Catalytic low-IR mixed metal oxide materials for the oxygen evolution reaction in acid

Abstract

Provided is a catalytic mixed metal oxide material that includes Ir, O, and which has the atomic formula of M1xM2yM3zIrtOu, or M1xM2yM3z(IrM4)tOu where between one and three elements labeled as M1 through M3 is selected from the group consisting of Ru, Sr, Fe, Co, Mn, Ni, Sb, Nb, W, and Sn and M4 is selected from Ru and Sr. Further provided is the use of the catalytic mixed metal oxide material in oxygen evolution reactions.

Description

Attorney Docket No.00172-004WO1 CATALYTIC LOW-Ir MIXED METAL OXIDE MATERIALS FOR THE OXYGEN EVOLUTION REACTION IN ACID CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 63 / 684,263, filed August 16, 2024, the disclosures of which are incorporated herein by reference for all purposes. FIELD OF THE INVENTION

[0002] The disclosure relates to catalytic mixed metal oxide materials, and more specifically, to electrocatalytic mixed metal oxide materials. BACKGROUND

[0003] The oxygen evolution reaction (OER) is of crucial importance for various applications, including fuel generation, electrowinning, and carbon storage. The amount of voltage beyond that which is thermodynamically required to achieve current flow for OER is termed the overpotential, and to improve the efficiency of a system which requires OER, should be minimized. OER in acid is uniquely difficult to achieve due to unfavorable energetics for many materials, and in most cases expensive iridium and ruthenium materials are used in such systems. As a result, there is a need for improved OER catalysts with high activity and a decreased amount of iridium / ruthenium loading. SUMMARY

[0004] The disclosure describes compositions comprising, consisting essentially of, or consisting of, a class of catalytic mixed metal oxide materials that are effective at low overpotentials. Additionally, the catalytic mixed metal oxide materials of the disclosure are tolerant of highly acidic environments such as environments with a pH less than 3, 1, or 0. the catalytic mixed metal oxide materials of the disclosure serve as oxidation catalysts and can accordinglyAttorney Docket No.00172-004WO1 catalyze a variety of reactions such as the Oxygen Evolution Reaction, the Oxygen Reduction Reaction, and redox reactions for flow batteries. In particular, the catalysts are ideally suited to catalyze the Oxygen Evolution Reaction. Catalysts for the oxygen evolution reaction are often placed in an environment with very low pH levels for applications such as electrowinning and electrolytic hydrogen evolution. However, the catalysts that are used in highly acidic conditions typically are comprised of very expensive components such as iridium and ruthenium oxides in large amounts. By decreasing the amount of iridium / ruthenium in the catalytic materials, the price associated with these catalysts can be reduced. Accordingly, an oxygen evolution system can include one or more electrodes exposed to an environment with a pH less than 3, 2, 1, or 0 where the electrode comprises a composition comprising as catalytic mixed metal oxide material disclosed herein that has much lower amounts of iridium and ruthenium than typically found in such OER catalytic materials and further excludes noble metals, like palladium, silver, platinum, and gold.

[0005] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Sr, Fe, Co, and oxygen. In another embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Fe, Mn, Ni, and oxygen. In yet another embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Sr, Ni, Mn, and oxygen. In a further embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Sr, Co, Ni, and oxygen. In yet a further embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Sr, Co, Mn, and oxygen. In another embodiment, the disclosure provides for a composition comprising aAttorney Docket No.00172-004WO1 catalytic oxide material that contains Ir, Ni, Mn, Co, and oxygen. In yet another embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Ru, Mn, Sr, Ni, and oxygen. In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Ru, Sr, Sb, Ti and oxygen. In another embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Ru, Sr, Nb, Mn and oxygen. In yet another embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Ru, Ti, Sb, Nb and oxygen. In a further embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Ru, Co, Mn, Sb and oxygen. In yet a further embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Ru, Sr, W, Sn and oxygen. In another embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains Ir, Ru, Co, Mn, W, and oxygen.

[0006] In a particular embodiment, the disclosure provides for a composition comprising: a catalytic oxide material comprising Ir, oxygen, and at least three additional metals and which has the atomic formula of M1xM2yM3zIrtOu,or M1xM2yM3z(IrM4)tOu; wherein, M1, M2, M3, and M4 are different metals, and wherein M1, M2, M3 are selected from Ru, Sr, Fe, Co, Mn, Ni, Sb, Nb, W, and Sn, and M4 is selected from Ru and Sr; wherein x+y+t+z=1; and wherein the catalytic oxide material has electrochemical activity in an acidic environment. In yet a further embodiment, the catalytic oxide material has the atomic formula of M1xM2yM3zIrtOu, and one of M1, M2, and M3 is Ru, Sr or Ni. In another embodiment, the catalytic oxide material has the atomic formula of M1xM2yM3zIrtOu, and M1, M2, and M3 are selected from: (a) Sr, Fe, and Co; (b) Fe, Mn, and Ni; (c) Sr, Ni, and Mn; (d) Sr,Attorney Docket No.00172-004WO1 Ni, and Co; (e) Sr, Mn, and Co; and (f) Ni, Mn, and Co. In yet another embodiment, M1xM2yM3zIrtOuis SrxCoyFezIrtOuwhere 0<x<0.3, 0<y≤0.7, 0<z≤0.3, 0<t<0.9; or 0<x≤0.8, 0.1≤y≤0.3, 0.1≤z≤0.3, 0.7≤t<1.0, and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In a further embodiment, M1xM2yM3zIrtOuis FexMnyNizIrtOuwhere 0<x<0.5, 0<y<0.4, 0<z<0.6, 0<t<0.9; or 0<x≤0.7, 0<y≤0.2, 0.3≤z≤0.8, 0.2≤t≤0.7, and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In another embodiment, M1xM2yM3zIrtOuis CoxMnyNizIrtOuwhere 0<x<0.6, 0<y<0.4, 0<z<0.4, 0<t<0.9, and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In yet a further embodiment, M1xM2yM3zIrtOuis SrxNiyMnzIrtOuwhere 0<x<0.6, 0<y<0.5, 0<z<0.3, 0<t<0.9; or 0.16≤x≤0.45, 0.03≤y≤0.30, 0.14≤z≤0.29, 0.02≤t≤0.10; and 0.09≤u≤0.45 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In another embodiment, M1xM2yM3zIRtOuis SrxCoyNizIrtOuwhere 0<x<0.6, 0<y<0.8, 0<z≤0.3, 0<t<0.9; or 0<x≤0.7, 0<y≤0.3, 0<z≤0.7, 0.3≤t<1 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In yet another embodiment, M1xM2yM3zIRtOuis SrxCoyMnzIrtOuwhere 0<x<0.5 ,0<y<0.7, 0<z<0.4, 0<t≤0.7; or 0<x<1, 0<y≤0.3, 0<z≤0.8, 0<t<1 and the oxygen fraction u is the number required in the lattice annealed at an elevated temperature in air. In a certain embodiment, the catalytic oxide material has the atomic formula of M1xM2yM3z(IrM4)tOuand M1, M2, M3 and M4 are selected from: (A) Sr, Mn, Ni, and Ru; (B) Ru, Ti, Sb, and Sr; (C) Ru, Mn, Nb, and Sr; (D) Ti, Nb, Sb, and Ru; (E) Co, Mn, Sb, and Ru; (F) Sr, W, Sn, and Ru; and (G) Co, Mn, W, and Ru. In a further embodiment, M1xM2yM3z(IRM4)tOuis SrxNiyMnz(IrRu)tOuwhere 0<x≤0.7, 0.4≤y<1, 0.4≤z<1, 0<t≤0.6; or 0<x≤0.7, 0.4≤y<1, 0.4≤z<1, 0<t≤0.6; andAttorney Docket No.00172-004WO1 the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In yet a further embodiment, M1xM2yM3z(IRM4)tOuis RuxTiySbz(IrSr)tOuwhere 0.1<x<0.8, 0<y<0.4, 0<z<0.4, 0.1<t<0.5; or 0.2≤x<1, 0<y≤0.3, 0<z≤0.4, 0.2≤t<1; and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In another embodiment, M1xM2yM3z(IRM4)tOuis RuxMnyNbz(IrSr)tOuwhere 0<x<0.8, 0<y<0.4, 0<z<0.3, 0<t<0.7; or 0<x<1, 0.5≤y<1, 0<z≤0.3, 0<t<1; and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In yet another embodiment, M1xM2yM3z(IRM4)tOuis TixNbySbz(IrRu)tOuwhere 0.1<x<0.5, 0<y≤0.2,an a further embodiment, M1xM2yM3z(IRM4)tOuis CoxMnySbz(IrRu)tOuwhere 0<x<0.5, 0<y<0.4, 0<z<0.8, 0.2<t<1; or 0<x≤0.2, 0<y≤0.2, 0<z≤0.2, 0.8≤t<1; and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In yet a further embodiment, M1xM2yM3z(IRM4)tOuis SrxWySnz(IrRu)tOuwhere 0<x<0.4, 0<y<0.2, 0<z<0.6, 0.2<t<0.9; or 0.2≤x<1, 0.2≤y<1, 0<z≤0.7, 0.3≤t<1; and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air. In another embodiment, M1xM2yM3z(IRM4)tOuis MnxWyCoz(IrRu)tOuwhere 0<x<0.4, 0<y<0.2, 0<z<0.6, 0.2<t<0.9; or 0.0<x<0.4, 0<y<0.2, 0<z≤0.8, 0.0<t<0.7; and the oxygen fraction u is the number required in the lattice annealed at an elevated temperature in air. In yet another embodiment, the amount of oxygen in the catalytic oxide material results from annealing the catalytic oxide material in air at an elevated temperature from about 500 °C to about 700 °C.

[0007] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material thatAttorney Docket No.00172-004WO1 contains oxygen, Ir, Sr, Fe, and Co, in proportions such that the compound is described compositionally as SrxCoyFezIrtOuwhere x+y+z+t=1; 0<x<0.3, 0<y≤0.7, 0<z≤0.3, 0<t<0.9; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0008] In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, Ir, Fe, Mn, and Ni, in proportions such that the compound is described compositionally as FexMnyNizIrtOuwhere x+y+z+t=1; 0<x<0.5, 0<y<0.4, 0<z<0.6, 0<t<0.9; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0009] In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, Ir, Co, Mn, and Ni, in proportions such that the compound is described compositionally as CoxMnyNizIrtOuwhere x+y+z+t=1; 0<x<0.6, 0<y<0.4, 0<z<0.4, 0<t<0.9; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0010] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, Ir, Sr, Ni, and Mn, in proportions such that the compound is described compositionally as SrxNiyMnzIrtOuwhere x+y+z+t=1; 0<x<0.6, 0<y<0.5, 0<z<0.3, 0<t<0.9; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0011] In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, Ir, Sr, Ni, and Co, in proportions such that the compound is described compositionally as SrxCoyNizIrtOuAttorney Docket No.00172-004WO1 where x+y+z+t=1: 0<x<0.6, 0<y<0.8, 0<z≤0.3, 0<t<0.9; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0012] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, Ir, Sr, Mn, and Co, in proportions such that the compound is described compositionally as SrxCoyMnzIrtOuwhere x+y+z+t=1; 0<x<0.5 ,0<y<0.7, 0<z<0.4, 0<t≤0.7; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0013] In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, Ir, Ni, Mn, and Co, in proportions such that the compound is described compositionally as NixMnyCozIrtOuwhere x+y+z+t=1; 0.2≤x≤0.8, 0<y≤0.3, 0<z≤0.3, 0.2≤t≤0.8; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0014] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, (IrRu), Sr, Mn, and Ni, where the Ir and Ru are provided at 1:3 molar ratios, in proportions such that the compound is described compositionally as SrxNiyMnz(IrRu)tOuwhere x+y+z+t=1; 0<x≤0.7, 0.4≤y<1, 0.4≤z<1, 0<t≤0.6; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0015] In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, (IrSr), Ru, Ti, and Sb, where the Ir and Sr are provided at 1:3 molar ratios, in proportions such that the compound is described compositionally as RuxTiySbz(IrSr)tOuAttorney Docket No.00172-004WO1 where x+y+z+t=1; 0.1<x<0.8, 0<y<0.4, 0<z<0.4, 0.1<t<0.5; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0016] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, (IrSr), Ru, Mn, and Nb, where the Ir and Sr are provided at 1:3 molar ratios, in proportions such that the compound is described compositionally as RuxMnyNbz(IrSr)tOuwhere x+y+z+t=1; 0<x<0.8, 0<y<0.4, 0<z<0.3, 0<t<0.7; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0017] In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, (IrRu), Ti, Nb, and Sb, where the Ir and Ru are provided at 1:3 molar ratios, in proportions such that the compound is described compositionally as TixNbySbz(IrRu)tOuwhere x+y+z+t=1; 0.1<x<0.5, 0<y≤0.2, 0<z<0.5, 0.2<t<0.8; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0018] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, (IrRu), Co, Mn, and Sb, where the Ir and Ru are provided at 1:3 molar ratios, in proportions such that the compound is described compositionally as CoxMnySbz(IrRu)tOuwhere x+y+z+t=1; 0<x<0.5, 0<y<0.4, 0<z<0.8, 0.2<t<1; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0019] In a certain embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, (IrRu), Sr, W, and Sn, where the Ir and RuAttorney Docket No.00172-004WO1 are provided at 1:3 molar ratios, in proportions such that the compound is described compositionally as SrxWySnz(IrRu)tOuwhere x+y+z+t=1; 0<x<0.4, 0<y<0.2, 0<z<0.6, 0.2<t<0.9; and the oxygen fraction u is the number required to provide an oxidized phase in the lattice after the combination is annealed at about 500 °C (e.g., 300°C to 700°C) in air.

[0020] In a particular embodiment, the disclosure provides for a composition comprising a catalytic oxide material that contains oxygen, (IrRu), Co, Mn, and W, where the Ir and Ru are provided at 1:3 molar ratios, in proportions such that the compound is described compositionally as MnxWyCoz(IrRu)tOuwhere x+y+z+t=1; 0<x<0.4, 0<y<0.2, 0<z<0.6, 0.2<t<0.9.

[0021] In a certain embodiment, the disclosure also provides for an electrode comprising the composition comprising a catalytic oxide material disclosed herein. In a further embodiment, the electrode is part of an oxygen evolution system. In yet a further embodiment, the electrode catalyzes the oxidation of water to oxygen gas. In another embodiment, the composition functions at the surface of the electrode, defines the surface or the electrode, or interacts with one or more components or the environment in which the electrode is positioned. In a further embodiment, the electrode is an anode.

[0022] In a particular embodiment, the disclosure also provides a method for electrolyzing water, comprising: contacting an aqueous medium with an anode and a cathode, wherein the anode comprises a catalytic oxide material disclosed herein; and applying a voltage to provide a current density to cause water in the aqueous solvent to be electrochemically split to form oxygen and hydrogen. In a further embodiment, the aqueous medium has a pH of less than 5 and the volage is applied under anodic conditions. In yet a further embodiment, the aqueous medium comprises sulfuric acid.Attorney Docket No.00172-004WO1

[0023] In a certain embodiment, the disclosure provides a water electrolysis system that comprises one or more water electrolysis cells, wherein the water electrolysis cell comprises: a proton-exchange membrane that a portion of which is coated on one side with one or more anode layers, and coated on the opposite side with one or more cathode layers, wherein anode layers comprises a composition comprising a catalytic oxide material disclose herein; an anode gas- diffusion layer in fluid contact with the one or more anode layers; a cathode gas-diffusion layer in fluid contact with the one or more cathode layers; a plurality of gaskets that prevent the flow of fluids and ions across the proton exchange membrane which is not coated by the one or more anode layers or the one or more cathode layers; and an anode separator and a cathode separator comprising channels for a fluid comprising water, and wherein the anode separator is in fluid contact with the anode gas-diffusion layer, and the cathode separator is in fluid contact with the anode gas-diffusion layer. In a further embodiment, the water electrolysis system comprises at least ten or more water electrolysis cells.

[0024] An electro-oxidation system such as an oxygen evolution system can include an anode in contact with an anolyte. One or more different layers of the anode can include, consist essentially of, or consist of one or more of the catalysts. In some instances, the anolyte has a pH less than 15 and greater than -1. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Sr, Fe, Co, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0026] FIG. 2 provides a (stack plot and / or geometric plotAttorney Docket No.00172-004WO1 in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Fe, Mn, Ni, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0027] FIG. 3 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Sr, Ni, Mn, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0028] FIG. 4 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Sr, Co, Ni, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0029] FIG. 5 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Sr, Co, Mn, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0030] FIG. 6 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ni, Mn, Co, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0031] FIG. 7 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ru, Mn, Sr, Ni, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in theAttorney Docket No.00172-004WO1 composition ranges in the above section.

[0032] FIG. 8 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ru, Sr, Sb, Ti and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0033] FIG. 9 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ru, Sr, Nb, Mn and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0034] FIG. 10 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ru, Ti, Sb, Nb and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0035] FIG. 11 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ru, Co, Mn, Sb and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0036] FIG. 12 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ru, Sr, W, Sn and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0037] FIG. 13 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Ru, Mn, W, Co, and oxygen, in 1MAttorney Docket No.00172-004WO1 sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0038] FIG. 14A provides a perspective view of an electrode that can include a catalyst of the disclosure.

[0039] Fig. 14B provides a schematic showing an electrode comprising a catalyst material of the disclosure.

[0040] FIG. 15A is a diagram illustrating an electrolysis system.

[0041] FIG. 15B provides a schematic showing a water electrolysis cell that comprises a proton exchange membrane comprising a coating of a catalyst material of the disclosure.

[0042] FIG. 16 demonstrates that the system containing SrxNiyMnz(IrRu)tOutraces at approximately 100 mA / cm2in 1M a range of disparate efficienciesaccording to the composition of matter tested. Sample 10 contains a composition of matter that comprises components that do not fit with a range specified for the material herein and further exhibited a high overpotential. Sample 257 contains a composition of matter that comprises components that fit with a range specified for the material herein and further exhibited a high overpotential and exhibited a low overpotential.

[0043] FIG. 17 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Co, Sr, Ni, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section.

[0044] FIG. 18 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Co, Sr, Mn, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in theAttorney Docket No.00172-004WO1 composition ranges in the above section.

[0045] FIG. 19 provides a (stack plot and / or geometric plot in black / white) indicating the electrochemical activity of the metal oxides comprising Ir, Co, Ni, Mn, and oxygen, in 1M sulfuric acid acidic media after durability testing. Darker colors indicated the most active catalysts described in the composition ranges in the above section. DETAILED DESCRIPTION

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing of the present invention. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0047] The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” “may” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures.

[0048] The singular forms “a,” “an” and “the” include plural references unless the context clearly dictates otherwise.

[0049] The present disclosure also contemplates other embodiments “comprising,” “consisting of” and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not.Attorney Docket No.00172-004WO1

[0050] The word “exemplary” is used throughout this application to mean “serving as an example, instance, or illustration.” Any system, method, device, technique, feature or the like described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other features.

[0051] Also, the use of “or” means “and / or” unless slated otherwise. Similarly, “comprise,” “comprises," “comprising” “include,” “includes,” and “including” are interchangeable and not intended to be limiting.

[0052] The disclosure describes the synthesis and provides a composition of matter that includes Ir, oxygen, and between one and four other elements to create a composition with atomic formula IruM2vM3wM4xM5yOz. For various formulations of the invention, there are compositional values with superior catalytic activity for the oxygen evolution reaction (OER) to be described in detail herein. The disclosure also demonstrates and described that for specific compositions described herein, the OER may be undertaken at low overpotentials in acidic media. As a result, the catalysts are an effective and cost-effective replacement for a purely Ir or purely Ir / Ru catalyst.

[0053] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Sr, Fe, and Co, in proportions such that the compound is described compositionally as SrxCoyFezIrtOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form (e.g., about 80-100%Attorney Docket No.00172-004WO1 pure). Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x≤0.8, 0.1≤y≤0.3, 0.1≤z≤0.3, and 0.7≤t<1.0 (see FIG. 1).

[0054] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Fe, Mn, and Ni, in proportions such that the compound is described compositionally as FexMnyNizIrtOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Specific values of x, y, z, and t which return the highest electrochemical activity and stability are 0.0<x≤0.7, 0.0≤y≤0.2, 0.3≤z≤0.8, and 0.2≤t<0.7 (see FIG. 2).

[0055] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Sr, Mn, and Ni, in proportions such that the compound is described compositionally as SrxNiyMnzIrtOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x≤0.7, 0.0<y≤0.3, 0.0<z≤0.7, and 0.3≤t<1 (see FIG. 3).

[0056] In a particular embodiment, the disclosure providesAttorney Docket No.00172-004WO1 for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Sr, Co, and Ni, in proportions such that the compound is described compositionally as SrxCoyNizIrtOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x<1, 0.0<y≤0.7, 0.0<z≤0.7, and 0.0<t<1 (see FIG. 4).

[0057] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Sr, Mn, and Co, in proportions such that the compound is described compositionally as SrxCoyMnzIrtOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x<1, 0.0<y≤0.3, 0.0<z≤0.8, and 0.0<t<1 (see FIG. 5).

[0058] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Ni, Mn, and Co, in proportions such that the compound is described compositionally as NixMnyCozIrtOu. The catalytic material isAttorney Docket No.00172-004WO1 synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.2<x≤0.8, 0.0<y≤0.3, 0.0<z≤0.3, and 0.2≤t<0.8 (see FIG. 6).

[0059] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Ru, Sr, Ni, and Mn, in proportions such that the compound is described compositionally as SrxNiyMnz(IrRu)tOu.The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Ir and Ru precursors are mixed in a 1:3 ratio so that the molar fraction of Ir present is never more than 0.25. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x≤0.7, 0.4≤y<1, 0.4≤z<1, and 0.0<t<0.6 (see FIG. 7).

[0060] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Sr, Ru, Ti, and Sb, in proportions such that the compound is describedcompositionally as RuxTiySbz(IrSr)tOu. The catalytic material issynthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging fromAttorney Docket No.00172-004WO1 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Ir and Sr precursors are mixed in a 1:3 ratio so that the molar fraction of Ir present is never more than 0.25. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.2<x<1, 0.0<y≤0.3, 0.0<z≤0.4, and 0.2≤t<1 (see FIG. 8).

[0061] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Sr, Ru, Mn, and Nb, in proportions such that the compound is described compositionally as RuxMnyNbz(IrSr)tOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Ir and Sr precursors are mixed in a 1:3 ratio so that the molar fraction of Ir present is never more than 0.25. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x<1, 0.5≤y<1, 0.0<z≤0.3, and 0.0<t<1 (see FIG. 9).

[0062] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Ru, Ti, Sb, and Nb, in proportions such that the compound is describedcompositionally as TixNbySbz(IrRu)tOu. The catalytic material issynthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging fromAttorney Docket No.00172-004WO1 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Ir and Ru precursors are mixed in a 1:3 ratio so that the molar fraction of Ir present is never more than 0.25. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x≤0.2, 0.0<y≤0.2, 0.0<z≤0.2, and 0.8≤t<1 (see FIG. 10).

[0063] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Ru, Co, Mn, and Sb, in proportions such that the compound is described compositionally as CoxMnySbz(IrRu)tOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Ir and Ru precursors are mixed in a 1:3 ratio so that the molar fraction of Ir present is never more than 0.25. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.0<x≤0.2, 0.0<y≤0.2, 0.0<z≤0.2, and 0.8≤t<1 (see FIG. 11).

[0064] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Ru, Sr, W, and Sn, in proportions such that the compound is describedcompositionally as SrxWySnz(IrRu)tOu. The catalytic material issynthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging fromAttorney Docket No.00172-004WO1 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Ir and Ru precursors are mixed in a 1:3 ratio so that the molar fraction of Ir present is never more than 0.25. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are 0.2<x<1, 0.2≤y<1, 0.0<z≤0.7, and 0.3≤t<1 (see FIG. 12).

[0065] In a particular embodiment, the disclosure provides for a composition that comprises, consists essentially of, or consists of a catalytic material having oxygen, Ir, Ru, Mn, W, and Co, in proportions such that the compound is described compositionally as MnxWyCoz(IrRu)tOu. The catalytic material is synthesized by combining the respective metal chloride or nitrate salts in aqueous form in concentrations ranging from 0.0001M to 0.25M in the intended compositional ratios and then depositing this mixture into an agarose film, drying the resulting agarose / precursor combination, and annealing in air at about 500 °C (e.g., 300°C to 700°C) to provide the catalyst in a substantially pure metal oxide form. Ir and Ru precursors are mixed in a 1:3 ratio so that the molar fraction of Ir present is never more than 0.25. Specific values of x, y, z, and t which provide the highest electrochemical activity and stability are ; 0.0<x<0.4, 0<y<0.2, 0<z≤0.8, 0.0<t<0.7 (see FIG. 13).

[0066] The components of the mixed metal oxide materials disclosed herein can be selected so as to provide a transparent or substantially transparent catalyst. For instance, the components of the above metal oxides can be selected such that the opacity of the catalyst is less than 40%, 60%, or 90% per 100 nm thickness when averaged over the visible spectrumAttorney Docket No.00172-004WO1

[0067] The catalytic mixed metal oxide materials of the disclosure are tolerant of highly acidic environments such as environments with a pH less than 3, 1, or 0. the catalytic mixed metal oxide materials of the disclosure serve as oxidation catalysts and can accordingly catalyze a variety of reactions such as the Oxygen Evolution Reaction, the Oxygen Reduction Reaction, and redox reaction for flow batteries. In particular, the catalysts are ideally suited to catalyze the Oxygen Evolution Reaction. Catalysts for the oxygen evolution reaction are often placed in an environment with these pH levels for applications such as electrowinning and electrolytic hydrogen evolution. However, the catalysts that are used in highly acidic conditions typically are comprised of very expensive components such as iridium and ruthenium oxides in large amounts. By decreasing the amount of iridium / ruthenium in the catalytic materials, the price associated with these catalysts can be reduced. Accordingly, an oxygen evolution system can include one or more electrodes exposed to an environment with a pH less than 3, 1, or 0 where the electrode comprises a composition comprising as catalytic mixed metal oxide material disclosed herein that has much lower amounts of iridium and ruthenium than typically found in such OER catalytic materials and further excludes noble metals, like palladium, silver, platinum, and gold.

[0068] Accordingly, the catalytic mixed metal oxide materials disclosed herein can serve as oxidation catalysts and can catalyze a variety of reactions such as the Oxygen Evolution Reaction, the Oxygen Reduction Reaction, and redox reaction for flow batteries. In particular, the catalysts can catalyze the Oxygen Evolution Reaction (OER). The Oxygen Evolution Reaction is where oxygen gas is evolved from water or other oxides. One example of the oxygen evolution reaction is the oxidation of water by: 2H2O^ O2+4H++4e-. Another example of the oxygen evolution reaction is 4OH- ^ O2+ 2H2O + 4e-.Attorney Docket No.00172-004WO1

[0069] FIG. 14A is a perspective view of an electrode that includes a catalyst of the disclosure. The electrode includes a catalytic layer 4 on an electrode base (target surface / substrate) 5. The catalytic layer 4 can include, consist of, or consist essentially of one or more components selected from the group consisting of M1xM2yM3zIrtOu,and / or M1xM2yM3z(IrM4)tOuas disclosed herein. The catalytic layer 4 can include components in addition to the one or more catalysts. For instance, the catalytic layer 4 can include one or more components selected from the group consisting of binders, polymers, membranes, electrical conductors, ionic conductors, solid electrolytes, porous materials, and inert support materials. The electrode base 5 represents the portion of the electrode having a traditional electrode construction. Alternately, the electrode base 5 represents the portion of the electrode having a traditional electrode construction but with a prior catalytic layer removed from the electrode. Accordingly, the catalytic layer 4 can be added to a common electrode or can replace a catalytic layer 4 on a common electrode.

[0070] The electrode base 5 can be a current collector such as a metal foil or sheet, mesh, or conducting fabric. As will become evident from the below illustration, the electrode base 5 can be or include a photoactive layer. For instance, the electrode base 5 can include or consist of a material that absorbs light and converts the absorbed light into excited electron-hole pairs that drive a chemical reaction such as electrolysis of water. Although the electrode base 5 is shown as a single layer of material, the electrode base 5 can include multiple layers of material. For instance, the electrode base 5 can include one or more layers of active material on a current collector. In instance where the electrode is employed to oxidize water, the electrode operates as an anode. During fabrication of the electrode, in someAttorney Docket No.00172-004WO1 instances, the electrode base serves as the support or substrate for the catalyst. Accordingly, the catalyst can be formed directly on the electrode base.

[0071] Although the catalytic layer 4 is illustrated as being located on one side of the electrode base 5, the catalytic layer 4 can be located on both sides of the electrode base. Additionally or alternately, the electrode base 5 can be embedded in the catalytic layer 4. For instance, electrode base 5 can be a mesh that is embedded in the catalytic layer 4. Although FIG. 14A illustrates the catalytic layer 4 as a continuous layer of material, the catalytic layer 4 can be patterned so there are openings through the catalytic layer 4 and / or so there are regions of the catalytic layer 4 that are not continuous with one another, such as would occur when the catalytic layer 4 is arranged in islands on the electrode base. Moreover, in this embodiment, various combination of catalysts provided herein can be present on an electrode base 5 forming discrete regions or islands.

[0072] In the illustration of FIG. 14A, the face of the catalytic layer is illustrated as being substantially planar. However, the surface area of the catalyst layer can be increased beyond what can be achieved with the planar face. In some instances, increasing the surface area of the catalyst can increase the catalytic current for a given overpotential. A variety of methods can be employed to increase the surface area of the catalyst. For instance, the catalytic layer can be porous and / or can be microstructured using techniques such as mesoscale self-assembly, soft lithograph, lithography, anodic etching, or other methods known to the art. In some instances, the catalytic layer is constructed such that the specific surface area of the catalytic layer is much greater than the geometric area of the electrode. This can be expressed as a surface roughness factor (specific surfaceAttorney Docket No.00172-004WO1 area / geometric area of the surface area of a planar electrode covered by the catalytic layer). A non-porous catalyst layer with a smooth surface would have a surface roughness factor of 1. The catalytic layer may have surface roughness factors greater than 1, 10, 100 or 1000.

[0073] FIG. 14B presents an example of an electrode comprising a catalytic mixed metal oxide material of the disclosure. The electrode 7 can include one or more of the catalytic mixed metal oxide materials disclosed herein as catalytic layer 4. For instance, catalytic layer 4 can include, consist of, or consist essentially of one or more components selected from the group consisting of M1xM2yM3zIrtOu,and / or M1xM2yM3z(IrM4)tOuas disclosed herein. Catalytic layer 4 may further comprise fillers, electrically conductive materials, diluents, and / or binders. Electrode 7 can further comprise electrode base 5. Electrode base 5 can be a current collector such as a metal foil or sheet, mesh, porous sintered plate, or conducting fabric. Although the electrode base 5 is shown as a single layer, electrode base 5 can include multiple layers of material. For instance, the electrode base 5 can include one or more layers of the same or different materials on a current collector. In instances where the electrode is employed to oxidize water, the electrode operates as an anode. During fabrication of electrode 7, in some instances, the electrode base 5 serves as the support for catalyst layer 4. Accordingly, the catalyst layer 4 can be layered directly on the electrode base 5. Although the catalytic layer 4 is illustrated as being located on one side of the electrode base 5, catalytic layer 4 can be located on both sides of the electrode base 5. Furthermore, other materials, well known to those in the art, may be placed between catalytic layer 4 and electrode base 5, such as a conductive layer containing platinum, fluorinated tin oxide, antimony tin oxide, or other conductive protective layers.Attorney Docket No.00172-004WO1

[0074] An electrode that comprises a catalytic mixed metal oxide material of the disclosure can be employed in an electro-oxidation system such as an oxygen evolution system, where the Oxygen Evolution Reaction (OER) is catalyzed at one or more electrodes included in the system.

[0075] FIG. 15A provides a general schematic of an electrode system for oxygen evolution. The system depicted comprises two chambers 15 and 18 separated by a membrane 11. Chambers 15 and 18 can be flow spaces that carry water or vapor, wherein chamber 15 comprises water in contact with anode 14 and chamber 18 comprises hydrogen ions and H2in contact with cathode 19. Anode 14 can comprise a substrate or base 5. Suitable materials for substrate or base 5 include, but are not limited to, metals, metal alloys, metal phosphide and metal oxides such as Ni, Cu, Cu / Au, NiPx, CoPx, CoOx, and NiFeOx. When the anode 14 is or includes a photoanode 14, the anode base or substrate 5 can include or consist of a photoanode light absorber selected to absorb light at a wavelength to which the photoanodes 14 will be exposed during operation. As described above, the substrate or base 5 of anode 14 includes a catalytic layer 4 on an electrode base (target surface / substrate) 5. The catalytic layer 4 includes, consists of, or consists essentially of one or more components selected from the group consisting of M1xM2yM3zIrtOu,and / or M1xM2yM3z(IrM4)tOuas disclosed herein. The catalytic layer 4 can include components in addition to the one or more catalysts. For instance, the catalytic layer 4 can include one or more components selected from the group consisting of binders, polymers, membranes, electrical conductors, ionic conductors, solid electrolytes, porous materials, and inert support materials. The electrode base 5 represents the portion of the electrode having a traditional electrode construction.

[0076] FIG. 15A also depicts membrane 11. A suitableAttorney Docket No.00172-004WO1 membrane 11 include, but are not limited to, polyaromatic polymers, fluorinated polymers functionalized with sulfonic acid groups. An example of a suitable fluorinated polymer functionalized with sulfonic acid groups is sold under the trademark NAFION^. A suitable thickness for the membrane 11 includes, but is not limited to, a thickness greater than 1 µm, 5 µm, or 10 µm and / or less than 500 µm, 1000 µm.

[0077] FIG. 15A also depicts an electrical pathway that includes the anode 14, the one or more electrical conductors 34 and the cathode 19. An external bias source 36 positioned along the electrical pathway so as to apply a bias between the cathode 19 and the anode 14. Suitable external bias source 36 includes, but is not limited to, batteries, fuel cells, and grid electricity.

[0078] FIG. 15A depicts cathode 19 present in chamber or flow space 18. The cathode 19 can include an optional cathode catalyst layer 24 on a cathode conductor 26. The cathode catalyst layer 24 can include one or more cathode catalysts selected to catalyze the half reaction that occurs at the cathode 19. Although the one or more cathode catalysts are shown as being included in a cathode catalyst layer 24, the one or more cathode catalysts can be included in the cathode conductor 26. Suitable cathode catalysts include, but are not limited to, reduction catalysts. When the half reaction at the cathode 22 is the hydrogen evolution reaction (HER), a suitable cathode catalyst includes, but is not limited to, Pt, Ni, NiPx, CoPx, NiMo, and combinations thereof. When the cathode 19 is not photoactive, suitable cathode conductors 26 include, but are not limited to, metals and metal oxides such as metals, metal alloys, metal phosphide and metal oxides such as Ni, Cu, Cu / Au, NiPx, CoPx, CoOx, NiFeOx. When the cathode 19 is or includes a photocathode 19, the cathode conductor 26 can include a photocathode light absorber selected to absorb light at a wavelength to which the photocathode 22 will beAttorney Docket No.00172-004WO1 exposed during operation.

[0079] FIG. 15B illustrates an example of a water electrolysis cell 100 capable of carrying out OER. Water electrolysis cell 100 includes an anode layer 12 in contact with a membrane 11. In a particular embodiment, anode layer 12 comprises a catalytic mixed metal oxide material of the disclosure. Anode layer 12 may further comprise fillers, electrically conductive materials, diluents, and / or binders. Although anode layer 12 is shown as a single layer of material, anode layer 12 can include multiple layers of material. For instance, anode layer 12 can include one or more layers of catalytic mixed metal oxide material of the disclosure deposited or layered on membrane 11. Electrolysis cell 100 further comprises cathode layer 13. In a particular embodiment, cathode layer 13 comprises a catalytic mixed metal oxide material of the disclosure. Cathode layer 13 may further comprise fillers, electrically conductive materials, diluents, and / or binders. Although cathode layer 13 is shown as a single layer of material, cathode layer 13 can include multiple layers of material. For instance, cathode layer 13 can include one or more layers of catalytic mixed metal oxide material of the disclosure deposited or layered on membrane 11. Separating cathode layer 13 from anode layer 12 is membrane 11. Membrane 11 provides an acidic and conductive medium for water splitting reactions. An example of membrane 11 is NafionTM, which is commercially available and frequently used by those skilled in the art. In a certain embodiment, anode layer 12 and cathode layer 13 are deposited or coated onto the surface of membrane 11 to form a catalyst-coated membrane 10. Electrolysis cell 100 further comprises layers or spaces that are configured to promote the diffusion of gases catalyzed by anode layer 12 and cathode layer 13. In a particular embodiment, anode layer 12 is in contact with anode gas- diffusion layer 20. In a further embodiment, anode gas-Attorney Docket No.00172-004WO1 diffusion layer 20 is located on the side opposite of anode layer 12 that is in contact with membrane 11. In another embodiment, cathode layer 13 is in contact with cathode gas- diffusion layer 30. In a further embodiment, cathode gas- diffusion layer 30 is located on the side opposite of cathode layer 13 that is in contact with proton-exchange membrane 11. Electrolysis cell 100 further comprises gasket 40 and gasket 50. Gasket 40 and gasket 50 are impermeable to fluids. Gasket 40 and gasket 50 can be made of any solid or sealing material that is impermeable to fluids, including plastic, rubber, silicone, etc. Specific examples of materials that can be used for gasket 40 and gasket 50 include EPDM, PTFE, low permeation butyl, low permeation FKM, VMQ, or any combination thereof. Gasket 40 and gasket 50 may be of selected of varying hardness from flexible to rigid. Gasket 40 and gasket 50 can have any shape or design, including O-Ring, profiled, spiral wound, etc. Anode separator 60 can comprise fluid channels or flow fields 65. Alternatively, anode separator 60 does not comprise raised fluid channels. Similarly, cathode separator 70 can comprise fluid channels or flow fields 75. Alternatively, cathode separator 70 does not comprise raised fluid channels. In particular embodiment, anode separator 60 and separator 70 are in the form of bipolar plates. Anode separator 60 and cathode separator 70 can be produced using a variety of techniques, including stamping, hydroforming, chemical etching, 3D printing, and presswork tooling. In a particular embodiment, anode separator 60 and cathode separator 70 are produced using a 3D printer or chemical etching. Chemical etching provides for simultaneous removal of metal, allowing for the creation of intricate channels or flow fields on both sides of the plate. Chemical etching also avoids introducing mechanical stress or burring, which can potentially compromise stack bonding and overall performance. This ensures the integrity of the etched plate while maintaining optimalAttorney Docket No.00172-004WO1 functionality and performance without any detrimental effects. Anode separator 60 and cathode separator 70 are typically made of metal (e.g., stainless steel, titanium, or aluminum) graphite, or carbon black. Anode separator 60 and cathode separator 70 are designed to evenly distribute the fuel and the oxidant to the catalyst-coated membrane. Anode separator 60 and cathode separator 70 also collect the generated electric current at the output terminals (not shown). In a further embodiment, the disclosure provides for a fuel cell or water electrolysis system that comprises a plurality of water electrolysis cell 100. In yet a further embodiment, the disclosure provides for a fuel cell or water electrolysis system that comprises 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 150, 200, 250, 300, 400, 500, 600, 700, 800, 900, 1000 or more, or a range that includes or is between any two of the foregoing numbers, of water electrolysis cell 100. In a particular embodiment, the fuel cell or water electrolysis system comprises a plurality of water electrolysis cell 100 that are physically contacting each other in a stacked manner.

[0080] In the illustration for FIG. 15B, the face of the anode layer 12 and cathode layer 13 are illustrated as being substantially planar. However, the surface area of the anode layer 12 and cathode layer 13 can be increased beyond what can be achieved with the planar face. In some instances, increasing the surface area of anode layer 12 and / or cathode layer 13 can increase the catalytic current for a given overpotential. A variety of methods can be employed to increase the surface area of the anode layer 12 and cathode layer 13. For instance, anode layer 12 and / or cathode layer 13 can be porous and / or can be micro-structured using techniques such as mesoscale self-assembly, soft lithograph, lithography, anodic etching, or other methods known to the art. In some instances, anode layer 12 and / or cathode layer 13 is constructed such that the specific surface area of theAttorney Docket No.00172-004WO1 catalytic layer is much greater than the geometric area or the electrode. This can be expressed as a surface roughness Factor (specific surface area / geometric area or the surface area or a planar electrode covered by the catalytic layer). A non-porous catalyst layer with a smooth surface would have a surface roughness factor of 1. The catalytic mixed metal oxide layer may have surface roughness factors greater than l, 10, 100 or 1000.

[0081] An electro-oxidation system such as an oxygen evolution system can include an anode in contact with an anolyte. One or more different layers of the anode can include, consist essentially of, or consist of one or more of the catalysts. In some instances, the anolyte has a pH less than 15 and greater than -1.

[0082] The disclosure further provides methods for electrolyzing water, comprising: contacting an aqueous medium with an anode and a cathode, wherein the anode comprises a catalytic oxide material disclosed herein; and applying a voltage to provide a current density to cause water in the aqueous solvent to be electrochemically split to form oxygen and hydrogen. In a further embodiment, the aqueous medium has a pH of less than 5 and the volage is applied under anodic conditions. In yet a further embodiment, the aqueous medium comprises sulfuric acid.

[0083] In some embodiments, there is provided a water electrolyzer system, comprising: an electrolytic cell configured to receive water; an anode comprising a catalytic oxide material disclosed herein; a cathode; and a voltage source to provide a current density to cause the water to be electrochemically split to form oxygen and hydrogen at the anode and cathode respectively. The water electrolyzer system can include one or more operating features, elements, or conditions and / or includes equipment or features thereof having one or more features, as described or illustrated orAttorney Docket No.00172-004WO1 claimed herein.

[0084] In some embodiments, there is provided a system for CO and / or CO2electroreduction to produce a multi-carbon compound, comprising: an electrolytic cell configured to receive a liquid electrolyte and CO and / or CO2gas; an anode comprising a catalytic oxide material disclosed herein; a cathode comprising a copper containing electroreduction catalyst; and a voltage source to provide a current density to cause the CO and / or CO2gas contacting the cathode to be electrochemically converted into the multi-carbon compound and to cause an oxygen evolution reaction at the anode. The system can also include one or more operating features, elements, or conditions and / or includes equipment or features thereof having one or more features, as described or illustrated or claimed herein.

[0085] The catalyst materials were tested for durability by submerging the substrate containing all catalyst compounds in 1M sulfuric acid. The substrate was attached to a potentiostat by titanium clips. This electrochemical cell utilized a Nickel mesh counter electrode for hydrogen evolution and a saturated calomel (SCE) reference electrode. A voltage of 1.5V (vs the SCE) was applied to the substrate (referred to as the 'working electrode') for 4 hours to enable oxygen evolution on the catalyst-containing substrate. The sample was run for 3 hours under these conditions to mimic the conditions in a proton exchange membrane water electrolyzer (PEMWE).

[0086] It will be understood that various modifications may be made without departing from the spirit and scope of this disclosure. Accordingly, other embodiments are within the scope of the following claims.

Claims

Attorney Docket No.00172-004WO1 WHAT IS CLAIMED IS:

1. A composition comprising: a catalytic oxide material comprising Ir, oxygen, and at least three additional metals and which has the atomic formula of M1xM2yM3zIrtOu,or M1xM2yM3z(IrM4)tOu; wherein, M1, M2, M3, and M4 are different metals, and wherein M1, M2, M3 are selected from Ru, Sr, Fe, Co, Mn, Ni, Sb, Nb, W, and Sn, and M4 is selected from Ru and Sr; wherein x+y+t+z=1; and wherein the catalytic oxide material has electrochemical activity in an acidic environment.

2. The composition of claim 1, wherein the catalytic oxide material has the atomic formula of M1xM2yM3zIrtOu, and one of M1, M2, and M3 is Ru, Sr or Ni.

3. The composition of claim 1 or claim 2, wherein the catalytic oxide material has the atomic formula of M1xM2yM3zIrtOu, and M1, M2, and M3 are selected from: (a) Sr, Fe, and Co; (b) Fe, Mn, and Ni; (c) Sr, Ni, and Mn; (d) Sr, Ni, and Co; (e) Sr, Mn, and Co; and (f) Ni, Mn, and Co.

4. The composition of any one of claims 1 to 3, wherein M1xM2yM3zIrtOuis SrxCoyFezIrtOuwhere 0<x<0.3, 0<y≤0.7, 0<z≤0.3, 0<t<0.9 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

5. The composition of any one of claims 1 to 3, wherein M1xM2yM3zIrtOuis FexMnyNizIrtOuwhere 0<x<0.5, 0<y<0.4, 0<z<0.6,Attorney Docket No.00172-004WO1 0<t<0.9 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

6. The composition of any one of claims 1 to 3, wherein M1xM2yM3zIrtOuis SrxNiyMnzIrtOuwhere 0<x<0.6, 0<y<0.5, 0<z<0.3, 0<t<0.9, and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

7. The composition of any one of claims 1 to 3, wherein M1xM2yM3zIRtOuis SrxCoyNizIrtOuwhere 0<x<0.6, 0<y<0.8, 0<z≤0.3, 0<t<0.9 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

8. The composition of any one of claims 1 to 3, wherein M1xM2yM3zIRtOuis SrxCoyMnzIrtOuwhere 0<x<0.5 ,0<y<0.7, 0<z<0.4, 0<t≤0.7 and the oxygen fraction u is the number required in the lattice annealed at an elevated temperature in air.

9. The composition of any one of claims 1 to 3, where M1xM2yM3zIRtOuis CoxMnyNizIrtOuwhere 0<x<0.6, 0<y<0.4, 0<z<0.4, 0<t<0.9 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

10. The composition of any one of claims 1 to 3, wherein the catalytic oxide material has the atomic formula of M1xM2yM3z(IrM4)tOuand M1, M2, M3 and M4 are selected from: (A) Sr, Mn, Ni, and Ru; (B) Ru, Ti, Sb, and Sr; (C) Ru, Mn, Nb, and Sr; (D) Ti, Nb, Sb, and Ru; (E) Co, Mn, Sb, and Ru; (F) Sr, W, Sn, and Ru; and (G) Co, Mn, W, and Ru.Attorney Docket No.00172-004WO1 11. The composition of claim 10, wherein M1xM2yM3z(IrM4)tOuis SrxNiyMnz(IrRu)tOuwhere 0<x≤0.7, 0.4≤y<1, 0.4≤z<1, 0<t≤0.6 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

12. The composition of claim 10, wherein M1xM2yM3z(IrM4)tOuis RuxTiySbz(IrSr)tOuwhere 0.1<x<0.8, 0<y<0.4, 0<z<0.4, 0.1<t<0.5 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

13. The composition of claim 10, wherein M1xM2yM3z(IrM4)tOuis RuxMnyNbz(IrSr)tOuwhere 0<x<0.8, 0<y<0.4, 0<z<0.3, 0<t<0.7 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

14. The composition of claim 10, wherein M1xM2yM3z(IrM4)tOuis TixNbySbz(IrRu)tOuwhere 0.1<x<0.5, 0<y≤0.2, 0<z<0.5, 0.2<t<0.8 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

15. The composition of claim 10, wherein M1xM2yM3z(IrM4)tOuis CoxMnySbz(IrRu)tOuwhere 0<x<0.5, 0<y<0.4, 0<z<0.8, 0.2<t<1 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

16. The composition of claim 10, wherein M1xM2yM3z(IrM4)tOuis SrxWySnz(IrRu)tOuwhere 0<x<0.4, 0<y<0.2, 0<z<0.6, 0.2<t<0.9 and the oxygen fraction u is the number required in the lattice after annealed at an elevated temperature in air.

17. The composition of claim 10, wherein M1xM2yM3z(IrM4)tOuis MnxWyCoz(IrRu)tOuwhere 0<x<0.4, 0<y<0.2, 0<z<0.6, 0.2<t<0.9 and the oxygen fraction u is the number required in the lattice annealed at an elevated temperature in air.Attorney Docket No.00172-004WO1 18. The composition of any one of claims 4 to 9, and 13 to 17, wherein the amount of oxygen in the catalytic oxide material results from annealing the catalytic oxide material in air at an elevated temperature from about 500 °C to 700 °C.

19. An electrode comprising the composition of any one of claims 1 to 18.

20. The electrode of claim 19, wherein the electrode is part of an oxygen evolution system 21. The electrode of claim 19 or claims 20, wherein the electrode catalyzes the oxidation of water to oxygen gas.

22. The electrode of any one of claims 19 to 21, wherein the composition functions at the surface of the electrode, defines the surface or the electrode, or interacts with one or more components or the environment in which the electrode is positioned.

23. A method for electrolyzing water, comprising: contacting an aqueous medium with an anode and a cathode, wherein the electrode of any one of claims 19 to 22 is the anode; and applying a voltage to provide a current density to cause water in the aqueous solvent to be electrochemically split to form oxygen and hydrogen.

24. The method of claim 23, wherein the aqueous medium has a pH of less than 5 and the volage is applied under anodic conditions.Attorney Docket No.00172-004WO1 25. The method of claim 24, wherein the aqueous medium comprises sulfuric acid.

26. A water electrolysis system that comprises one or more water electrolysis cells, wherein the water electrolysis cell comprises: a proton-exchange membrane that a portion of which is coated on one side with one or more anode layers, and coated on the opposite side with one or more cathode layers, wherein anode layers comprise the composition of any one of claims 1 to 18; an anode gas-diffusion layer in fluid contact with the one or more anode layers; a cathode gas-diffusion layer in fluid contact with the one or more cathode layers; a plurality of gaskets that prevent the flow of fluids and ions across the proton exchange membrane which is not coated by the one or more anode layers or the one or more cathode layers; and an anode separator and a cathode separator comprising channels for a fluid comprising water, and wherein the anode separator is in fluid contact with the anode gas-diffusion layer, and the cathode separator is in fluid contact with the anode gas-diffusion layer.

27. The water electrolysis system of claim 26, wherein the water electrolysis system comprises at least ten or more water electrolysis cells.

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