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

Abstract

The invention discloses a supported water electrolysis catalyst, a preparation method thereof and a water electrolysis membrane electrode, and belongs to the technical field of water electrolysis hydrogen production. The preparation method comprises the following steps: obtaining a mixture, wherein the mixture comprises titanium dioxide, a reducing agent and chlorine salt; the mixture is calcined in a reducing atmosphere, so that at least part of titanium dioxide on the surface layer of the titanium dioxide is reduced into titanium, a carrier with a titanium layer on the surface is obtained, and the atom proportion of zero-valent titanium in the titanium element of the carrier measured through XPS is 40%-60%; and mixing the carrier with a soluble iridium source liquid phase to carry out replacement reaction, so that at least part of titanium replaces iridium ions into iridium nanoparticles and forms the iridium nanoparticles on the surface of the carrier. According to the preparation method, the supported water electrolysis catalyst with high catalytic activity and high structural stability can be prepared on the basis of low precious metal consumption.

Description

Technical Field

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

[0002] With the large-scale access of renewable energy, green hydrogen production technology has received extensive attention. Proton exchange membrane (PEM) water electrolysis has become one of the most promising hydrogen production paths by water electrolysis due to its advantages such as fast startup, high energy conversion efficiency, and high hydrogen purity. The key to the PEM water electrolysis system lies in the efficient catalysis of the anodic oxygen evolution reaction (OER). Although the commonly used noble metal catalysts on the anode, such as IrO2 and RuO2, have excellent catalytic performance, their high cost and resource scarcity limit large-scale commercial applications.

[0003] How to reduce the usage amount of noble metals while maintaining or even improving the catalytic activity and structural stability of the catalyst is a major difficulty at present. 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 high catalytic activity and high structural stability on the basis of low noble metal usage.

[0005] The embodiments of the present application are implemented as follows: In a first aspect, an embodiment of the present application provides a preparation method of a supported water electrolysis catalyst, which includes: Obtain a mixture, the mixture includes titanium dioxide, a reducing agent, and a chloride salt, and the reducing agent includes at least one of NaBH4, LiAlH4, CaH2, and MgH2.

[0006] Calcine the mixture in a reducing atmosphere to reduce at least part of the titanium dioxide on the surface layer of the titanium dioxide to titanium, and obtain a support with a titanium layer on the surface, wherein the atomic proportion of zero-valent titanium in the titanium element measured by XPS of the support is 40%-60%.

[0007] Mix the support and a soluble iridium source in a liquid phase for a displacement reaction, so that at least part of the titanium displaces iridium ions to form iridium nanoparticles on the surface of the support.

[0008] The preparation method provided by this application involves calcining a mixture of titanium dioxide, a reducing agent, and a chloride salt in a reducing atmosphere. Using the chloride salt as an inert medium and a dispersant, the uniformity of the reaction environment during calcination is adjusted. By using the reducing agent and conducting the calcination in a reducing atmosphere, at least part of the titanium dioxide on the surface of the titanium dioxide is reduced to form a titanium layer on its surface, and the atomic proportion of zero-valent titanium in the titanium element measured by XPS is 40% - 60%. This can significantly improve the electronic conductivity of the carrier, provide a fast electron channel for subsequent electrochemical reactions, and improve the durability of the prepared catalyst. Then, the prepared carrier is mixed with a soluble iridium source in a liquid phase. By utilizing the reduction and displacement reaction between titanium and iridium ions, at least part of the titanium displaces the iridium ions to form iridium nanoparticles in situ on the surface of the carrier, forming a stable metal-carrier interface, improving the stability and anti-corrosion ability of the catalyst, and making it not easy to desorb. At the same time, using this preparation method can not only enable iridium to be highly dispersed and precisely coated on the surface of the carrier, significantly reducing the amount of iridium used without sacrificing activity, thereby reducing the overall cost, but also when part of the titanium displaces the iridium ions to form iridium nanoparticles 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.

[0009] In some alternative embodiments, the calcination temperature is lower than the decomposition temperature of the chloride salt and not lower than 650 °C.

[0010] In some alternative embodiments, the calcination temperature is 700 °C - 800 °C, and the calcination time is 2 h - 12 h.

[0011] In some alternative embodiments, the reducing atmosphere includes hydrogen and / or carbon monoxide.

[0012] In some alternative 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.

[0013] In some alternative embodiments, the added mass ratio of the titanium dioxide, the reducing agent, and the chloride salt is 1:5 - 8:6 - 12 in sequence.

[0014] In some alternative embodiments, the chloride salt includes at least one of NaCl, KCl, and LiCl.

[0015] In some alternative embodiments, the liquid-phase mixing includes: adding the carrier to an aqueous solution of the soluble iridium source and stirring for at least 1 h at 40 °C - 90 °C; 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.

[0016] In a second aspect, an example of the present application provides a supported water electrolysis catalyst prepared by the preparation method provided in the first aspect of the present application.

[0017] The catalyst prepared by the preparation method provided in the first aspect of the present application constructs a highly dispersed, high-binding strength, low-loading and efficient Ir / Ti@TiO2 water electrolysis catalytic system through an in-situ reduction-displacement dual strategy. Through the synergy of iridium nanoparticles on the carrier surface and interfacial catalysis, the supported water electrolysis catalyst can achieve high catalytic activity and high structural stability on the basis of low noble metal usage.

[0018] In a third aspect, an example 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. Among them, the anode catalyst layer includes the supported water electrolysis catalyst provided in the second aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 TEM image of the supported water electrolysis catalyst prepared in Example 1 of the present application; Figure 2 Partially enlarged TEM image of the supported water electrolysis catalyst prepared in Example 1 of the present application; Figure 3 LSV diagram of the supported water electrolysis catalysts of Example 1 and Comparative Examples 1-3 of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] The following will describe the implementation schemes of the present application in detail in combination with examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0022] The following specifically describes the supported water electrolysis catalyst, its preparation method, and the water electrolysis membrane electrode of the embodiments of the present application: How to reduce the amount of precious metals used while maintaining or even enhancing the catalytic activity and structural stability of the catalyst is a major challenge at present. In recent years, research has focused on strategies such as highly dispersed loading of precious metals, single-atom catalysts, and support modification. However, the existing technologies still have the following problems: 1. Insufficient conductivity of the support: Many solutions use titanium oxide or its variants as the support, but its intrinsic conductivity is low, which is not conducive to rapid electron transfer and limits the overall performance of the catalyst. 2. Difficulty in controlling the dispersion of iridium: Traditional wet chemical methods or adsorption methods often make it difficult to achieve uniform and stable loading of iridium atoms or nanoparticles, which easily causes agglomeration and reduces the 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 costly, which restricts commercial applications. 4. Weak binding force between the support and iridium: In some solutions, the binding between the support and iridium depends on physical adsorption or surface defects, and the binding force is not strong, which is easy to desorb and deactivate during long-term use.

[0023] In view of this, the present application is hereby proposed.

[0024] The first aspect of the present application provides a method for preparing a supported water electrolysis catalyst, which includes: Obtaining a mixture, the mixture includes titanium dioxide, a reducing agent, and a chloride salt, and the reducing agent includes at least one of NaBH4, LiAlH4, CaH2, and MgH2.

[0025] Calcining the mixture in a reducing atmosphere to reduce at least part of the titanium dioxide on the surface layer of the titanium dioxide to titanium, obtaining a support with a titanium layer on the surface, wherein the atomic proportion of zero-valent titanium in the titanium element of the support measured by XPS is 40%-60%.

[0026] Mixing the support with a soluble iridium source in a liquid phase for a displacement reaction, so that at least part of the titanium displaces iridium ions to form iridium nanoparticles on the surface of the support.

[0027] It can be understood that when the mixture is calcined in a reducing atmosphere, since the mixture contains a reducing agent, the reducing agent and the reducing atmosphere act together to effectively reduce at least part of the surface layer of the titanium dioxide to titanium, obtaining a support. At this time, the support is a core-shell structure, which includes a titanium dioxide core and a titanium layer (Ti 0 ), wherein the atomic proportion of zero-valent titanium in the titanium element of the support measured by XPS is 40%-60%. The titanium layer has good conductivity and good reducibility, which is conducive to improving the electron conductivity of the support, providing a rapid electron channel for subsequent electrochemical reactions, and also serving as a platform for subsequent in-situ displacement reactions with iridium ions, and can improve the durability of the prepared catalyst.

[0028] Exemplarily, the atomic proportion of zero-valent titanium in the titanium element determined by XPS for the support is any value among 40%, 43%, 45%, 47%, 50%, 53%, 55%, 58%, 60% or between any two values.

[0029] It can be understood that reducing at least part of the surface layer of titanium dioxide to titanium to obtain a support with a titanium layer on the surface includes: reducing most of the titanium dioxide in the titanium dioxide surface layer to titanium, and the remaining part remains titanium dioxide. At this time, the titanium dioxide surface 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%.

[0030] In this application, calcining the mixture containing the reducing agent in a reducing atmosphere can better control the reduction degree, make the reduction of the titanium dioxide surface layer more uniform and sufficient, effectively reduce the calcination temperature, obtain a support with good dispersion effect on the basis of effectively reducing energy consumption, ensure the uniformity of iridium loading on the subsequent support, and is beneficial to improving the electrochemical performance of the final supported water electrolysis catalyst.

[0031] Chloride salts, as inert media and dispersants, can improve the uniformity of the reaction environment during calcination, effectively prevent the agglomeration of the reduced support, and are beneficial to obtaining a dispersed support.

[0032] The reducing agent includes at least one of NaBH4, LiAlH4, CaH2, and MgH2. The above reducing agents have strong reducibility and can partially or completely reduce the TiO2 on the surface layer of titanium dioxide to Ti when calcined at high temperature in cooperation with the reducing gas. 0 . It can be understood that the specific choice of the reducing agent can be selected by weighing the reaction temperature and the difficulty of residue treatment.

[0033] After the support is mixed with the soluble iridium source in a liquid phase, the soluble iridium source provides iridium ions.

[0034] Mix the support with the soluble iridium source in a liquid phase. Without the need to additionally introduce a reducing agent, utilize the 0 electrochemical potential difference between Ti 3+ and Ir 4+ / Ir 0), and is closely deposited on the titanium surface. That is, through the in-situ displacement reaction between titanium and iridium ions, at least part of the titanium is oxidized to titanium ions, while the iridium ions are in-situ reduced to iridium nanoparticles and uniformly deposited on the surface of the carrier. Since the iridium nanoparticles are tightly bound to the surface of the carrier, a stable metal-support interface is formed, which can effectively improve the structural stability, corrosion resistance and durability of the supported water electrolysis catalyst. At the same time, it can also effectively avoid the aggregation of iridium nanoparticles and improve the dispersion, which is conducive to reducing the amount of iridium used without sacrificing the catalytic activity.

[0035] In the preparation method provided by this application, by calcining the mixture of titanium dioxide, reducing agent and chloride salt in a reducing atmosphere, using the chloride salt as an inert medium and a dispersant to adjust the uniformity of the reaction environment during calcination, and using the reducing agent and calcining in a reducing atmosphere, at least part of the titanium dioxide on the surface layer of titanium dioxide is reduced to form a titanium layer on its surface, and the atomic proportion of zero-valent titanium in the titanium element measured by XPS is 40%-60%, which can significantly improve the electronic conductivity of the carrier, provide a fast electron channel for subsequent electrochemical reactions, and improve the durability of the prepared catalyst. Then, the prepared carrier is mixed with a soluble iridium source in a liquid phase, and through the reduction displacement reaction between titanium and iridium ions, at least part of the titanium displaces the iridium ions to form iridium nanoparticles in-situ on the surface of the carrier, forming a stable metal-support interface, improving the stability and corrosion resistance of the catalyst, and not being easily desorbed. At the same time, using this preparation method can not only make iridium highly dispersed and precisely coated on the surface of the carrier, greatly reducing the amount of iridium used without sacrificing the activity, thereby reducing the overall cost, but also when part of the titanium displaces the iridium ions to form iridium nanoparticles on the surface of the carrier, the synergistic effect between the remaining titanium and iridium can be utilized, which is conducive to electron transfer and the stability of reaction intermediates, helps to increase the rate of the oxygen evolution reaction, and enhances the catalytic performance.

[0036] Among them, the average primary particle size of titanium dioxide can be 30-150 nm, and the average primary particle size can be measured by TEM.

[0037] Among them, the mixture can be obtained by ball milling or grinding and mixing titanium dioxide, reducing agent and chloride salt. Exemplarily, the time of ball milling or grinding and mixing can be controlled within 15 min - 30 min, which is conducive to the full and uniform dispersion of the three raw materials.

[0038] Among them, the preparation method further includes: naturally cooling the sintered material after calcination to room temperature, and washing the obtained solid with deionized water sufficiently until the pH of the washing liquid is close to neutral to remove excess inorganic salts and by-products, etc. Subsequently, the washed sintered material is vacuum dried at 50°C - 100°C to obtain the carrier.

[0039] Among them, the preparation method further includes: after the carrier and the soluble iridium source are mixed in liquid phase to complete the displacement reaction, the product can be filtered and recovered, and washed thoroughly with deionized water to remove residual iridium salts and side reactants. Finally, the obtained solid is vacuum dried again at 50°C - 100°C to obtain the supported water electrolysis catalyst.

[0040] In some preferred embodiments, the atomic proportion of zero-valent titanium in titanium element measured by XPS is 45% - 55%.

[0041] Controlling the atomic proportion of zero-valent titanium within the above range is beneficial to further improve the catalytic activity and durability of the prepared supported catalyst.

[0042] Exemplarily, the atomic proportion of zero-valent titanium in titanium element measured by XPS is any value among 45%, 47%, 49%, 51%, 53%, 55% or between any two values.

[0043] In some alternative embodiments, the calcination temperature is lower than the decomposition temperature of the chloride salt and not lower than 650°C.

[0044] Since the chloride salt serves as an inert medium and a dispersant, it is necessary to adjust the uniformity of the reaction environment 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.

[0045] Therefore, controlling the calcination temperature to be lower than the decomposition temperature of the chloride salt and not lower than 650°C can effectively reduce at least part of the surface layer of titanium dioxide to titanium to obtain the carrier within this temperature range.

[0046] In some alternative embodiments, the calcination temperature is 700°C - 800°C, and the calcination time is 2h - 12h.

[0047] Controlling the calcination temperature and time within the above range is beneficial to reducing the surface layer of titanium dioxide to titanium to obtain the carrier.

[0048] Exemplarily, the calcination temperature is any value among 700°C, 730°C, 750°C, 780°C, 800°C or between any two values.

[0049] Exemplarily, the calcination time is any value among 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or between any two values.

[0050] In some alternative embodiments, the reducing atmosphere includes hydrogen and / or carbon monoxide.

[0051] The above reducing atmosphere is beneficial to reducing the surface layer of titanium dioxide to titanium.

[0052] Exemplarily, the reducing atmosphere is hydrogen.

[0053] In some alternative embodiments, the added mass of the reducing agent is at least 5 times the added mass of titanium dioxide, and the added mass of the reducing agent is less than the added mass of the chloride salt.

[0054] By limiting the above addition amounts, it is beneficial to partially or completely reduce the TiO2 on the surface layer of titanium dioxide to Ti during high-temperature calcination 0 , and at the same time, the chloride salt with the above addition amount can more fully adjust the uniformity of the reaction environment during calcination, which is beneficial to obtaining a dispersed support after calcination.

[0055] In some alternative embodiments, the mass ratio of the added amounts of titanium dioxide, reducing agent, and chloride salt is 1:5-8:6-12 in sequence.

[0056] By limiting the above addition amounts, it is beneficial to partially or completely reduce the TiO2 on the surface layer of titanium dioxide to Ti during high-temperature calcination 0 , and at the same time, the chloride salt can fully adjust the uniformity of the reaction environment during calcination, which is beneficial to obtaining a dispersed support after calcination.

[0057] Exemplarily, the mass ratio of the added amounts of titanium dioxide, reducing agent, and chloride salt is any value among 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.

[0058] In some alternative embodiments, the chloride salt includes at least one of NaCl, KCl, and LiCl.

[0059] Exemplarily, the chloride salt is NaCl or KCl or LiCl, or the chloride salt is a mixture of NaCl and KCl.

[0060] The above chloride salts are all water-soluble chloride salts, which are convenient for subsequent removal and have good dispersion effects.

[0061] In some alternative embodiments, the liquid-phase mixing includes: adding a support to an aqueous solution of a soluble iridium source and stirring at 40°C - 90°C for at least 1 h.

[0062] By stirring at 40°C - 90°C for at least 1 h, it is beneficial for the in-situ displacement reaction between titanium and iridium ions, oxidizing titanium to titanium ions, and at the same time in-situ reducing iridium ions to iridium nanoparticles and uniformly depositing them on the surface of the support. The iridium nanoparticles are tightly bound to the surface of titanium, forming a stable metal-support interface, and improving the stability and anti-corrosion ability of the supported water electrolysis catalyst.

[0063] Exemplarily, stir at any value among 40°C, 50°C, 60°C, 70°C, 80°C, 90°C or between any two values for at least 1 h, for example, stir for any value among 1 h, 3 h, 5 h, 10 h or between any two values.

[0064] In some alternative embodiments, the mass ratio between the soluble iridium source and the carrier is 1:1 - 1:9.

[0065] It can be understood that by controlling the mass ratio between the soluble iridium source and the carrier, the amount of titanium replaced and the reduced iridium nanoparticles can be controlled.

[0066] It can be understood that when the content of the iridium source is less, the amount of titanium replaced is less. At this time, part of the titanium replaces the iridium ions, and the displaced iridium nanoparticles are in-situ generated on the surface of the remaining titanium.

[0067] In some alternative embodiments, the soluble iridium source includes one or more of iridium tetrachloride, iridium trichloride, iridic acid, iridium acetate, and iridium acetylacetonate.

[0068] The second aspect of the present application provides a supported water electrolysis catalyst, which is prepared by the preparation method provided in the first aspect of the present application.

[0069] The supported water electrolysis catalyst prepared by the above preparation method can balance high catalytic activity and high structural stability on the basis of low noble metal usage.

[0070] In some alternative 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.

[0071] Through the in-situ reduction-displacement dual strategy, a highly dispersed, high-binding-strength, low-loading and efficient Ir / Ti@TiO2 water electrolysis catalytic system is constructed. Through the synergy of iridium nanoparticles on the carrier surface and interfacial catalysis, the supported water electrolysis catalyst can balance high catalytic activity and high structural stability on the basis of low noble metal usage.

[0072] 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. Among them, the anode catalyst layer includes the supported water electrolysis catalyst provided in the second aspect of the present application.

[0073] The following further describes in detail the supported water electrolysis catalyst and its preparation method and the water electrolysis membrane electrode of the present application in conjunction with embodiments.

[0074] In the following examples and comparative examples, titanium dioxide (TiO2, rutile type, BET: 133m 2 / g) The average primary particle size of both the powder raw material and the titanium metal powder raw material is 50 nm.

[0075] Example 1 Supported water electrolysis catalyst, the preparation method of which includes: S1. Prepare a mixture.

[0076] Weigh titanium dioxide (TiO2) powder, sodium borohydride (NaBH4), and sodium chloride in a mass ratio of 1:5:8 in sequence, and ball mill for 20 min to mix evenly to obtain a mixture.

[0077] S2. Prepare a support.

[0078] Place the mixture in a ceramic crucible and put it in a tubular furnace. Under a hydrogen atmosphere (hydrogen flow rate is 200 mL / min), calcine at 700 °C for 2 h to achieve the reduction of the TiO2 surface layer and generate a metal titanium layer. During this high-temperature reduction process, NaBH4 decomposes in NaCl to release active hydrogen species, promoting the reduction of Ti 4+ to Ti, and depositing it on the surface of titanium oxide. After calcination, naturally cool to room temperature. The obtained solid is washed thoroughly with deionized water to remove excess inorganic salts and by-products until the pH of the washing liquid is close to neutral. Subsequently, dry the material in a vacuum drying oven at 60 °C for 12 hours to obtain a support. Perform XPS elemental analysis on the obtained support, and the results are shown in Table 1.

[0079] S3. Prepare a supported water electrolysis catalyst.

[0080] Take iridium chloride (H2IrCl6) and dissolve it in deionized water. Adjust the solution concentration to 0.1 mg / mL, and add hydrochloric acid to control the pH of the solution to 4 to ensure the stable existence of iridium ions, and obtain a soluble iridium precursor solution.

[0081] Mix the above dried support and the above obtained soluble iridium precursor solution at 51.25 mg / 500 ml, and magnetically stir at 40 °C for 6 h to carry out the in-situ displacement reaction of metal titanium and iridium ions. Titanium is oxidized to Ti 4+ , and at the same time, iridium ions are reduced to metallic iridium and in-situ deposited on the surface of the support. After the displacement reaction is completed, the product is recovered by filtration and washed thoroughly with deionized water to remove residual iridium salts and side reactants. The finally obtained solid is vacuum dried again at 60 °C for 12 h to obtain a supported water electrolysis catalyst. Perform XRF elemental analysis on the obtained supported water electrolysis catalyst, and the results are shown in Table 2.

[0082] Figure 1 and Figure 2 is the TEM image of the supported water electrolysis catalyst prepared in Example 1. It can be seen that iridium nanoparticles ( Figure 2The (black small particles) have a uniform particle size and are evenly distributed on the surface of the carrier.

[0083] Example 2 The difference from Example 1 is only that: MgH2 is used to replace NaBH4.

[0084] Example 3 The difference from Example 1 is only that: The mass ratio of titanium dioxide, sodium borohydride and sodium chloride added is 1:5:12 in sequence.

[0085] Example 4 The difference from Example 1 is only that: The calcination temperature is 750 °C.

[0086] Example 5 The difference from Example 1 is only that: Iridium tetrachloride is used to replace chloroiridic acid.

[0087] Comparative Example 1 Take chloroiridic acid (H2IrCl6) and dissolve it in deionized water, and add hydrochloric acid to control the pH of the solution to 4 to ensure the stable existence of iridium ions, obtaining an aqueous solution of chloroiridic acid.

[0088] Mix 1 g of titanium dioxide (TiO2) powder and 0.38 g of an aqueous solution of chloroiridic acid (Ir content 17.5 wt%) by ball milling at a rotation speed of 600 rmp for 20 min to obtain a mixture.

[0089] Place the mixture in a ceramic crucible and put it in a tube furnace. Under a hydrogen atmosphere (hydrogen flow rate is 200 mL / min), calcine at 700 °C for 2 h to obtain a supported water electrolysis catalyst with Ir impregnated and reduced and deposited on the surface of TiO2.

[0090] Comparative Example 2 The difference from Example 1 is only that: Replace titanium oxide with metal Ti powder of the same size particle diameter.

[0091] Comparative Example 3 The difference from Example 1 is only that: S1. Prepare a mixture.

[0092] Weigh titanium dioxide (TiO2) powder and sodium chloride in a mass ratio of 1:8 in sequence, and ball mill for 20 min to mix evenly to obtain a mixture.

[0093] S2. Prepare a carrier.

[0094] Place the mixture in a ceramic crucible and put it in a tube furnace. Under a hydrogen atmosphere (hydrogen flow rate is 200 mL / min), calcine it at 1100 °C for 2 h to achieve the reduction of the TiO2 surface layer and generate a metal titanium layer. After the calcination is completed, cool it naturally to room temperature. Wash the obtained solid thoroughly with deionized water to remove excess inorganic salts and by-products until the pH of the washing liquid is close to neutral. Subsequently, dry the material in a vacuum drying oven at 60 °C for 12 hours to obtain the support.

[0095] Perform XPS elemental analysis on the reduced supports (TiO2@Ti) in Examples 1-5 and Comparative Example 3, and perform XRF elemental analysis on the finally prepared supported water electrolysis catalysts in Examples 1-5 and Comparative Examples 1-3. The results are shown in Tables 1 and 2.

[0096] XPS (X-ray photoelectron spectrometer) test instrument: Model is Thermo Scientific K-Alpha, using a monochromatic Al Kα source (Mono Al Kα), and the energy is 1486.6 eV.

[0097] XRF (X-ray fluorescence spectrometer) test instrument: Model is X-MET-8000 Smart.

[0098] Among them, Table 1 shows the valence state ratio of Ti element in the reduced support (TiO2@Ti), and Table 2 shows the XRF elemental mass ratio of the prepared supported water electrolysis catalyst.

[0099] Table 1 Valence state ratio of Ti element in the reduced support (TiO2@Ti)

[0100] According to Table 1, since the reduction process of the above titanium dioxide is a surface reaction, the reaction proceeds from the outside to the inside, and there is a limitation in the detection depth of XPS analysis (the surface range of several nanometers). Among the surface titanium elements analyzed by XPS, the proportion of Ti 0 is the highest and is between 40% and 60%, and the proportion of Ti 4+ atoms also occupies a certain proportion, indicating that most of the surface layer of titanium dioxide is reduced to titanium, and the unreduced titanium dioxide is the main phase, located in the inner core or the incompletely reduced area. Ti 3+ represents the transition state, indicating the incompletely reduced part.

[0101] Table 2 XRF elemental ratio of the supported water electrolysis catalyst in Examples and Comparative Examples

[0102] Among them, the Ti element in Table 2 includes Ti 4+ 、Ti 3+ and Ti 0, where the total content of element Ir and element Ti is 100%.

[0103] According to Table 2, Figure 1 and 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.

[0104] Test Example 1 Electrochemical performance test: The electrochemical test was carried out on a CHI660E electrochemical workstation of Shanghai Chenhua and a rotating disk electrode device (Pine Company, USA). The main electrochemical performance tests of the catalyst were cyclic voltammetry (CV) test, linear sweep voltammetry (LSV) test, etc. All electrode potentials in the experiment were normalized using a reversible hydrogen electrode (RHE).

[0105] 1) Preparation of the working electrode Weigh 8 mg of the catalysts of the above-mentioned examples and comparative examples respectively with an electronic balance and add them to a 5 ml centrifuge tube. Then, pipette 2 ml of the prepared dispersion liquid (300 ml of isopropanol, 100 ml of water, and 0.31 g of 5 wt% Nafion solution D2020) into the centrifuge tube. Place the above mixed solution in a cell crusher and perform ultrasonic dispersion for 20 min to obtain a uniform catalyst ink. Then, use a 10 μL pipette to measure 10 μL of the catalyst ink and evenly drop it on the pre-polished and cleaned gold electrode (with an area of 0.196 cm 2 ) so that the ink does not overflow and is evenly spread on the electrode surface. Wait for it to dry naturally to form a catalytic layer, and then the working electrode can be obtained.

[0106] 2) Electrochemical performance test For the cyclic voltammetry test (Cyclicvoltammogram, CV), the potential range is 1.2~1.6 vs RHE (0.544~0.944 vs Hg2SO4), and the scanning rate is 50 mV / s. Before each test, it is necessary to introduce saturated N2 for 60 min (in an anaerobic environment), and scan at a scanning rate of 100 mV / s until the CV curve is stable to fully activate the catalyst.

[0107] Linear sweep voltammetry: In order to evaluate the OER electrocatalytic performance of the catalyst materials and their performance during this reaction process, anodic polarization measurements were carried out, and the results of linear sweep voltammetry (Linear sweep voltammetry, LSV) were used for judgment. The LSV scanning speed is 50 mV / s, the scanning range is 1.2~1.6 vs RHE, the scanning speed is 50 mV / s, and the rotation speed of the rotating disk electrode is 1600 rpm. The overpotential is 10 mA / cm in the LSV 2obtained by subtracting the ideal decomposition voltage of 1.23 V for water electrolysis from the corresponding voltage.

[0108] 3) HFR test The mass ratio of each component in the anode catalyst slurry is as follows: catalyst: perfluorosulfonic acid resin solution (Nafion D2020): water-alcohol solution (mass ratio of water to isopropanol is 3:1) = 1:0.25:10. The first anode catalyst slurry is sprayed on the transfer substrate, then dried at a constant temperature of 60 °C in an oven, and then the side of the catalyst layer facing away from the transfer substrate is transferred to the anode side of the proton exchange membrane by transfer to form an anode catalyst layer with a total thickness of 10 μm on the anode side of the proton exchange membrane. Preparation of the cathode catalyst layer: The mass ratio of each component in the cathode catalyst slurry is as follows: Pt / C catalyst (Pt loading 60%): perfluorosulfonic acid resin solution (Nafion D2020): water-alcohol solution (mass ratio of water to isopropanol is 1:10) = 1:1:15.

[0109] The cathode catalyst slurry is coated on the transfer membrane by slit coating, then dried at a constant temperature of 60 °C in an oven to form a cathode catalyst layer on the transfer membrane. The cathode catalyst layer is transferred to the proton membrane to obtain a hydrogen production membrane electrode for water electrolysis. Using a Gamry electrochemical test device, connect the electrolytic cell, select a frequency of 1000 - 10000 Hz, read the starting point resistance, and multiply it by the effective area of the membrane electrode to obtain the surface resistance HFR. The test results are shown in Table 3.

[0110] 4) Durability test In order to study the stability of the prepared catalyst in an acidic electrochemical environment, an accelerated durability test (ADT) is carried out on the catalyst, scanning 3000 cycles between 1.2 - 1.6 vs RHE (0.544 - 0.944 vs Hg2SO4) at a scanning rate of 100 mV / s. Before and after the cycle, CV and LSV data are collected according to the above method respectively, and the electrochemical stability of the catalyst is evaluated by comparing the overpotential loss of the catalyst at different cycle numbers. The results are shown in Table 3.

[0111] Table 3 Electrochemical test results of each example and comparative example

[0112] It can be seen from Table 3 that the supported water electrolysis catalyst provided by the examples of the present application has good catalytic activity and durability. In addition, it also has a lower surface resistance HFR, indicating that the electron transfer 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 improve the catalytic activity of the membrane electrode.

[0113] It can be seen from the comparison between Examples 1-5 and Comparative Example 1 that in Comparative Example 1, the impregnation reduction method was used, and the iridium particles in the prepared catalyst tended to agglomerate more. Moreover, there was no titanium layer on the surface of the carrier, and the binding force between the carrier and the iridium particles was weak. Therefore, the surface resistance HFR was large, and the activity per unit mass and durability were poor.

[0114] It can be seen from the comparison between Example 1 and Comparative Example 2 that although the overpotential of Comparative Example 2 was close to that of Example 1, since the main body of the carrier was nanoscale Ti particles, under the strong oxidation conditions of actual testing, the Ti particles would be significantly oxidized and agglomerated, resulting in poor durability of the catalyst. At the same time, the cost of pure Ti particles was much higher than that of TiO2 particles.

[0115] It can be seen from the comparison between Examples 1-5 and Comparative Example 3 that in Comparative Example 3, due to the relatively high reduction temperature and the absence of a solid-phase reducing agent, the proportion of metallic titanium on the surface of the carrier was low, resulting in a high surface resistance HFR. Moreover, the carrier would undergo obvious agglomeration during the reduction stage, affecting the uniform loading of subsequent iridium particles, and finally leading to a high overpotential and poor durability of the catalyst.

[0116] Figure 3 Figure of LSV of the supported water electrolysis catalyst prepared for Example 1 and Comparative Examples 1-3; According to Figure 3 It can be seen that the catalytic activity of Example 1 of this application is superior to that of Comparative Examples 1-3.

[0117] In summary, the supported water electrolysis catalyst, its preparation method and the water electrolysis membrane electrode provided by this application construct a highly dispersed, high-binding-strength, low-loading and efficient Ir / Ti@TiO2 water electrolysis catalytic system through the in-situ reduction-replacement dual strategy, enabling the supported water electrolysis catalyst to achieve both high catalytic activity and high durability on the basis of low noble metal usage.

[0118] The above are only specific embodiments of this application and are not used to limit this application. For those skilled in the art, various changes and modifications can be made to this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A preparation method of a supported water electrolysis catalyst, characterized in that, Comprising: Obtaining a mixture, the mixture comprising titanium dioxide, a reducing agent, and a chloride salt, the reducing agent comprising at least one of NaBH4, LiAlH4, CaH2, and MgH2; Calcining the mixture in a reducing atmosphere to reduce at least part of the titanium dioxide on the surface layer of the titanium dioxide to titanium, 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 measured by XPS is 40%-60%; Mixing the support and a soluble iridium source in a liquid phase to carry out a displacement reaction, so that at least part of the titanium displaces iridium ions to form iridium nanoparticles on the surface of the support.

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

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

4. The preparation method according to any one of claims 1 to 3, characterized in that, The reducing atmosphere comprises 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 1-3, characterized in that, The added mass ratio of the titanium dioxide, the reducing agent, and the chloride salt is 1:5 - 8:6 - 12 in sequence.

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

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

9. A supported water electrolysis catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1 - 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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