Transition metal doped iridium based composite catalysts and their preparation and use

Abstract

A transition metal doped iridium based composite catalyst, its preparation and use is disclosed, the catalyst consisting essentially of an amorphous oxide of iridium and a transition metal, the transition metal being selected from a group IVB metal, a group VB metal, or a combination thereof, the content ratio of iridium to transition metal in the catalyst being (0.4-0.7):(0.3-0.6) in molar terms, the XRD spectrum of the catalyst having no diffraction peaks corresponding to iridium oxide in the rutile phase and no diffraction peaks corresponding to the crystalline phase of the oxide of the transition metal. The catalyst is in the form of a nanopowder, has a uniform bulk structure, has high catalytic activity and uses a low amount of precious metal iridium, and exhibits excellent performance when applied to the anode of a proton exchange membrane water electrolysis device.

Description

[Technical field]

[0001] The present application relates to the field of hydrogen production by electrolysis of water, and in particular to transition metal doped iridium based composite catalysts, and their preparation and use. [Background technology]

[0002] Hydrogen generation technology by water electrolysis is a relatively simple method of hydrogen production. When a direct current is passed through an electrolysis device filled with an electrolyte, water molecules undergo an electrochemical reaction on the electrodes, and are decomposed into hydrogen and oxygen. Compared with alkaline water electrolysis technology, hydrogen generation technology by water electrolysis using proton exchange membranes (PEM) has the advantages of a fast response time, high current density, wide workload range, and high purity of hydrogen produced. Hydrogen generation technology by water electrolysis has the unparalleled advantage of using renewable energy for power generation, making it possible to obtain green hydrogen.

[0003] The core component of the device for PEM electrolysis of water is the membrane electrode (MEA), which is usually composed of a proton exchange membrane, an anode catalyst layer and a cathode catalyst layer on both sides of the proton exchange membrane, and an anode gas diffusion layer and a cathode gas diffusion layer on the outermost side. The membrane electrode assembly is where the electrochemical reaction occurs. The properties and structure of the membrane electrode directly affect the performance and life of the PEM electrolyzer. In the membrane electrode, the anode catalyst is one of the key materials and is the main rate-controlling step for hydrogen production by PEM electrolysis of water. At present, iridium oxide or iridium black catalyst is used in the anode catalyst layer of the membrane electrode of the commercial water PEM electrolyzer, but due to the scarcity of metallic iridium resources, the high price (-1000 yuan / g), and the iridium usage in the electrolyzer is only 2 mg / cm. 2 Therefore, reducing the amount of iridium used in the anode catalyst is one of the important breakthroughs for large-scale application of PEM water electrolysis.

[0004] Existing literature shows that adding other types of inexpensive metal oxides to iridium oxide catalysts can reduce costs: The preparation method of IrTi composite catalyst reported in the literature is mainly the Adams Fusion method (IrO2-TiO2: A High-Surface-Area, Active, and Stable Electrocatalyst for the Oxygen Evolution Reaction, ACS Catalysis, 2019, 9, 6974-6986), but the catalyst prepared by this method has obvious phase separation, and there are obvious IrO2 and TiO2 crystalline phase peaks in the XRD spectrum, which results in insufficient dispersion of iridium oxide and reduced utilization of the active component of iridium oxide.

[0005] The preparation method of IrNb catalysts reported in the literature is the pyrolysis method (Effect of preparation procedure of IrO2-Nb2O5anodes on surface and electrocatalytic properties, Journal of Applied Electrochemistry, 2005, 35, 925-924). This method is not environmentally friendly because it uses hydrochloric acid as a solvent, and is only suitable for preparing catalyst films on high-temperature resistant substrates (Ti), not for the preparation of powder catalysts.

[0006] One of the preparation methods of IrTa catalysts reported in the literature is the precipitation method (Preparation and evaluation of RuO2-IrO2, IrO2-Pt, IrO2-Ta2O5 catalysts for the oxygen evolution reaction in an SPE electrolyzer, Journal of Applied Electrochemistry, 2009, 39, 191-196). However, catalysts prepared by the precipitation method are only suitable for the preparation of iridium-tantalum composite oxide catalysts with high Ir content (Ir / Ta molar ratio 7:3 or more) due to the loss of metallic Ta to some extent, and the amount of precious metal used is high. Another preparation method is the Adams Fusion method (Synthesis, characterization and evaluation of IrO2based binary metal oxide electrocatalysts for oxygen evolution reaction, International Journal of Electrochemical Science, 2012, 7, 12064-12077). This method is also only suitable for preparing an iridium-tantalum composite oxide catalyst having a high Ir content (Ir / Ta molar ratio of 7:3 or more), and requires a large amount of precious metal to be used.

[0007] However, how to simply, efficiently and uniformly dope metal compounds into iridium oxide catalysts while maintaining the inherent catalytic activity and stability of iridium oxide remains a technical challenge that urgently needs to be solved in this field. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] IrO2-TiO2:A High-Surface-Area,Active,and Stable Electrocatalyst for the Oxygen Evolution Reaction, ACS Catalysis, 2019, 9, 6974-6986 [Non-Patent Document 2] Effect of preparation procedure of IrO2-Nb2O5 anodes on surface and electrocatalytic properties, Journal of Applied Electrochemistry, 2005, 35, 925-924 [Non-Patent Document 3] Preparation and evaluation of RuO2-IrO2, IrO2-Pt, IrO2-Ta2O5 catalysts for the oxygen evolution reaction in an SPE electrolyzer, Journal of Applied Electrochemistry, 2009, 39, 191-196 [Non-Patent Document 4] Synthesis, characterization and evaluation of IrO2 based binary metal oxide electrocatalysts for oxygen evolution reaction, International Journal of Electrochemical Science, 2012, 7, 12064-12077 Summary of the Invention

[0009] The object of the present application is to provide a transition metal doped iridium based composite catalyst, its preparation method and use, which is in the form of nanopowder, has a uniform bulk structure, has high catalytic activity, requires a low amount of precious metal iridium, and has excellent performance when used as an anode catalyst in proton exchange membrane electrolysis of water.

[0010] In order to achieve the above object, in one aspect, the present application provides a transition metal-doped iridium-based composite catalyst consisting essentially of amorphous iridium and a transition metal oxide, the transition metal being selected from a Group IVB metal, a Group VB metal, or a combination thereof, the content ratio of iridium to the transition metal in the catalyst being (0.4-0.7):(0.3-0.6) in terms of moles, and the XRD spectrum of the catalyst has no diffraction peaks corresponding to iridium oxide in the rutile phase, such as the (110) crystal plane diffraction peak and the (101) crystal plane diffraction peak of IrO2, and no diffraction peaks corresponding to the crystal phase of the transition metal oxide.

[0011] Preferably, in the XRD spectrum of the catalyst, the peak envelope is present only in the 2θ range of 10 to 70°.

[0012] In a further aspect, there is provided a method for preparing the iridium-based composite catalyst of the present application, the method comprising the steps of: 1) mixing an iridium source, a transition metal source, a complexing agent and a solvent, and reacting the resulting mixture at a pH of 6-10 to obtain a reactant, wherein the transition metal is selected from Group IVB metals, Group VB metals and combinations thereof, and the complexing agent is selected from C3-C8 organic polyacids and soluble salts thereof, preferably C4-C8 organic polyacids and soluble salts thereof; 2) removing the solvent from the reaction product obtained in step 1) by evaporation to obtain an iridium-based composite catalyst precursor; and 3) A step of calcining the iridium-based composite catalyst precursor in an oxygen-containing atmosphere to obtain an iridium-based composite catalyst.

[0013] In yet another aspect, there is provided a use of the iridium-based composite catalyst according to the present application as an oxygen evolution electrocatalyst in an electrochemical process.

[0014] In yet another aspect, the present application provides a membrane electrode suitable for proton exchange membrane electrolysis of water, comprising a proton exchange membrane, and a cathode catalyst layer and an anode catalyst layer disposed on either side of the proton exchange membrane, respectively, wherein the anode catalyst layer contains the iridium-based composite catalyst of the present application.

[0015] The iridium-based composite catalyst of the present application is essentially composed of amorphous iridium and transition metal oxides, and has an amorphous bulk structure. The XRD spectrum has no obvious crystalline diffraction peaks of iridium oxide and transition metal oxide, and the iridium and transition metal are more uniformly distributed in the catalyst, the bulk structure is uniform, and obvious phase separation is avoided, and the catalyst has low crystallinity and high specific surface area. When used as an anode catalyst for electrolyzing water through a proton exchange membrane to produce hydrogen, it has a higher catalytic activity than commercial iridium oxide catalysts, greatly reducing the amount of precious metals used, greatly reducing costs, and is worthy of expanding applications.

[0016] In addition, in the catalyst preparation method provided in the present application, a complexing agent is added to the iridium source and the transition metal source, so that the iridium source and the transition metal source are uniformly dispersed in the mixed solution through the complexing action, thereby simply and effectively doping the amorphous transition metal oxide in the finally prepared catalyst to obtain an iridium-based composite catalyst with a uniform bulk structure; In addition, in the present application, C3-C8 organic polyacids and their soluble salts, especially C4-C8 organic polyacids and their soluble salts, are used as complexing agents to avoid precipitation in the solution. In the reaction process, explosive raw materials such as sodium nitrate and highly corrosive solvents such as hydrochloric acid are not used. There is no need to use a high-temperature resistant Ti substrate, and no harmful gases such as NOx are emitted during calcination. The preparation method is simple to operate, the conditions are mild, the production cost is low, and the preparation process is more environmentally friendly.

[0017] Other features and advantages of the present application are described in detail in the specific embodiments section below. [Brief description of the drawings]

[0018] The figures are used to facilitate a better understanding of the present application and constitute a part of this specification, and are used to explain the present application together with the following specific embodiments, but are not intended to limit the present application. [Figure 1] 1 is a high-resolution transmission electron microscope spectrum of the catalyst product obtained in Example I-3. [Diagram 2] 1 shows XRD spectra of the catalyst products obtained in Examples I-1 to I-4 and the catalysts of Comparative Examples I-1 and I-2. [Diagram 3] 1 is an Ir4fXPS spectrum of the catalyst product obtained in Example I-3. [Figure 4] 1 is an XRD spectrum of the product obtained in Example II-1. [Diagram 5] 1 is an XRD spectrum of the product obtained in Comparative Example II-2. [Figure 6] 1 is an XPS spectrum of the product obtained in Example II-1. [Figure 7] 1 is a TEM spectrum of the product obtained in Example II-1. [Figure 8A] 1 is an XRD spectrum of the catalyst product obtained in Example III-1. [Figure 8B] Comparative Example III-2: XRD spectrum of the catalyst product obtained. [Figure 9] 1 is an XPS spectrum of the catalyst product obtained in Example III-1. [Figure 10] 1 is a TEM spectrum of the catalyst product obtained in Example III-1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Specific embodiments of the present application are described in detail below in conjunction with the drawings. It should be understood that the specific embodiments described herein are used only to illustrate and explain the present application, and are not used to limit the present application.

[0020] It should be understood that the specific numerical values ​​disclosed herein (including the endpoints of the numerical ranges) are not limited to the exact value of the numerical value, but also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. In addition, for the disclosed numerical ranges, the endpoints of the ranges, and the specific endpoints and values ​​within the ranges, can be combined in any way to obtain one or more new numerical ranges, and these new numerical ranges should also be considered to be specifically disclosed herein.

[0021] Unless otherwise specified, terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. If the definition of a term defined herein differs from the meaning commonly understood in the art, the definition herein shall prevail.

[0022] In this application, "satisfying the principle of electrical neutrality" means that the algebraic sum of the valences of all elements in the corresponding chemical formula is zero.

[0023] In this application, the "peak envelope" in the XRD spectrum refers to other forms of protrusions that appear in the XRD spectrum in addition to the obvious and sharp characteristic peaks that are conventionally considered by those skilled in the art. The "peak envelope" is generally characterized by low intensity and large width. Usually, the position of the peak envelope can only be expressed as a 2θ range, and the exact peak position cannot be determined like the crystalline phase peak. By combining the intensity, width, and position of the peak envelope, it can be determined that the peak envelope corresponds to an amorphous oxide, not a characteristic peak of a crystalline oxide.

[0024] In this application, the chemical composition of the catalyst is used only as a rough representation, which can be determined by X-ray fluorescence analysis (XRF analysis) and is consistent with the addition ratio of the relevant metal raw materials during preparation.

[0025] In this application, the molar ratio of Ir to transition metals measured by XPS analysis (denoted as M1) refers to the ratio of the peak area of ​​Ir to the peak area of ​​transition metal elements in the XPS spectrum, and can characterize the molar ratio of iridium to transition metal elements on the catalyst surface (usually within the thickness of about 1-2 nm of the outer surface); the molar ratio of Ir to transition metals measured by XRF analysis (denoted as M2) refers to the ratio of the peak area of ​​Ir to the peak area of ​​transition metal elements in the XRF spectrum, and can characterize the molar ratio of iridium to transition metal elements in the entire bulk structure of the catalyst. Obviously, when M1 / M2 (denoted as M0) is greater than 1, it indicates that the relative content of iridium elements on the catalyst surface is higher than the overall relative content of iridium elements in the bulk structure, which indicates that the catalyst surface is rich in iridium.

[0026] In this application, the "particle size" of a catalyst particle refers to the particle size measured by a transmission electron microscope. For example, "the particle size of the catalyst particle is 2 to 10 nm" means that the particle size of each particle of the catalyst in a transmission electron microscope spectrum is within the range of 2 to 10 nm.

[0027] In this application, the term "consisting essentially of" means that in addition to the mentioned component, the total content of other components in the catalyst is less than 10%, e.g., less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, or less than 0.5%.

[0028] In this application, except for the contents explicitly stated, any matter or item not mentioned can be directly applied to the aspects known in the art without any modification. In addition, any embodiment described in this specification can be freely combined with one or more other embodiments described in this specification, and the technical solution or technical idea formed thereby is considered to be part of the original disclosure or original record of this application, and should not be considered as new content not disclosed or anticipated in this specification, unless a person skilled in the art judges it to be an obviously unreasonable combination.

[0029] All patent and non-patent literature referred to herein, including but not limited to textbooks and journal articles, is hereby incorporated by reference in its entirety.

[0030] As described above, in a first aspect, the present application provides a transition metal-doped iridium-based composite catalyst, the transition metal-doped iridium-based composite catalyst being essentially composed of amorphous iridium and a transition metal oxide, the transition metal being selected from Group IVB metals, Group VB metals or a combination thereof, and the ratio of the iridium content to the transition metal content in the catalyst is (0.4-0.7):(0.3-0.6) in terms of moles.

[0031] The iridium-based composite catalyst of the present application is essentially composed of amorphous iridium and transition metal oxides, and has an amorphous bulk structure. In the XRD spectrum, there are no obvious crystalline diffraction peaks of iridium oxide and transition metal oxide, iridium and transition metal are more uniformly distributed in the catalyst, the bulk structure is uniform, and obvious phase separation is avoided. For example, in some particular embodiments, the XRD spectrum of the catalyst does not show diffraction peaks corresponding to iridium oxide in the rutile phase, i.e., the (110) crystal plane diffraction peak of IrO2 (2θ is about 28.027) and the (101) crystal plane diffraction peak (2θ is about 34.7), and also shows diffraction peaks corresponding to crystalline phases of transition metal oxides, e.g., diffraction peaks corresponding to crystalline phases of titanium oxide (for TiO2: 2θ of the diffraction peaks is 27.446, 36.085, 39.187, 41.225, 44.05, 54.322, 56.64, 62.74, 64.038, 65.478, 69.008, 69.788), diffraction peaks corresponding to the crystal phase of niobium oxide (in the case of Nb2O5: the 2θ of the diffraction peaks is 18.201, 23.707, 24.921, 26.426, 32.053, 35.743, 38.783, 43.915, 47.568, 51.283, 53.886, 54.581, 58.355, 67.306), and diffraction peaks corresponding to the crystal phase of tantalum oxide (in the case of Ta2O5: the 2θ of the diffraction peaks is 23.478, 24.585, 26.466, 29.365, 30.001, 36.665, 39.966, 40.339, 46.458, 47.995) are also not observed.

[0032] In a preferred embodiment, the XRD spectrum of the catalyst has a peak envelope only in the 2θ range of 10 to 70°, more preferably, has a peak envelope only in the 2θ range of 20 to 50°.

[0033] In a preferred embodiment, the iridium-based composite catalyst of the present application is represented by the following formula: Ir x M 1-x O ywhere M represents a transition metal, x is in the range of 0.4 to 0.7, and the value of y is such that the chemical formula satisfies the principle of electrical neutrality. More preferably, the transition metal M is selected from titanium (Ti), niobium (Nb), tantalum (Ta), or a combination thereof.

[0034] In a preferred embodiment, the Ir4f characteristic peak of the XPS spectrum of the catalyst includes an Ir(IV) characteristic peak and an Ir(III) characteristic peak, and the catalyst satisfies the following: the peak area of ​​the Ir(III) characteristic peak of the XPS spectrum of the catalyst is denoted as Q1, the peak area of ​​the Ir(IV) characteristic peak is denoted as Q2, Q1 / (Q1+Q2) is denoted as Q0, and Q0 is in the range of 0.2 to 0.6.

[0035] In a preferred embodiment, the catalyst is in the form of a nanoparticle powder, the particle size of the powder particles being in the range of 1-10 nm and the BET specific surface area of ​​the powder particles being in the range of 50-80 m 2 / g. More preferably, the ratio of the micropore volume in the catalyst particles to the total pore volume is 0 to 5%, preferably 0 to 3%.

[0036] In a second aspect, there is provided a method for preparing an iridium-based composite catalyst (in particular, the iridium-based composite catalyst of the present application), comprising the steps of: 1) mixing an iridium source, a transition metal source, a complexing agent and a solvent, and reacting the resulting mixture at a pH of 6-10 to obtain a reactant, wherein the transition metal is selected from Group IVB metals, Group VB metals and combinations thereof, and the complexing agent is selected from C3-C8 organic polyacids and soluble salts thereof, preferably C4-C8 organic polyacids and soluble salts thereof; 2) removing the solvent from the reaction product obtained in step 1) by evaporation to obtain an iridium-based composite catalyst precursor; and 3) A step of calcining the iridium-based composite catalyst precursor in an oxygen-containing atmosphere to obtain an iridium-based composite catalyst.

[0037] In a preferred embodiment, the iridium source is selected from chloroiridic acid, an alkali metal chloroiridate, or a combination thereof, more preferably the alkali metal chloroiridate is selected from potassium chloroiridate, sodium chloroiridate, or a combination thereof. According to the present application, chloroiridic acid and its soluble salts may or may not contain water of crystallization, and generally contain water of crystallization (such as compounds represented by the formula: H2IrCl6·6H2O or (NH4)2IrCl6·6H2O).

[0038] In a preferred embodiment, the transition metal source can be selected from a titanium source, a niobium source, a tantalum source or a combination thereof, more preferably the titanium source is selected from a soluble titanium salt, particularly preferably titanium sulfate, titanium oxysulfate or a combination thereof, the niobium source is an alcohol-soluble niobium compound, particularly preferably niobium pentachloride, ammonium niobate oxalate hydrate or a combination thereof, and the tantalum source is an alcohol-soluble tantalum compound, particularly preferably tantalum pentachloride.

[0039] In the method of the present application, there is no particular limitation on the organic polyacid and its soluble salt used as a complexing agent. From the viewpoint of industrial application, C3-C8 organic polyacids and their soluble salts, which are low in cost and abundant in source, are preferred, and C4-C8 organic polyacids and their soluble salts are particularly preferred. In a preferred embodiment, the complexing agent is selected from citric acid, tartaric acid, malic acid, sodium citrate, sodium malate, sodium tartrate, or a combination thereof. In the method of the present application, the above complexing agents are used, and no precipitation occurs in the mixed solution.

[0040] In a preferred embodiment, the molar ratio of the iridium source, calculated as iridium, to the transition metal source, calculated as transition metal, is 0.5-2.5:1, preferably 1-2.3:1, and the molar ratio of the complexing agent to the total amount of the iridium source and the transition metal source is 1-4:1, more preferably 1.3-3:1.

[0041] In the present application, the solvent used in step 1) is not strictly limited as long as it can dissolve the reactants used and does not adversely affect the reaction. In a particular preferred embodiment, the solvent used in step 1) is selected from water, alcohol, or a combination thereof.

[0042] In certain preferred embodiments, step 1) further comprises the steps of: 1A) mixing an iridium source, a first complexing agent, and water to obtain a first mixture; 1B) mixing a transition metal source, a second complexing agent and an organic solvent to obtain a second mixture, the organic solvent being miscible with water and having a boiling point in the range of room temperature to 120° C., preferably an alcohol solvent; 1C) adjusting the pH of the first mixture and the second mixture to 6 to 10, respectively; and 1D) mixing the first mixture with the second mixture after adjusting the pH in step 1C), further adjusting the pH of the resulting mixture to 6-10, and reacting to obtain a reactant; Here, the first complexing agent and the second complexing agent may be the same or different, and are each independently selected from C3 to C8 organic polyacids and soluble salts thereof, preferably C4 to C8 organic polyacids and soluble salts thereof, more preferably citric acid, tartaric acid, malic acid, sodium citrate, sodium tartrate, sodium malate, or a combination thereof.

[0043] In a further preferred embodiment, the molar ratio of the first complexing agent to the iridium source, calculated as iridium, is 1 to 4:1, preferably 1.7 to 3:1, the molar ratio of the second complexing agent to the transition metal source, calculated as transition metal, is 1 to 4:1, preferably 1.5 to 3.2:1, and the molar ratio of the iridium source, calculated as iridium, to the transition metal source, calculated as transition metal, is 1 to 2.5:1, preferably 1.2 to 2:1.

[0044] In a preferred embodiment, the reaction conditions in step 1) include: a temperature of 25-95° C., preferably 40-90° C., and a time of 0.5-6 hours, preferably 2-4 hours.

[0045] In a preferred embodiment, the reaction in step 1) is carried out at a pH of 8 to 9. Specifically, when the first complexing agent and the second complexing agent are used, it is preferable to adjust the pH to 8 to 9 when adjusting the pH of each in step 1C).

[0046] In the process of the present application, if the pH value needs to be adjusted or controlled at any step, the pH can be adjusted by adding a pH adjuster, which is preferably selected from sodium carbonate, sodium bicarbonate, sodium hydroxide, aqueous ammonia, or a combination thereof.

[0047] In the method of the present application, in step 2), the solvent in the reactant obtained in step 1) can be evaporated and removed by conventional methods in the art, for example, the solvent can be removed by vacuum distillation and / or rotary evaporation. In a specific embodiment, the evaporation / distillation temperature and time used can be easily determined according to the selected solvent and evaporation / distillation method, and will not be described in detail here.

[0048] In step 3) of the method of the present application, calcination is carried out under aerobic conditions, such as calcination in air or oxygen atmosphere, which removes organic matter in the precursor and also helps to form the catalyst pore structure. If the calcination is carried out under nitrogen, the catalytic effect of the catalyst is adversely affected. In a preferred embodiment, the oxygen-containing atmosphere used in step 3) may be pure oxygen or a mixed gas with an oxygen content of more than 20 wt.%, such as air.

[0049] In a preferred embodiment, the calcination conditions in step 3) include: a calcination temperature of 350-550° C., preferably 370-450° C., and a calcination time of 1-4 hours, preferably 1.5-3 hours.

[0050] In a preferred embodiment, the method of the present application further comprises a step of washing the calcined product of step 3), and the solvent used for washing is water, alcohol, or a mixed solution of alcohol and water. More preferably, a mixed solution of alcohol and water is used for washing, and the alcohol accounts for 10-95 wt %, preferably 30-60 wt %, of the mass of the mixed solution, which makes it easier to separate the catalyst by centrifugation. More preferably, the alcohol is selected from alcohols having 1-3 carbon atoms, and is preferably selected from methanol, ethanol, n-propanol, isopropanol, or a combination thereof. In a further preferred embodiment, the catalyst is washed until the pH of the liquid phase after washing is neutral or chloride ions are not detected.

[0051] In a further preferred embodiment, the method of the present application further comprises a step of drying after washing. The inventors of the present application have found that, when the catalyst is washed with water, it can be dried at room temperature or higher, but when washed with water, it is difficult to completely separate the catalyst by centrifugation, and when alcohol is used partially or completely for washing, drying at room temperature or higher reduces the catalytic performance of the catalyst. Therefore, preferably, the drying temperature is less than 10°C, preferably -30°C to 10°C, more preferably less than 0°C.

[0052] In a third aspect, there is provided an iridium-based composite catalyst prepared by the method of the present application.

[0053] In a fourth aspect, there is provided the use of the iridium-based composite catalyst of the present application as an oxygen evolution electrocatalyst in an electrochemical process.

[0054] According to the present application, the electrochemical process includes, but is not limited to, an oxygen evolution reaction process in an acidic or alkaline environment.

[0055] In a fifth aspect, there is provided a membrane electrode suitable for proton exchange membrane electrolysis of water, comprising a proton exchange membrane and a cathode catalyst layer and an anode catalyst layer disposed on either side of the proton exchange membrane, respectively, wherein the anode catalyst layer comprises the iridium-based composite catalyst of the present application.

[0056] In a preferred embodiment, the membrane electrode further includes an outermost cathode diffusion layer and an outermost anode diffusion layer, in which, from the cathode side to the anode side, the membrane electrode includes a cathode diffusion layer, a cathode catalyst layer, a proton exchange membrane, an anode catalyst layer, and an anode diffusion layer.

[0057] The membrane electrode provided in the present application is of a structure conventionally used in the art, and other components and materials contained therein, except for the anode catalyst layer, may be conventionally used in the art or prepared by methods known in the art. For example, the proton exchange membrane may be DuPont's Nafion 115 or Nafion 117 membrane, the cathode catalyst layer may be Pt / C or platinum black, the cathode diffusion layer may be titanium felt, porous titanium or carbon paper, and the anode diffusion layer may be titanium felt or porous titanium.

[0058] According to the present application, the membrane electrode can be prepared by conventional methods known in the art, and the present application does not have any strict limitations thereon.For example, the catalyst layer components can be formulated as an ink or slurry containing an aqueous and / or organic solvent, an optional polymer binder, and an optional proton-conducting polymer, and the ink or slurry can be deposited on the proton exchange membrane using conventional techniques such as spraying, printing, and doctor blade.

[0059] In a sixth aspect, there is provided a proton exchange membrane water electrolyzer comprising the membrane electrode of the present application and a cathode end plate and an anode end plate disposed on either side of the membrane electrode, respectively.

[0060] The proton exchange membrane water electrolysis device provided in the present application has a structure conventionally used in the art, and other parts and materials contained therein other than the membrane electrodes may be conventionally used in the art, and the details thereof will not be described here.

[0061] First type of embodiment According to a first type of embodiment of the present application, the iridium-based composite catalyst is an iridium-titanium composite catalyst essentially composed of an amorphous oxide of iridium and titanium, the content ratio of iridium to titanium in the catalyst is (0.4-0.7):(0.3-0.6) in terms of moles, and the XRD spectrum of the catalyst has a peak envelope only in the 2θ range of 30 to 35°.

[0062] In the iridium titanium composite catalyst according to the first type embodiment of the present application, the iridium and titanium elements are essentially present in the form of amorphous oxide, the bulk structure is amorphous, there is no obvious crystalline diffraction peak in the XRD spectrum, the iridium and titanium are more uniformly distributed in the catalyst, the bulk structure is uniform, obvious phase separation is avoided, the catalyst surface is rich in iridium, and when used as an anode catalyst for proton exchange membrane electrolysis of water to produce hydrogen, it has higher catalytic activity than commercial iridium oxide catalysts, and the usage of precious metals is greatly reduced.

[0063] In certain embodiments, the XRD spectrum of the iridium titanium composite catalyst does not have the (110) crystal plane diffraction peak and the (101) crystal plane diffraction peak of IrO2, and also does not have the corresponding diffraction peak of titanium oxide crystal phase.The absence of the two individual crystal plane diffraction peaks of IrO2 indicates that the iridium titanium composite catalyst does not contain iridium oxide in rutile phase, which further indicates that the bulk phase structure of the catalyst is uniform.

[0064] In a preferred embodiment, the iridium titanium composite catalyst is represented by the formula: Ir x Ti 1-x O ywhere x is in the range of 0.4 to 0.7, and the value of y is such that the chemical formula satisfies the principle of electroneutrality.

[0065] In a preferred embodiment, the iridium titanium composite catalyst has the following characteristics: the Ir / Ti molar ratio of the iridium titanium composite catalyst measured by XPS analysis is denoted as M1, the Ir / Ti molar ratio of the iridium titanium composite catalyst measured by XRF analysis is denoted as M2, and the ratio of M1 / M2 is denoted as M0, and M0 is in the range of 1.25-1.55. Obviously, at this time, the relative content of iridium element on the surface of the iridium titanium composite catalyst is higher than the overall relative content of iridium element in the bulk structure, which indicates that the catalyst surface is rich in iridium. Through a large number of experiments, the inventors of the present application have found that if the iridium titanium composite catalyst meets M0 within the above preferred range, the catalyst can obtain higher catalytic activity even under the condition of low content of precious metal iridium.

[0066] In a preferred embodiment, the Ir 4f characteristic peak of the XPS spectrum of the iridium titanium composite catalyst includes an Ir(IV) characteristic peak and an Ir(III) characteristic peak, and the iridium titanium composite catalyst has the following characteristics: the peak area of ​​the Ir(III) characteristic peak of the XPS spectrum of the iridium titanium composite catalyst is denoted as Q1, the peak area of ​​the Ir(IV) characteristic peak of the XPS spectrum is denoted as Q2, Q1 / (Q1+Q2) is denoted as Q0, and Q0 is in the range of 0.35-0.41. The inventors of the present application have found through experiments that when the iridium titanium composite catalyst satisfies the above preferred range of Q0, there is a certain amount of Ir(III) active species on the surface of the composite catalyst, so that the overvoltage of the catalyst is lower and the oxygen generation activity is higher.

[0067] In a particular preferred embodiment, the iridium titanium composite catalyst is in the form of a nanoparticle powder, with a particle size of 2 to 10 nm, preferably 4 to 7 nm, and a BET specific surface area of ​​50 to 80 m 2 / g range.

[0068] According to a first type of embodiment of the present application, a method for preparing an iridium titanium composite catalyst includes the following steps: 1) mixing an iridium source, a titanium source, a complexing agent, and water, adjusting the pH of the mixture to 6-10, and reacting to obtain a reactant, wherein the complexing agent is selected from C3-C8 organic polyacids and soluble salts thereof, preferably C4-C8 organic polyacids and soluble salts thereof; 2) removing water from the reaction material obtained in step 1) by evaporation to obtain an iridium-titanium composite catalyst precursor; and 3) A step of calcining the iridium-titanium composite catalyst precursor in an oxygen-containing atmosphere to obtain an iridium-titanium composite catalyst.

[0069] The inventors of the present application have found through experiments that in the process of preparing the catalyst, when a complexing agent is added to the iridium source and the titanium source, the iridium source and the titanium source are uniformly dispersed due to the complexing effect, and an iridium-titanium composite catalyst having a uniform bulk structure can be obtained. In addition, when a C3-C8 organic polyacid and its soluble salt, especially a C4-C8 organic polyacid and its soluble salt, is mixed with the iridium source and the titanium source as a complexing agent, precipitation can also be avoided. In addition, the above preparation method is simple to operate, has mild conditions, does not use explosive raw materials such as sodium nitrate in the reaction process, does not emit harmful gases such as NOx during calcination, has low production costs, and is more environmentally friendly in the process.

[0070] In a preferred embodiment, the titanium source is selected from soluble titanium salts, more preferably titanium sulfate, titanium oxysulfate, or a combination thereof.

[0071] In a preferred embodiment, the molar ratio of the iridium source to the titanium source is 0.5-2.5:1, preferably 1-2.3:1; the total molar ratio of the complexing agent to the iridium source and titanium source is 1-2:1, preferably 1.3-1.8:1.

[0072] In a preferred embodiment, the reaction conditions in step 1) include: a temperature of 35-95° C. for a time of 0.5-6 hours, preferably a temperature of 50-90° C. for a time of 2-4 hours.

[0073] In a preferred embodiment, the reaction in step 1) is carried out at pH 8-9.

[0074] In a preferred embodiment, the calcination conditions in step 3) include: a calcination temperature of 350-400° C., preferably 370-385° C., and a calcination time of 1-3 hours, preferably 1.5-2 hours.

[0075] Second Type of Embodiment According to a second embodiment of the present application, the iridium-based composite catalyst is an iridium-niobium composite catalyst essentially composed of an amorphous oxide of iridium and niobium, the content ratio of iridium to niobium in the catalyst is (0.5-0.7):(0.3-0.5) in terms of moles, and the XRD spectrum of the catalyst has a peak envelope only in the 2θ range of 25 to 40°.

[0076] In the iridium-niobium composite catalyst according to the second type of embodiment of the present application, the iridium and niobium elements are essentially present in the form of amorphous oxide, the XRD spectrum has no obvious crystal diffraction peaks, the iridium and niobium are uniformly distributed in the catalyst, the bulk structure is uniform, the catalyst has low crystallinity and large specific surface area. When used as an anode catalyst for electrolyzing water through a proton exchange membrane to produce hydrogen, the catalyst has higher catalytic activity than commercial iridium oxide catalysts, and the amount of precious metals used is greatly reduced, which greatly reduces costs and is worthy of expanding applications.

[0077] In certain embodiments, the XRD spectrum of the iridium niobium composite catalyst does not have the (110) crystal plane diffraction peak and the (101) crystal plane diffraction peak of IrO2, and does not have the diffraction peak corresponding to the niobium oxide crystal phase. The absence of the above two individual crystal plane diffraction peaks of IrO2 indicates that the iridium niobium composite catalyst does not contain rutile phase ruthenium oxide, which further indicates that the bulk phase structure of the catalyst is uniform.

[0078] In a preferred embodiment, the iridium niobium composite catalyst is represented by the formula: Ir x Nb 1-x O y where x is in the range of 0.5 to 0.7, preferably in the range of 0.62 to 0.67, and the value of y is such that the chemical formula satisfies the principle of electroneutrality.

[0079] In a preferred embodiment, the iridium niobium composite catalyst has the following characteristics: the Ir / Nb molar ratio of the iridium niobium composite catalyst measured by XPS analysis is denoted as M1, the Ir / Nb molar ratio of the iridium niobium composite catalyst measured by XRF analysis is denoted as M2, and the ratio of M1 / M2 is denoted as M0, where M0 is in the range of 0.99-1.02. Obviously, at this point, the relative content of iridium element on the surface of the iridium niobium composite catalyst is consistent with the overall relative content of iridium element in the bulk structure.

[0080] In a preferred embodiment, the Ir 4f characteristic peak of the XPS spectrum of the iridium niobium composite catalyst includes an Ir(IV) characteristic peak and an Ir(III) characteristic peak, and the iridium niobium composite catalyst has the following characteristics: the peak area of ​​the Ir(III) characteristic peak of the XPS spectrum of the iridium niobium composite catalyst is denoted as Q1, the peak area of ​​the Ir(IV) characteristic peak of the XPS spectrum is denoted as Q2, Q1 / (Q1+Q2) is denoted as Q0, and Q0 is in the range of 0.50-0.54. The inventors of the present application have found through experiments that when the iridium niobium composite catalyst satisfies the above preferred range of Q0, there is a certain amount of Ir(III) active species on the surface of the composite catalyst, so that the iridium niobium composite catalyst has a low overvoltage and a higher oxygen generation activity.

[0081] In a particular preferred embodiment, the iridium niobium composite catalyst is in the form of a nanoparticle powder, and the BET specific surface area of ​​the catalyst particles is 71 to 75 m 2 / g and the particle size is 1 to 5 nm, preferably 2 to 4 nm.

[0082] According to a second type of embodiment of the present application, a method for preparing an iridium niobium composite catalyst includes the following steps: 1) mixing an iridium source, a niobium source, a complexing agent, and a solvent, adjusting the pH of the mixture to 6-10, and reacting them to obtain a reactant, wherein the complexing agent is selected from C3-C8 organic polyacids and soluble salts thereof, preferably C4-C8 organic polyacids and soluble salts thereof; 2) removing the solvent in the reaction material obtained in step 1) by evaporation to obtain an iridium-niobium composite catalyst precursor; 3) A step of calcining the iridium-niobium composite catalyst precursor in an oxygen-containing atmosphere to obtain an iridium-niobium composite catalyst.

[0083] In the preparation method of the present application, a complexing agent is mixed with an iridium source and a niobium source to improve the uniformity of the dispersion of the iridium source and the niobium source in the mixed solution, and a C3-C8 organic polyacid and its soluble salt, especially a C4-C8 organic polyacid and its soluble salt, is used as a complexing agent to avoid precipitation in the solution. The reaction process does not use highly corrosive solvents such as hydrochloric acid, and does not require a high-temperature resistant Ti substrate. The preparation method is simple in operation and has mild conditions.

[0084] In a preferred embodiment, step 1) further comprises the steps of: 1A) mixing an iridium source, a first complexing agent, and water to obtain a first mixture; 1B) combining a niobium source, a second complexing agent, and an organic solvent to obtain a second mixture; 1C) adjusting the pH of each of the first mixture and the second mixture to 6 to 10; 1D) after adjusting the pH in step 1C), mixing the first mixture with the second mixture, further adjusting the pH of the resulting mixture to 6-10, and reacting to obtain a reactant; Here, the first complexing agent and the second complexing agent may be the same or different, and each is independently selected from C3 to C8 organic polyacids and soluble salts thereof, preferably C4 to C8 organic polyacids and soluble salts thereof.

[0085] In a more preferred embodiment, the organic solvent comprises an alcohol, such as methanol, ethanol, isopropanol, and the like.

[0086] In a preferred embodiment, the niobium source is an alcohol soluble niobium compound, more preferably selected from niobium pentachloride, ammonium niobate oxalate hydrate, or a combination thereof.

[0087] In a preferred embodiment, the first complexing agent and the second complexing agent may be the same or different and are each independently selected from citric acid, tartaric acid, malic acid, sodium citrate, sodium tartrate, sodium malate, or combinations thereof.

[0088] In a preferred embodiment, the molar ratio of the first complexing agent to the iridium source calculated as iridium is 1 to 4:1, preferably 2 to 3:1, the molar ratio of the second complexing agent to the niobium source calculated as niobium is 1 to 4:1, preferably 1.5 to 2.5:1, and more preferably the molar ratio of the iridium source calculated as iridium to the niobium source calculated as niobium is 1 to 2.33:1, preferably 1.7 to 2:1.

[0089] In a preferred embodiment, the reaction conditions in step 1) include: a temperature of 45-85° C., preferably 60-70° C., and a reaction time of 2-6 hours, preferably 3-4 hours.

[0090] In a preferred embodiment, the reaction in step 1) is carried out at a pH of 8 to 9. Specifically, when the first complexing agent and the second complexing agent are used, the pH is preferably adjusted to 8 to 9 when the pH is adjusted in step 1C), respectively.

[0091] In the method of the present application, the aqueous solution of iridium source and the alcoholic solution of niobium source are preferably prepared under alkaline conditions.Compared with the acidic solution, the alkaline conditions can make the catalytic effect of the finally prepared iridium-niobium composite catalyst better.

[0092] In a preferred embodiment, the firing conditions in step 3 include: a firing temperature of 350 to 550° C., preferably 380 to 450° C., and a firing time of 1 to 3 hours, preferably 1 to 2 hours.

[0093] Third Type of Embodiment According to a third type of embodiment of the present application, the iridium-based composite catalyst is an iridium-tantalum composite catalyst essentially composed of amorphous oxides of iridium and tantalum, the content ratio of iridium to tantalum in the catalyst is (0.5-0.7):(0.3-0.5) in terms of moles, and the XRD spectrum of the catalyst has peak envelopes only in the 2θ ranges of 25-35° and 40-41°.

[0094] In the iridium-tantalum composite catalyst according to the third embodiment of the present application, iridium element and tantalum element are essentially present in the form of amorphous oxide. Iridium oxide and tantalum oxide are thoroughly mixed to form a uniform amorphous structure without obvious crystallization phenomenon, which is beneficial to improve the catalytic activity and stability of the catalyst. The composite catalyst can also effectively reduce the amount of iridium used and save costs.

[0095] In certain embodiments, the XRD spectrum of the iridium tantalum composite catalyst does not have the diffraction peaks of the (110) crystal plane and the (101) crystal plane of IrO2, and also does not have the diffraction peaks corresponding to the crystal phase of tantalum oxide.The absence of the diffraction peaks of the above two individual crystal planes of IrO2 indicates that the iridium tantalum composite catalyst does not contain iridium oxide in rutile phase, which further indicates that the two elements are uniformly mixed in the catalyst bulk phase.

[0096] In a preferred embodiment, the iridium tantalum composite catalyst is represented by the formula: Ir x Ta 1-x O y where x is in the range of 0.5 to 0.7, preferably in the range of 0.55 to 0.66, and the value of y is such that the above chemical formula satisfies the principle of electroneutrality.

[0097] In a preferred embodiment, the iridium tantalum composite catalyst has the following characteristics: the Ir / Ta molar ratio of the iridium tantalum composite catalyst measured by XPS analysis is designated as M1, the Ir / Ta molar ratio of the iridium tantalum composite catalyst measured by XRF analysis is designated as M2, and the ratio of M1 / M2 is designated as M0, where M0 is in the range of 0.98-1.04. Obviously, at this point, the relative content of iridium element on the surface of the iridium tantalum composite catalyst is consistent with the overall relative content of iridium element in the bulk structure.

[0098] In a preferred embodiment, the Ir4f characteristic peak of the XPS spectrum of the iridium tantalum composite catalyst includes an Ir(IV) characteristic peak and an Ir(III) characteristic peak, and the iridium tantalum composite catalyst has the following characteristics: the peak area of ​​the Ir(III) characteristic peak of the XPS spectrum of the iridium tantalum composite catalyst is denoted as Q1, the peak area of ​​the Ir(IV) characteristic peak of the XPS spectrum is denoted as Q2, and Q1 / (Q1+Q2) is denoted as Q0, where Q0 is in the range of 0.22-0.27. The inventors of the present application have found through experiments that when the iridium tantalum composite catalyst satisfies the above preferred range of Q0, there is a certain amount of Ir(III) active species on the surface of the composite catalyst, so that the iridium tantalum composite catalyst has a low overvoltage and a higher oxygen generation activity.

[0099] In a particular preferred embodiment, the iridium tantalum composite catalyst is in the form of a nanoparticle powder, and the BET specific surface area of ​​the catalyst particles is 50 to 70 m 2 / g; the particle size is 2-7 nm.

[0100] According to a third type of embodiment of the present application, a method for preparing an iridium tantalum composite catalyst includes the following steps: 1) mixing an iridium source, a tantalum source, a complexing agent, and a solvent, adjusting the pH of the mixture to 6-10, and reacting to obtain a reactant, wherein the complexing agent is selected from C3-C8 organic polyacids and soluble salts thereof, preferably C4-C8 organic polyacids and soluble salts thereof; 2) removing the solvent in the reaction material obtained in step 1) by evaporation to obtain an iridium-tantalum composite catalyst precursor; 3) The iridium-tantalum composite catalyst precursor is calcined in an oxygen-containing atmosphere to obtain an iridium-tantalum composite catalyst.

[0101] The method of the present application has a simple process and mild conditions. By using C3-C8 organic polyacids and their soluble salts, especially C4-C8 organic polyacids and their soluble salts as complexing agents, the mixing uniformity of the iridium source and the tantalum source can be improved, which is beneficial for the preparation of an amorphous structure composite catalyst in which iridium oxide and tantalum oxide are uniformly mixed. The method can achieve high utilization rate of iridium atoms and tantalum atoms (atom utilization rate reaches 100%) and high production efficiency, and can reduce the usage of precious metal iridium. During the preparation process, no exhaust gas such as NOx is emitted, which is green and environmentally friendly.

[0102] In a preferred embodiment, step 1) further comprises the steps of: 1A) mixing an iridium source, a first complexing agent, and water to obtain a first mixture; 1B) combining a tantalum source, a second complexing agent, and an organic solvent to obtain a second mixture; 1C) adjusting the pH of the first mixture and the second mixture to 6 to 10, respectively; and 1D) After adjusting the pH in step 1C), the first mixture and the second mixture are mixed, the pH of the resulting mixture is further adjusted to 6-10, and reacted to obtain a reactant, in which the first complexing agent and the second complexing agent may be the same or different and are each independently selected from C3-C8 organic polyacids and soluble salts thereof, preferably C4-C8 organic polyacids and soluble salts thereof.

[0103] In a further preferred embodiment, the organic solvent comprises an alcohol.

[0104] In a preferred embodiment, the tantalum source is an alcohol soluble tantalum compound, more preferably tantalum pentachloride.

[0105] In a preferred embodiment, the first complexing agent and the second complexing agent may be the same or different and are each independently selected from citric acid, tartaric acid, malic acid, sodium citrate, sodium tartrate, sodium malate, or combinations thereof.

[0106] In a preferred embodiment, the molar ratio of the first complexing agent to the iridium source calculated as iridium is 1 to 4:1, preferably 1.7 to 2.4:1, the molar ratio of the second complexing agent to the tantalum source calculated as tantalum is 1 to 4:1, preferably 2.0 to 3.2:1, and more preferably the molar ratio of the iridium source calculated as iridium to the tantalum source calculated as tantalum is 1 to 2.33:1, preferably 1.22 to 1.94:1.

[0107] In a preferred embodiment, the reaction conditions in step 1) include: a temperature of 25-75° C., preferably 40-60° C.; and a reaction time of 0.5-6 hours, preferably 3-4 hours.

[0108] In a preferred embodiment, the reaction in step 1) is carried out at a pH of 8 to 9. Specifically, when the first complexing agent and the second complexing agent are used, it is preferable to adjust the pH to 8 to 9 when adjusting the pH of each in step 1C).

[0109] In the method of the present application, the aqueous solution of iridium source and the alcoholic solution of tantalum source are preferably prepared under alkaline conditions.Compared with the acidic solution, the alkaline conditions can make the catalytic effect of the iridium tantalum catalyst finally prepared better.

[0110] In a preferred embodiment, the calcination conditions in step 3) include: a calcination temperature of 350-450° C., preferably 370-400° C., and a calcination time of 2-4 hours, preferably 2.5-3 hours.

[0111] In some particularly preferred embodiments, the present application provides the following technical solutions: A1. An iridium-titanium composite catalyst comprising an amorphous oxide of iridium and titanium, characterized in that the XRD spectrum of the iridium-titanium composite catalyst shows an amorphous peak envelope only at 30 to 35°.

[0112] A2. The iridium titanium composite catalyst according to item A1, characterized in that the iridium titanium composite catalyst has the following features: The Ir / Ti molar ratio of the iridium titanium composite catalyst measured by XPS analysis is denoted as M1; The Ir / Ti molar ratio of the iridium titanium composite catalyst measured by XRF analysis is denoted as M2; M0 defined by the following formula (1) is a value between 1.20 and 1.55. M0=M1 / M2 formula (1).

[0113] A3. The iridium titanium composite catalyst according to item A1, characterized in that the particle size of the iridium titanium composite catalyst is 2 to 10 nm; Optionally, the chemical composition of the iridium titanium composite catalyst is Ir x Ti 1-x O2, where x is a value between 0.4 and 0.7.

[0114] A4. The iridium-titanium composite catalyst according to item A1, characterized in that the XRD spectrum of the iridium-titanium composite catalyst does not have a diffraction peak of the (110) crystal plane of IrO2, nor has a diffraction peak of the (101) crystal plane of IrO2.

[0115] A5. The iridium titanium composite catalyst according to item A1, wherein the Ir4f characteristic peak of the XPS spectrum of the iridium titanium composite catalyst includes an Ir(IV) characteristic peak and an Ir(III) characteristic peak, and the iridium titanium composite catalyst has the following properties: The peak area of ​​the Ir(III) characteristic peak in the XPS spectrum of the iridium-titanium composite catalyst is denoted as Q1. The peak area of ​​the Ir(IV) characteristic peak in the XPS spectrum of the iridium-titanium composite catalyst is denoted as Q2. Q0 defined by the following formula (2) is any value between 0.35 and 0.41. Q0=Q1 / (Q1+Q2) Equation (2).

[0116] A6. A method for preparing an iridium titanium composite catalyst, comprising the steps of: 1) mixing an iridium source, a titanium source, a complexing agent, and water, adjusting the pH of the mixture to 6-10, and obtaining a first material by reaction, wherein the complexing agent is selected from C3-C8 organic polyacids and soluble salts thereof, preferably C4-C8 organic polyacids and soluble salts thereof; 2) separating water from the first material to obtain an iridium titanium composite catalyst precursor; 3) calcining the iridium titanium composite catalyst precursor in an oxygen-containing atmosphere.

[0117] A7. The method according to item A6, wherein the iridium source is selected from one or more of chloroiridic acid and alkali metal chloroiridate, preferably the alkali metal chloroiridate is selected from one or more of potassium chloroiridate and sodium chloroiridate; the titanium source is selected from soluble titanium salts, preferably one or more of titanium sulfate and titanium oxysulfate; the complexing agent is selected from one or more of citric acid, tartaric acid, malic acid, sodium citrate, sodium tartrate, and sodium malate; Preferably, the molar ratio of the iridium source, calculated as iridium, to the titanium source, calculated as titanium, is 0.5 to 2.5:1, preferably 1 to 2.3:1; More preferably, the total molar ratio of the complexing agent to the iridium source and the titanium source is 1-2:1, and preferably 1.3-1.8:1.

[0118] A8. The method according to item A6, wherein the reaction conditions in step 1) include: a temperature of 35-95°C, a time of 0.5-6 hours, preferably a temperature of 50-90°C, and a time of 2-4 hours; Optionally, in step 1), the pH is 8 to 9; Optionally, the pH is adjusted by adding a pH adjuster, optionally selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, and aqueous ammonia.

[0119] A9. The method according to item A6, characterized in that in step 3), the conditions of the calcination treatment include a calcination temperature of 350 to 400°C, preferably 370 to 385°C, and a calcination time of 1 to 3 hours, preferably 1.5 to 2 hours.

[0120] A10. The method according to item A6, characterized in that the method further comprises: washing the product obtained by the calcination treatment, the solvent used in the washing treatment is a mixed solution of alcohol and water, and the alcohol accounts for 10-95% by weight, preferably 30-60% by weight, of the mass of the mixed solution; Preferably, the alcohol is selected from one or more of methanol, ethanol, n-propanol, and isopropanol.

[0121] A11. An iridium titanium composite catalyst prepared by the method according to any one of items A6 to A10.

[0122] A12. Use of the iridium titanium composite catalyst according to any one of items A1 to A5 and A11 as an oxygen evolution electrode catalyst in electrochemistry.

[0123] A13. A proton exchange membrane water electrolysis device comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, a cathode diffusion layer, and an anode diffusion layer, characterized in that the anode catalyst layer employs the iridium-titanium composite catalyst described in any one of items A1 to A5 and A12.

[0124] B1. An iridium-niobium composite catalyst comprising an amorphous oxide of iridium and niobium, characterized in that the XRD spectrum of the iridium-niobium composite catalyst shows an amorphous peak envelope only at 25 to 40°.

[0125] B2. The iridium niobium composite catalyst according to item B1, characterized in that the iridium niobium composite catalyst has the following features: The Ir / Nb molar ratio of the iridium-niobium composite catalyst measured by XPS analysis is denoted as M1. The Ir / Nb molar ratio of the iridium-niobium composite catalyst measured by XRF analysis is denoted as M2. M0 defined by the following formula (1) is a value between 0.99 and 1.02. M0=M1 / M2 formula (1).

[0126] B3. The iridium niobium composite catalyst according to item B1, wherein the Ir 4f characteristic peak in the XPS spectrum of the iridium niobium composite catalyst includes an Ir(IV) characteristic peak and an Ir(III) characteristic peak, and the iridium niobium composite catalyst has the following properties: The peak area of ​​the Ir(III) characteristic peak in the XPS spectrum of the iridium-niobium composite catalyst is denoted as Q1. The peak area of ​​the Ir(IV) characteristic peak in the XPS spectrum of the iridium-niobium composite catalyst is denoted as Q2. Q0 defined by the following formula (2) is a value between 50% and 54%. Q0=Q1 / (Q1+Q2)×100% Formula (2)

[0127] B4. The iridium-niobium composite catalyst according to item B1, wherein the chemical composition of the iridium-niobium composite catalyst is represented by the following formula (A): Ir x Nb 1-x O 2.5-0.5x Formula (A), Here, x is a value between 0.5 and 0.7, and preferably, x is a value between 0.62 and 0.67. Preferably, the iridium-niobium composite catalyst includes iridium-niobium composite catalyst particles, and the iridium-niobium composite catalyst particles have a BET specific surface area of ​​71 to 75 m. 2 / g and the particle size is 1 to 5 nm.

[0128] B5. The iridium-niobium composite catalyst according to item B1, characterized in that the XRD spectrum of the iridium-niobium composite catalyst does not have a diffraction peak of the (110) crystal plane of IrO2, nor a diffraction peak of the (101) crystal plane of IrO2.

[0129] B6. A method for preparing an iridium niobium composite catalyst, the method comprising the steps of: 1) a step of mixing an iridium source, a niobium source, a complexing agent, and a solvent, adjusting the pH of the mixture to 6 to 10, and obtaining a raw material mixture by reaction, wherein the complexing agent is selected from C3 to C8 organic polyacids and soluble salts thereof, and preferably selected from C4 to C8 organic polyacids and soluble salts thereof; 2) separating the solvent from the raw material mixture to obtain an iridium-niobium composite catalyst precursor; 3) Calcining the iridium niobium composite catalyst precursor in an oxygen-containing atmosphere.

[0130] B7. The method according to item B6, wherein step 1) comprises the following steps: 1A) performing a first mixing of an iridium source, a first complexing agent, and water to obtain a first mixture; 1B) performing a second mixing of a niobium source, a second complexing agent, and an organic solvent to obtain a second mixture; 1C) adjusting the pH of each of the first mixture and the second mixture to 6 to 10; 1D) After adjusting the pH in step 1C), the first mixture and the second mixture are mixed to react, and the pH is adjusted to 6 to 10 to obtain a raw material mixture; Here, the first complexing agent and the second complexing agent may be the same or different, and are each independently selected from C3 to C8 organic polyacids and soluble salts thereof, preferably C4 to C8 organic polyacids and soluble salts thereof; Optionally, the organic solvent comprises an alcohol.

[0131] B8. The method according to item B7, wherein the iridium source is selected from one or more of chloroiridic acid and alkali metal chloroiridate; preferably, the alkali metal chloroiridate is selected from one or more of potassium chloroiridate and sodium chloroiridate; the niobium source is selected from one or two of niobium pentachloride and ammonium niobate oxalate hydrate; the first complexing agent and the second complexing agent may be the same or different and are each independently selected from one or more of citric acid, tartaric acid, malic acid, sodium citrate, sodium tartrate, and sodium malate; Preferably, the molar ratio of the first complexing agent to the iridium source, calculated as iridium, is from 1 to 4:1, preferably from 2 to 3:1; Preferably, the molar ratio of the second complexing agent to the niobium source, calculated as niobium, is from 1 to 4:1, preferably from 1.5 to 2.5:1; Preferably, the molar ratio of the iridium source, calculated as iridium, to the niobium source, calculated as niobium, is 1-2.33:1, preferably 1.7-2:1.

[0132] B9. The method according to item B6, wherein the conditions for carrying out the reaction in step 1) comprise: a temperature of 45-85°C, preferably 60-70°C, a reaction time of 2-6 hours, preferably 3-4 hours; Preferably, in step 1), the pH is 8 to 9; Optionally, the pH is adjusted by adding a pH adjuster, optionally selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, and aqueous ammonia.

[0133] B10. The method according to item B6, characterized in that in step 3), the conditions of the firing treatment include a firing temperature of 350 to 550° C. and a firing time of 1 to 3 hours.

[0134] B11. The method according to item B6, further comprising a step of washing the product obtained by the calcination treatment; the solvent used in the washing treatment is a mixed solution of alcohol and water, and the alcohol accounts for 10-95% by weight, preferably 30-60% by weight, of the mass of the mixed solution; Preferably, the alcohol is selected from one or more of methanol, ethanol, n-propanol, and isopropanol.

[0135] B12. An iridium niobium composite catalyst prepared by the method according to any one of items B6 to B11.

[0136] B13. Use of the iridium niobium composite catalyst according to any one of items B1 to B5 and B12 as an oxygen evolution electrode catalyst in electrochemistry.

[0137] B14. A proton exchange membrane water electrolysis device comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, a cathode diffusion layer, and an anode diffusion layer, characterized in that the anode catalyst layer employs the iridium-niobium composite catalyst described in any one of Items B1 to B5 and B12.

[0138] C1. An iridium-tantalum composite catalyst comprising iridium and an amorphous oxide of tantalum, characterized in that the XRD spectrum of the iridium-tantalum composite catalyst has peak envelopes only at 25-35° and 40-41°.

[0139] C2. The iridium tantalum composite catalyst according to item C1, characterized in that the XRD spectrum of the iridium titanium composite catalyst does not have a diffraction peak of the (110) crystal plane of IrO2, and does not have a diffraction peak of the (101) crystal plane of IrO2.

[0140] C3. The iridium-tantalum composite catalyst according to item C1, characterized in that the iridium-tantalum composite catalyst has a chemical composition shown in the following formula (1): Ir x Ta 1-x O 2.5-0.5x Formula (1); Here, x is any value from 0.5 to 0.7, and preferably, x is any value from 0.55 to 0.66.

[0141] C4. The iridium tantalum composite catalyst according to item C1, characterized in that it has the following features: The Ir / Ta molar ratio of the iridium-tantalum composite catalyst measured by XPS analysis is denoted as M1. The Ir / Ta molar ratio of the iridium-tantalum composite catalyst measured by XRF analysis is denoted as M2, M0 defined by the following formula (2) is a value between 0.98 and 1.04. M0=M1 / M2 formula (2)

[0142] C5 The iridium tantalum composite catalyst according to item C1, wherein the Ir 4f characteristic peak of the XPS spectrum of the iridium tantalum composite catalyst includes an Ir(IV) characteristic peak and an Ir(III) characteristic peak, and the iridium tantalum composite catalyst has the following characteristics: The peak area of ​​the Ir(III) characteristic peak in the XPS spectrum of the iridium-tantalum composite catalyst is denoted as Q1. The peak area of ​​the Ir(IV) characteristic peak in the XPS spectrum of the iridium-tantalum composite catalyst is denoted as Q2. Q0 defined by the following formula (3) is a value between 0.22 and 0.27. Q0=Q1 / (Q1+Q2) Equation (3).

[0143] C6. The iridium-tantalum composite catalyst according to item C1, wherein the iridium-tantalum composite catalyst comprises iridium-tantalum composite catalyst particles, and the BET specific surface area of ​​the iridium-tantalum composite catalyst particles is 50 to 70 m 2 / g and a particle size of 2 to 7 nm.

[0144] C7. A method for preparing an iridium tantalum composite catalyst, characterized in that the method comprises the following steps: 1) mixing an iridium source, a tantalum source, a complexing agent and a solvent, adjusting the pH of the mixture to 6-10, and reacting to obtain a reactant, wherein the complexing agent is selected from one or more C3-C8 organic polyacids and soluble salts thereof, preferably one or more C4-C8 organic polyacids and soluble salts thereof; 2) separating the solvent from the reactants to obtain an iridium tantalum composite catalyst precursor; 3) calcining the iridium tantalum composite catalyst precursor in an oxygen-containing atmosphere.

[0145] C8. The method according to item C7, characterized in that step 1) comprises the following steps: 1A) performing a first mixing of an iridium source, a first complexing agent, and water to obtain a first mixture; 1B) performing a second mixing of a tantalum source, a second complexing agent, and an organic solvent to obtain a second mixture; 1C) Adjust the pH of the first mixture and the second mixture to 6-10, respectively; 1D) After adjusting the pH in step 1C), mixing the first mixture with the second mixture, adjusting the pH to 6 to 10, and reacting to obtain a reactant; Wherein, the first complexing agent and the second complexing agent may be the same or different, and each is independently selected from one or more C3-C8 organic polyacids and soluble salts thereof, preferably one or more C4-C8 organic polyacids and soluble salts thereof; Optionally, the organic solvent comprises an alcohol.

[0146] C9. The method according to item C8, wherein the iridium source is selected from one or more of chloroiridic acid and alkali metal chloroiridate, preferably the alkali metal chloroiridate is selected from one or two of potassium chloroiridate and sodium chloroiridate; Tantalum sources include tantalum pentachloride, the first complexing agent and the second complexing agent may be the same or different and are each independently selected from one or more of citric acid, tartaric acid, malic acid, sodium citrate, sodium tartrate, and sodium malate; Preferably, the molar ratio of the first complexing agent to the iridium source, calculated as iridium, is from 1 to 4:1, more preferably from 1.7 to 2.4:1; Preferably, the molar ratio of the second complexing agent to the tantalum source, calculated as tantalum, is from 1 to 4:1, more preferably from 2.0 to 3.2:1; Preferably, the molar ratio of the iridium source calculated as iridium to the tantalum source calculated as tantalum is 1-2.33:1, more preferably 1.22-1.94:1.

[0147] C10. The method according to item C7, wherein the conditions for carrying out the reaction in step 1) include a temperature of 25 to 75°C, preferably 40 to 60°C, and a reaction time of 0.5 to 6 hours, preferably 3 to 4 hours; Preferably, in step 1), the pH is 8 to 9; Optionally, the pH is adjusted by adding a pH adjuster, optionally selected from one or more of sodium carbonate, sodium bicarbonate, sodium hydroxide, and aqueous ammonia.

[0148] C11. The method according to item C7, wherein in step 3), the conditions of the calcination treatment include a calcination temperature of 350 to 450°C, preferably 370 to 400°C, and a calcination time of 2 to 4 hours, preferably 2.5 to 3 hours; Optionally, the method further comprises a step of washing the product obtained by the calcination treatment, the solvent used in the washing treatment is a mixed solution of alcohol and water, the alcohol accounts for 10-95% by weight of the mixed solution, preferably 30-60% by weight; Preferably, the alcohol is selected from one or more of methanol, ethanol, n-propanol, and isopropanol.

[0149] C12. An iridium tantalum composite catalyst prepared by the method according to any one of items C7 to C11.

[0150] C13. Use of the iridium tantalum composite catalyst according to any one of items C1 to C12 as an oxygen evolution electrode catalyst in electrochemistry.

[0151] C14. A proton exchange membrane water electrolysis device comprising a proton exchange membrane, a cathode catalyst layer, an anode catalyst layer, a cathode diffusion layer, and an anode diffusion layer, characterized in that the anode catalyst layer employs the iridium-tantalum composite catalyst described in any one of Items C1 to C6 and C12. EXAMPLES

[0152] The present application will be described in detail below with reference to specific examples. The following examples are intended to help those skilled in the art to further understand the present application, but are not intended to limit the present application in any way.

[0153] The instruments and test methods used in the following examples and comparative examples are as follows: The model of X-ray fluorescence spectrometer (XRF) is Rigaku 3013 X-ray fluorescence spectrometer, and the analytical test conditions of X-ray fluorescence spectrometry are as follows: the scan time is 100 seconds, and the atmosphere is air.

[0154] The elements on the surface of the material are detected by X-ray photoelectron spectroscopy (XPS). The X-ray photoelectron spectroscopy equipment used is an ESCALab220i-XL type X-ray electron spectrometer with Avantage V5.926 software, manufactured by VG Scientific. The test conditions for X-ray photoelectron spectroscopy are as follows: excitation source is monochromatic A1Kα X-ray, power is 330W, and base vacuum during the analysis test is 3×10 -9 mbar. Additionally, the electron binding energies are corrected using the C1s peak of elemental carbon (284.3 eV).

[0155] The model of high-resolution transmission electron microscope (HRTEM) was JEM-2100 (HRTEM) (JEOL Ltd.), and the test conditions of HRTEM were as follows: accelerating voltage, 200 kV;

[0156] BET test method: The pore structure characteristics of the samples were determined by Quantachrome AS-6B analyzer, and the specific surface area was obtained by Brunauer-Emmett-Taller (BET) method.

[0157] X-ray diffraction analysis (XRD) was performed on a Shimadzu XRD-6000 X-ray diffractometer from Japan; the test conditions included: tube voltage 40 kV, tube current 40 mA, Cu target Kα radiation, and 2θ scan range 5°–80°.

[0158] The overpotential is measured using the following equipment and method: the model of electrochemical workstation is PARSTAT3000A-DX, the model of rotating disk electrode is 636A. A three-electrode system is used, with a saturated calomel electrode as the reference electrode, a platinum sheet as the counter electrode, and a glassy carbon electrode as the working electrode. The electrolyte used under acidic conditions is a 0.5M H2SO4 solution. The catalyst to be tested is uniformly dispersed in a mixed solution of isopropanol, water, and Nafion by ultrasonication, and then dropped onto the surface of the glassy carbon electrode, and the working electrode is obtained after air drying, with a catalyst loading of 0.38mg / cm2. 2 The test temperature is 25°C, and oxygen is passed through the solution for 30 minutes before the test to saturate the solution with oxygen. The rotation speed is 2500 rpm, the scanning range of the linear polarization curve is 1.2-1.5 V (vs. RHE), and the scanning rate is 5 mV / s. The voltage of the linear polarization curve after scanning is corrected by the ohmic internal resistance of the reference electrode and the solution to obtain the corrected voltage. The current is corrected by the background current and the normalized area to obtain the corrected current and current density. 10 mA / cm 2 The voltage corresponding to the current density of was selected from the corrected polarization curve. The voltage value minus the theoretical value (1.23 V) was the catalyst overpotential.

[0159] The molar ratios of O in the approximate chemical compositions of the catalysts obtained in the following Examples and Comparative Examples are approximate values ​​calculated when Ir and Ti are tetravalent and Nb and Ta are pentavalent.

[0160] Example I Series The following series of Examples I are used to illustrate the preparation and application of the iridium titanium composite catalyst according to the present application. All the raw materials used in the series of Examples I were obtained through commercial routes and were analytically pure unless otherwise specified. The chloroiridic acid raw material was liquid, with a mass fraction of Ir of 35 wt%. For ease of use, it was prepared into a solution with a mass concentration of 0.182 mol / L and can also be prepared into a solution with a higher concentration. The purity of titanium sulfate was 96 wt%, and the purity of citric acid was analytically pure.

[0161] Example I-1. Catalyst Ir 0.4 Ti 0.6 Preparation of O (1) 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid was taken, 1.36 g (5.44 mmol) of titanium sulfate was weighed, and 2.63 g (13.7 mmol) of citric acid was weighed. The solution was stirred at 90°C to thoroughly mix the chloroiridic acid, titanium sulfate, and citric acid, and a certain amount of Na2CO3 was added to adjust the solution to about pH=8. The molar ratio of the iridium source calculated as iridium to the titanium source calculated as titanium was 0.669:1, and the total molar ratio of the complexing agent to the iridium source and titanium source was 1.5:1.

[0162] (2) The solution of step (1) was stirred for 30 minutes, and then a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8 to 9, followed by stirring for an additional 3 hours.

[0163] (3) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0164] (4) The catalyst was taken out, cooled, crushed, and placed flat on a porcelain boat. The temperature was increased to 380° C. at a rate of 5° C. / min in an oxygen atmosphere and maintained for 2 hours.

[0165] (5) After cooling to room temperature, the catalyst was washed with a 1:1 solvent mixture of ethanol and water and centrifuged three times (pH paper detection was neutral), and the washed catalyst was ultrasonically dispersed in an aqueous solution and dried overnight in a forced air drying oven (60 °C). The obtained catalyst product was denoted as CAT-I-1.

[0166] From the XRF test analysis, the approximate chemical composition of CAT-I-1 is Ir 0.40 Ti 0.60 It turned out to be O2.

[0167] TEM test analysis showed that the particle size of CAT-I-1 was 5-10 nm.

[0168] Example I-2. Catalyst Ir 0.5 Ti 0.5 Preparation of O (1) 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid was taken, 0.91 g (3.64 mmol) of titanium sulfate was weighed out, and 2.10 g (10.92 mmol) of citric acid was weighed out. The solution was stirred at 90°C to thoroughly mix the chloroiridic acid, titanium sulfate, and citric acid, and a certain amount of Na2CO3 was added to adjust the solution to about pH = 8. The molar ratio of the iridium source calculated as iridium to the titanium source calculated as titanium was 1:1, and the total molar ratio of the complexing agent to the iridium source and titanium source was 1.5:1.

[0169] (2) The solution of step (1) was stirred for 30 minutes, and then a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8 to 9, followed by stirring for an additional 3 hours.

[0170] (3) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0171] (4) After the catalyst was taken out and cooled, it was crushed and placed flat on a porcelain boat, and the temperature was increased to 380°C at a rate of 5°C / min in an oxygen atmosphere and maintained for 2 hours.

[0172] (5) After cooling to room temperature, the catalyst was washed with a 1:1 mixture of ethanol and water and centrifuged three times (pH paper showed neutrality), the washed catalyst was ultrasonically dispersed in an aqueous solution and dried overnight in a forced air drying oven (60°C). The obtained catalyst product was designated as CAT-I-2.

[0173] From the XRF test analysis, the approximate chemical composition of CAT-I-2 is Ir 0.50 Ti 0.50 It turned out to be O2.

[0174] TEM test analysis showed that the grain size of CAT-I-2 was 3-8 nm.

[0175] Example I-3. Catalyst Ir 0.6 Ti 0.4 Preparation of O (1) 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid was taken, 0.61 g (2.44 mmol) of titanium sulfate was weighed out, and 1.75 g (9.1 mmol) of citric acid was weighed out. The solution was stirred at 90°C to thoroughly mix the chloroiridic acid, titanium sulfate, and citric acid, and a certain amount of Na2CO3 was added to adjust the solution to about pH = 8. The molar ratio of the iridium source calculated as iridium to the titanium source calculated as titanium was 1.5:1, and the total molar ratio of the complexing agent to the iridium source and titanium source was 1.5:1.

[0176] (2) The solution of step (1) was stirred for 30 minutes, and then a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8 to 9, followed by stirring for an additional 3 hours.

[0177] (3) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0178] (4) The catalyst was taken out and cooled, then crushed and placed flat on a porcelain boat. The temperature was then increased to 380°C at a rate of 5°C / min in an oxygen atmosphere and maintained at that temperature for 2 hours.

[0179] (5) After cooling to room temperature, the catalyst was washed with a 1:1 mixture of ethanol and water and centrifuged three times (pH paper showed neutrality), the washed catalyst was ultrasonically dispersed in an aqueous solution and dried overnight in a forced air oven (60°C). The resulting catalyst product was designated as CAT-I-3.

[0180] From the XRF test analysis, the approximate chemical composition of CAT-I-3 is Ir 0.60 Ti 0.40 It turned out to be O2.

[0181] TEM test analysis shows that the particle size of CAT-I-3 is 2-5 nm. The high-resolution transmission electron microscope spectrum of the obtained catalyst CAT-I-3 is shown in Figure 1, which shows that the catalyst particles provided in the present application are uniform in size and the particle size can reach nanometer dimensions.

[0182] Example I-4. Catalyst Ir 0.7 Ti 0.3 Preparation of O (1) 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid was collected, 0.39 g (1.56 mmol) of titanium sulfate was weighed out, and 1.50 g (7.8 mmol) of citric acid was weighed out. The solution was stirred at 90°C to thoroughly mix the chloroiridic acid, titanium sulfate, and citric acid, and a certain amount of Na2CO3 was added to adjust the solution to about pH = 8. The molar ratio of the iridium source calculated as iridium to the titanium source calculated as titanium was 2.33:1, and the total molar ratio of the complexing agent to the iridium source and titanium source was 1.5:1.

[0183] (2) The solution of step (1) was stirred for 30 minutes, and then a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8 to 9, followed by stirring for an additional 3 hours.

[0184] (3) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0185] (4) The catalyst was taken out and cooled, then crushed and placed flat on a ceramic boat. The temperature was then increased to 380°C at a rate of 5°C / min in an oxygen atmosphere and maintained at that temperature for 2 hours.

[0186] (5) After cooling to room temperature, the catalyst was washed with a 1:1 mixture of ethanol and water, centrifuged three times (pH paper showed neutrality), and the washed catalyst was ultrasonically dispersed in an aqueous solution and dried overnight in a forced air oven (60°C). The resulting catalyst product was designated as CAT-I-4.

[0187] From the XRF test analysis, the approximate chemical composition of CAT-I-4 is Ir 0.70 Ti 0.30 It turned out to be O2.

[0188] TEM test analysis showed that the grain size of CAT-I-4 was 3-7 nm.

[0189] Example I-5. Catalyst Ir 0.54 Ti 0.46 Preparation of O A catalyst was prepared with reference to Example I-4 with the following exceptions: 20mL (3.64mmol) of chloroiridic acid aqueous solution was taken, 0.78g (3.12mmol) of titanium sulfate was weighed, 1.94g (10.11mmol) of citric acid was weighed, the molar ratio of iridium source calculated as iridium to titanium source calculated as titanium was 1.17:1, and the total molar ratio of complexing agent to iridium source and titanium source was 1.5:1. The rest of the process was the same as in Example I-4. The obtained catalyst product was designated as CAT-I-5.

[0190] From the XRF test analysis, the approximate chemical composition of CAT-I-5 is Ir 0.54 Ti 0.46 It turned out to be O2.

[0191] TEM test analysis showed that the grain size of CAT-I-5 was 4-7 nm.

[0192] Example I-6. Catalyst Ir 0.70 Ti 0.30 Preparation of O A catalyst was prepared with reference to Examples 1-4 with the following exceptions: The iridium source was replaced by 3.64 mmol of potassium chloroiridate, the titanium source was replaced by 1.56 mmol of titanium oxysulfate, and citric acid was replaced by 7.8 mmol of malic acid as a complexing agent.

[0193] The calcination conditions were adjusted as follows: the temperature was increased to 370° C. at a rate of 5° C. / min and maintained for 1.5 hours.

[0194] The resulting catalyst product was designated as CAT-I-6.

[0195] From the XRF test analysis, the approximate chemical composition of CAT-I-6 is Ir 0.70 Ti 0.30 It turned out to be O2.

[0196] TEM test analysis showed that the grain size of CAT-I-6 was 3-8 nm.

[0197] Example I-7. Catalyst Ir 0.70 Ti 0.30 Preparation of O A catalyst was prepared with reference to Example I-4 with the following exceptions.

[0198] 10.4 mmol of citric acid was weighed out, and the total molar ratio of the complexing agent to the iridium source and titanium source was 2:1. The rest of the process was the same as in Example I-4. The obtained catalyst product was designated as CAT-I-7.

[0199] From the XRF test analysis, the approximate chemical composition of CAT-I-7 is Ir 0.70 Ti 0.30 It turned out to be O2.

[0200] TEM test analysis showed that the grain size of CAT-I-7 was 4-9 nm.

[0201] Comparative example I-1 A commercially available iridium dioxide catalyst was used, product number 206237, purchased from Sigma Aldrich Company, and designated as DI-1.

[0202] Comparative example I-2 A catalyst was prepared with reference to Example I-1, with the following exceptions: No citric acid complexing agent was added, and the rest of the process was the same as in Example I-1, and the resulting catalyst product was designated as DI-2.

[0203] From the XRF test analysis, the approximate chemical composition of DI-2 is Ir 0.40 Ti 0.60 It turned out to be O2.

[0204] From the XRD spectrum shown in FIG. 2, it can be seen that the catalysts of Comparative Examples I-1 and I-2 both exhibit obvious crystalline phase peaks, with the crystalline phase peaks at 28.0° and 34.2° corresponding to the (110) and (101) crystal planes of IrO2, respectively; on the other hand, the catalysts of Examples I-1 to I-4 do not exhibit the crystalline phase peaks of IrO2, nor the crystalline phase peaks of titanium oxide, but only exhibit peak envelopes in the 2θ range of 30 to 35°, indicating that the iridium and titanium oxides therein are amorphous (non-crystalline).

[0205] The catalysts prepared in the examples and comparative examples were analyzed, and the M1 (Ir / Ti molar ratio) obtained by XPS analysis, the M2 (Ir / Ti molar ratio) obtained by XRF analysis, M0 (M1 / M2), Q0, and electrochemical performance test data (overvoltage, indicated as G, test current density 10 mA / cm 2 ) are shown in Table I-1 below.

[0206] [Table 1]

[0207] The data in Table I-1 reveals the following: Compared with DI-1 (the existing commercially available iridium dioxide catalyst), the catalysts CAT-I-1 to CAT-I-7 prepared by the method provided in the present application have higher Q0 and lower overpotential, which indicates that the distribution rate of the surface active species Ir(III) of CAT-I-1 to CAT-I-7 is higher and the oxygen evolution activity is higher. Compared with the iridium dioxide catalyst, the catalysts provided in the present application can greatly reduce the usage of the precious metal iridium.

[0208] Compared with DI-2 (no complexing agent was added during the preparation process), the catalysts CAT-I-1~CAT-I-7 prepared by the method provided in the present application have smaller particle size, which indicates that the method provided in the present application can effectively improve the dispersion and avoid particle aggregation; the M0 of CAT-I-1~CAT-I-7 is higher, which indicates that iridium is more abundant on the catalyst surface; CAT-I-1~CAT-I-7 have higher Q0 and lower overpotential, which indicates that the distribution rate of active species Ir(III) on the surface of CAT-I-1~CAT-I-7 is higher and the oxygen evolution activity is higher.

[0209] Furthermore, comparing CAT-I-1 with CAT-I-2~CAT-I-5 (using the same type of preparation raw materials), during the preparation process, CAT-I-2~CAT-I-5 met the molar ratio of iridium source calculated as iridium to titanium source calculated as titanium of 1~2.3:1, and CAT-I-2~CAT-I-5 had higher M0 and Q0, and lower overpotential, which indicates that the surface of CAT-I-2~CAT-I-5 catalysts is more rich in iridium, the distribution rate of surface active species Ir(III) is higher, and the oxygen evolution activity is higher.

[0210] Comparing CAT-I-4 and CAT-I-7, it can be seen that CAT-I-4 meets the "total molar ratio of complexing agent to iridium source and titanium source is 1.3~1.8:1" during the preparation process. The particle size of CAT-I-4 is smaller, M1, M0 and Q0 are higher, and the overpotential is lower, which indicates that the surface of CAT-I-4 catalyst is more rich in iridium, the distribution rate of surface active species Ir(III) is higher, and the oxygen evolution activity is higher.

[0211] Example II Series The following series of Examples II are used to illustrate the preparation and use of iridium-niobium composite catalysts according to the present application. All raw materials used in the series of Examples II were obtained through commercial channels and were analytically pure unless otherwise specified. Chloroiridic acid or alkali metal chloroiridic acid salts were prepared into aqueous solutions with a concentration of 0.182 mol / L for use, and can also be prepared into solutions with higher concentrations for use. Niobium pentachloride was prepared into organic solutions with a concentration of 0.185 mol / L for use. The purity of citric acid was analytically pure.

[0212] Example II-1. Catalyst Ir 0.5 Nb 0.5 O 2.25 Preparation of (1) 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid was taken, and 1.05 g (first complexing agent, 5.47 mmol) of citric acid was weighed out. The solution was stirred at 50°C to thoroughly mix the citric acid and chloroiridic acid, and a certain amount of Na2CO3 was added to adjust the solution to about pH=8. The molar ratio of the first complexing agent to the iridium source calculated as iridium was 1.5:1.

[0213] (2) 19.7 mL (3.64 mmol) of niobium pentachloride ethanol solution was taken, and 1.05 g of citric acid (second complexing agent, 5.47 mmol) was added thereto, and the mixture was stirred at 50°C to thoroughly mix the citric acid and niobium chloride, and then the pH was adjusted again to about pH=8 with Na2CO3 solution, and the molar ratio of the second complexing agent to the niobium source calculated as niobium was 1.5:1; In the above process, the molar ratio of the iridium source, calculated as iridium, to the niobium source, calculated as niobium, was 1:1.

[0214] (3) The aqueous solution from step 1 was added to the ethanol solution from step 2, and the mixture was stirred at 50°C for 30 minutes, after which a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8-9, and the solution was stirred for another 3 hours.

[0215] (4) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0216] (5) The catalyst was taken out and cooled, then crushed and placed flat on a porcelain boat. The temperature was then increased to 400°C at a rate of 2°C / min in an oxygen atmosphere and maintained at that temperature for 2 hours.

[0217] (6) After cooling to room temperature, the catalyst was washed with a 1:1 mixture of ethanol and water, centrifuged three times (pH test paper was neutral), and the centrifuge tube containing the catalyst was placed in a freeze-drying oven (-20°C) and dried overnight. The resulting catalytic product was designated as CAT-II-1.

[0218] From the XRF test analysis, the approximate chemical composition of CAT-II-1 is Ir 0.5 Nb 0.5 O 2.25 It was found to be.

[0219] The TEM electron micrograph of CAT-II-1 is shown in Figure 7, where the grain size is uniform and can reach nanometer dimensions. According to the TEM test, the grain size of CAT-II-1 is 2-5 nm.

[0220] The BET analysis showed that the BET specific surface area of ​​CAT-II-1 was 72.3 m 2 / g.

[0221] The XRD spectrum of CAT-II-1 is shown in Figure 4. From Figure 4, it can be seen that the XRD spectrum of CAT-II-1 does not contain the crystalline phase peaks of IrO2 and niobium oxide, but only contains the peak envelope in the 2θ range of 25-40°, which indicates that the iridium and niobium oxides therein are in amorphous form.

[0222] The XPS spectrum of CAT-II-1 is shown in Figure 6. From Figure 6, it can be seen that CAT-II-1 has an active species Ir(III) on the surface. The specific values ​​of XPS Q0 are listed in Table II-1.

[0223] Example II-2. Catalyst Ir 0.6 Nb 0.4 O 2.2 Preparation of (1) Take 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid, weigh out 1.05 g of citric acid (first complexing agent, 5.47 mmol), and stir at 50°C to thoroughly mix the citric acid and chloroiridic acid. Add a certain amount of Na2CO3 to adjust the solution to about pH=8. The molar ratio of the first complexing agent to the iridium source calculated as iridium was 1.5:1.

[0224] (2) 13.1 mL (2.43 mmol) of niobium pentachloride ethanol solution was taken, 0.7 g of citric acid (second complexing agent, 3.64 mmol) was added thereto, and the mixture was stirred at 50°C to thoroughly mix the citric acid and niobium chloride, and then the mixture was adjusted to about pH=8 again with Na2CO3 solution, and the molar ratio of the second complexing agent to the niobium source calculated as niobium was 1.5:1. In the above process, the molar ratio of the iridium source calculated as iridium to the niobium source calculated as niobium was 1.5:1.

[0225] (3) The aqueous solution from step 1 was added to the ethanol solution from step 2 and stirred at 60°C for 30 minutes, after which a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8-9 and the solution was stirred for an additional 3 hours.

[0226] (4) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0227] (5) The catalyst was taken out and cooled, then crushed and placed flat on a porcelain boat. The temperature was then increased to 400°C at a rate of 2°C / min in an oxygen atmosphere and maintained at that temperature for 2 hours.

[0228] (6) After cooling to room temperature, the catalyst was washed with a 1:1 solvent mixture of ethanol and water, centrifuged three times (pH paper detection was neutral), and the centrifuge tube containing the catalyst was placed in a freeze-drying oven (-20°C) to dry overnight. The obtained catalytic product was designated as CAT-II-2.

[0229] From the XRF test analysis, the approximate chemical composition of CAT-II-2 is Ir 0.6 Nb 0.4 O 2.2 It was found to be.

[0230] TEM examination and BET analysis showed that the particle size of CAT-II-2 was 2-4 nm and the BET specific surface area was 72.9 m 2 / g.

[0231] Example II-3. Catalyst Ir 0.7 Nb 0.3 O 2.15 Preparation of (1) 30 mL (5.46 mmol) of an aqueous solution of chloroiridic acid was taken, and 1.58 g (8.22 mmol) of citric acid was weighed out and taken, and the solution was stirred at 50°C to thoroughly mix the citric acid and chloroiridic acid, and a certain amount of Na2CO3 was added to adjust the solution to about pH = 8, and the molar ratio of the first complexing agent to the iridium source calculated as iridium was 1.5:1.

[0232] (2) Take 12.6mL (2.34mmol) of niobium pentachloride ethanol solution, add 0.67g of citric acid (second complexing agent, 3.49mmol), stir the mixture at 50℃ to mix citric acid and niobium chloride thoroughly, then adjust the solution to about pH=8 with Na2CO3 solution, the molar ratio of the second complexing agent to the niobium source calculated as niobium was 1.5:1. In the above process, the molar ratio of the iridium source calculated as iridium to the niobium source calculated as niobium was 2.33:1.

[0233] (3) The aqueous solution from step 1 was added to the ethanol solution from step 2 and stirred at 60°C for 30 minutes, after which a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8-9 and the solution was stirred for an additional 3 hours.

[0234] (4) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0235] (5) After the catalyst was taken out and cooled, it was crushed and placed flat on a porcelain boat. The temperature was then increased to 400°C at a rate of 2°C / min in an oxygen atmosphere and maintained for 2 hours.

[0236] (6) After cooling to room temperature, the catalyst was washed with a 1:1 solvent mixture of ethanol and water and centrifuged three times (pH paper showed neutrality), and the centrifuge tube containing the catalyst was placed in a freeze-drying oven (-20°C) and dried overnight. The resulting catalytic product was designated as CAT-II-3.

[0237] From the XRF test analysis, the approximate chemical composition of CAT-II-3 is Ir 0.7 Nb 0.3 O 2.15 It was found to be.

[0238] TEM examination and BET analysis showed that the particle size of CAT-II-3 was 3-5 nm and the BET specific surface area was 74.5 m 2 / g.

[0239] Example II-4. Catalyst Ir 0.65 Nb0.35 O 2.25 Preparation of A catalyst was prepared with reference to Example II-1, with the following exceptions: 3.64 mmol of the aqueous chloroiridic acid solution was taken and 1.75 g of citric acid (first complexing agent, 9.10 mmol) was added, the molar ratio of first complexing agent to iridium source, calculated as iridium, was 2.5:1. 1.96 mmol of niobium pentachloride ethanol solution was taken and 0.75 g of citric acid (second complexing agent, 3.9 mmol) was added, the molar ratio of second complexing agent to niobium source, calculated as niobium, was 2:1. In the above process, the molar ratio of the iridium source, calculated as iridium, to the niobium source, calculated as niobium, was 1.86:1. The rest of the process was the same as in Example II-1. The obtained catalyst product was designated as CAT-II-4.

[0240] From the XRF test analysis, the approximate chemical composition of CAT-II-4 is Ir 0.65 Nb 0.35 O 2.25 It was found to be.

[0241] TEM examination and BET analysis showed that the particle size of CAT-II-4 was 2-4 nm and the BET specific surface area was 71.2 m 2 / g.

[0242] Example II-5. Catalyst Ir 0.5 Nb 0.5 O 2.25 Preparation of A catalyst was prepared with reference to Example II-1, with the following exceptions: The iridium source was replaced by potassium chloroiridate, the first complexing agent was replaced by malic acid; the niobium source was replaced by ammonium niobate oxalate hydrate, and the second complexing agent was replaced by tartaric acid, and the molar addition numbers were the same as in Example II-1.

[0243] The calcination conditions were adjusted as follows: the temperature was increased to 380° C. at a rate of 2° C. / min and maintained for 1 h. The rest of the process was the same as in Example II-1. The obtained catalyst product was designated as CAT-II-5.

[0244] From the XRF test analysis, the approximate chemical composition of CAT-II-5 is Ir 0.5 Nb 0.5 O 2.25 It was found to be.

[0245] TEM examination and BET analysis showed that the particle size of CAT-II-5 was 2-4 nm and the BET specific surface area was 71.6 m 2 / g.

[0246] Comparative Example II-1 A commercially available iridium dioxide catalyst was used, product number 206237, purchased from Sigma Aldrich Company, designated as D-II-1.

[0247] Comparative Example II-2 A catalyst was prepared with reference to Example II-1, with the following exceptions: Without adding the first complexing agent and the second complexing agent, the rest of the process was the same as in Example II-1, and the obtained catalyst product was designated as D-II-2.

[0248] From the XRF analysis, the approximate chemical composition of D-II-2 is Ir 0.5 Nb 0.5 O 2.25 It was found to be.

[0249] TEM examination and BET analysis showed that the particle size of D-II-2 was 30-70 nm and the BET specific surface area was 21.2 m 2 / g.

[0250] After the XRD test, obvious crystalline phase peaks appear in the XRD spectrum of D-II-2, as shown in Fig. 5. Here, the crystalline phase peak around 23° corresponds to the (001) crystal plane of Nb2O5, and the crystalline phase peaks around 28° and 35° correspond to the (110) and (101) crystal planes of IrO2, respectively.

[0251] The catalysts obtained in the above examples and comparative examples were analyzed. M1 (Ir / Nb molar ratio) obtained by XPS analysis, M2 (Ir / Nb molar ratio) and M0 (M1 / M2) obtained by XRF analysis, particle size of catalyst particles, BET specific surface area, Q0, and electrochemical performance test data (overvoltage, indicated as G, test current density is 10 mA / cm 2 ) are shown in Table II-1 below.

[0252] [Table 2]

[0253] According to the data in Table II-1 above, we can see that: Compared with D-II-1 (the existing commercially available iridium dioxide catalyst), the catalysts CAT-II-1 to CAT-II-5 prepared by the method provided in the present application have higher Q0 and lower overpotential, which indicates that the distribution rate of the surface active species Ir(III) of CAT-II-1 to CAT-II-5 is higher and the oxygen evolution activity is higher. Compared with the iridium dioxide catalyst, the catalysts provided in the present application can effectively reduce the usage of the precious metal iridium.

[0254] Compared with D-II-2 (the first complexing agent and the second complexing agent are not added during the preparation process), the particle size of the catalysts CAT-II-1~CAT-II-5 prepared by the method provided in the present application is smaller, which indicates that the method provided in the present application can effectively improve the dispersion and avoid the aggregation of particles; the M0 of CAT-II-1~CAT-II-5 is close to 1, which indicates that the element dispersion on the surface and the element dispersion in the bulk structure are more uniform; the M1 of CAT-II-1~CAT-II-5 is higher, which indicates that the iridium is more abundant on the catalyst surface; and the Q0 of CAT-II-1~CAT-II-5 is higher and the overpotential is lower, which indicates that the distribution rate of the surface active species Ir(III) of CAT-II-1~CAT-II-5 is higher and the oxygen evolution activity is higher.

[0255] Furthermore, comparing CAT-II-4 with CAT-II-1~CAT-II-3 (using the same type of preparation raw materials), it can be seen that in the preparation process, CAT-II-4 meets the following conditions: the molar ratio of the first complexing agent to the iridium source calculated as iridium is 2~3:1, the molar ratio of the second complexing agent to the niobium source calculated as niobium is 1.5~2.5:1, and the molar ratio of the iridium source calculated as iridium to the niobium source calculated as niobium is 1.5~2:1. Compared with catalysts CAT-II-1~CAT-II-3, catalyst CAT-II-4 has lower overpotential and higher oxygen evolution activity.

[0256] Series of Examples III The following series of Examples III are used to illustrate the preparation and use of the iridium tantalum composite catalyst according to the present application. All raw materials used in the series of Examples III were obtained through commercial channels and were analytically pure unless otherwise specified. Here, chloroiridic acid or alkali metal chloroiridic acid salt was prepared into an aqueous solution with a concentration of 0.182 mol / L for use, and can also be prepared into a solution with a higher concentration for use. Tantalum pentachloride was prepared into an organic solution with a concentration of 0.279 mol / L for use. The purity of citric acid was analytically pure.

[0257] Example III-1. Catalyst Ir 0.5 Ta 0.5 O 2.25 Preparation of

[0258] (1) 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid was taken, and 1.05 g (first complexing agent, 5.47 mmol) of citric acid was weighed out, and the citric acid and the chloroiridic acid were thoroughly mixed by stirring at 50°C, and a certain amount of Na2CO3 was added to adjust the solution to about pH=8; where the molar ratio of the first complexing agent to the iridium source calculated as iridium was 1.5:1.

[0259] (2) Take 13.1 mL (3.64 mmol) of the tantalum pentachloride ethanol solution, add 1.05 g of citric acid (first complexing agent, 5.47 mmol), and stir the mixture at 50°C to thoroughly mix the citric acid and tantalum chloride, then adjust the solution to about pH=8 with Na2CO3 solution, where the molar ratio of the second complexing agent to the tantalum source, calculated as tantalum, was 1.5:1. In the above process, the molar ratio of the iridium source, calculated as iridium, to the tantalum source, calculated as tantalum, was 1:1.

[0260] (3) The aqueous solution from step (1) was added to the ethanol solution from step (2), and the solution was stirred at 60°C for 30 minutes. Then, a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8-9, and the solution was further stirred for 3 hours.

[0261] (4) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0262] (5) After the catalyst was removed and cooled, it was crushed and placed flat on a porcelain boat. The temperature was increased to 370°C at a rate of 2°C / min in an oxygen atmosphere and maintained for 2 hours.

[0263] (6) After cooling to room temperature, the catalyst was washed with a 1:1 solvent mixture of ethanol and water and centrifuged three times (pH paper detection was neutral), and the centrifuge tube containing the catalyst was placed in a freeze-drying oven (-10°C) and dried overnight. The obtained catalytic product was denoted as CAT-III-1.

[0264] From the XRF test analysis, the approximate chemical composition of CAT-III-1 is Ir 0.5 Ta 0.5 O 2.25 It was found to be.

[0265] TEM examination and BET analysis showed that the particle size of CAT-III-1 was 2-5 nm and the BET specific surface area was 68.7 m 2 / g. A TEM electron micrograph of CAT-III-1 is shown in Figure 10, which shows that the catalyst particles are uniform and of nanometer dimensions.

[0266] From the XRD analysis, as shown in Fig. 8A, it can be seen that the catalyst CAT-III-1 only exhibits peak envelopes within the 2θ ranges of 25-35° and 40-41°, and does not exhibit the crystalline phase peaks of IrO2 or tantalum oxide, which indicates that the iridium tantalum oxide therein is in amorphous form without obvious crystallization phenomenon.

[0267] From the XPS analysis, as shown in Fig. 9, the Ir4f characteristic peak in the XPS spectrum of catalyst CAT-III-1 contains Ir(IV) characteristic peak and Ir(III) characteristic peak, which indicates that the catalyst contains highly active Ir(III) species.

[0268] Example III-2. Catalyst Ir 0.6 Ta 0.4 O 2.2 Preparation of (1) 20 mL (3.64 mmol) of an aqueous solution of chloroiridic acid was collected, and 1.05 g of citric acid (first complexing agent, 5.47 mmol) was weighed out and taken, and the citric acid and chloroiridic acid were thoroughly mixed by stirring at 50°C, and a certain amount of Na2CO3 was added to adjust the solution to about pH = 8. The molar ratio of the first complexing agent to the iridium source calculated as iridium was 1.5:1.

[0269] (2) 8.7 mL (2.43 mmol) of tantalum pentachloride ethanol solution was taken, 0.7 g of citric acid (second complexing agent, 3.64 mmol) was added, and the mixture was stirred at 50°C to thoroughly mix the citric acid and tantalum chloride, and then adjusted to about pH=8 with Na2CO3 solution, where the molar ratio of the second complexing agent to the tantalum source, calculated as tantalum, was 1.5:1. In the above process, the molar ratio of the iridium source, calculated as iridium, to the tantalum source, calculated as tantalum, was 1.5:1.

[0270] (3) The aqueous solution from step 1 was added to the ethanol solution from step 2 and stirred at 60°C for 30 minutes, after which a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8-9 and the solution was stirred for an additional 3 hours.

[0271] (4) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0272] (5) After the catalyst was taken out and cooled, it was crushed and placed flat on a porcelain boat. The temperature was then increased to 400°C at a rate of 2°C / min in an oxygen atmosphere and maintained for 2 hours.

[0273] (6) After cooling to room temperature, the catalyst was washed with a 1:1 solvent mixture of ethanol and water and centrifuged three times (pH paper detection was neutral), and the centrifuge tube containing the catalyst was placed in a freeze-drying oven (-10°C) and dried overnight. The obtained catalytic product was denoted as CAT-III-2.

[0274] From the XRF test analysis, the approximate chemical composition of CAT-III-2 is Ir 0.6 Ta 0.4 O 2.2 It was found to be.

[0275] TEM examination and BET analysis showed that the particle size of CAT-III-2 was 3-6 nm and the BET specific surface area was 61.9 m 2 / g.

[0276] Example III-3. Catalyst Ir 0.7 Ta 0.3 O 2.15 Preparation of (1) 30 mL (5.46 mmol) of an aqueous solution of chloroiridic acid was taken, and 1.58 g (first complexing agent, 8.22 mmol) of citric acid was weighed out and taken, and the citric acid and chloroiridic acid were thoroughly mixed by stirring at 50°C, and a certain amount of Na2CO3 was added to adjust the solution to about pH = 8, where the molar ratio of the first complexing agent to the iridium source calculated as iridium was 1.5:1.

[0277] (2) Take 8.4 mL (2.34 mmol) of the tantalum pentachloride ethanol solution, add 0.67 g of citric acid (second complexing agent, 3.49 mmol), and stir the mixture at 50°C to thoroughly mix the citric acid and tantalum chloride, then adjust the solution to about pH=8 with Na2CO3 solution, where the molar ratio of the second complexing agent to the tantalum source, calculated as tantalum, was 1.5:1. In the above process, the molar ratio of the iridium source, calculated as iridium, to the tantalum source, calculated as tantalum, was 2.33:1.

[0278] (3) The aqueous solution from step 1 was added to the ethanol solution from step 2 and stirred at 60°C for 30 minutes, after which a certain amount of sodium carbonate solution was added to adjust the pH of the solution to 8-9 and the solution was stirred for an additional 3 hours.

[0279] (4) After cooling, the solution was rotary dried at 70°C and then placed in an oven at 120°C to dry overnight.

[0280] (5) The catalyst was taken out and cooled, then crushed and placed flat on a porcelain boat. The temperature was then increased to 400°C at a rate of 2°C / min in an oxygen atmosphere and maintained at that temperature for 2 hours.

[0281] (6) After cooling to room temperature, the catalyst was washed with a 1:1 solvent mixture of ethanol and water and centrifuged three times (pH paper detection was neutral), and the centrifuge tube containing the catalyst was placed in a freeze-drying oven (-10°C) and dried overnight. The obtained catalytic product was denoted as CAT-III-3.

[0282] From the XRF test analysis, the approximate chemical composition of CAT-III-3 is Ir 0.7 Ta 0.3 O 2.15 It was found to be.

[0283] TEM examination and BET analysis showed that the particle size of CAT-III-3 was 4-7 nm and the BET specific surface area was 56.7 m 2 / g.

[0284] Example III-4. Catalyst Ir 0.5 Ta 0.5 O 2.25 Preparation of A catalyst was prepared according to Example III-1 with the following exceptions: The iridium source was replaced by potassium chloroiridate, the first complexing agent was replaced by tartaric acid, the second complexing agent was replaced by malic acid, and the molar number added was the same as in Example III-1.

[0285] The calcination conditions were adjusted as follows: the temperature was increased to 400°C at a rate of 2°C / min and maintained for 1 hour; The rest of the process was the same as in Example III-1. The obtained catalyst product was designated as CAT-III-4.

[0286] From the XRF test analysis, the approximate chemical composition of CAT-III-4 is Ir 0.5 Ta 0.5 O 2.25 It was found to be.

[0287] TEM examination and BET analysis showed that the particle size of CAT-III-4 was 3-5 nm and the BET specific surface area was 65.2 m 2 / g.

[0288] Example III-5. Catalyst Ir 0.63 Ta 0.37 O 2.18 Preparation of A catalyst was prepared according to Example III-1 with the following exceptions: 5.46 mmol of the aqueous chloroiridic acid solution was taken and 1.89 g of citric acid (first complexing agent, 9.83 mmol) was added, the molar ratio of first complexing agent to iridium source, calculated as iridium, was 1.8:1. 3.20 mmol of the tantalum chloride ethanol solution was taken and 1.60 g of citric acid (second complexing agent, 8.32 mmol) was added, the molar ratio of the second complexing agent to the tantalum source, calculated as tantalum, was 2.6:1. In the above process, the molar ratio of the iridium source, calculated as iridium, to the tantalum source, calculated as tantalum, was 1.7:1. The rest of the process was the same as in Example III-1. The obtained catalyst product was designated as CAT-III-5.

[0289] From the XRF test analysis, the approximate chemical composition of CAT-III-5 is Ir 0.63 Ta 0.37 O 2.18 It was found to be.

[0290] TEM examination and BET analysis showed that the particle size of CAT-III-5 was 3-6 nm and the BET specific surface area was 60.7 m 2 / g.

[0291] Comparative example III-1 A commercially available iridium dioxide catalyst was used, purchased from Sigma Aldrich Company, product number 206237, and designated as D-III-1.

[0292] Comparative example III-2 A catalyst was prepared with reference to Example III-1, with the following exceptions: The first complexing agent and the second complexing agent were not added, but the remaining process was the same as that of Example III-1, and the obtained catalyst product was designated as D-III-2, and its XRD spectrum is shown in Figure 8B.

[0293] From the XRF analysis, the approximate chemical composition of D-III-2 is Ir 0.5 Ta 0.5 O 2.25 It was found to be.

[0294] TEM examination and BET analysis showed that the particle size of D-III-2 was 30-80 nm and the BET specific surface area was 28.2 m 2 / g. TEM electron micrographs of D-III-2 showed that the particles of product D-III-2 were aggregated into large clumps.

[0295] As can be seen from FIG. 8B, the catalyst obtained in Comparative Example III-2 exhibits obvious crystalline phase peaks, among which the crystalline phase peaks at 2θ of around 28° and 35° correspond to the (110) and (101) crystal planes of IrO2, respectively.

[0296] The catalysts obtained in the examples and comparative examples were analyzed to determine the particle size, BET specific surface area, M1 (Ir / Ta, XPS), M2 (Ir / Ta, XRF), M0 (M1 / M2), Q0, and electrochemical performance test data (overvoltage, expressed in G, test current density 10 mA / cm 2 ) are shown in Table III-1 below.

[0297] [Table 3]

[0298] According to the data in Table III-1 above, we can see that: Compared with D-III-1 (the existing commercially available iridium dioxide catalyst), the catalysts CAT-III-1 to CAT-III-5 prepared by the method provided in the present application have higher Q0 and lower overpotential, which indicates that the distribution rate of the surface active species Ir(III) of CAT-III-1 to CAT-III-5 is higher and the oxygen evolution activity is higher. Compared with the iridium dioxide catalyst, the catalysts provided in the present application can effectively reduce the usage of the precious metal iridium.

[0299] Compared with D-III-2 (the first complexing agent and the second complexing agent were not added during the preparation process), the catalysts CAT-III-1~CAT-III-5 prepared by the method provided in the present application have smaller particle size, which indicates that the method provided in the present application can effectively improve the dispersion and avoid particle aggregation; the M0 of CAT-III-1~CAT-III-5 is close to 1, which indicates that the element dispersion on the surface and the element dispersion in the bulk structure are more uniform; the M1 of CAT-III-1~CAT-III-5 is higher, which indicates that the catalyst surface is more rich in iridium; the Q0 of CAT-III-1~CAT-III-5 is higher and the overpotential is lower, which indicates that the distribution rate of the surface active species Ir(III) of CAT-III-1~CAT-III-5 is higher and the oxygen evolution activity is higher.

[0300] Furthermore, comparing CAT-III-1~CAT-III-3 with CAT-III-5 (using the same type of preparation raw materials), it can be seen that during the preparation process, CAT-III-5 meets the following conditions: the molar ratio of the first complexing agent to the iridium source calculated as iridium is 1.7~2.4:1, the molar ratio of the second complexing agent to the tantalum source calculated as tantalum is 2~3.2:1, and the molar ratio of the iridium source calculated as iridium to the tantalum source calculated as tantalum is 1.22~1.94:1. Compared with CAT-III-1~CAT-III-3, CAT-III-5 has a higher Q0 and a lower overpotential; this indicates that CAT-III-5 has a higher distribution rate of surface active species Ir(III) and a higher oxygen evolution activity.

[0301] Example III-6. Preparation of membrane electrode

[0302] (1) After washing, the Nafion 117 proton exchange membrane is placed on a 7 x 7 cm 2 Cut to dimensions, actual spray area is 5 x 5 cm 2 It was.

[0303] (2) 100 mg of the prepared CAT-III-3 catalyst was weighed out, 14 mL of isopropanol and 6 mL of ultrapure water were added, and then 200 mg of a 5 wt % Nafion solution was added, followed by ultrasonic treatment in an ice bath at an ultrasonic output of 900 W for 40 minutes.

[0304] (3) 100 mg of 40 wt% Pt / C catalyst was weighed out, 14 mL of isopropanol and 6 mL of ultrapure water were added, 500 mg of 5 wt% Nafion solution was added, and the mixture was subjected to ultrasonic treatment in an ice bath at an ultrasonic output of 600 W for 30 minutes.

[0305] (4) The Nafion 117 membrane was placed flat on the vacuum absorption platform, the mold was pressed onto it, the temperature of the vacuum absorption platform was set to 85 °C, and the slurries prepared in steps (2) and (3) were sprayed on both sides of the Nafion 117 membrane in the order of first the anode and then the cathode.

[0306] (5) The sprayed membrane electrode was placed in a hot press machine and hot pressed. The hot press temperature was set to 120° C., the hot press pressure was set to 3 bar, and the hot press time was set to 2 minutes to obtain the desired membrane electrode.

[0307] Although the preferred embodiments of the present application have been described in detail above in conjunction with the drawings, the present application is not limited to the specific details of the above embodiments, and within the scope of the technical concept of the present application, various simple modifications can be made to the technical solutions of the present application, and all these simple modifications fall within the protection scope of the present application.

[0308] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe the various possible combinations.

[0309] Furthermore, the various embodiments of the present application may be combined in any manner as long as such combination is not contrary to the spirit of the present application, and such combinations should also be considered as contents disclosed in the present application.

Claims

1. A transition metal-doped iridium-based composite catalyst substantially composed of an amorphous oxide of iridium and a transition metal, An iridium-based composite catalyst wherein the transition metal is selected from metals of Group IVB, metals of Group VB, or a combination thereof, the content ratio of iridium to the transition metal in the catalyst is (0.4-0.7):(0.3-0.6) in moles, and the XRD spectrum of the catalyst does not have a diffraction peak corresponding to iridium oxide in the rutile phase, nor does it have a diffraction peak corresponding to the crystalline phase of the oxide of the transition metal.

2. The iridium-based composite catalyst according to claim 1, wherein in the XRD spectrum of the catalyst, a peak envelope exists only in the 2θ range of 10 to 70°.

3. The following equation: Ir ｘ M １－ｘ O ｙ It has a chemical composition represented by the formula, where M represents a transition metal, x is in the range of 0.4 to 0.7, and the value of y is such that the chemical formula satisfies the principle of electrical neutrality. The iridium-based composite catalyst according to claim 1 or 2, wherein the transition metal is selected from titanium (Ti), niobium (Nb), tantalum (Ta), or a combination thereof.

4. The catalyst is of formula: Ir ｘ Ti １－ｘ O ｙ It has a chemical composition represented by the formula, where x is in the range of 0.4 to 0.7, and the value of y is such that the chemical formula satisfies the principle of electrical neutrality. wherein the catalyst has a chemical composition represented by the formula: Ir ｘ Nb １－ｘ O ｙ where x is in the range of 0.5 to 0.7, and the value of y is such that the chemical formula satisfies the principle of electrical neutrality, or The catalyst is of formula: Ir ｘ Ta １－ｘ O ｙ The iridium-based composite catalyst according to claim 3, having a chemical composition represented by , where x is in the range of 0.5 to 0.7, and the value of y is such that the chemical formula satisfies the principle of electroneutrality.

5. The transition metal is titanium (Ti), and the XRD spectrum of the catalyst has a peak envelope only in the 2θ range of 30 to 35°. The transition metal is niobium (Nb), and the XRD spectrum of the catalyst has a peak envelope only in the 2θ range of 25 to 40°, or The iridium-based composite catalyst according to claim 1 or 2, wherein the transition metal is tantalum (Ta), and the XRD spectrum of the catalyst has a peak envelope only in the 2θ range of 25-35° and 40-41°.

6. The 4f characteristic peak of Ir in the XPS spectrum of the catalyst includes the Ir(IV) characteristic peak and the Ir(III) characteristic peak. The catalyst is as follows: The peak area of ​​the Ir(III) characteristic peak in the XPS spectrum of the catalyst is Q １ It is expressed as, The peak area of ​​the aforementioned Ir(IV) characteristic peak is Q ２ It is expressed as, Q １ / (Q １ +Q ２ ) is Q ０ It is expressed as, Q ０ The iridium-based composite catalyst according to claim 1 or 2, wherein the value is in the range of 0.2 to 0.

6.

7. The transition metal is titanium (Ti), Q ０ It is in the range of 0.35 to 0.

41. The transition metal is niobium (Nb), Q ０ It is in the range of 0.50 to 0.

54. or The transition metal is tantalum (Ta), Q ０ The iridium-based composite catalyst according to claim 6, wherein the coefficient is in the range of 0.22 to 0.

27.

8. The molar ratio of Ir to the transition metal determined by XPS analysis of the catalyst is M １ The molar ratio of Ir to the transition metal determined by XRF analysis is M. ２ It is expressed as M １ / M ２ The ratio is M ０ It is expressed as: The transition metal is titanium (Ti), M ０ It is in the range of 1.20 to 1.

55. The transition metal is niobium (Nb), M ０ If it is in the range of 0.99 to 1.02, or The transition metal is tantalum (Ta), M ０ The iridium-based composite catalyst according to claim 1 or 2, wherein the coefficient is in the range of 0.98 to 1.

04.

9. The catalyst is in the form of nanoparticle powder, The powder particles have a particle size in the range of 1 to 10 nm, and the BET specific surface area of ​​the powder particles is 50 to 80 m². ２ The iridium-based composite catalyst according to claim 1 or 2, wherein the concentration is in the range of / g and the ratio of micropore volume to total pore volume is 0 to 5%.

10. A method for preparing an iridium-based composite catalyst according to claim 1 or 2, 1) A step of mixing an iridium source, a transition metal source, a complexing agent, and a solvent, and reacting the resulting mixture at a pH of 6 to 10 to obtain a reactant, wherein the transition metal is selected from metals of Group IVB, metals of Group VB, and combinations thereof, and the complexing agent is selected from C3 to C8 organic polyacids and their soluble salts. 2) A step of evaporating and removing the solvent from the reactant obtained in step 1) to obtain an iridium-based composite catalyst precursor, and 3) A method comprising the step of obtaining the iridium-based composite catalyst by calcining the iridium-based composite catalyst precursor in an oxygen-containing atmosphere.

11. The iridium source is selected from iridium chloride, alkali metal iridium chloride salts, or a combination thereof. The alkali metal iridium chloride salt is selected from potassium iridium chloride, sodium iridium chloride, or a combination thereof. The transition metal source is selected from a titanium source, a niobium source, a tantalum source, or a combination thereof. The titanium source is selected from soluble titanium salts. The niobium source is selected from alcohol-soluble niobium compounds. The tantalum source is selected from alcohol-soluble tantalum compounds. The method according to claim 10, wherein the solvent is selected from water, alcohol, or a combination thereof.

12. The molar ratio of the iridium source calculated as iridium to the transition metal source calculated as a transition metal is 0.5 to 2.5:

1. The molar ratio of the complexing agent is 1 to 4:1 with respect to the total amount of the iridium source and the transition metal source. The method according to claim 10, wherein the transition metal source is a titanium source, the molar ratio of the iridium source calculated as iridium to the titanium source calculated as titanium is 0.5 to 2.5:1, and the molar ratio of the complexing agent is 1 to 2:1 with respect to the total amount of the iridium source and the titanium source.

13. The above step 1) further: 1A) A step of mixing the iridium source, the first complexing agent and water to obtain the first mixture, 1B) A step of mixing the transition metal source, a second complexing agent, and an organic solvent to obtain a second mixture, wherein the organic solvent is miscible with water and has a boiling point in the range of room temperature to 120°C. 1C) A step of adjusting the pH of the first mixture and the second mixture to 6 to 10, and The process comprises the steps of: 1D) After adjusting the pH in step 1C), mixing the first mixture with the second mixture, further adjusting the pH of the resulting mixture to 6-10, and obtaining a reactant by reaction. The method according to claim 11, wherein the first complexing agent and the second complexing agent may be the same or different, and each may be independently selected from C3-C8 organic polyacids and their soluble salts.

14. The transition metal is niobium (Nb), the molar ratio of the first complexing agent to the iridium source calculated as iridium is 1 to 4:1, the molar ratio of the second complexing agent to the niobium source calculated as niobium is 1 to 4:1, and the molar ratio of the iridium source calculated as iridium to the niobium source calculated as niobium is 1 to 2.33:1, or The method according to claim 13, wherein the transition metal is tantalum (Ta), the molar ratio of the first complexing agent to the iridium source calculated as iridium is 1 to 4:1, the molar ratio of the second complexing agent to the tantalum source calculated as tantalum is 1 to 4:1, and the molar ratio of the iridium source calculated as iridium to the tantalum source calculated as tantalum is 1 to 2.33:

1.

15. The reaction conditions in step 1) include a temperature of 25 to 95°C and a time of 0.5 to 6 hours. The reaction in step 1) is carried out at a pH of 8 to 9. The method according to claim 10, wherein in step 1), the pH is adjusted by adding a pH adjusting agent, and the pH adjusting agent is selected from sodium carbonate, sodium bicarbonate, sodium hydroxide, aqueous ammonia, or a combination thereof.

16. The method according to claim 10, wherein the firing conditions in step 3) include a firing temperature of 350 to 550°C and a firing time of 1 to 4 hours.

17. The process further comprises a step of washing the calcined product of step 3), wherein the washing solvent is a mixed solution of alcohol and water, and the alcohol accounts for 10 to 95% by weight of the mixed solution. The method according to claim 10, wherein the alcohol is selected from methanol, ethanol, n-propanol, isopropanol, or a combination thereof.

18. Use of the iridium-based composite catalyst according to claim 1 or 2 as an oxygen evolution electrode catalyst in an electrochemical process.

19. The system comprises a proton exchange membrane and a cathode catalyst layer and an anode catalyst layer, respectively, arranged on both sides of the proton exchange membrane. A membrane electrode suitable for proton exchange membrane electrolysis of water, wherein the anode catalyst layer contains the iridium-based composite catalyst described in claim 1 or 2.

Images