Catalysts containing active site groups having boron groups, metal hydroxide groups, or metal oxide groups

Abstract

The catalyst comprises catalyst particles including a first metal atom and an active site group bonded to the first metal atom by one or more oxo bridges. The active site group includes a boron group, a metal hydroxide group, or a metal oxide group. The metal hydroxide group includes a second metal atom or beryllium, and the metal oxide group includes a second metal atom. The second metal atom is different from the first metal atom and includes aluminum, gallium, indium, or bismuth.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 448,016, filed February 24, 2023, the entire contents of which are incorporated herein by reference. [Background technology]

[0002] Some electrochemical cells, such as hydrogen fuel cells and water electrolysis systems, use proton exchange membranes (PEMs) to selectively transport protons. PEMs are semipermeable membranes that are impermeable to gases but allow protons (H + ) transport. PEMs generally consist of a porous skeleton and strong acid functional groups. For example, polyfluorosulfonic acid-based PEMs contain a porous skeleton of poly(tetrafluoroethylene) (PTFE) with sulfonic acid groups. The easily dissociated sulfonic acid groups function as proton transport agents within the membrane. In a hydrogen fuel cell, hydrogen gas (H2) is transported at the anode to protons (H + ) and electrons. The protons pass through the PEM and combine with oxygen gas (O2) at the cathode to produce water, while the electrons flow through an external circuit to generate electricity. In a water electrolysis system, on the other hand, electricity is used to convert water into oxygen gas (O2) and protons (H + The protons pass through the PEM and combine with electrons at the cathode to produce hydrogen gas (H2).

[0003] A membrane electrode assembly (MEA) can include a PEM disposed between first and second catalyst layers. The catalyst layers are conductive electrodes (anode and cathode) containing electrochemical catalyst particles, such as metals, metal alloys, or metal oxides. The catalyst particles can be supported on a catalytic solid support, which typically comprises electrically conductive, high-surface-area carbon (e.g., graphite or graphene). The electrochemical catalyst reduces the activation energy required to drive electrochemical reactions at the electrodes, such as the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in water electrolysis applications, and the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) in fuel cell applications.

[0004] In water electrolysis, the oxygen evolution reaction (OER) is expressed by the following electrochemical half-reaction (Equation (1)): 2H2O――(catalyst)―→O2+4H + +4e - (1) The OER mechanism is a complex, multi-step electrochemical process involving four-electron transfer, in which a metal oxide catalyst reversibly binds to an oxygen-containing intermediate. The proposed OER mechanism proceeds through the following four steps, shown in Equations 1a-1d: H2O+X * ―――→X * OH+H + +e - (1a) X * OH―――→X * O+H + +e - (1b) H2O+X * O―――→X * OOH+H + +e - (1c) X * OOH―――→X * +O2+H + +e - (1d) where X * represents a catalyst, and an asterisk ( * ) represents the active site of the catalyst. * OH, X * O and X* OOH represents the intermediate species bound to the catalytically active site.

[0005] As shown in reaction equation (1a), the first step of OER is the hydroxylation step, in which a water molecule is converted into a proton (H + ) and hydroxide ions (OH - ), and hydroxide ions reversibly bind to the active sites of the anode catalyst. This binding can occur directly to the metal atoms or at oxygenation centers via the participation of lattice oxygen atoms present on the surface of the metal oxide catalyst (lattice oxygen involvement). The subsequent steps of OER (reactions (1b), (1c), and (1d)) involve multiple electron transfer and oxidation steps, after which oxygen gas (O2) is released at the anode, freeing the active sites of the catalyst for the next catalytic cycle. The hydroxylation reaction step (1a) is often the rate-limiting step in OER.

[0006] Iridium(IV) oxide (IrO2) and its various surface hydroxide compositions are currently the catalyst of choice for the anode in water electrolysis (OER) and other applications due to their excellent performance, energy efficiency, and high stability over a wide range of pH conditions. Iridium(IV) oxide can be combined with ruthenium oxide (ruthenium(IV) oxide (RuO2)) or other platinum group metals to improve performance. However, platinum group metals, including iridium and ruthenium, are expensive and have low natural abundance. Therefore, there is a need for catalysts that use reduced amounts of iridium and / or ruthenium and / or utilize non-platinum group metals while providing optimal reversible substrate binding, stability under harsh redox conditions, fast reaction rates, and low energy losses during electrochemical processes. Summary of the Invention

[0007] The following presents a simplified summary of one or more embodiments of the devices, compositions, and / or methods described herein to provide a basic understanding of such embodiments. This summary is not an exhaustive overview of all contemplated embodiments, and is not intended to identify key or critical elements of all embodiments or to delineate the scope of such embodiments. Its sole purpose is to present some concepts of one or more embodiments of the devices, compositions, and / or methods in a simplified form as a prelude to the more detailed description that is presented later herein.

[0008] In some exemplary embodiments, a catalyst comprises a catalyst particle comprising a first metal atom and an active site group bonded to the first metal atom by one or more oxo bridges, the active site group comprising a boron group, a metal hydroxide group, or a metal oxide group, the metal hydroxide group comprising a second metal atom or beryllium, the metal oxide group comprising the second metal atom, the second metal atom being different from the first metal atom and comprising aluminum, gallium, indium, or bismuth.

[0009] In some exemplary embodiments, the catalyst comprises a first metal atom and an active site group comprising a boron atom or a second metal atom, wherein the boron atom or the second metal atom is bonded to the first metal atom by one or more oxo bridges, and the second metal atom is different from the first metal atom and comprises aluminum, gallium, indium, bismuth, or beryllium.

[0010] In some exemplary embodiments, a method for preparing a catalyst includes modifying a catalyst particle comprising a first metal atom with an active site group, wherein the active site group comprises a boron group, a metal hydroxide group, or a metal oxide group, wherein the metal hydroxide group comprises a second metal atom or beryllium, and wherein the metal oxide group comprises the second metal atom, wherein the second metal atom is different from the first metal atom and comprises aluminum, gallium, indium, or bismuth.

[0011] In some exemplary embodiments, a method for preparing a catalyst includes conducting an oxygen evolution reaction (OER) using any of the catalysts described herein, as represented by the electrochemical half-reaction of Equation (1): 2H2O――(catalyst)―→4H + +4e - (1)

[0012] In some exemplary embodiments, a method for preparing a catalyst includes performing the oxygen reduction reaction (ORR), represented by the electrochemical half-reaction of equation (2), using any of the catalysts described herein. O2+4H + +4e - --(catalyst)-->2H2O (2)

[0013] In some exemplary embodiments, the catalyst layer comprises a catalyst support, any of the catalysts described herein, and an ionomer.

[0014] In some exemplary embodiments, a membrane electrode assembly includes a cathode, an anode, and a proton exchange membrane disposed between the cathode and the anode, wherein at least one of the cathode or the anode includes a catalyst layer comprising a catalyst support and any of the catalysts described herein.

[0015] In some exemplary embodiments, a method for producing ammonia includes combining nitrogen and hydrogen according to reaction equation (3) using any of the catalysts described herein. N2 + 3H2 - (catalyst) - → 2NH3 (3)

[0016] To understand the concepts described herein, various embodiments are described below by way of example with reference to the drawings, which illustrate various embodiments and constitute a part of this specification. The illustrated embodiments are merely examples and are not intended to limit the scope of the disclosure. Throughout the drawings, the same or similar reference numerals refer to the same or similar elements. [Brief explanation of the drawings]

[0017] [Figure 1A] FIG. 1 shows an exemplary reaction scheme for producing an iridium(IV) oxide catalyst modified with boron groups. [Figure 1B] FIG. 1 shows an exemplary reaction scheme for producing an iridium(IV) oxide catalyst modified with boron groups. [Figure 1C] FIG. 1 shows an exemplary reaction scheme for producing an iridium(IV) oxide catalyst modified with boron groups. [Figure 2A] FIG. 1 shows an exemplary reaction scheme for preparing an iridium (IV) oxide catalyst modified with bismuth hydroxide groups. [Figure 2B] FIG. 1 shows an exemplary reaction scheme for preparing an iridium (IV) oxide catalyst modified with bismuth hydroxide groups. [Figure 2C] FIG. 1 shows an exemplary reaction scheme for preparing an iridium (IV) oxide catalyst modified with bismuth hydroxide groups. [Figure 3] FIG. 1 shows an exemplary reaction scheme for producing an iridium (IV) oxide catalytic material modified with boron and bismuth hydroxide groups. [Figure 4A] FIG. 1 shows an exemplary reaction scheme for producing a catalyst based on bismuth(III) oxide (BiO). [Figure 4B] FIG. 1 shows an exemplary reaction scheme for producing a catalyst based on bismuth(III) oxide (BiO). [Figure 5A] FIG. 1 shows an exemplary reaction scheme for preparing a boron-modified iridium(IV) catalyst using iridium(III) chloride. [Figure 5B] FIG. 1 shows an exemplary reaction scheme for preparing a boron-modified iridium(IV) catalyst using iridium(III) chloride. [Figure 5C] FIG. 1 shows an exemplary reaction scheme for preparing a boron-modified iridium(IV) catalyst using iridium(III) chloride. [Figure 6A]FIG. 1 shows an exemplary reaction scheme for preparing an iridium(IV) catalyst modified with bismuth hydroxide groups using iridium(III) chloride. [Figure 6B] FIG. 1 shows an exemplary reaction scheme for preparing an iridium(IV) catalyst modified with bismuth hydroxide groups using iridium(III) chloride. [Figure 6C] FIG. 1 shows an exemplary reaction scheme for preparing an iridium(IV) catalyst modified with bismuth hydroxide groups using iridium(III) chloride. [Figure 7] FIG. 1 illustrates an exemplary proton exchange membrane water electrolysis system. [Figure 8] FIG. 1 illustrates an exemplary proton exchange membrane fuel cell. DETAILED DESCRIPTION OF THE INVENTION

[0018] As described herein, the catalyst comprises a first metal atom (M 1 ) and a first metal atom (M 1 and active site groups bonded to a second metal atom (M 2 ) or beryllium, and the metal oxide group contains a second metal atom (M 2 ) containing a second metal atom (M 2 ) is the first metal atom (M 1 ), may be aluminum, gallium, indium, or bismuth. In some examples, the first metal atom (M 1 ) is a transition metal (e.g., nickel, cobalt, or iron). In other examples, the first metal atom (M 1 ) is a platinum group metal (e.g., iridium or ruthenium). In yet another example, the first metal atom (M 1 ) is bismuth. The boron atom of the boron group and / or the second metal atom (M) of the metal hydroxide or metal oxide group 2 ) is connected to the first metal atom (M1 ) bonded to the boron atom of the boron group and the second metal atom (M 2 ) is electron deficient and therefore readily combines with hydroxide ions and other reactive intermediates, transporting the hydroxide ions and intermediates to adjacent metal atoms (e.g., the first metal atom (M 1 )) and / or oxygen atoms (e.g., lattice oxygen atoms). Thus, the boron atoms and the second metal atoms (M 2 ) functions as a gateway for catalytic substrate binding.

[0019] For example, in the hydroxylation step (1a) in OER, the boron atom of the boron group or the second metal atom (M 2 ) smoothly and quickly accepts bonding with hydroxide anions. 2 The rapid binding of hydroxide ions to the catalyst (Figure 1A-1C, Figure 2A-2C, Figure 3, Figure 5A-5C, and Figure 6A-6C) results in a faster reaction rate and a lower overpotential for the OER compared to conventional electrochemical catalysts. Furthermore, the catalysts described herein efficiently bind to the OER intermediate species without overlying or overlying the catalyst. The catalysts described herein also have efficient catalytic throughput in the OER due to their high stability under the harsh redox conditions of water electrolysis, fast reaction rates, and low energy loss during the electrochemical process. Consequently, the inherent molecular properties of the catalysts described herein allow for reduced platinum group metal usage (Figures 1A-1C, Figures 2A-2C, Figure 3, Figure 5A-5C, and Figure 6A-6C examples) or even the complete elimination of platinum group metal usage (Figures 4A and 4B examples).

[0020] In addition to OER, the catalysts described herein can be used in other electrochemical reactions (e.g., ORR, HER, or HOR) and even in other non-electrochemical applications, such as the Haber-Bosch process for ammonia production. Exemplary uses and applications of the catalysts are described in detail below.

[0021] In order to understand the various aspects of this disclosure, various definitions are provided below. In the event of a conflict with any patent application publication or patent incorporated by reference herein, the present specification, including definitions, will control.

[0022] As used herein, "catalyst particle" refers to a particle in "black" or pure form (e.g., excluding catalyst supports and catalyst additives to which the catalyst particle may be bound) that increases the rate of a reaction without modifying the overall standard Gibbs free energy change of the reaction. A catalyst particle may be a single molecule (including, but not limited to, a monomeric molecule), a group of molecules, a crystalline structure (e.g., in the form of a metal oxide), a polymeric molecule, or an oligomeric molecule. A catalyst particle may have any suitable size and shape, such as a microparticle, nanoparticle, or nanotube. A catalyst particle may comprise, for example, a metal, a metal alloy, a metal oxide, a metal halide (e.g., a metal chloride), or a composite comprising at least one of a metal, a metal alloy, a metal oxide, or a metal halide.

[0023] As used herein, "electrochemical catalyst particles" or "electrochemical catalyst" refers to catalyst particles that reduce the activation energy required to carry out an electrochemical reaction, such as OER, HER, HOR, and / or ORR, and / or increase the rate of the electrochemical reaction. Suitable electrochemical catalyst particles include, but are not limited to, platinum group metals (PGM) (e.g., platinum, palladium, iridium, ruthenium, osmium, and rhodium), transition metals (e.g., silver, gold, cobalt, copper, iron, nickel, rhenium, and mercury), post-transition metals (e.g., bismuth and tin), metal alloys (e.g., PGM-transition metal alloys and platinum-ruthenium alloys), metal oxides (e.g., PGM oxides [iridium(IV) oxide, ruthenium(IV) oxide, iridium-ruthenium oxide, platinum(IV) oxide, magnesium oxide, and cerium(IV) oxide]), metal halides (e.g., platinum(IV) chloride, iridium(III) chloride, platinum(IV) bromide, iridium(III) bromide), and / or complexes of metals, metal alloys, metal oxides, and / or metal halides.

[0024] As used herein, the term "catalyst support" refers to a substance that can be used to support catalyst particles, excluding catalyst particles (e.g., a substance or material to which catalyst particles can be bonded or supported). Examples of catalyst supports include, but are not limited to, carbon (e.g., graphite, carbon nanotubes, and / or graphene), titanium dioxide, Sb-doped SnO2 nanoparticles, ITO (tin-doped indium oxide), and the ion-exchange-modified catalyst supports described in International Patent Application No. PCT / US2022 / 046105, filed October 7, 2022, which is incorporated herein by reference in its entirety.

[0025] As used herein, "catalyst" refers to catalyst particles as well as catalyst particles present with a catalyst support on which the catalyst particles are supported or bound. The catalyst may also include catalytic additives such as promoters (e.g., metalloids).

[0026] As used herein, "electrochemical catalyst" or "electrochemical catalyst" refers to electrochemical catalyst particles in "black" or pure form, as well as electrochemical catalyst particles present with a catalyst support on which the electrochemical catalyst particles are supported or bound. Electrochemical catalysts may also include catalytic additives, such as promoters.

[0027] As used herein, "metal" includes alkali metals, alkaline earth metals, transition metals, lanthanides, actinides, and post-transition metals.

[0028] In this specification, the term "transition metal" refers to elements in the d block of the periodic table (elements included in groups 3 to 12).

[0029] As used herein, "late transition metals" means aluminum, gallium, indium, tin, thallium, lead, bismuth, and polonium.

[0030] As used herein, "metalloid" means boron, silicon, germanium, arsenic, antimony, tellurium, and astatine.

[0031] As used herein, "platinum group metals" or "PGM" means platinum, palladium, iridium, ruthenium, osmium, and rhodium.

[0032] As used herein, the term "composite" refers to a material made up of a combination of two or more different constituent materials, each of which retains its own inherent properties while exhibiting properties that the constituent materials do not possess alone.

[0033] As used herein, "ionomer" refers to a polymer composed of macromolecules in which a small but significant proportion (e.g., about 15 mol % or less) of the constituent units have ionic and / or ionizable groups (e.g., sulfonic acid groups, carboxylic acid groups, phosphate groups, tetravalent boron-based acid groups, etc.).

[0034] As used herein, "alkyl" refers to saturated aliphatic groups, including straight-chain alkyl groups, branched-chain alkyl groups, cycloalkyl (alicyclic) groups, alkyl-substituted cycloalkyl groups, and cycloalkyl-substituted alkyl groups. Terms such as "alkyl" encompass both substituted and unsubstituted groups. Examples of acyclic alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, n-butyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, n-heptyl, n-octyl, n-decyl, n-undecyl, and dodecyl. Examples of cyclic alkyl groups include, but are not limited to, cyclopropyl, cyclobutyl, and cyclohexyl.

[0035] As used herein, "aryl" refers to an aromatic carbocyclic group, whether monocyclic (e.g., phenyl), polycyclic (e.g., biphenyl), or fused polycyclic, in which at least one ring is aromatic (e.g., 1,2,3,4-tetrahydronaphthyl, naphthyl, anthryl, or phenanthryl). For example, at least one ring has a conjugated π-electron system, and other adjacent rings may be cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, and / or heterocyclic. A "carbocyclic aryl group" refers to an aryl group in which the ring atoms of the aromatic ring are carbon atoms. Carbocyclic aryl groups include monocyclic carbocyclic aryl groups and naphthyl groups, which are polycyclic or fused compounds (e.g., two or more adjacent ring atoms are common to two adjacent rings). Terms such as "aryl" encompass both substituted and unsubstituted groups. Examples of aryl groups include, but are not limited to, phenyl, naphthyl, tetrahydronaphthyl, indanyl, and indenyl.

[0036] As used herein, the term "alkoxyl" or "alkoxy" refers to an alkyl group having an oxygen radical attached thereto, and is represented by the general formula RO, where R is an alkyl group. Examples of alkoxyl groups include, but are not limited to, methoxy, ethoxy, propoxy, and tert-butoxy groups.

[0037] As used herein, the term "aryloxy" refers to an aryl group having an oxygen radical attached thereto, and is represented by the general formula Ar-O, where Ar is an aryl group. Examples of aryloxy groups include, but are not limited to, phenoxy groups.

[0038] As used herein, an "oxo bridge" refers to a bridging oxo ligand (O 2- ) means

[0039] Exemplary catalysts are described below. The catalysts include catalyst particles and may optionally include other components (e.g., catalyst supports and / or additives (e.g., promoters)). The catalyst particles are metal complexes, which contain a first metal atom (M 1 ) and the first metal atom (M 1 and an active site group bonded to a first metal atom (M 1 ) is the metal center of the catalyst particle and may be, by way of non-limiting example, a transition metal (e.g., nickel, cobalt, iron), a platinum group metal, or bismuth. The active site groups include boron groups, metal hydroxide groups, or metal oxide groups. The metal hydroxide groups are bonded to a second metal atom (M 2 ) or beryllium (Be), and the metal oxide group contains a second metal atom (M 2 ) containing a second metal atom (M 2 ) is the first metal atom (M 1 ), which may be aluminum, gallium, indium, or bismuth. The catalyst particles may be monometallic complexes (when the active site groups include boron groups), bimetallic complexes, or trimetallic complexes in which one or more active site groups are oxo-bridged to one or more metal centers. The catalyst particles are formed by coupling the hydroxyl groups of an active site reagent (e.g., a boron compound (e.g., boric acid, boronic acid, boronic ester, etc.), a mixture of boron trioxide and water, a metal hydroxide, or a metal oxyhydroxide) with the first metal atom (M) of the metal oxide catalyst particle. 1 ) followed by proton transfer from the bound hydroxyl group to a lattice oxygen atom of the metal oxide catalyst particle. Alternatively, the catalyst particle may be formed directly by a substitution reaction of an active site reagent with a metal chloride catalyst particle in the presence of water and oxygen. Exemplary reaction schemes for forming the catalyst are described in more detail below.

[0040] In some examples, the catalyst particles comprise metal oxide catalyst particles and first metal atoms (M 1 ) and oxo-bridged active site groups. Metal oxide catalyst particles are particles in which the cations of at least one metal are present in the form of an oxide (O 2-) anions ionically bonded to the metal oxides. Metal oxides include single metal oxides (also called simple oxides) and mixed metal oxides (also called complex oxides). Single metal oxides contain cations of a single metal in a single oxidation state. Mixed metal oxides contain cations of a metal and one or more other elements (e.g., another metal or a non-metal). Mixed metal oxides also include materials in which cations of a single metal are in multiple different oxidation states.

[0041] Examples of metal oxides constituting the catalyst particles include, but are not limited to, iridium (IV) oxide (IrO2), ruthenium (IV) oxide (RuO2), platinum (IV) oxide (PtO2), palladium (II) oxide (PdO), osmium dioxide (OsO2), osmium (VIII) oxide (OsO4), rhodium oxide (RhO2), bismuth (III) oxide (Bi2O3), nickel (II) oxide (NiO), cobalt (II) oxide (CoO), cobalt (II, III) oxide (Co3O4), lead oxide (PbO2), iron oxide (e.g., iron (II, III) oxide (Fe3O4)), nickel iron oxide (NiFeO x ) (e.g., Ni(Fe)O(OH), FeO(OH)NiO(OH), Ni 1-x Fe x (OH)2 / Ni 1-x Fe x O(OH)), manganese oxide (MnO x) (e.g., manganese(II) oxide (MnO), manganese(II,III) oxide (Mn3O4), manganese(III) oxide (Mn2O3), manganese dioxide (MnO2), manganese(VI) oxide (MnO3), manganese(VII) oxide (Mn2O7)), ruthenium-iridium oxide (RuIrO2), ruthenium-tantalum oxide (RuTaO2), platinum-ruthenium oxide (PtRuO2), ruthenium-cobalt oxide (RuC o3O2), ruthenium tin oxide (RuSnO), iridium tin oxide (IrSnO2), ruthenium iridium tantalum oxide, ruthenium titanium tin oxide, iridium titanium platinum oxide, lanthanum nickel oxide (LaNiO3), lanthanum cobalt oxide (LaCoO3), strontium cobalt oxide (SrCoO3), and strontium nickel oxide (SrNiO3).

[0042] Metal oxides have a variety of crystalline structures and polymorphs. For example, transition metal oxides, such as iridium(IV) oxide and ruthenium(IV) oxide, generally have a rutile-like structure, although other structures, such as perovskites, spinels, or amorphous structures, are also available. Metal oxides may be doped (e.g., with tin, cobalt, nickel, and / or fluorine) or may contain impurities and / or defects. Metal oxides may be surface hydroxylated in the presence of water or water vapor or by aqueous reaction conditions during the synthesis of the metal oxide.

[0043] In other examples, the catalyst particles may be single molecules (e.g., monomers), groups of molecules (e.g., those that form nanoparticles), polymers, or oligomers. In some examples, these catalyst particles contain a first metal atom (M 1 ) containing a second metal atom (M 2The halo groups are replaced with active site groups via a substitution reaction with an active site reagent (e.g., a boron compound, a mixture of boron trioxide and water, a metal hydroxide, or a metal oxyhydroxide) containing a metal halide. Exemplary reaction schemes for preparing catalysts using metal halides are described in more detail below.

[0044] The boron group of the catalyst particle contains a trivalent boron (B) atom, and the boron atom is connected to a first metal atom (M) by one or two oxo bridges. 1 In some examples, the boron group comprises the following structural formulas (Ia) and (Ib): [ka] where the open boron bond forms part of an oxo bridge and R 1 , R 2 and R 3 may be the same or different and each independently represent a hydroxyl group (OH), an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. In some examples, the alkyl group has 1 to 20 carbon atoms. In other examples, the alkyl group has 1 to 10 carbon atoms. In still other examples, the alkyl group has 1 to 5 carbon atoms. In some examples, the aryl group has 1 to 20 carbon atoms. In other examples, the aryl group has 1 to 10 carbon atoms. In still other examples, the aryl group has 1 to 5 carbon atoms. In some examples, the alkoxy group has the general formula —O—R4, where O is bonded to the boron atom of (Ia) or (Ib) and R4 is an alkyl group having 1 to 10, 1 to 5, or 1 to 3 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, or an isopropyl group).

[0045] Boron has three electrons (2s) in its outermost shell. 2 , 2p 1 ) is a p-block element. The trivalent boron atom in the boron group is sp 2The boron atom is electron-deficient (i.e., two electrons short of a stable octet electron configuration) due to its hybrid orbital and empty p orbital. As a result, the boron atom smoothly and quickly accepts the bond with hydroxide anion, serving as a gateway for the hydroxylation step of OER (Equation (1a)). Furthermore, the rapid bonding of hydroxide ion with boron atom increases the reaction rate and reduces the overpotential of OER compared to conventional electrochemical catalysts. After the hydroxylation step, the bound hydroxide ion is transferred from the boron atom to the adjacent first metal (M 1 ) are transferred or relayed to oxygen atoms of the catalyst center (e.g., iridium) and / or catalyst particle, and subjected to the subsequent OER step (Equations (1b)-(1d)). Once the boron active sites are freed, they become available for the next catalytic cycle and can recombine with the hydroxide ion resulting from the dissociation of water.

[0046] The increased number of oxygen atoms donated by the boron groups provides a cooperative environment for hydroxide ion binding through the participation of lattice oxygen. Furthermore, the boron-modified catalysts have high stability at both low and high pH and promote OER under acidic conditions using proton exchange membranes (PEMs) and alkaline conditions using anion exchange membranes (AEMs).

[0047] The metal hydroxide group has the formula M 2 One or two hydroxyl groups of the metal hydroxide represented by (OH)3 or Be(OH)2 and the first metal atom (M 1 ), where M 2 is the second metal atom of the catalyst particle and is aluminum (Al), gallium (Ga), indium (In), or bismuth (Bi), and Be is beryllium. The metal oxide group has the formula M 2 The hydroxyl group of the metal oxyhydroxide represented by O(OH) and the first metal atom (M 1) is formed by reaction with a first metal atom (M ) of the catalyst particle. The metal hydroxide group includes an aluminum hydroxide group, a gallium hydroxide group, an indium hydroxide group, a bismuth hydroxide group, or a beryllium hydroxide group. The metal oxide group includes an aluminum oxide group, a gallium oxide group, an indium oxide group, or a bismuth oxide group. As used herein, the term "metal hydroxide / oxide group" is a generic term that refers to both a metal hydroxide group and a metal oxide group. The metal hydroxide / oxide group is formed by reaction of a first metal atom (M ) of the catalyst particle with a first metal atom (M ) of the catalyst particle by one or two oxo bridges. 1 ) and a second metal atom (M 2 ) or beryllium, and one or two terminal hydroxyl groups derived from a metal hydroxide or a terminal oxo group derived from a metal oxyhydroxide. The metal hydroxide groups include structures (IIa), (IIb), and (IIc) shown below. [ka] where the open bond forms part of an oxo bridge and M 2 is a second metal atom and is aluminum (Al), gallium (Ga), indium (In), or bismuth (Bi), and Be is beryllium. The metal oxide group includes the structure (IId) shown below. [ka] where M 2 The open bond with M forms part of an oxo bridge. 2 is the second metal atom.

[0048] Similarly to the boron atoms of the boron-modified catalyst particles, the metal atoms of the metal hydroxide / oxide groups (e.g., the second metal atom M 2 and beryllium) are electron-deficient and therefore readily and rapidly accept hydroxide anions, serving as a gateway for the hydroxylation step of OER (Equation (1a)). The second metal atom (M 2The rapid binding of hydroxide ions to the metal atom (M) results in a faster reaction rate and reduces the overpotential of the OER compared to conventional electrocatalysis. After the hydroxylation step (1a), the bound hydroxide ions are transferred to a second metal atom (M 2 ) to an adjacent metal center (e.g., the first metal atom M 1 ) and / or the oxygen atoms of the catalyst particles, which are then transferred or relayed to the oxygen atoms of the catalyst particles for the subsequent OER step (reactions (1b)-(1d)). Once the metal active site of the metal hydroxide / oxide group is released, a second metal atom (M 2 ) is available for the next catalytic cycle and can recombine with the hydroxide ion resulting from the dissociation of water.

[0049] The increased number of oxygen atoms provided by the metal hydroxide / oxide groups and oxo bridges provides a cooperative environment for hydroxide ion binding through the participation of lattice oxygen. Furthermore, catalyst particles modified with metal hydroxide / oxide groups have high stability at both low and high pH, ​​promoting OER under acidic conditions using proton exchange membranes (PEMs) and alkaline conditions using anion exchange membranes (AEMs).

[0050] The catalyst particles may have any suitable degree of modification with active site groups. In some examples, the catalyst particles include two or more different active site groups (e.g., boron groups, metal hydroxide groups, and / or metal oxide groups).

[0051] The oxo-bridged boron atom and / or the oxo-bridged second metal atom (M 2 ) plays an important gateway role in catalytic substrate binding, and then transfers the substrate to the first metal atom (M 1 ) to form the initial complex with the reactive intermediate (e.g., OH) of the redox reaction. This makes the catalyst more potent than conventional electrochemical catalysts. Furthermore, the hydroxyl environment around the catalyst surface keeps the catalyst active and stable, minimizing the use of platinum group metals.

[0052] The catalysts described herein can be synthesized by any suitable method. In some examples, metal oxide or metal halide catalyst particles are combined with an active site reagent. The active site reagent reacts with the metal oxide or metal halide catalyst particles to modify them with active site groups. The active site reagent can be a boron compound, a mixture of diboron trioxide (BO) and water (which react to form boric acid), a metal hydroxide (e.g., M 2 (OH)3 or Be(OH)2), and / or metal oxyhydroxides (e.g., M 2 O(OH)).

[0053] Boron compounds include, for example, boric acid (B(OH)3), boronic acids, or boronate esters. Boronic acids are represented by the general formula B(OH)(R5)(R6), where R5 is a hydroxyl group, an alkyl group, or an aryl group, and R6 is an alkyl group or an aryl group. In some examples, R5 and / or R6 have 1 to 20 carbon atoms. In other examples, R5 and / or R6 have 1 to 10 carbon atoms. In still other examples, R5 and / or R6 have 1 to 5 carbon atoms. Boronic esters are represented by the general formula B(OH)(R7)(R8), where R7 is a hydroxyl group, an alkoxy group, or an aryloxy group, and R8 is an alkoxy group or an aryloxy group. In some examples, R7 and / or R8 have 1 to 10 carbon atoms. In other examples, R7 and / or R8 have 1 to 5 carbon atoms. In yet other examples, R7 and / or R8 have 1 to 3 carbon atoms (eg, a methyl, ethyl, propyl, or isopropyl group).

[0054] Metal hydroxides include aluminum(III) oxide hydroxide (Al(OH)3), gallium(III) oxide hydroxide (Ga(OH)3), indium(III) oxide hydroxide (In(OH)3), bismuth(III) oxide hydroxide (Bi(OH)3), and beryllium(II) oxide hydroxide (Be(OH)2). Metal oxyhydroxides include aluminum(III) oxide oxyhydroxide (AlO(OH)), gallium(III) oxide oxyhydroxide (GaO(OH)), indium(III) oxide oxyhydroxide (InO(OH)), and bismuth(III) oxide oxyhydroxide (BiO(OH)).

[0055] In some examples, the catalyst particles and the active site reagent are combined in a solvent. Suitable solvents include water and mixed aqueous solvents containing water and dimethylacetamide (DMA), dimethylformamide (DMF), N-methylpyrrolidone (NMP), and / or glyme-based solvents. Glyme-based solvents include, for example, monoglyme (dimethoxyethane), diglyme (bis(2-methoxyethyl)ether), triglyme, tetraglyme, ethylglyme, ethyldiglyme, butylglyme, butyldiglyme, pentaglyme, hexaglyme, polyglyme, dipropylene glycol dimethyl ether, and dipropylene glycol dimethyl ether (P2). In yet other examples, the reaction is carried out by mechanochemical mixing (e.g., ball milling) under dry conditions without the use of a solvent. In some examples, the reaction is carried out by directly reacting metal oxide catalyst particles (e.g., iridium(IV) oxide or platinum(IV) oxide) or metal halide catalyst particles (e.g., iridium chloride or platinum chloride) with the active site reagent. In some examples, the reaction is carried out at a temperature ranging from room temperature (e.g., about 25° C.) to about 120° C. In some examples, the reagents are mixed by mechanical stirring and / or sonication (e.g., sonication).

[0056] As previously mentioned, in some instances, the reaction involves combining a metal oxide catalyst particle with an active site reagent. In this case, the metal oxide catalyst particle is surface-modified by a surface modification reaction. The reaction mechanism involves one or two hydroxyl groups of the active site reagent attaching to a first metal atom (M 1 ), followed by proton transfer from the hydroxyl group to an adjacent lattice oxygen atom. The molar ratio of active site reagent to metal oxide catalyst particles may be adjusted to obtain the desired catalytic performance while minimizing the amount of platinum group metal used.

[0057] In other examples, the reaction involves combining a metal halide catalyst particle with an active site reagent. In this case, the metal halide catalyst particle is modified by a substitution reaction that replaces a halo group with an active site group from the active site reagent. In some examples, an oxidation reaction is performed to convert a first metal atom (M 1 The oxidation state of iridium(III) chloride is also changed. For example, in the reaction of iridium(III) chloride with an active site reagent, the chloro group is replaced by an active site group, and iridium(III) is oxidized to iridium(IV). The reaction of the metal halide with the active site reagent is carried out in the presence of water and oxygen (e.g., oxygen gas or air), and in some instances may be carried out in a one-pot process. The resulting catalyst particles may be monomer molecules (e.g., those with terminal hydroxyl groups) or may be part of a larger oligomeric or polymeric structure formed during the reaction.

[0058] Metal halide catalyst particles are particles in which the cations of one or more metals are fluoride (F - ), chloride (Cl - ), bromide (Br - ), and iodide (I -) anions ionically bonded to the metal halides. Metal halides include single metal halides and mixed metal halides. Single metal halides contain cations of a single metal in a single oxidation state. Mixed metal halides contain cations of a metal and one or more other elements (e.g., other metals or non-metals). Mixed metal halides also include materials in which cations of a single metal are in multiple different oxidation states. Examples of metal halides that may comprise the metal halide catalyst particles include, but are not limited to, platinum group metal chlorides (e.g., platinum(II) chloride (PtCl), platinum(IV) chloride (PtCl), palladium(II) chloride (PdCl), iridium(III) chloride (IrCl), ruthenium(III) chloride (RuCl)), transition metal chlorides (e.g., titanium(II) chloride (TiCl), titanium(III) chloride (TiCl), titanium(IV) chloride (TiCl), zirconium(IV) chloride (ZrCl), vanadium(II) chloride (VCl), vanadium(III) chloride (VCl), vanadium(IV) chloride (VCl), vanadium(V) chloride (VCl), chromium(II) chloride (CrCl), chromium(III) chloride (CrCl), molybdenum chloride (MoCl), x ), iron(II) chloride (FeCl), iron(III) chloride (FeCl), nickel(II) chloride (NiCl), copper(II) chloride (CuCl), zinc(II) chloride (ZnCl), cadmium(II) chloride (CdCl), cobalt(II) chloride (CoCl), gold(III) chloride (AuCl)), late transition metal chlorides (e.g., gallium(II) chloride (GaCl), gallium(III) chloride (GaCl), indium(III) chloride (InCl), tin(II) chloride (SnCl), tin(IV) chloride (SnCl), bismuth(III) chloride (BiCl)), aluminum trifluoride, fluoroaluminum chloride, cobalt(II) bromide, cobalt-manganese bromide, rhodium iodide, ruthenium iodide, iridium iodide, and potassium iodide. In some instances, the metal halide is preferably a platinum group metal chloride (eg, platinum(IV) chloride or iridium(III) chloride) or bismuth(III) chloride.

[0059] Exemplary modified metal oxide catalysts and reaction schemes for synthesizing the modified metal oxide catalysts are shown and described below with reference to Figures 1A-1C, 2A-2C, 3, and 4A-4B. The following examples are illustrative only and not limiting. In the following examples, a representative portion of an iridium (IV) oxide particle is shown. Iridium (IV) oxide has the general formula (IrO2) n The iridium(IV) oxide has a rutile-like structure represented by the formula: where iridium is six-coordinated. Iridium(IV) oxide may have its surface hydroxylated to various degrees. Figures 1A-1C, 2A-2C, and 3 show only two six-coordinated iridium atoms at or near the surface of the iridium(IV) oxide particle. It is understood that iridium(IV) oxide may include other units (e.g., unit cells) and components (e.g., surface hydroxyl groups, defects, dopants, etc.) not shown in the figures.

[0060] 1A-1C show exemplary reaction schemes for preparing boron-modified iridium(IV) oxide catalysts. As shown in FIGS. 1A-1C, the boron-modified iridium(IV) oxide catalysts are prepared by combining iridium(IV) oxide with boric acid. The iridium(IV) oxide and boric acid can be combined in any suitable manner, such as by mechanical stirring in a solvent, by mechanochemical reaction (e.g., ball milling), and / or by sonication, as described above.

[0061] In the example of Figure 1A, the molar ratio of iridium(IV) oxide to boric acid is approximately 1:1. That is, one mole of boric acid is combined with one mole of iridium(IV) oxide particles. Alternatively, if the reaction is carried out by ball milling, the molar amount of boric acid is approximately equal to the molar amount of modified iridium(IV) oxide particles expected to be produced by ball milling. The reaction mechanism in Figure 1A generally involves two hydroxyl groups of a boric acid molecule bonding with an iridium atom on the surface of an iridium(IV) oxide particle, followed by the transfer of a proton from the hydroxyl group to an adjacent lattice oxygen atom. Thus, in reaction product (a), the boron atom is bonded to the iridium atom by two oxo bridges.

[0062] In the example shown in Figure 1B, the molar ratio of iridium(IV) oxide to boric acid is approximately 1:2. The reaction mechanism generally involves one or two hydroxyl groups from each boric acid molecule bonding to an iridium atom, followed by the transfer of a proton from the hydroxyl group to an adjacent lattice oxygen atom. In this reaction scheme, the boron atom is bonded to the iridium atom by one or two oxo bridges. As shown in Figure 1B, various reaction products can be obtained. In reaction product (b), each boron atom is bonded to the iridium atom by two oxo bridges. In reaction product (c), one boron atom is bonded to the iridium atom by one oxo bridge and the other boron atom is bonded to another iridium atom by two oxo bridges. In reaction product (d), each boron atom is bonded to the iridium atom by one oxo bridge. In reaction product (e), each boron atom is linked to the same iridium atom by one oxo bridge.

[0063] In the example shown in Figure 1C, the molar ratio of iridium(IV) oxide to boric acid is 1:3. As in Figure 1B, various reaction products can be obtained. In reaction product (f), two boron atoms are each bonded to an iridium atom by two oxo bridges, and a third boron atom is bonded to one of the iridium atoms by one oxo bridge. In reaction product (g), two boron atoms are each bonded to the same iridium atom by one oxo bridge, and a third boron atom is bonded to another iridium atom by two oxo bridges. In reaction product (h), two boron atoms are each bonded to the same iridium atom by one oxo bridge, and a third boron atom is bonded to another iridium atom by one oxo bridge.

[0064] The reaction products (a)-(h) in Figures 1A-1C are metal complexes in which boron is bound to iridium(IV) through one or two oxo bridges. It is understood that the reaction schemes shown in Figures 1A-1C are merely illustrative, and various oxo bridge arrangements and combinations can be obtained. Furthermore, other molar ratios can be used to achieve the desired degree of modification of the iridium(IV) oxide surface. For example, the molar ratio of iridium(IV) oxide to boric acid can be set based on the size or total surface area of ​​the iridium(IV) oxide particles. For example, the molar ratio of iridium(IV) oxide to boric acid can be set so that approximately 25%, 50%, 75%, or 100% of the iridium(IV) oxide particle surface is modified with boron groups. Furthermore, other boron compounds (e.g., boronic acids, boronic acid esters, mixtures of diboron trioxide and water, etc.) can be used in place of or in addition to boric acid.

[0065] Figures 2A-2C show exemplary reaction schemes for producing iridium(IV) oxide catalysts modified with bismuth hydroxide groups. Figures 2A-2C are similar to Figures 1A-1C, except that in Figures 2A-2C, iridium(IV) oxide is combined with bismuth hydroxide (Bi(OH)) instead of boric acid.

[0066] In the example shown in Figure 2A, the molar ratio of iridium(IV) oxide to bismuth hydroxide is approximately 1:1. The reaction mechanism generally involves two hydroxyl groups from a bismuth hydroxide molecule bonding with an iridium atom on the surface of the iridium(IV) oxide catalyst particle, followed by the transfer of a proton from the hydroxyl group to an adjacent lattice oxygen atom. In the reaction product (a), the bismuth atom is bonded to the iridium atom by two oxo bridges.

[0067] In the example shown in Figure 2B, the molar ratio of iridium(IV) oxide to bismuth hydroxide is approximately 1:2. The reaction mechanism generally involves one or two hydroxyl groups from each bismuth hydroxide molecule bonding to an iridium atom, followed by the transfer of a proton from the hydroxyl group to an adjacent lattice oxygen atom. In this reaction scheme, the bismuth atom is bonded to the iridium atom by one or two oxo bridges. As shown in Figure 2B, various reaction products can be obtained. In reaction product (b), each bismuth atom is bonded to an iridium atom by two oxo bridges. In reaction product (c), one bismuth atom is bonded to an iridium atom by one oxo bridge, and the other bismuth atom is bonded to another iridium atom by two oxo bridges. In reaction product (d), each bismuth atom is bonded to an iridium atom by one oxo bridge. In reaction product (e), each bismuth atom is linked to the same iridium atom by one oxo bridge.

[0068] In the example shown in Figure 2C, the molar ratio of iridium(IV) oxide to bismuth hydroxide is 1:3. As in Figure 2B, various reaction products can be obtained. In reaction product (f), two bismuth atoms are each bonded to an iridium atom by two oxo bridges, and a third bismuth atom is bonded to one of the iridium atoms by one oxo bridge. In reaction product (g), two bismuth atoms are each bonded to the same iridium atom by one oxo bridge, and a third bismuth atom is bonded to another iridium atom by two oxo bridges. In reaction product (h), two bismuth atoms are each bonded to the same iridium atom by one oxo bridge, and a third bismuth atom is bonded to another iridium atom by one oxo bridge.

[0069] The reaction products (a)-(h) in Figures 2A-2C are bimetallic complexes in which bismuth is linked to iridium via one or two oxo bridges. It is understood that the reaction schemes shown in Figures 2A-2C are merely illustrative, and various oxo bridge arrangements and combinations can be achieved. Furthermore, other molar ratios can be used to achieve the desired degree of modification of the iridium(IV) oxide surface. For example, the molar ratio of iridium(IV) oxide to bismuth hydroxide can be adjusted based on the size or total surface area of ​​the iridium(IV) oxide particles and the desired degree of modification. For example, the molar ratio of iridium(IV) oxide to bismuth hydroxide can be set so that approximately 25%, 50%, 75%, or 100% of the iridium(IV) oxide particle surface is modified with bismuth hydroxide groups. Additionally, other metal hydroxides and / or metal oxyhydroxides (e.g., aluminum hydroxide, aluminum oxyhydroxide, gallium hydroxide, gallium oxyhydroxide, indium hydroxide, indium oxyhydroxide, and beryllium hydroxide) may be used as an alternative or in addition to bismuth hydroxide.

[0070] Figure 3 shows another exemplary reaction scheme for producing an iridium(IV) oxide catalyst material modified with both boron and bismuth hydroxide groups. As shown in Figure 3, iridium(IV) oxide is combined with both boric acid and bismuth hydroxide. In the example shown in Figure 3, the molar ratio of iridium(IV) oxide:boric acid:bismuth hydroxide is 1:1:1. The reaction mechanism generally involves one or two hydroxyl groups from the boric acid and one or two hydroxyl groups from the bismuth hydroxide bonding to an iridium atom on the surface of the iridium(IV) oxide catalyst particle, followed by the transfer of a proton from the hydroxyl group to an adjacent lattice oxygen atom. In this reaction scheme, the boron and bismuth atoms are bonded to the iridium atom by one or two oxo bridges. As shown in Figure 3, various reaction products can be obtained. In reaction product (a), the boron and bismuth atoms are each bonded to the iridium atom by two oxo bridges. In reaction product (b), the boron atom is bonded to the iridium atom by one oxo bridge, and the bismuth atom is bonded to the iridium atom by two oxo bridges. In reaction product (c), the boron atom and the bismuth atom are each bonded to the iridium atom by one oxo bridge. In reaction product (d), the boron atom and the bismuth atom are each bonded to the same iridium atom by one oxo bridge.

[0071] It is understood that the reaction scheme shown in Figure 3 is merely illustrative, and that various oxo-bridge sequences and combinations can be achieved. Furthermore, other molar ratios may be used to obtain the desired catalytic performance while minimizing iridium usage. For example, the molar ratio of iridium(IV) oxide to boric acid and bismuth hydroxide can be adjusted based on the size or total surface area of ​​the iridium(IV) oxide particles to obtain the desired degree of modification of the iridium(IV) oxide surface. For example, the molar ratio of iridium(IV) oxide:boric acid:bismuth hydroxide can be set so that approximately 25%, 50%, 75%, or 100% of the iridium(IV) oxide particle surface is modified with boron and / or bismuth hydroxide groups. Furthermore, any of the boron compounds described herein may be used in place of or in addition to boric acid. Furthermore, any of the metal hydroxides and / or metal oxyhydroxides described herein may be used in place of or in addition to bismuth hydroxide. 1A-3, boric acid and / or bismuth hydroxide are combined with iridium(IV) oxide (or a composite material including iridium(IV) oxide), but boric acid and / or bismuth hydroxide (or other active site reagents) can be combined in a similar manner with other metal oxides or metal oxide composites, including catalytic materials and / or composites including one or more platinum group metals, transition metals, and / or post-transition metals.

[0072] 4A and 4B show exemplary reaction schemes for producing non-PGM catalysts based on bismuth(III) oxide (BiO) catalyst particles. As shown, bismuth(III) oxide is combined with boric acid to produce a boron-modified bismuth(III) oxide catalyst. The bismuth(III) oxide and boric acid can be combined in any suitable manner, such as by mechanical agitation in a solvent, by mechanochemical reaction (e.g., ball milling), and / or by sonication, as described above.

[0073] In the example shown in Figure 4A, the molar ratio of bismuth(III) oxide to boric acid is approximately 1:2. Each hydroxyl group of two molecules of boric acid bonds to a bismuth atom of bismuth(III) oxide through a dehydration reaction. In this reaction product, the boron atom is oxo-bridged to the same bismuth atom. Therefore, bismuth(III) oxide is modified with two boron groups. In the example shown in Figure 4B, the molar ratio of bismuth(III) oxide to boric acid is 1:4. This reaction is similar to that shown in Figure 4A, except that in this reaction, boric acid bonds to both bismuth atoms of bismuth(III) oxide. Therefore, bismuth(III) oxide is modified with four boron groups.

[0074] It is understood that the reaction schemes shown in Figures 4A and 4B are merely illustrative and that various modifications are possible. For example, other boron compounds may be used in place of boric acid, and suitable compounds described herein may be used. Furthermore, one or more metal hydroxides and / or metal oxyhydroxides may be used in place of or in addition to boric acid, including the metal hydroxides and / or metal oxyhydroxides described herein. Furthermore, other metal oxide catalyst particles, such as gallium(III) oxide (Ga2O3), indium(III) oxide (In2O3), and composites thereof, may be used in place of or in addition to bismuth(III) oxide.

[0075] Exemplary reaction schemes for synthesizing modified catalysts using iridium(III) chloride (IrCl) catalyst particles are now shown and described with reference to Figures 5A-5C and 6A-6C. The following examples are illustrative only and not limiting.

[0076] As shown in Figures 5A-5C, boron-modified iridium(IV) catalyst particles are produced by combining trihydrate iridium(III) chloride with boric acid in the presence of oxygen. The trihydrate iridium(III) chloride and boric acid can be combined in any suitable manner, such as by mechanical stirring in a solvent, by mechanochemical reaction (e.g., ball milling), and / or by sonication, as described above.

[0077] In the example shown in Figure 5A, the molar ratio of trihydrate iridium(III) chloride to boric acid is approximately 1:3. The reaction mechanism in Figure 5A is a substitution reaction between the hydroxyl groups of three molecules of boric acid and the chloro groups of the iridium(III) chloride molecules. The reaction product (a) contains one iridium atom and three oxo-bridged boron groups. Each of the three boron atoms is linked to the iridium atom by an oxo-bridge, increasing the oxidation state of the iridium from +3 to +4. The resulting boron-modified catalyst particle is a hexacoordinate iridium(IV) complex.

[0078] The reaction scheme in Figure 5B is similar to that in Figure 5A, except that the reaction product (b) contains one iridium atom and two boron groups oxo-bridged. Each of the two boron atoms is linked to the iridium atom by two oxo bridges, increasing the oxidation state of the iridium from +3 to +4. The resulting boron-modified catalyst particle is a hexacoordinate iridium(IV) complex.

[0079] In the example shown in Figure 5C, the molar ratio of trihydrate iridium(III) chloride to boric acid is approximately 2:1. The reaction product (c) contains two iridium centers and one boron group oxo-bridged to one iridium center. The boron atom is connected to the iridium center by two oxo-bridges, increasing the oxidation state of the iridium from +3 to +4. The resulting boron-modified catalyst particle is a hexacoordinate iridium(IV) complex.

[0080] The reaction products (a)-(c) shown in Figures 5A-5C are hexacoordinate complexes in which the boron atom is linked to the iridium center by one or two oxo bridges. The reaction products (a)-(c) shown in Figures 5A-5C may be part of a molecular group, such as an oligomeric molecule or a polymeric molecule in which repeating units are linked by oxygen ligands. For example, the reaction may induce oligomerization and / or polymerization of the boron-group-modified catalyst particles. In other examples, the reaction products (a)-(c) are single-molecule (e.g., monomer) complexes in which the oxygen ligands form part of the terminal hydroxyl groups. The reaction products (a)-(c) may be fabricated into any suitable shape or structure, such as nanoparticles, nanotubes, or thin films. The reaction schemes shown in Figures 5A-5C are merely illustrative, and it is understood that various boron group and oxo bridge compositions can be obtained depending on the stoichiometry of the iridium(III) chloride and boric acid. For example, other molar ratios may be used to obtain the desired composition of boron-modified iridium(IV) catalyst particles. Furthermore, other metal halides may be used in place of iridium(III) chloride, and other active site reagents may be used in place of boric acid.

[0081] For example, as shown in Figures 6A-6C, bismuth hydroxide-modified iridium(IV) catalyst particles are produced by combining trihydrate iridium(III) chloride with bismuth hydroxide in the presence of oxygen. The trihydrate iridium(III) chloride and bismuth hydroxide can be combined in any suitable manner, such as by mechanical stirring in a solvent, by mechanochemical reaction (e.g., ball milling), and / or by sonication, as described above.

[0082] In the example shown in Figure 6A, the molar ratio of trihydrate iridium(III) chloride to bismuth hydroxide is approximately 1:3. The reaction mechanism in Figure 6A involves the substitution of the hydroxyl groups of three molecules of bismuth hydroxide with the chloro group of one molecule of iridium(III) chloride, followed by the oxidation of iridium(III). The reaction product (a) contains one iridium atom and three oxo-bridged bismuth hydroxide groups. (The original text uses the term "three boron atoms," but the context interprets it as "three bismuth atoms.") Each of the three bismuth atoms is linked to an iridium atom by an oxo-bridge, increasing the oxidation state of the iridium from +3 to +4. The resulting bismuth hydroxide-modified catalyst particle is a hexacoordinate iridium(IV) complex.

[0083] The reaction scheme in Figure 6B is similar to that in Figure 6A, except that the reaction product (b) contains two oxo-bridged bismuth hydroxide groups with one iridium atom, as shown in Figure 6B. (The original text uses the term "two boron atoms," but in this context it is interpreted as "two bismuth atoms.") Each of the two bismuth atoms is linked to an iridium atom by two oxo-bridges, increasing the oxidation state of the iridium from +3 to +4. The resulting bismuth hydroxide-modified catalyst particles are hexacoordinate iridium(IV) complexes.

[0084] In the example shown in Figure 6C, the molar ratio of trihydrate iridium(III) chloride to bismuth hydroxide is approximately 2:1. The reaction product (c) contains two iridium(IV) centers and one bismuth hydroxide group oxo-bridged to one of these iridium(IV) centers. The bismuth atom (originally "the boron atom," but interpreted in context as "the bismuth atom") is linked to the iridium(IV) center by two oxo-bridges, increasing the oxidation state of iridium from +3 to +4. The resulting bismuth hydroxide-modified catalyst particle is a hexacoordinate iridium(IV) complex.

[0085] The reaction products (a)-(c) shown in Figures 6A-6C are hexacoordinate complexes in which the bismuth atom is linked to the iridium center by one or two oxo bridges. The reaction products (a)-(c) shown in Figures 6A-6C may be part of a molecular group, such as an oligomer or a polymer in which repeating units are linked by oxygen ligands. For example, the reaction may induce oligomerization and / or polymerization of the bismuth hydroxide group-modified catalyst particles. In other examples, the reaction products (a)-(c) are single-molecule (e.g., monomer) complexes in which the oxygen ligands form part of the terminal hydroxyl groups. The reaction products (a)-(c) may be fabricated into any suitable shape or structure, such as nanoparticles, nanotubes, or thin films. The reaction schemes shown in Figures 6A-6C are merely illustrative, and it is understood that various bismuth hydroxide group and oxo bridge compositions can be obtained depending on the stoichiometry of the iridium(III) chloride and bismuth hydroxide. For example, other molar ratios may be used to obtain the desired composition of bismuth hydroxide-modified iridium(IV) catalyst particles. Additionally, other metal halides may be used in place of iridium(III) chloride, and other active site reagents may be used in place of bismuth hydroxide.

[0086] 5A-6C, iridium(III) chloride is combined with one active site reagent. In other examples, iridium(III) chloride (or other metal halide) may be combined with two or more different active site reagents.

[0087] The catalysts described herein can be used in a variety of electrochemical cells, such as water electrolysis systems and fuel cells. Figure 7 shows an exemplary proton exchange membrane water electrolysis system 700 (PEM water electrolysis system 700). The PEM water electrolysis system 700 uses electrical power to split water into oxygen (O2) and hydrogen (H2) through an electrochemical reaction. The configuration of the PEM water electrolysis system 700 is merely exemplary, and other suitable configurations and other suitable water electrolysis systems incorporating boron-containing porous membranes may be used.

[0088] 7, PEM water electrolysis system 700 includes a membrane electrode assembly 702 (MEA 702), porous transport layers 704-1 and 704-2, bipolar plates 706-1 and 706-2, and a power supply 708. Depending on the particular embodiment, PEM water electrolysis system 700 may include additional or alternative components not shown in FIG.

[0089] The MEA 702 includes a PEM 710 disposed between a first catalyst layer 712-1 and a second catalyst layer 712-2. The PEM 710 electrically insulates the first catalyst layer 712-1 from the second catalyst layer 712-2 while absorbing protons (H + ), and is impermeable to gases such as hydrogen and oxygen. The PEM 710 can be implemented as either an organic PEM or an inorganic PEM. Examples of organic PEMs include synthetic and natural polymers. Examples of synthetic polymers include sulfonic acid-functionalized polymers, such as Nafion® (available in various configurations and grades from EI DuPont, including Nafion-H, Nafion HP, Nafion 117, Nafion 115, Nafion 212, Nafion 211, Nafion NE1035, and Nafion XL), Aquivion® (available in various configurations and grades from Solvay, including Aquivion® E98-05, Aquivion® PW98, and Aquivion® PW87S), Gore-Select® (available from W.L. Gore & Associates), Flemion™ (available from Asahi Glass Co.), and Pemion+™ (available from Ionomr Innovations), or any combination, derivative, grade, or configuration thereof. Examples of natural polymers include lignin, cellulose, or chitin. Examples of inorganic PEMs include amorphous inorganic materials (eg, glass, fused silica, or ceramics) and / or crystalline inorganic materials (eg, quartz, single crystal silicon, or alumina).

[0090] The first catalyst layer 712-1 and the second catalyst layer 712-2 are conductive electrodes having embedded electrochemical catalyst particles (not shown). For example, the electrochemical catalyst particles of the first catalyst layer 712-1 and / or the second catalyst layer 712-2 may include any of the modified catalysts described herein. In some examples, the modified catalyst is supported on an ion-exchange functionalized catalyst support described in International Patent Application Publication No. PCT / US2022 / 046105.

[0091] In some examples, the first catalyst layer 712-1 and / or the second catalyst layer 712-2 include a supported catalyst mixed with an ionomer (an ion-conducting polymer). The ionomer binds the catalyst within the electrode, binds the catalyst layer on the PEM, and provides a pathway for cations (e.g., protons) to improve cation conductivity. The ionomer used in the first catalyst layer 712-1 and the second catalyst layer 712-2 can be any suitable ionomer, including any of the ionomers described herein.

[0092] MEA 702 is disposed between porous transport layers 704-1 and 704-2, between which are disposed bipolar plates 706-1 and 706-2 having flow channels 714-1 and 714-2.

[0093] In the MEA 702, the first catalyst layer 712-1 functions as the anode, and the second catalyst layer 712-2 functions as the cathode. When the PEM water electrolysis system 700 is driven by the power source 708, the oxygen evolution reaction (OER) occurs at the anode 712-1, as represented by the following electrochemical half-reaction (Equation (1)): 2H2O――(catalyst)―→O2+4H + +4e - (1) Protons are conducted from the anode 712-1 to the cathode 712-2 through the PEM 710, and electrons are conducted from the anode 712-1 to the cathode 712-2 through a conductive path around the PEM 710. The PEM 710 transports protons (H +) and water transport, but is impermeable to oxygen and hydrogen. At the cathode 712-2, protons combine with electrons to undergo the hydrogen evolution reaction (HER), which is represented by the following electrochemical half-reaction (Equation (2)): 4H + +4e - --(catalyst)-->2H2(2)

[0094] OER and HER are two complementary electrochemical reactions that split water electrolytically, and are represented by the overall water electrolysis reaction (reaction equation (3)) below. 2H2O―――→2H2+O2(3)

[0095] FIG. 8 illustrates an exemplary proton exchange membrane fuel cell 800 (PEM fuel cell 800). PEM fuel cell 800 produces electrical power as a result of an electrochemical reaction. In this example, the electrochemical reaction involves reacting hydrogen gas (H) with oxygen gas (O) to produce water and electrical power. The configuration of PEM fuel cell 800 is exemplary only, and other suitable configurations and other suitable proton exchange membrane fuel cells incorporating boron-containing porous membranes may be used.

[0096] As shown in Figure 8, PEM fuel cell 800 includes a membrane electrode assembly 802 (MEA 802), porous transport layers 804-1 and 804-2, and bipolar plates 806-1 and 806-2. An electrical load 808 is electrically connected to MEA 802 and may be driven by PEM fuel cell 800. PEM fuel cell 800 may include additional or alternative components not shown in Figure 8, depending on the particular embodiment.

[0097] The MEA 802 includes a PEM 810 disposed between a first catalyst layer 812-1 and a second catalyst layer 812-2. The PEM 810 electrically insulates the first catalyst layer 812-1 from the second catalyst layer 812-2 while absorbing protons (H + ), and is impermeable to gases such as hydrogen and oxygen. PEM 810 may be implemented with any suitable PEM, including any of the PEMs described herein.

[0098] The first catalyst layer 812-1 and the second catalyst layer 812-2 are conductive electrodes with embedded electrochemical catalysts (not shown).

[0099] For example, the electrochemical catalyst particles of the first catalyst layer 812-1 and / or the second catalyst layer 812-2 may include any of the modified catalysts described herein. In some examples, the modified catalyst is supported on an ion-exchange functionalized catalyst support described herein.

[0100] In some examples, the first catalyst layer 812-1 and / or the second catalyst layer 812-2 include a supported catalyst mixed with an ionomer (an ion-conducting polymer). The ionomer binds the catalyst within the electrode, binds the catalyst layer on the PEM, and provides a pathway for cations (e.g., protons) to improve cation conductivity. The ionomer used in the first catalyst layer 812-1 and the second catalyst layer 812-2 can be any suitable ionomer, including any of the ionomers described herein.

[0101] The MEA 802 is disposed between porous transport layers 804-1 and 804-2, which are further disposed between bipolar plates 806-1 and 806-2 containing flow channels 814. In the MEA 802, the first catalyst layer 812-1 functions as the cathode and the second catalyst layer 812-2 functions as the anode. The cathode 812-1 and the anode 812-2 are electrically connected to a load 808, and power generated by the PEM fuel cell 800 drives the load 808.

[0102] During operation of the PEM fuel cell 800, hydrogen gas (H2) is supplied to the anode side of the PEM fuel cell 800, and oxygen gas (O2) is supplied to the cathode side of the PEM fuel cell 800. At the anode 812-2, hydrogen molecules are catalytically converted to protons (H2O) according to the following hydrogen oxidation reaction (H2O) (equation (4)): + ) and electrons (e - ) 2H2――(catalyst)―→4H + +4e - (4) Protons are conducted from anode 812-2 to cathode 812-1 through PEM 810, and electrons are conducted from anode 812-2 to cathode 812-1 via a conductive path outside PEM 810 and load 808. At cathode 812-1, the protons and electrons combine with oxygen gas to produce water according to the oxygen reduction reaction (ORR) (Equation (5)): O2+4H + +4e - --(catalyst)-->2H2O (5) Therefore, the overall electrochemical reaction of the PEM fuel cell 800 is expressed by the following reaction equation (6): 2H2+O2――――→2H2O (6)

[0103] In this overall reaction, PEM fuel cell 800 produces water at cathode 812-1. The water may travel from cathode 812-1 to anode 812-2 through PEM 810 and may be removed through outlets on the cathode and / or anode sides of PEM fuel cell 800. This overall reaction produces electrons at the anode to power load 808.

[0104] In some examples, one or more of the ionomer, membrane, and PEM of system 700 or system 800 may be implemented with the ionomer, membrane, and / or PEM described in International Patent Application No. PCT / US2021 / 029705 (filed April 28, 2021), International Patent Application No. PCT / US2021 / 038956 (filed June 24, 2021), International Patent Application No. PCT / US2022 / 039845 (filed August 9, 2022), International Patent Application No. PCT / US2022 / 043878 (filed September 16, 2022), and U.S. Provisional Application No. 63 / 302,755 (filed January 25, 2022), all of which are incorporated herein by reference in their entireties.

[0105] As previously mentioned, the modified catalysts described herein can be used in applications other than water electrolysis and hydrogen fuel cell applications. In some examples, the modified catalysts described herein are used in the Haber-Bosch process for ammonia synthesis. The Haber-Bosch process converts atmospheric nitrogen (N2) into ammonia (NH3) by reacting with hydrogen (H2) using a metal catalyst under high temperature and pressure. The Haber-Bosch process is represented by the following reaction equation (7): N2 + 3H2 - (catalyst) - → 2NH3 (7)

[0106] Catalysts promote the cleavage of the triple bond of atmospheric nitrogen. Catalysts used in the conventional Haber-Bosch process generally include iron-based catalysts such as ferrite (α-Fe), iron oxides (e.g., magnetite (Fe3O4), wüstite (FeO)), and / or iron supported on iron oxides (with optional promoters). However, iron-based catalysts have various drawbacks, including the need for high pressures and temperatures (e.g., 400–550 °C) for efficient catalytic activity and the complex manufacturing process of iron-based catalysts. Furthermore, hydrogen gas (H2) often reduces iron oxide to metallic iron, reducing catalytic performance.

[0107] In some examples, the Haber-Bosch process (e.g., Equation (7)) is carried out using a modified catalyst described herein. Any modified catalyst described herein can be used. In some examples, the modified Haber-Bosch catalyst is an iron oxide (e.g., magnetite or wüstite) surface modified with boron or metal hydroxide / oxide groups. The modified iron oxide catalyst can be produced by any suitable method, including by substituting a Haber-Bosch metal oxide (e.g., iron oxide) for iridium(IV) oxide using any of the reaction schemes shown in Figures 1A-3. The boron and / or metal hydroxide / oxide groups of the modified Haber-Bosch catalyst stabilize the catalyst in the presence of hydrogen and further reduce the activation energy of the chemical processes involved in this conversion, allowing the Haber-Bosch process to be carried out at lower temperatures and pressures compared to conventional Haber-Bosch catalysts.

[0108] The modified catalysts described herein can also be used in a variety of other applications not explicitly described herein, including alkaline anion exchange membrane (AEM) fuel cells, AEM water electrolysis systems, electrochemical reduction of carbon dioxide (CO2) (e.g., to produce carbon monoxide, methanol, formic acid, methane, ethylene, ethanol, etc.), other electrochemical reduction reactions, and organic compound synthesis and polymerization reactions.

[0109] In the foregoing description, various examples have been described with reference to the accompanying drawings. However, it will be apparent to those skilled in the art that various modifications and variations thereto, as well as additional embodiments, may be implemented. For example, specific features of one embodiment described herein may be combined with or substituted for features of other embodiments described herein. Accordingly, the description and drawings herein should be interpreted as illustrative, and not restrictive.

[0110] The advantages and features of the present disclosure can be further illustrated by the following examples. [Example]

[0111] Example 1: A catalyst comprising catalyst particles comprising a first metal atom and an active site group bonded to the first metal atom by one or more oxo bridges, wherein the active site group comprises a boron group, a metal hydroxide group, or a metal oxide group, wherein the metal hydroxide group comprises a second metal atom or beryllium, and wherein the metal oxide group comprises a second metal atom, wherein the second metal atom is different from the first metal atom and comprises aluminum, gallium, indium, or bismuth.

[0112] Example 2: The catalyst of Example 1, wherein the first metal atom comprises a platinum group metal.

[0113] Example 3: A catalyst as described in any of the preceding examples, wherein the first metal atom comprises bismuth.

[0114] Example 4: A catalyst according to any of the preceding examples, wherein the first metal atom comprises nickel, cobalt, or iron.

[0115] Example 5: A catalyst according to any of the preceding examples, wherein the active site group comprises a boron group, the boron group comprising a trivalent boron atom bonded to the first metal atom by one or more oxo bridges.

[0116] Example 6: The active site group comprises a boron group, and the boron group has the following formula (Ia) or (Ib): [ka] where R 1 , R 2 , and R 3 may be the same or different and are each independently a hydroxyl group (OH), an alkyl group, an aryl group, an alkoxy group, or an aryloxy group.

[0117] Example 7: R 1 and R 2 or R 3 and at least one of the general formula —O—R 4wherein O is bonded to the boron atom of (Ia) or (Ib) above, and R 4 The catalyst of Example 6, wherein is an alkyl group.

[0118] Example 8: A catalyst according to any of Examples 1-4, wherein the active site groups comprise bismuth hydroxide groups or bismuth oxide groups.

[0119] Example 9: A catalyst comprising a first metal atom and an active site group comprising a boron atom or a second metal atom, wherein the boron atom or the second metal atom is bonded to the first metal atom by one or more oxo bridges, and the second metal atom is different from the first metal atom and comprises aluminum, gallium, indium, bismuth, or beryllium.

[0120] Example 10: The catalyst of Example 9, wherein the first metal atom comprises a platinum group metal.

[0121] Example 11: A method for preparing a catalyst, comprising modifying catalyst particles comprising a first metal atom with active site groups, wherein the active site groups comprise boron groups, metal hydroxide groups, or metal oxide groups, wherein the metal hydroxide groups comprise a second metal atom or beryllium, and wherein the metal oxide groups comprise a second metal atom, wherein the second metal atom is different from the first metal atom and comprises aluminum, gallium, indium, or bismuth.

[0122] Example 12: The method of manufacture described in Example 11, wherein the catalyst particles comprise a metal oxide.

[0123] Example 13: The method of preparation described in Example 12, wherein the metal oxide comprises an oxide of a platinum group metal.

[0124] Example 14: The method of preparation described in Example 12, wherein the metal oxide comprises iridium (IV) oxide or ruthenium (IV) oxide.

[0125] Example 15: The method of Example 12, wherein the metal oxide comprises platinum (IV) oxide.

[0126] Example 16: The method of example 12, wherein the metal oxide comprises bismuth (III) oxide.

[0127] Example 17: The method of example 11, wherein the catalyst particles comprise a metal halide.

[0128] Example 18: The method of Example 17, wherein the metal halide comprises a platinum group metal.

[0129] Example 19: The method of Example 17, wherein the metal halide comprises platinum(IV) chloride or iridium(III) chloride.

[0130] Example 20: The method of example 17, wherein the metal halide comprises bismuth(III) chloride.

[0131] Example 21: The method of any of Examples 11-20, wherein the catalyst particles comprise iron oxide.

[0132] Example 22: The method of any of Examples 11-21, wherein modifying the catalyst particles with active site groups comprises combining the catalyst particles with a boron compound.

[0133] Example 23: The method of example 22, wherein the boron compound comprises boric acid.

[0134] Example 24: The method of Example 22, wherein the boron compound comprises a boronic acid.

[0135] Example 25: The method of Example 22, wherein the boron compound comprises a boronic acid ester.

[0136] Example 26: The method of any of Examples 11-21, wherein modifying the catalyst particles with active site groups comprises combining the catalyst particles with diboron trioxide and water.

[0137] Example 27: The method of any of Examples 11-21, wherein modifying the catalyst particles with active site groups comprises combining the catalyst particles with a metal hydroxide, wherein the metal hydroxide comprises a second metal atom or beryllium.

[0138] Example 28: The method of any of Examples 11-21, wherein modifying the catalyst particles with active site groups comprises combining the catalyst particles with a metal oxyhydroxide comprising a second metal atom.

[0139] Example 29: A method comprising the step of conducting an oxygen evolution reaction (OER) represented by the electrochemical half-reaction of the following reaction equation (1) using the catalyst described in any one of Examples 1 to 10. 2H2O――(catalyst)―→4H + +4e - (1)

[0140] Example 30: A method comprising the step of conducting an oxygen reduction reaction (ORR) represented by the electrochemical half-reaction of reaction equation (2) using the catalyst according to any one of Examples 1 to 10. O2+4H + +4e - --(catalyst)-->2H2O (2)

[0141] Example 31: A catalyst layer comprising a catalyst support, a catalyst according to any one of Examples 1 to 10, and an ionomer.

[0142] Example 32: A membrane electrode assembly comprising a cathode, an anode, and a proton exchange membrane disposed between the cathode and the anode, wherein at least one of the cathode or the anode is provided with a catalyst layer comprising a catalyst support and the catalyst described in any of Examples 1 to 10.

[0143] Example 33: The membrane electrode assembly of Example 32, wherein the catalyst layer further comprises an ionomer.

[0144] Example 34: A method for producing ammonia, comprising combining nitrogen and hydrogen according to reaction formula (3) using the catalyst described in any one of Examples 1 to 10. N2 + 3H2 - (catalyst) - → 2NH3 (3)

[0145] Example 35: The method of example 34, wherein the catalyst comprises catalyst particles comprising iron oxide, and the first metal atoms comprise iron.

Claims

1. A catalyst comprising: a catalyst particle comprising a first metal atom and an active site group bonded to the first metal atom by one or more oxo bridges; the active site group comprises a boron group, a metal hydroxide group, or a metal oxide group; the metal hydroxide group comprises a second metal atom or beryllium; the metal oxide group contains the second metal atom, The catalyst, wherein the second metal atom is different from the first metal atom and comprises aluminum, gallium, indium, or bismuth.

2. The catalyst of claim 1 , wherein the first metal atom comprises a platinum group metal.

3. The catalyst of claim 1 , wherein the first metal atom comprises bismuth.

4. The catalyst of claim 1 , wherein the first metal atom comprises nickel, cobalt, or iron.

5. the active site group comprises a boron group; 2. The catalyst of claim 1, wherein the boron group comprises a trivalent boron atom bonded to the first metal atom by the one or more oxo bridges.

6. the active site group comprises a boron group; The boron group has the following general formula (Ia) or (Ib): 【Chemistry 1】 Here, R １ , R ２ , and R ３ may be the same or different and are each independently a hydroxyl group (OH), an alkyl group, an aryl group, an alkoxy group, or an aryloxy group.

7. R １ And, R ２ or R ３ and at least one of the general formula -O-R ４ wherein O is bonded to the boron atom of (Ia) or (Ib), and R ４ The catalyst of claim 6, wherein is an alkyl group.

8. 10. The catalyst of claim 1, wherein the active site groups comprise bismuth hydroxide groups or bismuth oxide groups.

9. A catalyst comprising: a first metal atom; and and an active site group comprising a boron atom or a second metal atom; the boron atom or the second metal atom is bonded to the first metal atom by one or more oxo bridges; The catalyst, wherein the second metal atom is different from the first metal atom and comprises aluminum, gallium, indium, bismuth, or beryllium.

10. 10. The catalyst of claim 9, wherein the first metal atom comprises a platinum group metal.

11. A method for producing a catalyst, comprising: modifying catalyst particles comprising first metal atoms with active site groups; the active site group comprises a boron group, a metal hydroxide group, or a metal oxide group; the metal hydroxide group comprises a second metal atom or beryllium; the metal oxide group contains the second metal atom; The method of manufacturing, wherein the second metal atoms are different from the first metal atoms and comprise aluminum, gallium, indium, or bismuth.

12. The method of claim 11 , wherein the catalyst particles comprise a metal oxide.

13. The method of claim 12 , wherein the metal oxide comprises an oxide of a platinum group metal.

14. The method of claim 12, wherein the metal oxide comprises iridium (IV) oxide or ruthenium (IV) oxide.

15. 13. The method of claim 12, wherein the metal oxide comprises platinum (IV) oxide.

16. The method of claim 12 , wherein the metal oxide comprises bismuth (III) oxide.

17. The method of claim 11 , wherein the catalyst particles comprise a metal halide.

18. 18. The method of claim 17, wherein the metal halide comprises a platinum group metal.

19. 18. The method of claim 17, wherein the metal halide comprises platinum (IV) chloride or iridium (III) chloride.

20. 18. The method of claim 17, wherein the metal halide comprises bismuth (III) chloride.

21. The method of claim 11 , wherein the catalyst particles comprise iron oxide.

22. 12. The method of claim 11, wherein the step of modifying the catalyst particles with the active site groups comprises combining the catalyst particles with a boron compound.

23. 23. The method of claim 22, wherein the boron compound comprises boric acid.

24. 23. The method of claim 22, wherein the boron compound comprises a boronic acid.

25. 23. The method of claim 22, wherein the boron compound comprises a boronic ester.

26. 12. The method of claim 11, wherein the step of modifying the catalyst particles with the active site groups comprises combining the catalyst particles with diboron trioxide and water.

27. 12. The method of claim 11, wherein modifying the catalyst particles with the active site groups comprises combining the catalyst particles with a metal hydroxide, the metal hydroxide comprising the second metal atom or beryllium.

28. 12. The method of claim 11, wherein modifying the catalyst particles with the active site groups comprises combining the catalyst particles with a metal oxyhydroxide containing the second metal atom.

29. A method for producing an oxygen evolution reaction (OER) using the catalyst of claim 1, which is represented by the electrochemical half-reaction of equation (1): 2H ２ O→(catalyst)→4H ＋ +4e － (1).

30. A method for carrying out an oxygen reduction reaction (ORR) represented by the electrochemical half-reaction of equation (2) using the catalyst of claim 1: O ２ +4H ＋ +4e － → (catalyst) → 2H ２ O (2).

31. A catalyst layer, Catalyst carrier, The catalyst of claim 1, and A catalyst layer comprising an ionomer.

32. A membrane electrode assembly, cathode, an anode, and a proton exchange membrane disposed between the cathode and the anode; At least one of the cathode or the anode is Catalyst support and A membrane electrode assembly comprising a catalyst layer comprising the catalyst according to claim 1.

33. 33. The membrane electrode assembly of claim 32, wherein the catalyst layer further comprises an ionomer.

34. 10. A method for producing ammonia, comprising using the catalyst of claim 1 to combine nitrogen and hydrogen according to reaction equation (3): N ２ +3H ２ →(Catalyst)→2NH ３ (3).

35. 35. The method of claim 34, wherein the catalyst comprises catalyst particles comprising iron oxide, and the first metal atoms comprise iron.

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