potential to the electrolytic cell; whereby CO2 undergoes at least one reduction reaction at the cathode to provide at least one product selected from the group consisting of methanol, methane, methanediol and formic acid.
  • the transition metal oxide is selected from the group consisting of T1O 2 , HfC>2, OsC>2, RI7O2, CrC>2, NbC>2, MnC>2, PdC>2, Pt02, Re02, Zr02, VO2 and M0O2.
  • an electric potential that can preferably be a low applied potential such as a potential of less than -1.0 V, preferably less than -0.9 V, preferably less than -0.8 V, preferably less than -0.7 V, more preferably less than -0.6 V, more preferably at a potential of less than -0.5 V.
  • the applied potential can also be varied depending on the transition metal oxide being used in the catalyst, and the desired product(s), so as obtain desired reaction products for any given catalyst surface.
  • the cell can be operated at ambient conditions of temperature and pressure to produce the desired products, using protons provided by the electrolyte solution in the cell.
  • Another aspect of the invention thus relates to process for the catalytic reduction of carbon dioxide, comprising steps of (i) introducing CO 2 to a solution comprising at least one electrolyte in an electrolytic cell so that the CO 2 comes into contact with at least one cathode electrode surface; and (ii) applying a potential to said electrolytic cell, whereby CO 2 reacts with protons to form at least one product selected from methanol, methane, methanediol and formic acid; wherein the cathode electrode surface comprises at least one catalyst surface comprising at least one transition metal oxide.
  • the invention also provides a device for the reduction of CO 2 .
  • An aspect of the invention thus relates to an electrochemical device for the reduction of carbon dioxide to at least one reaction product, the device comprising at least one electrochemical cell that comprises an anode and a cathode, wherein the cathode comprises at least one cathode electrode having at least one catalyst surface comprising at least one transition metal oxide.
  • the at least one transition metal oxide can be selected from the group consisting of HfC>2, lrC>2, T1O2, OsC>2, RI7O2, CrC>2, NbC>2, MnC>2, PdC>2, Pt0 2 , ReC>2, ZrC>2, VO2 and M0O2.
  • the at least one transition metal oxide is selected from the group consisting of T1O2, RI7O2, CrC>2, M0O2, MnC>2, PdC> 2 and PtC> 2 .
  • the at least one transition metal oxide is selected from the group consisting of RhC>2, CrC>2, MnC>2, M0O2, PdC>2 and PtC>2.
  • the at least one transition metal oxide can also be selected from the group consisting of RhC> 2 , CrC> 2 , MnC> 2 , M0O2 and PdC>2 or RhC>2, CrC>2, MnC>2, and PdC>2.
  • the at least one transition metal oxide is selected from the group consisting of RhC> 2 , CrC> 2 , MoC> 2 and MnC> 2 or RhC> 2 , CrC> 2 , and MnC> 2
  • the at least one transition metal oxide is RhC> 2 .
  • the at least one transition metal oxide is CrC> 2 .
  • the at least one transition metal oxide is MnC> 2 .
  • the at least one transition metal oxide is M0O2.
  • FIG. 1 shows a model system of a (1 10) surface of a TMOs in its rutile structure.
  • Large balls indicate metal atoms, small balls indicate carbon atoms and intermediate balls indicate oxygen atoms.
  • CO is spectator and in all cases located on bridge site (except for Ir0 2 where we results are shown when CO is on a bridge site or on a cus site) while CO2RR takes place on other bridge and cus sites.
  • FIG. 2 shows in a) side view and b) top view of HCOOH on Ru0 2 surface c) Side view and d) top view of HCOO + H + complex on Ti0 2 surface.
  • CO is spectator.
  • Ti0 2 and Cr0 2 dissociate HCOOH to the HCOO +H + complex but other surfaces such as Ir0 2 , Nb0 2 , Mo0 2 , Os0 2 , Hf0 2 , Pt0 2 , Rh0 2 , Mn0 2 , Pd0 2 can form the undissociated HCOOH species on their surfaces similar to Ru0 2 .
  • FIG. 3 shows free energy diagram forformic acid production at 0 vs RHE. The more endergonic step for each TMO indicates the required reducing potential.
  • FIG. 4 shows theoretical volcano for formation of formic acid from scaling relations (lines). For each of the TMOs the explicit limiting potential values are included (diamond). Each line is for one electron-proton transfer step, indicated by the numbers in parenthesis after each chemical equation to show the sequence of the reaction towards formic acid.
  • FIG. 5 shows free energy diagram for methanediol production at 0 vs RHE. The most endergonic step for each TMO indicates the required reducing potential.
  • FIG. 6 shows theoretical volcano for formation of methanediol from scaling relations (lines). For each of the TMOs the explicit limiting potential values are included (diamond). Each line is for one electron-proton transfer step, indicated by the numbers in parenthesis after each chemical equation to show the sequence of the reaction towards methanediol.
  • FIG. 7 shows theoretical volcano for formation of methanol from scaling relations (lines). For each of the TMOs the explicit limiting potential values are included (diamond). Each line is for one electron-proton transfer step, indicated by the numbers in parenthesis after each chemical equation to show the sequence of the reaction towards methanol.
  • FIG. 8 shows theoretical volcano for formation of methane from scaling relations (lines). For each of the TMOs the explicit limiting potential values are included (diamond). Each line is for one electron-proton transfer step, indicated by the numbers in parenthesis after each chemical equation to show the sequence of the reaction towards methane.
  • FIG. 9 shows theoretical activity and selectivity volcano for methane, methanol, methanediol and formic acid production.
  • Solid line on left and upper solid right on right indicate left and right sides of the volcano for formation of formic acid.
  • Dashed line on left and lower solid line on right denote left and right sides of the volcano for formation of methane and methanol, and finally, solid line on left and lower solid line on right are for formation of methanediol.
  • Two dashed lines (one in -0.34 eV and the other in -0.21 ) also separate the volcano into two main areas: the right area (AGOH>-0.21 eV) that is selective toward formic acid and the left area (AGOH ⁇ -0.34 eV) that is selective toward methane, methanol and methanediol. Furthermore, there is an area between -0.34 eV and -0.21 eV which is very active but without any specific selectivity.
  • FIG. 10 shows free energy diagram for OCHO, H and COOH on the TMO surfaces at 0 V. Negative values for H and COOH for each TMO are showing higher possibilities for getting poisoned by those species. For each metal oxide, the columns indicate free energy for OCHO (left column), H (right column) and COOH (middle column), respectively.
  • FIG. 11 shows scaling figure for COOH adsorption free energy vs. hydrogen binding free energy. If COOH is formed as a species on the surface, it can lead to CO formation or CO poisoning. A strong H binding energy will lead to H poisoning and H 2 formation whereas a weak H adsorption would prevent proton adsorption until at more negative potentials. Here, we can see an area which indicate weaker COOH and hydrogen binding energies. Based on our analysis, we concluded that if a catalyst is found there, it would be the most promising candidate for CO2RR, since there is smaller chance of surface poisoning by CO and H.
  • FIG. 12 shows scaling figure for OH binding free energy vs. hydrogen binding free energy, where the OH is chosen as it is the descriptor on our volcano-graphs, and the catalysts with the lowest onset potentials for CO2RR are located within the dashed lines.
  • the hydrogen binding free energy can be used as an estimate of hydrogen evolution activity. Comparing hydrogen evolution activity with CO2RR activity show that Cr0 2 is more selective towards CO2RR than HER and the only candidate located in this active and selective area.
  • FIGs 13-20 show scaling relations for CO2RR network studied in this work as illustrated in the above figures.
  • This network includes OCHO (FIG. 13), HCOOH (FIG. 14), H 2 COOH (FIG. 15), O (FIG. 17), CH 2 0 (FIG. 16), CH3O+OH (FIG. 19), CH 3 0 (FIG. 18), OH, O+OH (FIG. 20) as intermediates.
  • FIGs 21 -33 show free energy diagrams for all the metal oxide catalysts investigated. Different reaction pathways for formic acid, methanediol, methanol, and methane products are also presented in these figures. Potential limiting step is only presented for methanol with highlighted line.
  • FIG. 34 shows four different surface types that are observed when water is included in the model.
  • Each of the surfaces correspond to the respective four types of surfaces as described in Table 7 herein, from top to bottom (i.e., a) shows the first category that includes RUC>2, NbC>2, M0O2 and ZrC>2, b) shows the second category that includes lrC>2 and OsC>2, c) shows the third category that includes T1O2, and d) shows the fourth category that includes Pt0 2 , RI7O2, CrC>2, VO2, MnC>2 and PdC>2.)
  • FIG. 35 shows a theoretical volcano plot for formation of formic acid from scaling relations (lines) in the presence of water. For each of the TMOs the explicit limiting potential values are included (filled squares).
  • FIG. 36 shows a theoretical volcano for formation of methane and methanol from scaling relations (lines) in the presence of water. For each of the TMOs the explicit limiting potential values are included (filled squares).
  • FIG. 37 shows a theoretical volcano for formation of formic acid, methane and methanol from scaling relations (lines) in the presence of water.
  • the explicit limiting potential values are included (filled squares).
  • FIG. 38 shows a scaling figure for COOH adsorption free energy vs. hydrogen binding free energy in the presence of water molecules. If COOH is formed as a species on the surface, it can lead to CO formation or CO poisoning. A strong H binding energy will lead to H poisoning and H2 formation whereas a weak H adsorption would prevent proton adsorption until at more negative potentials. The area that indicates weak COOH and hydrongen binding energies is likely to indlude promising catalysts for CO2RR.
  • FIG. 39 shows scaling figure for OH binding free energy vs. hydrogen binding free energy in the presence of water, where OH is chosen as it is the descriptor on the volcano graphs. Comparing hydrogen evolution activity with CO2RR activity shows that Mn0 2 , Cr0 2 and Rh0 2 are more selective towards CO2RR than HER.
  • FIG. 40 shows scaling figure for OH binding free energy vs. hydrogen binding free energy for both 25% and 50% coverage of CO as a spectator species, where OH is chosen as it is the descriptor on the volcano graphs.
  • the present invention also covers the exact terms, features, values and ranges etc. in case these terms, features, values and ranges etc. are used in conjunction with terms such as about, around, generally, substantially, essentially, at least etc. (i.e., "about 3" shall also cover exactly 3 or “substantially constant” shall also cover exactly constant).
  • the present invention is based on the surprising discovery that on the surface of certain transition metal oxide catalysts, it is possible to reduce carbon dioxide under conditions of low temperature and pressure, including at ambient temperature and pressure, using a low applied potential. Given the surge in atmospheric C0 2 levels and the resulting impact on climate, the invention provides important advances in carbon neutral energy technology. Carbonaceous fuel, such as methanol or methane, can be used in current transportation systems without major investments in infrastructure or new technologies, and can also avoid or minimize use of battery-based energy storage.
  • the invention therefore provides an important advance in the development of technologies that can reduce C0 2 levels to produce organic feedstock such as combustible fuels.
  • the invention provides processes and systems for the electrochemical reduction of CO2 at ambient temperature and pressure.
  • Reaction products include methane, methanol, methanediol and/or formic acid.
  • the reduction of CO2 can be geared to produce the desired product or mixture of products, by selecting the appropriate catalyst surface and/or adjusting the applied voltage to electrochemical cell.
  • an electrolytic cell is used that can be any cell from a range of conventional commercially suitable and feasible electrolytic cell designs that can accommodate a special purpose cathode in accordance with the invention.
  • the cell and system can in certain embodiment have one or more cathode cells and one or more anode cells.
  • An electrolytic cell in the present context is an electrochemical cell that undergoes a redox reaction when electrical energy is applied to the cell.
  • Carbon dioxide (CO2) can be provided by any one of bicarbonate (HC03 ). carbonate (CO3 2 ) and/or carbonic acid (H2CO 3 ).
  • bicarbonate and carbonate can be provided as bicarbonate or carbonate salts, either in pure form or in a mixture into a solution, that can preferably be an aqueous solution.
  • a mixture of any of bicarbonate, carbonate and carbonic acid will reach equilibrium in solution.
  • An alternate source of CO2 is the gaseous form of the compound, CC>2 ( g ) .
  • Gaseous CO2 can be provided as a sole source of CO2, or it can be provided as a supplement to other sources of CO2 in the cell, including the aforementioned bicarbonate, carbonate and carbonic acid.
  • the proton donor in the electrochemical reactions taking place in the reduction of CO2 can be any suitable substance that is capable of donating protons in the electrolytic cell.
  • the proton donor can for example be an acid, such as any suitable organic or inorganic acid.
  • the proton donor can be provide in an acidic, neutral or alkaline aqueous solutions.
  • the electrolytic cell in general comprises at least three general parts or components, a cathode electrode, an anode electrode and an electrolyte.
  • the electrochemical reduction of carbon dioxide is the conversion of carbon dioxide to more reduced chemical species using electrical energy.
  • the different parts or components can be provided in separate containers, or they can be provided in a single container.
  • the electrolyte can be an aqueous solution in which ions are dissolved.
  • the aqueous solution can be a neutral, an alkaline or an acidic solution.
  • the aqueous solution is an acidic solution.
  • the catalyst on the electrode surface should ideally have the following characteristics: It should (a) be chemically stable, it should (b) not become reduced or otherwise consumed during the electrolytic process, it should facilitate the formation of carbon- containing products, and (d) use of the catalyst should lead to the production of minimal amount of hydrogen gas.
  • the catalyst oxides according to the invention fulfill these characteristics.
  • the catalyst can comprise one or more stabiliser that serves the role of preventing degradation of the catalyst.
  • Suitable stabilisers should be more stable to degradation than the metal oxide(s) being employed, but otherwise are inert with respect to the catalytic reactions taking place on the electrode surface.
  • Exemplary stabilisers include, but is not limited to, metal oxycarbides, metal oxynitrides, bimetallic oxides and the like.
  • the transition metal oxides can also be provided as a thin layer (e.g., as few layers or as a monolayer) on a stable and conductive surface.
  • the electrolyte solution can be non-aqueous or aqueous.
  • the electrolyte solution can comprise, or consist of an aqueous solutions containing dissolved electrolytes (salts).
  • the electrolytic cell comprises one or more aqueous electrolytic solutions, in one or more cell compartments. Individual cell compartments can be separated by suitable barriers, such as membranes that allow electrolytes to pass through.
  • Aqueous electrolyte solutions may comprise any of various typical inorganic or organic salts such as but limited to soluble salts of e.g. chloride, nitrate, chlorate bromide, etc. e.g.
  • the aqueous electrolyte solutions may also comprise any one, or a combination of, alkali or alkaline earth metal oxides, such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, rubidium hydroxide and cesium hydroxide.
  • the aqueous electrolyte solution can preferably comprise carbonate, bicarbonate or carbonic acid.
  • the aqueous electrolyte solution can also further comprise one or more organic or inorganic acids.
  • Inorganic acids can include mineral acids that include but are not limited to, hydrochloric acid, nitric acid, phosphoric acid, sulphuric acid, boric acid, hydrofluoric acid, hydrobromic acid, and perchloric acid.
  • the electrolyte can alternatively be provided as a protic or aprotic, non-aqueous solution.
  • the electrolyte can be provided as an ionic liquid, i.e. as a molten salt, for example a sodium chloride salt.
  • the essential feature of the present invention concerns the composition and structure of the cathode electrode.
  • Transition metal oxides have a wide variety of surface structures which affect the surface energy of these compounds and influence their chemical properties.
  • the relative acidity and basicity of the atoms present on the surface of metal oxides are also affected by the coordination of the metal cation and oxygen anion, which alter the catalytic properties of these compounds.
  • the transition metal oxide catalyst on the cathode electrode surface comprises one or more of the following: ruthenium oxide (RUO 2 ), hafnium oxide (HfC> 2 ), iridium oxide (lrC> 2 ), titanium oxide (T1O2), osmium oxide (OSO2), rhodium oxide (RhC>2), chromium oxide (CrC>2), niobium oxide (NbC>2), manganese oxide (MnC>2), palladium oxide (PdC>2), platinum oxide (PtC>2), rhenium oxide (ReC>2), zirconium oxide (ZrC>2), vanadium oxide (VO2) and molybdenum oxide (M0O2).
  • the transition metal oxide catalyst comprises one or more of of hafnium oxide (HfC>2), iridium oxide (lrC>2), osmium oxide (OSO2), rhodium oxide (RhC>2), chromium oxide (CrC>2), niobium oxide (NbC>2), manganese oxide (MnC>2), palladium oxide (PdC>2), rhenium oxide (ReC> 2 ), zirconium oxide (ZrC> 2 ), vanadium oxide (VO 2 ) and molybdenum oxide (M0O2).
  • the transition metal oxide catalyst comprises one or more of of hafnium oxide (HfC>2), titanium oxide (T1O2), osmium oxide (OSO2), rhodium oxide (RhC>2), chromium oxide (CrC>2), niobium oxide (NbC>2), manganese oxide (MnC>2), palladium oxide (PdC>2), platinum oxide (PtC>2), rhenium oxide (ReC>2), zirconium oxide (ZrC>2), vanadium oxide (VO2) and molybdenum oxide (M0O 2 ).
  • the transition metal oxide catalyst comprises one or more of of hafnium oxide (HfC>2), osmium oxide (OSO2), rhodium oxide (RhC>2), chromium oxide (CrC>2), niobium oxide (NbC>2), manganese oxide (MnC>2), palladium oxide (PdC>2), rhenium oxide (ReC>2), zirconium oxide (ZrC> 2 ), vanadium oxide (VO 2 ) and molybdenum oxide (M0O 2 ).
  • the transition metal oxide catalyst comprises one or more of titanium oxide (T1O2), hafnium oxide (HfC>2), osmium oxide (OSO2), rhodium oxide (RhC>2), chromium oxide (CrC>2), manganese oxide (MnC>2), molybdenum oxide (M0O2), zirconium oxide (ZrC>2), vanadium oxide (VO 2 ).
  • the transition metal oxide catalyst comprises one or more hafnium oxide (HfC>2), osmium oxide (OSO2), rhodium oxide (RhC>2), chromium oxide (CrC>2), manganese oxide (MnC>2), molybdenum oxide (M0O2), zirconium oxide (Zr02), vanadium oxide (VO2).
  • the transition metal oxide catalyst comprises one or more of rhodium oxide (RhC>2), chromium oxide (CrC>2), manganese oxide (MnC>2), molybdenum oxide (M0O2), zirconium oxide (ZrC>2), vanadium oxide (VO2).
  • the transition metal oxide catalyst comprises one or more of of rhodium oxide (RhC>2), chromium oxide (CrC>2), manganese oxide (MnC>2) and molybdenum oxide (M0O2).
  • the transition metal oxide catalyst comprises one or more of of rhodium oxide (RhC>2), chromium oxide (CrC>2), manganese oxide (MnC>2).
  • a suitable surface crystal structure may be preferred.
  • the catalyst comprise at least one surface having a rutile structure.
  • Other crystal structures known in the art e.g., rocksalt structure, zincblende structure, anatase structure, perovskite structure
  • rocksalt structure e.g., rocksalt structure, zincblende structure, anatase structure, perovskite structure
  • Several different surface facets may exist for a given crystal structure (polycrystalline surfaces).
  • the (1 10) facet of rutile exhibits the lowest surface free energy and is therefore in general thermodynamically most stable.
  • the transition metal oxides can be of rutile structure with a (1 10) facet providing the catalytic surface.
  • the (100) and/or the (1 1 1 ) facets of the rocksalt structure can be chosen.
  • the catalyst surface is a transition metal rutile surface.
  • the surface can have any suitable facet, including but not limited to the (1 10) facet.
  • the surface facet comprises, or consists of, the (1 10) facet of a transition metal oxide selected from the group consisting of Ru0 2 , Hf0 2 , Ir0 2 , Ti0 2 , Os0 2 , Rh0 2 , Cr0 2 , Nb0 2 , Mn0 2 , Pd0 2 , Pt0 2 , Re0 2 , Zr0 2 , V0 2 and Mo0 2 .
  • the surface facet can comprise, or consist of, the (1 10) facet of a transition metal oxide selected from the group consisting of Hf0 2 , Ir0 2 , Os0 2 , Rh0 2 , Cr0 2 , Nb0 2 , Mn0 2 , Pd0 2 , Re0 2 , Zr0 2 , V0 2 and Mo0 2 .
  • a transition metal oxide selected from the group consisting of Hf0 2 , Ir0 2 , Os0 2 , Rh0 2 , Cr0 2 , Nb0 2 , Mn0 2 , Pd0 2 , Re0 2 , Zr0 2 , V0 2 and Mo0 2 .
  • the catalyst comprises the (1 10) facet of the rutile structure of one or more oxide selected from Rh0 2 , Cr0 2 , Mn0 2 , Pd0 2 and Pt0 2 .
  • the catalyst comprises the (1 10) facet of the rutile structure of one or more oxide selected from Rh0 2 , Cr0 2 , Mn0 2 , Mo0 2 , and Pd0 2 .
  • the catalyst comprises a the (1 10) facet of the rutile structure of one or more oxide selected from Rh0 2 , Cr0 2 , Mo0 2 and Mn0 2 .
  • the catalyst comprises a the (1 10) facet of the rutile structure of Mn0 2 . In another preferred embodiment, the catalyst comprises a the (1 10) facet of the rutile structure Cr0 2 . In another preferred embodiment, the catalyst comprises a the (1 10) facet of the rutile structure of one or more oxide selected from Rh0 2 . In another preferred embodiment, the catalyst comprises a the (1 10) facet of the rutile structure of one or more oxide selected from MO0 2 .
  • a rutile metal oxide surface having a (1 10) facet contains metal atoms of two different coordination environments, where rows of sixfold coordinated metal atoms alternate with rows of fivefold coordinated metal atoms along the [001] direction. Whereas the sixfold coordinated metal atoms have approximately the same geometry as bulk, the fivefold coordinated metal atoms have an unsaturated bond perpendicular to the surface. Thus two distinct surface sites are found, coordinatively unsaturated sites (cus-sites) on top of the 5-fold coordinated metal atoms and bridging sites (br-sites) between two sixfold coordinated metal atoms.
  • the catalyst surface is provided as a pure transition metal oxide, i.e. the catalyst comprises a single transition metal oxide, i.e. the catalyst for example does not contain a mixture of transition metal oxides or one transition metal oxide that is coated by one or several layers of a second (or more) transition metal oxide.
  • the catalyst according to the invention can comprise a single transition metal oxide.
  • the catalyst can also comprise, or consist of, a mixture of two or more such oxides.
  • Such mixed oxides can comprise a single structure, for example a rutile structure.
  • the mixed metal oxides can also comprise a mixture of oxides that are of different crystal structures and/or oxides with different catalytic facets. Accordingly, such mixed oxides can further comprise a single, or a mixture of, facets.
  • Mixed oxide catalysts can be grown or manufactured separately and then assembled into mixed catalysts comprising the different metal oxides, wherein the oxides in the mixture have the same or different crystal structures.
  • running a current through the electrolytic cell leads to a chemical reaction in which carbon dioxide (CO2) is reduced in a series of steps with protons to ultimately form one or more products, including methane, methanol, formic acid and methanediol.
  • CO2 carbon dioxide
  • the running of current is achieved by applying a voltage to the cell.
  • the invention makes possible electrolytic production of these products at a low electrode potential, which is beneficial in terms of energy efficiency and equipment demands.
  • the electrolytic cell can be operated at an ambient pressure of about 1 atmospheres.
  • the electrolytic cell can also be operated at higher pressure, i.e. pressure that is greater than ambient pressure.
  • the cell can be operated at a pressure of up to 30 atmospheres, up to 20 atmospheres or up to 10 atmospheres.
  • the electrolytic cell is operated at a pressure that is in the range of 1 to 30 atmospheres, in the range of 1 to 20 atmospheres, in the range of 1 to 10 atmospheres, in the range of 1 to 5 atmospheres or in the range of 1 to 3 atmospheres.
  • the electrolytic cell can also be operated at a pressure that is in the range of 2 to 20 atmospheres, in the range of 3 to 20 atmospheres, in the range of 4 to 20 atmospheres, or in the range of 5 to 20 atmospheres, such as at about 5 atmospheres, about 6 atmospheres, about 7 atmospheres, about 8 atmospheres, about 9 atmospheres, about 10 atmospheres, about 1 1 atmospheres, about 12 atmospheres, about 13 atmospheres, about 14 atmospheres, about 15 atmospheres, about 16 atmospheres, about 17 atmospheres, about 18 atmospheres, about 19 atmospheres or about 20 atmospheres.
  • the electric potential can be applied as a constant or variable electric potential. Pulsed electric fields generated by such pulsed potentials can be varied by adjusting a number of parameters, such as: electric field intensity, rise time of voltage pulses, number of pulses, frequency of pulses, pulse wave shape, treatment time (i.e. the time the pulse is applied, resulting in the product of the number of pulses and the duration of each pulse).
  • product can be formed at an electrode potential at less than about -0.7 V, less than about -0.6 V, less than about 0.5 V, less than about -0.4 V, or less than about -0.3 V.
  • product formation occurs at electrode potential in the range of about -0.7 V to about 0.0 V, such as in the range of about -0.5 V to about 0.0 V, or in the range of about -0.35 V to about 0.0 V.
  • the upper limit (i.e., more negative potential limit) of the range can be about -0.3 V, about -0.4 V, about -0.5 V, about -0.6 V, or about -0.7 V.
  • the lower limit (i.e. less negative potential limit) of the range can be about 0.0 V, about -0.1 V, about -0.2 V, or about -0.3 V.
  • composition of products obtained in the reduction of CO2 can be altered by selective adjustment of applied potential for any given catalyst surface.
  • volcano plots show that, depending on the relative binding energies of adsorbed intermediates, the selectivity changes depending on the applied voltage.
  • formic acid can specifically be formed at an electrode potential that is in the range of about -0.3 V to about -0.1 V.
  • methanol, methane and methanediol can selectively be formed using an electrode potential of about -0.4 V to about -0.2 V.
  • any one or a mixture of formic acid, methanol, methane and methanediol can be formed at an electrode potential of about -0.3 V to about - 0.2 V.
  • the preferred catalyst can be selected from MnC>2, M0O2, RI7O2 and CrC>2. In certain embodiments, the catalyst comprises CrC>2. In certain other embodiments, the catalyst comprises RhC>2. In certain other embodiments, the catalyst comprises MnC>2. In certain other embodiments, the catalyst comprises M0O2.
  • the catalyst surface is a MnC>2 , MoC>2or CrC>2 surface having a rutile structure, and the applied voltage for selective formation of methanol, methane and/or methanediol is in the range of about -0.4 V to about -0.2 V.
  • the catalyst surface is a MnC>2, MoC>2 or CrC>2 surface having a rutile structure
  • the applied voltage for selective formation of formic acid selectively is in the range of about -0.3 V to about 0.0 V, preferably in the range of about -0.3V to about -0.1V.
  • the catalyst surface is a MnC>2, MoC>2 or CrC>2 surface having a rutile structure, and the applied voltage for the generation of any one of formic acid, methanol, methane and/or methanediol can be formed at an electrode potential of about -0.3 V to about -0.2 V.
  • An advantage of the present invention is the efficiency of product (i.e., methanol, methane, methanediol and/or formic acid) formation over the side-product hh formation, which has been a challenge in prior art investigations and trials, due to the competing binding energies of hydrogen over oxygen on the catalyst surface.
  • product i.e., methanol, methane, methanediol and/or formic acid
  • less than about 50% moles H2 are formed compared to moles product formed, and preferably less than about 40% moles H2, less than about 30% moles H2, less than about 20% moles H2, less than about 10% moles H2, less than about 5% moles H2, less than about 2% moles H2, or less than about 1 % moles H2.
  • the pathway of CO2 reduction depends on the relative energies of reaction intermediates.
  • the pathway can depend on the system within which the reaction takes place, including for example the catalytic surface being used in the reaction.
  • the active part of an industrial heterogeneous catalyst is most commonly a solid surface, e.g. a metal or metal oxide.
  • the surface offers a low-barrier energy path from reactants to products, by binding reactants and reaction intermediates.
  • the binding energy of reactants to the surface must be strong enough to produce reaction intermediates, but weak enough to allow products to leave the surface, allowing more reactions to take place on the surface.
  • This duality is the basis of the so-called Sabatier principle, which states that for a reaction, there is an optimum binding energy for an intermediate, such that both stronger and weaker binding leads to lower activity.
  • the result is a volcano-shaped relationship, commonly referred to as a Volcano plot.
  • Catalyst activity can in general be modified by altering the local electronic structure by strain, ligand, substitution and/or alloying. These alterations lead to changes in binding energies of reaction intermediates, and thereby alter the thermodynamics of the overall reaction profile.
  • the concept of scaling relations is based on the linear relationship between binding energies of adsorbates that bind through the same type of atoms (e.g., C * , CH * and CH2 * binding through a C atom). Based on such relationships, the energetics of elementary steps of a chemical reaction pathway can be expressed by using a few binding energies as descriptors, allowing modelling of such pathways using fewer parameters.
  • a method for the electrolytic reduction of C0 2 comprising: providing an electrolytic cell comprising at least one reaction chamber comprising at least one anode and at least one cathode, wherein the at least one cathode comprises at least one catalyst surface comprising at least one transition metal oxide; placing at least one electrolyte solution between the at least one anode and the at least one cathode, so that the at least one anode and the at least one cathode come into contact with the electrolyte solution; providing C0 2 in the electrolyte solution; and applying electrical potential to the electrolytic cell; whereby C0 2 undergoes at least one reduction reaction at the cathode to provide at least one product selected from the group consisting of methanol, methane, methanediol and formic acid.
  • the at least one transition metal oxide is selected from the group consisting of Ti02, Hf0 2 , 0s0 2 , Rh0 2 , Cr0 2 , Nb0 2 , Mn0 2 , Pd0 2 , Pt0 2 , Re0 2 , Zr0 2 , V0 2 and Mo0 2 , preferably Hf0 2 , 0s0 2 , Rh0 2 , Cr0 2 , Nb0 2 , Mn0 2 , Pd0 2 , Re0 2 , Zr0 2 , V0 2 and Mo0 2 , preferably Hf0 2 , 0s0 2 , Rh0 2 , Cr0 2 , Nb0 2 , Mn0 2 , Pd0 2 , Re0 2 , Zr0 2 , V0 2 and Mo0 2
  • the at least one transition metal oxide is selected from the group consisting of Rh0 2 , Cr0 2 , Mo0 2 and Mn0 2 .
  • the catalyst surface is provided as a pure transition metal oxide.
  • the catalyst surface comprises a mixture of transition metal oxides.
  • the catalyst surface is provided on a cathode that comprises at least one metal, metal alloy or steel, including stainless steel.
  • the C0 2 is comprised in a solution in the electrolytic cell, wherein the solution comprises at least one electrolyte that is provided between the anode and the cathode.
  • the electrolyte comprises at least one source of carbon dioxide selected from bicarbonate and carbonic acid.
  • any one of the embodiments 1 -13 characterized in that the method is carried out at a pressure in the range of 1 to 30 atmospheres, preferably in the range of 1 to 20 atmospheres, preferably in the range of 1 to 10 atmospheres, more preferably in the range of 1 to 5 atmospheres.
  • the catalyst surface comrises at least one surface having a rutile structure.
  • the catalyst surface comprises at least one surface having a (1 10) facet.
  • An electrochemical device for the reduction of carbon dioxide to at least one reaction product comprising at least one electrochemical cell that comprises an anode and a cathode, wherein the cathode comprises at least one cathode electrode having at least one catalyst surface comprising at least one transition metal oxide.
  • the at least one transition metal oxide is selected from the group consisting of HfC>2, OsC>2, RI7O2, CrC>2, NbC>2, MnC>2, PdC>2, ReC>2, ZrC>2, VO2 and M0O2, more preferably selected from the group consisting of RhC>2, CrC>2, MnC>2, M0O2, and PdC>2, most preferably selected from the group consisting of RhC>2, CrC>2, MnC>2, M0O2, PdC>2.
  • a process for the catalytic reduction of carbon dioxide comprising: introducing CO2 to a solution comprising at least one electrolyte in an electrolytic cell so that the CO2 comes into contact with at least one cathode electrode surface; and applying a potential to said electrolytic cell, whereby C0 2 reacts with protons to form at least one product selected from methanol, methane, methanediol and formic acid; wherein the cathode electrode surface comprises at least one catalyst surface comprising at least one transition metal oxide.
  • the at least one transition metal oxide is selected from the group consisting of HfC>2, OsC>2, RI7O2, CrC>2, NbC>2, MnC>2, PdC>2, ReC>2, ZrC>2, VO2 and M0O2, more preferably selected from the group consisting of RhC>2, CrC>2, MnC>2, MoC>2 and PdC>2.
  • the electronic structure calculations were performed using DFT within the BEEF-vdW functional in the VASP software (Wellendorff et al. (2012) Phys Rev B 85). All the lattice parameters were optimized based on BEEF-vdW for ruthenium oxide (RUO2), iridium oxide (lrC>2), niobium oxide (NbC>2), platinum oxide (PtC>2), titanium oxide (T1O2), chromium oxide (CrC>2), manganese oxide (MnC>2), rhodium oxide (RhC>2), osmium oxide (OSO2), hafnium oxide (HfC>2), molybdenum oxide (M0O2) and palladium oxide (PdC>2) in their rutile crystal structure.
  • the BEEF-vdW lattice parameters for these metal oxides are calculated and presented in the following lattice table:
  • Lattice table Shown are optimized lattice parameters for different metal oxides studied.
  • a plane wave basis set with a cutoff energy of 350 eV was used to expand the valence electron orbitals and the PAW method was used to represent core electrons (Blochl, Phys Rev B (1994) 50, 17953-79).
  • Monkhorst Pack grid was used in order to reduce the number of k-points, which were 4x4x1 in all cases.
  • the atomic structure of the various reactants and products was found by minimizing the energy until atomic forces had dropped below 0.03 eV/A.
  • the electrode was represented by a slab of four atomic layers with four metal atoms and eight oxygen atoms in each layer, and the slabs were separated with at least 16 A of vacuum. Atoms in the bottom two layers were fixed while the atoms in the top two layers along with the adsorbed intermediates were allowed to fully relax. The dipole correction was used in all cases to decouple the electrostatic interaction between the periodically repeated slabs.
  • the rutile (1 10) surface contains metal atoms of two different coordination environments. Rows of six-fold coordinated metal atoms alternate with rows of five-fold coordinated metal atoms along the [001] direction. Whereas the six-fold coordinated metal atoms have approximately the same geometry as bulk, the five-fold coordinated metal atoms have an unsaturated bond perpendicular to the surface. Thus, two distinct surface sites are found, coordinatively unsaturated sites (cus-sites) on top of the five-fold coordinated metal atoms and bridging sites (br-sites) between two six-fold coordinated metal atoms (FIG. 1 ). We found that the br-sites generally bind adsorbates stronger than the cus-sites do.
  • Ir0 2 two different free energy diagrams; see FIGs 22 & 23
  • Ir0 2 two different free energy diagrams; see FIGs 22 & 23
  • the differences between free energy of adsorbed CO when it is on the br-site and cus-site is 0.1 1 eV
  • C0 2 RR will happen while CO is on cus-site as spectator.
  • Ir0 2 when CO is on the bridge site we also include Ir0 2 when CO is on the bridge site.
  • the bullet for Ir0 2 is for when CO spectator is on a br-site, while the black bullets are for when the CO spectator is on a cus-site.
  • the computational hydrogen electrode (CHE) model is a tool to approximate the reaction free energy of an electrochemical reaction (Norskov et al. J Phys Chem (2004) 108, 17886-92) at a certain applied potential.
  • the potential effects have been included by adding an implicit term, eU.
  • the reaction free energy at an arbitrary potential U vs. the standard hydrogen electrode (SHE) is given by
  • AEDFT is calculated with DFT and DEZRE and AS are zero-point energy corrections and entropy differences which are calculated within the harmonic approximation for the adsorbed species, while the values for the gas phase species are taken from thermodynamical tables (Atkins & Paula, Atkins’ Physical Chemistry (2009)).
  • AEsoi is the adsorbate stabilization term due to the solvent, which is not included in this study.
  • DHok t is changes in internal energy because of temperature.
  • OCHO formate
  • COOH carboxyl
  • HER A major competing reaction with CO2RR is the HER.
  • Table 1 we estimate the onset potential for HER on the TMOs by calculating the binding free energy of a H adatom on the surfaces.
  • CO formation should also be taken into account, as it can result in CO poisoning. CO formation only happens via COOH intermediate where CO2 is protonated to form carboxyl through the following reaction:
  • COOH + (H + + + e ) ® CO + H 2 0(l) (7) which may poison the surface of the catalyst because we find that the CO reduction to CHO or COH has high thermochemical barriers on those TMOs.
  • the CO admolecules that may be formed on the surfaces are therefore spectator species during CO2RR.
  • HCOOH(aq) can adsorb on the surface in undissociated form (see RUC>2 in FIG. 2).
  • RUC>2 in FIG. 2 We have included this possibility in this work and found that surfaces of T1O2 and CrC>2 will rather dissociate the formic acid into the HCOO and H + complex where HCOO binds to the bridge sites on the surface through its oxygen atoms but the proton binds to a surface oxygen atom (see T1O2 in FIG. 2).
  • the undissociated HCOOH species is the intermediate that forms on the RUO2, Ir02, Hf02, OSO2, and M0O2.
  • Formic acid and methanediol are a two and four-step electron transfer products of CO2RR, respectively.
  • RhC>2, PtC>2, MnC>2, and PdC>2 cannot adsorb the HCOOH intermediate on their surfaces and therefore these catalysts have the potential of producing aqueous formic acid.
  • FIGs 3 and 4 and Table 3 show that among these candidates, PtC>2 and RhC>2 have the smallest onset potentials towards formic acid, or -0.14 V and -0.19 V, respectively.
  • Table 1 the onset potentials for the HER are estimated from the adsorption free energy of a H adatom.
  • RhC the hydrogen binding free energy is -0.06 eV whereas the binding free energy of OCHO is -0.19 eV, and therefore a higher efficiency towards formic acid is expected than towards H2.
  • Pt0 2 the hydrogen binding free energy is -0.16 eV but the binding free energy of OCHO is 0.14 eV, and therefore HER is expected to dominate over CO2RR.
  • Rh0 2 has low activity towards HER (in CO2 saturated solution) but high activity towards formic acid, and thus these factor make Rh02 the best candidate for production of formic acid. It should be noted here that without CO2 in the solution, Rh0 2 is predicted here to have very small onset potential for HER.
  • CrC>2 is another candidate located very close to the top of the formic acid volcano (FIG. 4), with predicted onset potential of -0.27 V (Table 1 ).
  • the free energy of the adsorbed HCOOH species (actually as a HCOO +H + complex on Cr0 2 as explained above) is only 0.01 eV lower than the free energy of HCOOH (aq) and therefore Cr0 2 is expected to both evolve formic acid as well as more reduced products (discussed below).
  • the hydrogen binding free energy on Cr0 2 is 0.29 eV whereas the OCHO binding free energy is -0.33 eV, meaning that this catalyst should be much more selective towards CO2RR than HER.
  • the OH removal potential may be considered as a representative of the left leg for both the methanol and the methane volcanos.
  • the HCOOH (aq) ® H 2 COOH step is PLS.
  • those TMOs will start evolving formic acid at smaller potentials.
  • the surfaces need to be cleaned of OH species, but in all of the reaction pathways presented in Tables 1 and 2 the OH removal is the last or the second last step.
  • OH removal potentials ranges from -2 V to 0.5 V for all the TMO catalysts, they can be categorized based on the strength of OH binding energy (Table 1 ). Due to high OH removal potential for some of these catalysts, the HER may become a dominant reaction compared to the CO2RR, and this may affect the activity and selectivity of the catalysts. Even if the earlier intermediate steps in CO2RR for producing methane or methanol are feasible at low overpotential, in order to remove OH, the reaction must be carried out at higher overpotentials where HER would be relatively fast.
  • FIG 9 presents a“selectivity volcano” for formic acid, methanediol, methanol, and methane products.
  • the CO2RR is more selective towards formic acid, but for AGOH ⁇ -0.21 eV, the selectivity is more towards methane, methanol, and methanediol.
  • the PLS towards formic acid and methanediol coincide each other, which means that the formation of those products need almost the same thermodynamic onset potentials.
  • Cr0 2 is located on the top of the volcano for methanediol, methanol, and methane and the onset potential towards formic acid is very similar, and therefore it is predicted to form all these four products of C0 2 RR.
  • the important thing about Cr0 2 is that it can adsorb the formic acid as an intermediate on its surface and continue its reduction towards methane, methanol, and methanediol with much smaller applied potential than compared to Ru0 2 , Ti0 2 and Ir0 2 .
  • the binding energy of the OH species on the surface needs to be between -0.5 eV and -0.34 eV, where the OH binding energy is moderate.
  • the possible candidate needs to have a low activity towards HER as well.
  • Another criteria that needs to be considered here is the CO poisoning.
  • the only pathway which may lead to CO poisoning is through the COOH intermediate. Minimizing the rate towards hydrogen evolution and CO poisoning along with binding OH in a moderate way are the three criteria that should be considered at the same time in order to find a promising candidate.
  • the binding free energy of OCHO, COOH and H are compared in Figure 10 and used in further analysis below.
  • the candidates with weak H and COOH binding free energies will have low tendency to evolve hydrogen and poison the surface with CO.
  • the candidates also need to bind OCHO moderately, between 0 and -0.5 eV which is similar as the interval for the OH binding free energy since OCHO and OH scale linearly, almost one-to-one.
  • FIG. 1 1 we show that the COOH binding free energy and hydrogen binding free energy are correlated linearly.
  • the region (and candidates very close to this region) with weak (positive) hydrogen and weak COOH binding free energy is where one should be looking for the promising candidate(s) because there the rates towards HER and the CO poisoning is lower.
  • Moderate OH binding free energy is another restriction, which needs to be added into the picture. All the design parameters (moderate OH binding, weak hydrogen binding and weak COOH binding) are included in FIG. 12, where the OH binding free energy is plotted as a function of the H binding free energy (since COOH and H are correlated linearly we only include the H binding here).
  • the charge difference in the double layer sets up the applied electric potential explicitly and therefore the proton-electron transfer barriers can be calculated as a function of explicitly varied potential.
  • This approach is necessary in order to reproduce the experimentally observed product distribution as a function of both the metal type and the applied potential.
  • the TCM-CHE approach is sufficiently accurate to predict the onset potentials for various reactions on different catalyst’s materials, including CO 2 RR on metal catalysts, both in terms of which product is formed on Cu and when the metal catalyst is varied.
  • transition metal oxides When transition metal oxides are exposed to an aqueous environment, water molecules can be adsorbed onto the metal oxide surface. These water molecules in turn can affect functional properties of metal oxide surfaces, including their catalytic potential.
  • the slab consists of four atomic layers with four metal atoms and eight oxygen atoms in each layer, and the exposed liquid phase was presented by 22 H2O molecules.
  • the system was subject to periodic boundary conditions in all direction.
  • atoms in the bottom two layers were fixed while the atoms in the top two layers along with the water molecules were allowed to reconstruct during MD run.
  • the time step for MD runs is 0.5 fs.
  • Canonical ensemble (NVT) conditions were imposed by a Nose- Hoover thermostat with a target temperature of 300 K. 1 ps of equilibration period was followed by 3 ⁇ 4 ps of production period. The convergence of the vertical energy gap can be monitored by the time accumulative averages.
  • the first two protonation steps in CO2RR may lead to the formation of aqueous formic acid or adsorbed HCOOH species on the surface.
  • HCOOH(aq) on T1O2 surface should be in a dissociated form (HCOO + H + ).
  • HCOO + H + dissociated form
  • PtC>2, RI7O2, CrC>2, MnC>2, PdC>2 are the only catalysts that cannot adsorb the HCOOH intermediate on their surfaces and therefore these catalysts have the potential of producing aqueous formic acid.
  • FIG. 35 there is shown a theoretical volcano plot for the formation of formic acid using scaling relations (indicated by lines) in the presence of water. For each transition metal oxide, the limiting potential value is indicated by filled squares.
  • FIG. 36 shows a theoretical volcano for formation of methane and methanol from scaling relations (lines) in the presence of water.
  • the explicit limiting potential values are shwon by filled squares.
  • FIG. 37 shows formation of formic acid, methane and methanol from scaling relations (shown by lines) in the presence of water.
  • the explicit limiting potential values are indicated by filled squares.
  • FIG. 38 there is shown a scaling figure for COOH adsorption free energy vs. hydrogen binding free energy in the presence of water molecules. If COOH is formed as a species on the surface, it can lead to CO formation or CO poisoning. A strong H binding energy will lead to H poisoning and H 2 formation whereas a weak H adsorption would prevent proton adsorption until at more negative potentials. The area that indicates weak COOH and hydrongen binding energies is likely to include promising catalysts for C02RR. A scaling figure for OH binding free energy vs. hydrogen binding free energy in the presence of water is shown in FIG. 39, where OH is chosen as it is the descriptor on the volcano graphs. Comparing hydrogen evolution activity with CO 2 RR activity shows that MnC> 2 , CrC> 2 and RhC> 2 are more selective towards CO 2 RR than HER.

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Abstract

L'invention concerne un procédé de réduction électrolytique de CO2 qui comprend l'utilisation d'une cellule électrolytique comprenant au moins une chambre de réaction comprenant au moins une anode et au moins une cathode ; la mise en place d'au moins une solution d'électrolyte entre au moins une anode et au moins une cathode, ladite cathode comprenant au moins une surface de catalyseur comprenant au moins un oxyde de métal de transition ; fournir du CO2 dans la solution d'électrolyte ; et appliquer un potentiel électrique à la cellule électrolytique, de sorte que le CO2 subit au moins une réaction de réduction au niveau de la cathode pour fournir au moins un produit choisi dans le groupe constitué par le méthanol, le méthane, le méthanediol et l'acide formique. L'invention concerne également un dispositif électrochimique de réduction électrochimique de CO2 qui comprend au moins une cathode comprenant un oxyde de métal de transition.
EP19720060.3A 2018-04-11 2019-04-11 Électroréduction de dioxyde de carbone sur des catalyseurs à base d'oxyde de métal de transition Pending EP3775321A1 (fr)

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