Supported water electrolysis catalyst and preparation method thereof and water electrolysis membrane electrode

Abstract

A supported water electrolysis catalyst, a preparation method thereof, and a water electrolysis membrane electrode, belonging to the technical field of water electrolysis hydrogen production. The preparation method comprises: obtaining a mixture, the mixture comprising titanium dioxide, a reducing agent, and a chloride salt; calcining the mixture under a reducing atmosphere to reduce at least a portion of the titanium dioxide on the surface of the titanium dioxide to titanium, thereby obtaining a carrier having a titanium layer on the surface, wherein the atomic proportion of zero-valent titanium in the titanium element determined by XPS is 40%-60%; mixing the carrier with a soluble iridium source liquid phase to carry out a replacement reaction, so that at least a portion of the titanium replaces the iridium ions with iridium nanoparticles and forms them on the surface of the carrier. The above preparation method can produce a supported water electrolysis catalyst that has both high catalytic activity and high structural stability while using a low amount of precious metals.

Description

Technical Field

[0001] The present application relates to the technical field of water electrolysis hydrogen production, and in particular to a supported water electrolysis catalyst and a preparation method thereof, and a water electrolysis membrane electrode. Background Art

[0002] With the large-scale integration of renewable energy, green hydrogen production technologies have garnered widespread attention. Proton exchange membrane (PEM) water electrolysis has become one of the most promising pathways for hydrogen production due to its fast startup, high energy conversion efficiency, and high hydrogen purity. The key to PEM water electrolysis systems lies in the efficient catalysis of the oxygen evolution reaction (OER) at the anode. While commonly used noble metal catalysts at the anode, such as IrO2 and RuO2, possess excellent catalytic performance, their high cost and resource scarcity limit their large-scale commercial application.

[0003] How to reduce the use of precious metals while maintaining or even improving the catalytic activity and structural stability of the catalyst is currently a major difficulty. Summary of the Invention

[0004] The present application provides a supported water electrolysis catalyst, a preparation method thereof, and a water electrolysis membrane electrode, which can achieve both high catalytic activity and high structural stability on the basis of low usage of precious metals.

[0005] The embodiment of the present application is implemented as follows:

[0006] In a first aspect, the present application provides an example method for preparing a supported water electrolysis catalyst, which comprises:

[0007] A mixed material is obtained, wherein the mixed material includes titanium dioxide, a reducing agent and a chloride salt, and the reducing agent includes at least one of NaBH4, LiAlH4, CaH2 and MgH2.

[0008] The mixture is calcined in a reducing atmosphere to reduce at least a portion of the titanium dioxide on the surface of the titanium dioxide to titanium, thereby obtaining a carrier having a titanium layer on the surface, wherein the atomic proportion of zero-valent titanium in the titanium element of the carrier determined by XPS is 40%-60%.

[0009] The carrier is mixed with a soluble iridium source liquid phase to carry out a replacement reaction, so that at least a portion of the titanium replaces the iridium ions to form iridium nanoparticles that are formed on the surface of the carrier.

[0010] The preparation method provided in this application comprises calcining a mixture of titanium dioxide, a reducing agent, and a chloride salt under a reducing atmosphere, using the chloride salt as an inert medium and dispersant to adjust the uniformity of the reaction environment during calcination. The calcination is performed using a reducing agent and a reducing atmosphere, so that at least a portion of the titanium dioxide on the surface of the titanium dioxide is reduced to form a titanium layer on the surface, and the atomic proportion of zero-valent titanium in the titanium element, as determined by XPS, is 40%-60%. This significantly improves the electronic conductivity of the support, provides a fast electron channel for subsequent electrochemical reactions, and improves the durability of the prepared catalyst. The prepared support is then mixed with a soluble iridium source liquid phase, and a reduction-displacement reaction between titanium and iridium ions is utilized to cause at least a portion of the titanium to replace the iridium ions with iridium nanoparticles, which are then formed in situ on the surface of the support, forming a stable metal-support interface, improving the stability and corrosion resistance of the catalyst and making it less prone to desorption. At the same time, the preparation method not only allows iridium to be highly dispersed and precisely coated on the carrier surface, significantly reducing the amount of iridium used without sacrificing activity, thereby reducing overall costs, but also when part of the titanium replaces the iridium ions with iridium nanoparticles and forms them on the surface of the carrier, the synergistic effect between the remaining titanium and iridium can be utilized, which is beneficial to electron transfer and the stability of reaction intermediates, helps to increase the rate of the oxygen evolution reaction, and enhances the catalytic performance.

[0011] In some optional embodiments, the calcination temperature is lower than the decomposition temperature of the chloride salt and not lower than 650°C.

[0012] In some optional embodiments, the calcination temperature is 700° C.-800° C., and the calcination time is 2 h-12 h.

[0013] In some optional embodiments, the reducing atmosphere includes hydrogen and / or carbon monoxide.

[0014] In some optional embodiments, the added mass of the reducing agent is at least 5 times the added mass of the titanium dioxide, and the added mass of the reducing agent is less than the added mass of the chloride salt.

[0015] In some optional embodiments, the added mass ratios of titanium dioxide, reducing agent and chloride salt are 1:5-8:6-12, respectively.

[0016] In some optional embodiments, the chloride salt includes at least one of NaCl, KCl and LiCl.

[0017] In some optional embodiments, the liquid phase mixing includes: adding the carrier to an aqueous solution of a soluble iridium source and stirring at 40°C-90°C for at least 1 hour; and / or, the mass ratio between the soluble iridium source and the carrier is 1:1-1:9; and / or, the soluble iridium source includes one or more of iridium tetrachloride, iridium trichloride, chloroiridic acid, iridium acetate and iridium acetylacetonate.

[0018] In the second aspect, the present application provides an example of a supported water electrolysis catalyst, which is prepared by the preparation method provided in the first aspect of the present application.

[0019] The catalyst prepared by the preparation method provided in the first aspect provided in the present application constructs a highly dispersed, high-binding-strength, low-load and high-efficiency Ir / Ti@TiO2 electrolytic water catalytic system through an in-situ reduction-replacement dual strategy. Through the synergy of iridium nanoparticles on the carrier surface and interfacial catalysis, the supported water electrolysis catalyst can achieve both high catalytic activity and high structural stability on the basis of low precious metal usage.

[0020] In a third aspect, the present application provides an example of a water electrolysis membrane electrode, which includes a proton exchange membrane and an anode catalyst layer formed on the anode side of the proton exchange membrane, wherein the anode catalyst layer includes the supported water electrolysis catalyst provided in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 TEM image of the supported water electrolysis catalyst prepared in Example 1 of the present application;

[0023] Figure 2 This is a partial enlarged TEM image of the supported water electrolysis catalyst prepared in Example 1 of the present application;

[0024] Figure 3 1 and 2 are LSV diagrams of the supported water electrolysis catalysts of Example 1 and Comparative Examples 1-3 of the present application. DETAILED DESCRIPTION

[0025] The embodiments of the present application will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0026] The following is a detailed description of the supported water electrolysis catalyst, its preparation method, and the water electrolysis membrane electrode according to the embodiments of the present application:

[0027] How to reduce the amount of precious metals used while maintaining or even improving the catalytic activity and structural stability of the catalyst is currently a major difficulty. Research in recent years has focused on strategies such as high-dispersion loading of precious metals, single-atom catalysts, and carrier modification. However, existing technologies still have the following problems: 1. Insufficient carrier conductivity: Many solutions use titanium oxide or its variants as a carrier, but its intrinsic conductivity is low, which is not conducive to rapid electron transport and limits the overall performance of the catalyst. 2. Iridium dispersion is difficult to control: Traditional wet chemical methods or adsorption methods often have difficulty achieving uniform and stable loading of iridium atoms or nanoparticles, which easily causes agglomeration and reduces catalytic efficiency. 3. High iridium usage and high cost pressure: High loading of precious metals is a common practice to ensure performance, but precious metal resources are scarce and expensive, which restricts commercial application. 4. Weak binding between the carrier and iridium: In some solutions, the binding between the carrier and iridium relies on physical adsorption or surface defects, and the binding force is not strong, which is prone to desorption and inactivation during long-term use.

[0028] In view of this, this application is hereby filed.

[0029] The first aspect of the present application provides a method for preparing a supported water electrolysis catalyst, which comprises:

[0030] A mixed material is obtained, wherein the mixed material includes titanium dioxide, a reducing agent and a chloride salt, and the reducing agent includes at least one of NaBH4, LiAlH4, CaH2 and MgH2.

[0031] The mixture is calcined in a reducing atmosphere to reduce at least a portion of the titanium dioxide on the surface of the titanium dioxide to titanium, thereby obtaining a carrier having a titanium layer on the surface, wherein the atomic proportion of zero-valent titanium in the titanium element of the carrier determined by XPS is 40%-60%.

[0032] The carrier is mixed with a soluble iridium source liquid phase to carry out a replacement reaction, so that at least a portion of the titanium replaces the iridium ions to form iridium nanoparticles that are formed on the surface of the carrier.

[0033] It is understood that when the mixture is calcined under a reducing atmosphere, since the mixture contains a reducing agent, the reducing agent and the reducing atmosphere can effectively reduce at least part of the surface layer of titanium dioxide to titanium, thereby obtaining a carrier. In this case, the carrier has a core-shell structure, which includes a titanium dioxide core and a titanium layer (Ti) formed on the surface of the titanium dioxide core. 0 ), where the atomic proportion of zero-valent titanium in the titanium element of the carrier determined by XPS is 40%-60%. The titanium layer has good conductivity and reducibility, which is beneficial to improving the electronic conductivity of the carrier and providing a fast electron channel for subsequent electrochemical reactions. It also serves as a platform for subsequent in-situ exchange reactions with iridium ions and can improve the durability of the prepared catalyst.

[0034] Illustratively, the atomic proportion of zero-valent titanium in the titanium element of the carrier determined by XPS is any one of 40%, 43%, 45%, 47%, 50%, 53%, 55%, 58%, 60%, or between any two values.

[0035] It can be understood that reducing at least a portion of the surface titanium dioxide to titanium to obtain a carrier with a titanium layer on the surface includes: most of the titanium dioxide on the surface of the titanium dioxide is reduced to titanium, and the remaining portion is still titanium dioxide. At this time, the surface of the titanium dioxide includes reduced titanium and unreduced titanium dioxide. At this time, as long as the atomic proportion of zero-valent titanium in the titanium element determined by XPS is 40%-60%, it will be sufficient.

[0036] In the present application, the mixture containing the reducing agent is calcined under a reducing atmosphere, which can better control the degree of reduction, make the surface of titanium dioxide reduced more uniformly and fully, and effectively reduce the calcination temperature. It can effectively reduce energy consumption and obtain a carrier with good dispersion effect, ensure the uniformity of the subsequent iridium loading on the carrier, and help improve the electrochemical performance of the final supported water electrolysis catalyst.

[0037] Chloride salt, as an inert medium and dispersant, can improve the uniformity of the reaction environment during calcination, effectively prevent the carrier from agglomerating after reduction, and is conducive to obtaining a dispersed carrier.

[0038] The reducing agent includes at least one of NaBH4, LiAlH4, CaH2 and MgH2. The reducing agent has strong reducing properties and can partially or completely reduce the TiO2 on the surface of titanium dioxide to TiO2 during high temperature calcination in combination with reducing gas. 0 It is understood that the selection of a specific reducing agent can be made by weighing the reaction temperature and the difficulty of residue treatment.

[0039] After the carrier is mixed with the soluble iridium source liquid, the soluble iridium source provides iridium ions.

[0040] The carrier is mixed with a soluble iridium source liquid, and Ti 0 With Ir 3+ / Ir 4+ The electrochemical potential difference between the iridium ions reduces the iridium ions to metallic iridium (Ir 0) and are densely deposited on the titanium surface. Specifically, titanium and iridium ions undergo an in situ exchange reaction, oxidizing at least a portion of the titanium to titanium ions while simultaneously reducing the iridium ions in situ to iridium nanoparticles that are uniformly deposited on the surface of the support. Because the iridium nanoparticles are tightly bound to the support surface, a stable metal-support interface is formed, effectively improving the structural stability, corrosion resistance, and durability of the supported water electrolysis catalyst. This also effectively prevents agglomeration of the iridium nanoparticles and enhances their dispersibility, thereby reducing the amount of iridium used without sacrificing catalytic activity.

[0041] The preparation method provided in this application comprises calcining a mixture of titanium dioxide, a reducing agent, and a chloride salt under a reducing atmosphere, using the chloride salt as an inert medium and dispersant to adjust the uniformity of the reaction environment during calcination. The calcination is performed using a reducing agent and a reducing atmosphere, so that at least a portion of the titanium dioxide on the surface of the titanium dioxide is reduced to form a titanium layer on the surface, and the atomic proportion of zero-valent titanium in the titanium element, as determined by XPS, is 40%-60%. This significantly improves the electronic conductivity of the support, provides a fast electron channel for subsequent electrochemical reactions, and improves the durability of the prepared catalyst. The prepared support is then mixed with a soluble iridium source liquid phase, and a reduction-displacement reaction between titanium and iridium ions is utilized to cause at least a portion of the titanium to replace the iridium ions with iridium nanoparticles, which are then formed in situ on the surface of the support, forming a stable metal-support interface, improving the stability and corrosion resistance of the catalyst and making it less prone to desorption. At the same time, the preparation method not only allows iridium to be highly dispersed and precisely coated on the carrier surface, significantly reducing the amount of iridium used without sacrificing activity, thereby reducing overall costs, but also when part of the titanium replaces the iridium ions with iridium nanoparticles and forms them on the surface of the carrier, the synergistic effect between the remaining titanium and iridium can be utilized, which is beneficial to electron transfer and the stability of reaction intermediates, helps to increase the rate of the oxygen evolution reaction, and enhances the catalytic performance.

[0042] The average primary particle size of titanium dioxide may be 30-150 nm, and the average primary particle size may be measured by TEM.

[0043] The mixture can be obtained by ball milling or grinding titanium dioxide, a reducing agent and a chloride salt. For example, the ball milling or grinding time can be controlled within 15 min to 30 min, which is conducive to the full and uniform dispersion of the three raw materials.

[0044] The preparation method further includes: naturally cooling the sintered material after calcination to room temperature, washing the obtained solid with deionized water until the pH of the washing liquid is close to neutral to remove excess inorganic salts and by-products, and then vacuum drying the washed sintered material at 50°C-100°C to obtain a carrier.

[0045] The preparation method further includes: after the carrier is mixed with the soluble iridium source liquid phase to complete the replacement reaction, the product can be filtered and recovered, and fully washed with deionized water to remove residual iridium salt and side reactants. The final solid is vacuum-dried again at 50°C-100°C to obtain a supported water electrolysis catalyst.

[0046] In some preferred embodiments, the atomic proportion of zero-valent titanium in the titanium element determined by XPS is 45%-55%.

[0047] Controlling the atomic ratio of zero-valent titanium within the above range is beneficial to further improving the catalytic activity and durability of the prepared supported catalyst.

[0048] For example, the atomic percentage of zero-valent titanium in the titanium element determined by XPS is any one of 45%, 47%, 49%, 51%, 53%, 55%, or between any two values.

[0049] In some optional embodiments, the calcination temperature is lower than the decomposition temperature of the chloride salt and not lower than 650°C.

[0050] Since chloride salt acts as an inert medium and dispersant, the uniformity of the reaction environment needs to be adjusted during calcination. If the calcination temperature is higher than the decomposition temperature of the chloride salt, the chloride salt will decompose, and the effect of the chloride salt in adjusting the uniformity of the reaction environment will be poor.

[0051] Therefore, the calcination temperature is controlled to be lower than the decomposition temperature of the chloride salt and not lower than 650° C. Within this temperature range, at least a portion of the surface layer of titanium dioxide can be effectively reduced to titanium to obtain a carrier.

[0052] In some optional embodiments, the calcination temperature is 700° C.-800° C., and the calcination time is 2 h-12 h.

[0053] Controlling the calcination temperature and time within the above range is beneficial for reducing the surface layer of titanium dioxide to titanium to obtain a carrier.

[0054] Illustratively, the calcination temperature is any one of 700° C., 730° C., 750° C., 780° C., 800° C., or between any two values.

[0055] Illustratively, the calcination time is any one of 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, and 12 h, or is between any two values.

[0056] In some optional embodiments, the reducing atmosphere includes hydrogen and / or carbon monoxide.

[0057] The above reducing atmosphere is conducive to reducing the surface layer of titanium dioxide to titanium.

[0058] Illustratively, the reducing atmosphere is hydrogen.

[0059] In some optional embodiments, the added mass of the reducing agent is at least 5 times the added mass of the titanium dioxide, and the added mass of the reducing agent is less than the added mass of the chloride salt.

[0060] The above-mentioned addition amount is limited to partially or completely reduce the TiO2 on the surface of titanium dioxide to Ti during high temperature calcination. 0 At the same time, the above-mentioned added amount of chloride salt can more fully adjust the uniformity of the reaction environment during calcination, which is conducive to obtaining a dispersed carrier after calcination.

[0061] In some optional embodiments, the added mass ratios of titanium dioxide, reducing agent and chloride salt are 1:5-8:6-12, respectively.

[0062] The above-mentioned addition amount is limited to partially or completely reduce the TiO2 on the surface of titanium dioxide to Ti during high temperature calcination. 0 At the same time, chloride salt can fully adjust the uniformity of the reaction environment during calcination, which is conducive to obtaining a dispersed carrier after calcination.

[0063] Exemplarily, the added mass ratio of titanium dioxide, reducing agent and chloride salt is any one of 1:5:6, 1:5:10, 1:5:12, 1:6:7, 1:6:10, 1:6:12, 1:7:8, 1:7:10, 1:7:12, 1:8:9, 1:8:11, 1:8:12 or between any two values.

[0064] In some optional embodiments, the chloride salt includes at least one of NaCl, KCl and LiCl.

[0065] Illustratively, the chloride salt is NaCl or KCl or LiCl, or the chloride salt is a mixture of NaCl and KCl.

[0066] The above chloride salts are all water-soluble chloride salts, which are convenient for subsequent removal and have good dispersion effect.

[0067] In some optional embodiments, the liquid phase mixing comprises: adding the carrier to an aqueous solution of a soluble iridium source, and stirring at 40° C.-90° C. for at least 1 hour.

[0068] By stirring at 40°C-90°C for at least 1 hour, an in-situ exchange reaction between titanium and iridium ions is facilitated, titanium is oxidized to titanium ions, and iridium ions are simultaneously reduced in situ to iridium nanoparticles and uniformly deposited on the surface of the support. The iridium nanoparticles are tightly bound to the surface of the titanium to form a stable metal-support interface, thereby improving the stability and corrosion resistance of the supported water electrolysis catalyst.

[0069] Illustratively, stirring is performed at any one of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or between any two of the values ​​for at least 1 h, for example, stirring is performed at any one of 1 h, 3 h, 5 h, 10 h, or between any two of the values.

[0070] In some optional embodiments, the mass ratio between the soluble iridium source and the carrier is 1:1-1:9.

[0071] It is understood that the amount of replaced titanium and reduced iridium nanoparticles can be controlled by controlling the mass ratio between the soluble iridium source and the support.

[0072] It is understandable that when the iridium source content is lower, the amount of titanium replaced is less. At this time, part of the titanium replaces the iridium ions, and the replaced iridium nanoparticles are in-situ generated on the surface of the remaining titanium.

[0073] In some optional embodiments, the soluble iridium source includes one or more of iridium tetrachloride, iridium trichloride, chloroiridic acid, iridium acetate, and iridium acetylacetonate.

[0074] The second aspect of the present application provides a supported water electrolysis catalyst, which is prepared by the preparation method provided by the first aspect of the present application.

[0075] The supported water electrolysis catalyst prepared by the above preparation method can achieve both high catalytic activity and high structural stability on the basis of low usage of precious metals.

[0076] In some optional embodiments, the supported water electrolysis catalyst includes: a titanium dioxide core, a titanium layer coated on the surface of the titanium dioxide core, and iridium nanoparticles in situ generated on the surface of the titanium layer.

[0077] Through the in-situ reduction-replacement dual strategy, a highly dispersed, high-binding strength, low-loading and efficient Ir / Ti@TiO2 electrolytic water catalytic system was constructed. Through the synergy of iridium nanoparticles on the carrier surface and interfacial catalysis, the loaded water electrolysis catalyst can achieve both high catalytic activity and high structural stability on the basis of low precious metal usage.

[0078] The third aspect of the present application provides a water electrolysis membrane electrode, which includes a proton exchange membrane and an anode catalyst layer formed on the anode side of the proton exchange membrane, wherein the anode catalyst layer includes the supported water electrolysis catalyst provided in the second aspect of the present application.

[0079] The supported water electrolysis catalyst, its preparation method, and water electrolysis membrane electrode of the present application are further described in detail below with reference to the examples.

[0080] In the following examples and comparative examples, titanium dioxide (TiO2, rutile, BET: 133m 2The average primary particle size of the raw titanium powder and the raw titanium metal powder was 50 nm.

[0081] Example 1

[0082] The supported water electrolysis catalyst, the preparation method of which comprises:

[0083] S1. Prepare a mixture.

[0084] Titanium dioxide (TiO2) powder, sodium borohydride (NaBH4) and sodium chloride were weighed in sequence according to a mass ratio of 1:5:8, and ball-milled for 20 minutes to mix them evenly to obtain a mixture.

[0085] S2. Prepare the carrier.

[0086] The mixture was placed in a ceramic crucible and placed in a tube furnace. It was calcined at 700℃ for 2h under a hydrogen atmosphere (hydrogen flow rate of 200 mL / min) to reduce the TiO2 surface layer and form a metallic titanium layer. During the high-temperature reduction process, NaBH4 decomposes in NaCl to release active hydrogen species, which promotes the TiO2 to form a titanium layer. 4+ The precipitate was reduced to Ti and deposited on the titanium oxide surface. After calcination, the solid was cooled naturally to room temperature, and the resulting solid was thoroughly washed with deionized water to remove excess inorganic salts and byproducts until the pH of the washing solution was near neutral. The material was then dried in a vacuum oven at 60°C for 12 hours to obtain a support. XPS elemental analysis of the obtained support is shown in Table 1.

[0087] S3. Prepare a supported water electrolysis catalyst.

[0088] Chloroiridic acid (H2IrCl6) was dissolved in deionized water, the solution concentration was adjusted to 0.1 mg / mL, and hydrochloric acid was added to control the solution pH to 4 to ensure the stable presence of iridium ions, thereby obtaining a soluble iridium precursor solution.

[0089] The dried support and the soluble iridium precursor solution obtained above were mixed at a ratio of 51.25 mg / 500 ml, and magnetically stirred at 40°C for 6 h to carry out an in situ substitution reaction between metallic titanium and iridium ions. Titanium was oxidized to Ti 4+ , while the iridium ions were reduced to metallic iridium and deposited in situ on the support surface. After the replacement reaction was complete, the product was recovered by filtration and thoroughly washed with deionized water to remove residual iridium salts and side products. The resulting solid was vacuum-dried again at 60°C for 12 hours to obtain a supported water electrolysis catalyst. XRF elemental analysis of the supported water electrolysis catalyst is shown in Table 2.

[0090] Figure 1 and Figure 2 TEM image of the supported water electrolysis catalyst prepared in Example 1. It can be seen that the iridium nanoparticles ( Figure 2 The small black particles) have uniform particle size and are evenly distributed on the surface of the carrier.

[0091] Example 2

[0092] The only difference between it and Example 1 is that MgH2 is used to replace NaBH4.

[0093] Example 3

[0094] The only difference between it and Example 1 is:

[0095] The added mass ratios of titanium dioxide, sodium borohydride and sodium chloride are 1:5:12, respectively.

[0096] Example 4

[0097] The only difference between it and Example 1 is:

[0098] The calcination temperature is 750°C.

[0099] Example 5

[0100] The only difference between it and Example 1 is:

[0101] Iridium tetrachloride was used instead of chloroiridic acid.

[0102] Comparative Example 1

[0103] Chloroiridic acid (H2IrCl6) was dissolved in deionized water, and hydrochloric acid was added to control the pH of the solution to 4 to ensure the stable presence of iridium ions, thereby obtaining a chloroiridic acid aqueous solution.

[0104] 1 g of titanium dioxide (TiO2) powder and 0.38 g of chloroiridic acid aqueous solution (Ir content: 17.5 wt%) were ball-milled at a speed of 600 rpm for 20 min to obtain a mixture.

[0105] The mixture was placed in a ceramic crucible and placed in a tube furnace. It was calcined at 700°C for 2h under a hydrogen atmosphere (hydrogen flow rate of 200 mL / min) to obtain a supported water electrolysis catalyst with Ir impregnated and reduced on the TiO2 surface.

[0106] Comparative Example 2

[0107] The only difference between it and Example 1 is:

[0108] Replace titanium oxide with metal Ti powder of the same particle size.

[0109] Comparative Example 3

[0110] The only difference between it and Example 1 is:

[0111] S1. Prepare a mixture.

[0112] Titanium dioxide (TiO2) powder and sodium chloride were weighed in sequence in a mass ratio of 1:8, and ball-milled for 20 minutes to mix them evenly to obtain a mixture.

[0113] S2. Prepare the carrier.

[0114] The mixture was placed in a ceramic crucible in a tube furnace and calcined at 1100°C for 2 hours under a hydrogen atmosphere (hydrogen flow rate of 200 mL / min) to reduce the TiO2 surface layer and form a metallic titanium layer. After calcination, the mixture was cooled to room temperature. The resulting solid was washed thoroughly with deionized water to remove excess inorganic salts and byproducts until the pH of the washing solution was close to neutral. The material was then dried in a vacuum oven at 60°C for 12 hours to obtain the support.

[0115] The reduced supports (TiO2@Ti) in Examples 1-5 and Comparative Example 3 were subjected to XPS elemental analysis, and the supported water electrolysis catalysts finally prepared in Examples 1-5 and Comparative Example 1-3 were subjected to XRF elemental analysis. The results are shown in Tables 1 and 2.

[0116] XPS (X-ray photoelectron spectrometer) testing instrument: Model is Thermo Scientific K-Alpha, using a monochromatized Al Kα source (Mono Al Kα) with an energy of 1486.6 eV.

[0117] XRF (X-ray fluorescence spectrometer) testing instrument: Model is X-MET-8000Smart.

[0118] Among them, Table 1 shows the valence ratio of the Ti element in the reduced support (TiO2@Ti), and Table 2 shows the XRF element mass ratio of the prepared supported water electrolysis catalyst.

[0119] Table 1 Valence ratio of Ti element in the reduced support (TiO2@Ti)

[0120]

[0121] According to Table 1, since the reduction process of titanium dioxide is a surface reaction, the reaction proceeds from the outside to the inside, and the XPS analysis has a detection depth limitation (a few nanometers deep from the surface), the Ti content in the surface titanium element analyzed by XPS is 0 The highest proportion is more than 40% and less than 60%, Ti 4+ Atoms also account for a certain proportion, indicating that most of the titanium dioxide surface is reduced to titanium, and the titanium dioxide that has not been reduced is the main phase, located in the core or in the incompletely reduced area. 3+ Represents the transition state, indicating the incomplete reduction portion.

[0122] Table 2 XRF element ratios of supported water electrolysis catalysts in the examples and comparative examples

[0123]

[0124] Among them, the Ti elements in Table 2 include Ti 4+ 、Ti 3+ and Ti 0 , wherein the total content of element Ir and element Ti is 100%.

[0125] According to Table 2, Figure 1 as well as Figure 2 It can be seen that the supported water electrolysis catalyst has a low but uniform iridium loading, which helps to save costs and has high activity.

[0126] Test Example 1

[0127] Electrochemical performance test:

[0128] Electrochemical testing was conducted using a Shanghai Chenhua CHI660E electrochemical station and a rotating disk electrode (Pine, USA). The catalysts were primarily tested using cyclic voltammetry (CV) and linear sweep voltage (LSV) measurements. All electrode potentials in the experiments were normalized using a reversible hydrogen electrode (RHE).

[0129] 1) Preparation of working electrode

[0130] 8 mg of the catalyst from each of the above examples and comparative examples was weighed using an electronic balance and added to a 5 ml centrifuge tube. 2 ml of the prepared dispersion (300 ml of isopropanol, 100 ml of water, and 0.31 g of 5 wt% Nafion D2020 solution) was then added to the centrifuge tube. The mixed solution was placed in a cell crusher and ultrasonically dispersed for 20 minutes to obtain a uniform catalyst ink. Then, 10 μL of the catalyst ink was evenly dropped onto a pre-polished and cleaned gold electrode (area 0.196 cm) using a 10 μL pipette. 2 ) on the electrode surface to prevent the ink from overflowing and to evenly spread it on the electrode surface. Wait for it to dry naturally to form a catalytic layer, and you have a working electrode.

[0131] 2) Electrochemical performance test

[0132] Cyclic voltammogram (CV) tests were performed over a potential range of 1.2–1.6 vs RHE (0.544–0.944 vs Hg₂SO₄) at a scan rate of 50 mV / s. Before each test, saturated N₂ was introduced for 60 minutes (in an oxygen-free environment) at a scan rate of 100 mV / s until the CV curve stabilized, ensuring full catalyst activation.

[0133] Linear Sweep Voltammetry: To evaluate the OER electrocatalytic performance of the catalyst materials and their performance during the reaction, anodic polarization measurements were performed, using linear sweep voltammetry (LSV) results as the basis for evaluation. The LSV scan rate was 50 mV / s over a range of 1.2–1.6 vs RHE, with a scan rate of 50 mV / s and a rotating disk electrode speed of 1600 rpm. The overpotential was 10 mA / cm in the LSV. 2 The corresponding voltage is obtained by subtracting the ideal decomposition voltage of water electrolysis, 1.23V.

[0134] 3) HFR test

[0135] The anode catalyst slurry was prepared in the following mass ratios: catalyst: perfluorosulfonic acid resin solution (Nafion D2020): hydroalcoholic solution (water: isopropanol, mass ratio 3:1) = 1:0.25:10. The first anode catalyst slurry was sprayed onto a transfer substrate and then oven-dried at 60°C. The catalyst layer, facing away from the transfer substrate, was then transferred to the anode side of the proton exchange membrane via transfer printing, forming a 10μm thick anode catalyst layer on the anode side of the proton exchange membrane. Preparation of the cathode catalyst layer: The cathode catalyst slurry was prepared in the following mass ratios: Pt / C catalyst (Pt loading 60%): perfluorosulfonic acid resin solution (Nafion D2020): hydroalcoholic solution (water: isopropanol, mass ratio 1:10) = 1:1:15.

[0136] The cathode catalyst slurry was applied to a transfer film using a slot-coating method and then dried in an oven at 60°C to form a cathode catalyst layer on the transfer film. The cathode catalyst layer was then transferred to a proton exchange membrane to form a water electrolysis hydrogen production membrane electrode. Using Gamry's electrochemical testing equipment, connected to the electrolyzer, at a frequency of 1000-10000 Hz, the starting point resistance was read and multiplied by the effective area of ​​the membrane electrode to obtain the surface resistance (HFR). The test results are shown in Table 3.

[0137] 4) Durability test

[0138] To investigate the stability of the prepared catalyst in an acidic electrochemical environment, an accelerated durability test (ADT) was performed on the catalyst. Cycles were performed at a scan rate of 100 mV / s between 1.2 and 1.6 vs RHE (0.544 and 0.944 vs Hg2SO4) for 3000 cycles. CV and LSV data were collected before and after the cycles as described above. The electrochemical stability of the catalyst was evaluated by comparing the overpotential loss of the catalyst at different cycle numbers. The results are shown in Table 3.

[0139] Table 3 Electrochemical test results of various embodiments and comparative examples

[0140]

[0141] As can be seen from Table 3, the supported water electrolysis catalyst provided in the examples of this application has good catalytic activity and durability. Furthermore, it has a low surface resistivity (HFR), indicating that the electron transport path in the catalyst layer is smoother and the charge transfer efficiency between the catalyst active sites and the current collector / electrolyte is higher, which can enhance the catalytic activity of the membrane electrode.

[0142] From the comparison of Examples 1-5 and Comparative Example 1, it can be seen that the iridium particles in the catalyst prepared by the impregnation reduction method in Comparative Example 1 tend to agglomerate more, and there is no titanium layer on the surface of the carrier. The binding force between the carrier and the iridium particles is weak, so the surface resistance HFR is large, and the unit mass activity and durability are poor.

[0143] From the comparison between Example 1 and Comparative Example 2, it can be seen that although the overpotential of Comparative Example 2 is close to that of Example 1, since the main body of the carrier is nano-scale Ti particles, under the strong oxidation conditions of the actual test, the Ti particles will be significantly oxidized and agglomerated, resulting in poor durability of the catalyst. At the same time, the cost of pure Ti particles is much higher than that of TiO2 particles.

[0144] By comparing Examples 1-5 and Comparative Example 3, it can be seen that in Comparative Example 3, due to the high reduction temperature and the absence of a solid-phase reducing agent, the proportion of metallic titanium on the carrier surface is low, resulting in a higher surface resistance HFR, and the carrier will undergo obvious agglomeration during the reduction stage, affecting the subsequent uniform loading of iridium particles, ultimately resulting in a higher overpotential of the catalyst and poorer durability.

[0145] Figure 3 The LSV diagram of the supported water electrolysis catalyst prepared in Example 1 and Comparative Examples 1-3; Figure 3 It can be seen that the catalytic activity of Example 1 of the present application is better than that of Comparative Examples 1-3.

[0146] In summary, the supported water electrolysis catalyst, its preparation method, and water electrolysis membrane electrode provided in this application, through the in situ reduction-replacement dual strategy, construct a highly dispersed, high binding strength, low-load and high-efficiency Ir / Ti@TiO2 electrolysis water catalytic system, so that the supported water electrolysis catalyst can achieve both high catalytic activity and high durability on the basis of low precious metal usage.

[0147] The foregoing description is merely a specific embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a supported water electrolysis catalyst, characterized in that: include: obtaining a mixture comprising titanium dioxide, a reducing agent, and a chloride salt, wherein the reducing agent comprises at least one of NaBH 4 , LiAlH 4 , CaH 2 , and MgH 2 ; calcining the mixture under a reducing atmosphere to reduce at least a portion of the titanium dioxide on the surface of the titanium dioxide to titanium, thereby obtaining a support having a titanium layer on the surface, wherein the atomic proportion of zero-valent titanium in the titanium element of the support as determined by XPS is 40%-60%; The carrier is mixed with a soluble iridium source liquid phase to perform a replacement reaction, so that at least a portion of the titanium replaces the iridium ions to form iridium nanoparticles and form them on the surface of the carrier.

2. The preparation method according to claim 1, characterized in that The calcination temperature is lower than the decomposition temperature of the chloride salt and not lower than 650°C.

3. The preparation method according to claim 2, characterized in that The calcination temperature is 700° C.-800° C., and the calcination time is 2 h-12 h.

4. The preparation method according to any one of claims 1 to 3, characterized in that The reducing atmosphere includes hydrogen and / or carbon monoxide.

5. The preparation method according to any one of claims 1 to 3, characterized in that The added mass of the reducing agent is at least 5 times the added mass of the titanium dioxide, and the added mass of the reducing agent is less than the added mass of the chloride salt.

6. The preparation method according to any one of claims 1 to 3, characterized in that The added mass ratios of the titanium dioxide, the reducing agent and the chloride salt are 1:5-8:6-12 respectively.

7. The preparation method according to any one of claims 1 to 3, characterized in that The chloride salt includes at least one of NaCl, KCl and LiCl.

8. The preparation method according to any one of claims 1 to 3, characterized in that The liquid phase mixing comprises: adding the carrier to an aqueous solution of a soluble iridium source and stirring at 40° C. to 90° C. for at least 1 hour; and / or, The mass ratio between the soluble iridium source and the carrier is 1:1-1:9; and / or, The soluble iridium source includes one or more of iridium tetrachloride, iridium trichloride, chloroiridic acid, iridium acetate and iridium acetylacetonate.

9. A supported water electrolysis catalyst, characterized in that The invention discloses a novel novel polyol according to claim 1 , wherein the polyol is prepared by the preparation method according to any one of claims 1 to 8.

10. A water electrolysis membrane electrode, characterized in that: It comprises a proton exchange membrane and an anode catalyst layer formed on the anode side of the proton exchange membrane, wherein the anode catalyst layer comprises the supported water electrolysis catalyst according to claim 9.

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