Supported iridium oxide catalyst, preparation method thereof and water electrolysis hydrogen production membrane electrode

Abstract

The invention relates to a supported iridium oxide catalyst, a preparation method thereof and a water electrolysis hydrogen production membrane electrode, and belongs to the technical field of noble metal catalysts. The supported iridium oxide catalyst comprises an oxide carrier and iridium oxide particles supported on the oxide carrier, wherein the loading capacity of the iridium oxide particles is greater than or equal to 50wt%; the ratio of the ECSA measured value to the ECSA theoretical value of the supported iridium oxide catalyst meets the condition that the ratio of the ECSA measured value to the ECSA theoretical value is more than or equal to 0.4 and less than or equal to 0.8; and the ratio of the average particle size ra of the iridium oxide particles to the average particle size rs of the oxide carrier is greater than or equal to 0.004 and less than or equal to 0.15. Under the condition of high loading capacity, the microstructure and distribution of iridium oxide particles are synchronously controlled, and collaborative optimization of ECSA and three-phase interface TPB length is realized, so that the activity and long-term stability of the catalyst are effectively improved.

Description

Technical Field

[0001] This application relates to the field of precious metal catalyst technology, and in particular to a supported iridium oxide catalyst and its preparation method, and a water electrolysis hydrogen production membrane electrode. Background Technology

[0002] Compared to alkaline water electrolysis systems, proton exchange membrane (PEM) water electrolysis technology has significant advantages such as high current density, fast start-up response, high hydrogen purity, and small system size, and is considered to be the mainstream direction for large-scale "green hydrogen" production in the future.

[0003] In the PEM water electrolysis process, the anodic oxygen evolution reaction (OER) is the rate-limiting step of the entire system. Its reaction kinetics are slow, requiring a highly efficient and stable anodic catalyst to reduce overpotential and improve energy efficiency. Currently, iridium oxide (IrO2) has become the most promising OER catalyst due to its excellent chemical stability and moderate overpotential characteristics. Furthermore, considering that iridium is a precious metal, scarce and expensive, supported iridium oxide catalysts are commonly used to improve its atom utilization and reduce its dosage. This involves dispersing iridium oxide on the surface of a support to increase the specific surface area and electrochemical activity of the catalyst, while simultaneously reducing catalyst cost.

[0004] However, existing supported iridium oxide catalysts still suffer from problems such as insufficient utilization of catalyst activity and low long-term stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a supported iridium oxide catalyst and its preparation method, as well as a water electrolysis hydrogen production membrane electrode, to effectively solve the problems of insufficient activity utilization and low long-term stability of existing supported iridium oxide catalysts. In a first aspect, embodiments of this application provide a supported iridium oxide catalyst, comprising an oxide support and iridium oxide particles supported on the oxide support; wherein the loading of the iridium oxide particles is ≥50wt%; the ratio of the ECSA measured value to the ECSA theoretical value of the supported iridium oxide catalyst satisfies: 0.4≤ECSA measured value / ECSA theoretical value≤0.8; the average particle size r of the iridium oxide particles is... a and the average particle size r of the oxide support s The ratio satisfies: 0.004 ≤ r a / r s ≤0.15. In the above-mentioned technical solution, this application achieves synergistic optimization of the electrochemical active surface area (ECSA) and the three-phase interface (TPB) length by simultaneously controlling the microstructure and distribution of iridium oxide particles under high loading conditions, thereby effectively improving the catalyst activity and stability.

[0006] The iridium oxide particles, with a loading of ≥50 wt%, can contact each other on the oxide support surface, forming a continuous conductive pathway and thus creating a continuous electron transport network at the electrode scale. The ratio of ECSA measured values ​​to ECSA theoretical values ​​is further used as a quantitative control index for the catalyst particle distribution. When this ratio is between 0.4 and 0.8, the iridium oxide particles neither excessively agglomerate nor fail to maintain sufficient contact, thereby further improving catalyst activity and stability. Furthermore, by controlling the particle size ratio of iridium oxide particles to the oxide support to be between 0.004 and 0.15, high-load iridium oxide particles can form a uniform, interconnected conductive network structure on the oxide support surface, significantly extending electron and ion transport paths, increasing the effective length of TPB (transient photochemical barrier), and improving interfacial reaction utilization.

[0007] In some embodiments, the average particle size r of the iridium oxide particles a The average particle size r of the oxide support is 2nm~5nm. s The range is 30nm to 500nm.

[0008] In the above technical solution, by controlling the particle size of iridium oxide particles and the oxide support within the aforementioned range, combined with the control of the particle size ratio range, a multi-point contact nano-interconnected structure can be established on the surface of the oxide support. This allows the electronic conductors, ionic conductors, and reaction phases in the anode catalyst layer to form a continuous contact network at the nanoscale, thereby effectively extending the TPB length, significantly shortening the electron and proton transport paths, and reducing the interfacial polarization resistance. This improves the interfacial reaction rate and overall conductivity, reduces interfacial resistance, and further enhances catalyst activity. Furthermore, the iridium oxide particles achieve stable bonding through nano-dispersion and anchoring on the support surface, and the nano-interconnected structure can inhibit the migration and sintering of iridium oxide under electrolysis conditions, helping to maintain the long-term stability of the TPB structure, thereby further improving the structural stability and durability of the catalyst. This also further improves catalyst utilization and reduces production costs. In some embodiments, the oxide support includes at least one of titanium oxide, zirconium oxide, tungsten oxide, tin dioxide, cerium oxide, niobium pentoxide, tantalum pentoxide, or antimony tin oxide. In the aforementioned technical solutions, these oxide supports possess high specific surface area, abundant surface hydroxyl groups, and good stability. They can anchor iridium oxide particles through coordination and / or hydrogen bonding, further confining them with pore structures, effectively improving the uniform dispersion of iridium oxide particles and increasing the utilization rate of active sites. Furthermore, these oxide supports exhibit good electrical conductivity, which facilitates the formation of continuous electronic pathways by iridium oxide particles, reducing interfacial contact resistance and improving electron / proton coupling efficiency, thereby further enhancing catalyst activity and long-term stability. In some embodiments, the loading of iridium oxide particles is 55wt% to 70wt%. In the above technical solution, the loading of iridium oxide particles is controlled within the above range. Combined with the synergistic control of ECSA and TPB, it is beneficial to further improve the continuity and stability of the conductive path, thereby further improving the catalyst activity and stability, while reducing production costs. In some embodiments, the ECSA measurement value of the supported iridium oxide catalyst is ≥40m. 2 / g. In the above technical solutions, the supported iridium oxide catalyst has a higher ECSA measurement value, which indicates that the catalyst has a higher active site density and a higher utilization rate of precious metals, which can further improve catalytic activity and reduce production costs. Secondly, embodiments of this application provide a method for preparing the supported iridium oxide catalyst provided in the first aspect of this application, comprising the following steps: According to the target loading, the iridium precursor is dissolved in a solvent to prepare a precursor solution; the oxide support is placed in the precursor solution for impregnation, and after impregnation, it is separated and pre-dried in sequence. The impregnation is repeated multiple times, and finally dried and calcined to obtain the supported iridium oxide catalyst.

[0009] In the above technical solution, by configuring the precursor solution and combining multiple impregnation loading and calcination, the target loading amount (≥50wt%) can be precisely controlled, and the iridium precursor can be uniformly and stably loaded on the oxide support. This ensures that the iridium oxide particles formed after calcination neither excessively agglomerate nor fail to maintain sufficient contact, and the catalyst satisfies 0.4≤ECSA measured value / ECSA theoretical value≤0.8. Combined with further calcination, the average particle size r of the iridium oxide particles can be effectively controlled. a and the average particle size r of the oxide support s The ratio satisfies: 0.004 ≤ r a / r s ≤0.15. This preparation method can effectively improve the catalytic activity and long-term stability of supported iridium oxide catalysts, and it is simple to operate and easy to apply industrially.

[0010] In some embodiments, the concentration of the iridium precursor in the precursor solution is 0.01 mol / L to 0.05 mol / L. In the above technical solution, the concentration of the iridium precursor is within a suitable range, which is beneficial to improving the dispersibility and stability of iridium oxide particles loaded on the oxide support, reducing agglomeration, and improving the adsorption efficiency during the impregnation process. In some embodiments, the iridium precursor includes at least one of iridium trichloride, iridium chloroacetic acid, iridium nitrate, or iridium acetylacetonate. In the above technical solution, the iridium precursor has good solubility in conventional water and / or alcohol-water systems, and can form iridium oxide after calcination with low impurity residue.

[0011] In some implementations, the impregnation is repeated 2 to 6 times. In the above technical solution, the number of repeated impregnations is within a suitable range, which is beneficial to further improve the uniformity and dispersion of iridium oxide particles on the oxide carrier, improve the stability of the load, and facilitate precise control of the load amount. It is also beneficial to improve production efficiency and reduce production costs. In some embodiments, the pre-drying temperature is 60°C to 80°C and the time is 30 min to 60 min. In the above technical solution, pre-drying the impregnated product at a certain temperature is beneficial for removing solvent, promoting uniform and stable loading of iridium precursor, and also helps to increase the adsorption amount in the next impregnation process. In some embodiments, the mass ratio of oxide support to precursor solution is 1:(10~20). In the above technical solution, by controlling the mass ratio of the oxide carrier and the precursor solution used in the impregnation process within a suitable range, it is beneficial to fully wet and transfer mass, improve the uniformity, dispersion and stability of the load, and at the same time, it is beneficial to improve production efficiency and reduce production costs. In some embodiments, the impregnation step is carried out under stirring or ultrasonic conditions at a temperature of 25°C to 40°C for a time of 30 to 60 minutes.

[0012] In the above technical solution, by controlling the process parameters of the impregnation step, it is beneficial to rapidly adsorb the oxide support and achieve uniform and stable loading of the iridium precursor. In some embodiments, the drying step is performed at a temperature of 80°C to 120°C for 10 to 12 hours.

[0013] In the above technical solution, by controlling the temperature and time of the drying step, it is beneficial to promote the complete evaporation of the solvent and reduce the impact on the calcination process, so as to further improve the dispersion uniformity and adhesion stability of iridium oxide particles. In some embodiments, after the drying step, the temperature is further increased to 200°C to 250°C at a heating rate of 1°C / min to 3°C / min, and held at that temperature for 0.5h to 1h.

[0014] In the above technical solution, the pre-decomposition treatment after drying can promote the dehydration and decomposition of the iridium precursor and fix it on the surface of the oxide carrier, thereby reducing migration and aggregation in the subsequent calcination step and further improving the dispersion uniformity of iridium oxide particles. In some embodiments, the calcination step is carried out at a temperature of 400°C to 500°C for 2 hours to 4 hours.

[0015] In the above technical solution, by controlling the calcination conditions within a suitable range, it is beneficial for the iridium precursor to be fully converted into iridium oxide particles. The particle size, uniformity, and dispersion can be controlled accordingly, reducing the impact on the pore structure of the support, thereby further improving the catalytic activity and long-term stability.

[0016] In some embodiments, the calcination step includes: heating to 300°C to 350°C at a first heating rate, and then heating to 400°C to 500°C at a second heating rate; wherein the first heating rate is higher than the second heating rate, and the first heating rate and the second heating rate are each independently 1°C / min to 2°C / min.

[0017] In the above technical solution, by slowly increasing the temperature in stages, the grain growth rate can be controlled to be relatively slow, which results in the generated iridium oxide particles having a smaller nanometer size and more uniform particle size. The particles are evenly dispersed, which is conducive to the formation of a continuous electronic conduction network.

[0018] Thirdly, embodiments of this application provide a water electrolysis hydrogen production membrane electrode, including a proton exchange membrane and an anode catalyst layer disposed on one side of the proton exchange membrane, wherein the anode catalyst layer includes the supported iridium oxide catalyst provided in the first aspect of this application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a TEM image of the supported iridium oxide catalyst provided in Example 1 of this application. Detailed Implementation

[0021] The following detailed description, with appropriate reference to the accompanying drawings, discloses the supported iridium oxide catalyst, the method for preparing the supported iridium oxide catalyst, and embodiments of a water electrolysis hydrogen production membrane electrode using the supported iridium oxide catalyst. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a thorough understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0022] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0023] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0024] Current research on supported iridium oxide catalysts for PEM water electrolysis mainly focuses on: reducing IrO2 loading to increase the electrochemical active surface area (ECSA); optimizing IrO2 particle dispersion and crystal structure; and enhancing conductivity and interfacial stability. Although some progress has been made in improving catalyst activity and stability, it is difficult to balance high activity, high conductivity and connectivity, and long-term stability for the following reasons: (1) When the IrO2 loading is low, although the dispersibility can be improved and the ECSA can be improved, the conductive network formed between the IrO2 particles is discontinuous, the electron transport efficiency is reduced, and thus the actual active sites are not fully utilized and the long-term stability is poor. When the IrO2 loading is increased to improve conductivity, the nanoparticles are prone to agglomeration, which will lead to a significant decrease in ECSA and a significant decrease in reactivity, that is, it is impossible to achieve both high activity and high durability.

[0025] (2) Existing technologies only describe the dispersion of catalysts by observing ECSA or transmission electron microscopy (TEM), lacking comprehensive characterization indicators that can simultaneously reflect the number of active sites and conductivity, i.e., structural optimization lacks quantifiable parameters.

[0026] (3) Conventional impregnation or coprecipitation methods are difficult to form a continuous nanoscale interface. The electron contact between IrO2 particles and the support is insufficient, resulting in a limited three-phase interface (TPB), high interfacial resistance, and low electron / proton coupling efficiency, which leads to a decrease in catalyst activity and durability.

[0027] Based on this, embodiments of this application provide a supported iridium oxide catalyst, comprising an oxide support and iridium oxide particles supported on the oxide support; wherein, the loading of the iridium oxide particles is ≥50wt%; the ratio of the ECSA measured value to the ECSA theoretical value of the supported iridium oxide catalyst satisfies: 0.4≤ECSA measured value / ECSA theoretical value≤0.8; the average particle size r of the iridium oxide particles is... a and the average particle size r of the oxide support s The ratio satisfies: 0.004 ≤ r a / r s ≤0.15.

[0028] In this embodiment, the "oxide support" is an oxide particle or powder with a high specific surface area (porous structure), such as titanium oxide particles. This application does not specifically limit the type of oxide support; any oxide support that can remain stable under PEM conditions is acceptable.

[0029] In this embodiment, "the loading of iridium oxide particles" refers to the percentage of the mass of iridium oxide particles relative to the total mass of the entire supported iridium oxide catalyst. The loading of iridium oxide particles in the supported iridium oxide catalyst can be obtained using conventional testing methods and equipment. For example, the supported iridium oxide catalyst can be digested in an appropriate amount of aqua regia to obtain a sample solution. The sample solution can then be tested using inductively coupled plasma optical emission spectrometry (ICP-OES) to obtain the emission characteristic spectrum, calculate the concentration of Ir element, and then convert the result to obtain the loading of iridium oxide particles.

[0030] As an example, the loading of iridium oxide particles can be any one of 50wt%, 55wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, or a range between any two of these values.

[0031] In the embodiments of this application, "ECSA" refers to Electro Chemical Active Surface Area, which is the total surface area of ​​active sites in the catalyst that actually participate in the electrochemical reaction.

[0032] ECSA measurements can be obtained using cyclic voltammetry (CV). For example, a glassy carbon rotating disk electrode (RDE, Pine Research Instrumentation) can be used as the working electrode, connected to a CHI 600E (CHInstruments) electrochemical workstation. A Hydroflex hydrogen reference electrode (Gaskatel) can be used as the reference electrode, and a platinum wire coil can be used as the counter electrode. An aqueous solution of H₂SO₄ is used as the electrolyte. The ECSA measurement is calculated by determining the average charge during hydrogen adsorption and desorption.

[0033] The theoretical ECSA value can be calculated based on the geometric surface area of ​​the catalyst, reflecting the ideal exposed area. It is typically assumed that the catalyst particles are of an ideal shape (e.g., spherical) and the calculation is based on their size and density; the formula for calculating the theoretical ECSA is as follows: Theoretical ECSA = 4πr 2 Where: r is the radius of the catalyst particle, obtained by collecting the particle sizes of multiple particles (300) in the TEM, which is the average particle size; N is the number of particles in the catalyst. Assuming 1g of catalyst, N=1g / m (mass of one particle), m=ρV, where V is the volume of a single particle (V=4πr). 3 / 3), where ρ is the density of iridium oxide (taken as 11.6 g / cm³).

[0034] As an example, the ECSA measured value / ECSA theoretical value can be any one of 0.4, 0.5, 0.6, 0.7, 0.8 or a range between any two points.

[0035] In this embodiment, the average particle size of iridium oxide particles refers to the average particle size of iridium oxide particles in multiple supported iridium oxide catalysts; the average particle size of the oxide support refers to the average particle size of the oxide support in multiple supported iridium oxide catalysts. In the supported iridium oxide catalyst, the average particle size r of the iridium oxide particles... a and the average particle size r of the oxide support s The ratio can be obtained using conventional testing methods and equipment. For example, TEM testing can be performed on supported iridium oxide catalysts. By observing the TEM images and statistically analyzing the particle size using ImageJ software (more than 100 statistical analyses), the average particle size can be obtained by fitting the statistical data with a normal distribution curve, and then r can be calculated. a / r s .

[0036] As an example, r a / r s It can be any single value among 0.004, 0.01, 0.05, 0.10, and 0.15, or a range between any two values.

[0037] ECSA measured value / ECSA theoretical value: ECSA characterizes the ratio of actually exposed and connected active sites on the support surface, and can serve as a quantitative indicator of the dispersion state of iridium oxide particles. The three-phase interface (TPB) is a linear interface where electrons, ions, and reactants co-contact; its effective length directly affects the number of effective active sites and charge / mass transport efficiency of the catalyst, ultimately influencing catalytic activity and long-term stability. In this application, by simultaneously controlling the microstructure and distribution of iridium oxide particles at a high loading, the improvement of ECSA increases the number of active sites, the extension of TPB improves the utilization efficiency of active sites, and the high-loading conductive network ensures the continuity of electron transport. These three elements constitute a complementary system, and through synergistic control, high catalyst activity and high stability are effectively achieved.

[0038] Among them, the loading of iridium oxide particles is ≥50wt%, which can contact each other on the surface of the oxide carrier to form a continuous conductive path, thereby forming a through electron transport network at the electrode scale.

[0039] By further controlling the ratio of measured ECSA to theoretical ECSA within the range of 0.4–0.8, iridium oxide particles are neither excessively agglomerated nor fail to maintain sufficient contact. This ensures both high ECSA and the continuity of the conductive network, thus achieving a balance between high activity and long-term stability. This parameterized control method provides measurable and repeatable quantitative data on catalyst structure quality.

[0040] By further controlling the particle size ratio of iridium oxide particles to oxide support within the range of 0.004 to 0.15, high-load iridium oxide particles can form a uniform and interconnected conductive network structure on the surface of the oxide support, significantly extending the electron and ion transport paths, increasing the effective length of TPB, and improving the utilization rate of interfacial reactions.

[0041] In some embodiments, the average particle size r of the iridium oxide particles a The average particle size r of the oxide support is 2nm~5nm. s The range is 30 nm to 500 nm. As an example, the average particle size r of iridium oxide particles... a The value is any single point or range between any two points from 2nm, 3nm, 4nm, and 5nm; the average particle size r of the oxide support. s It can be any single value or a range between any two values ​​in the range of 30nm, 60nm, 100nm, 200nm, 300nm, 400nm, and 500nm.

[0042] Furthermore, the specific surface area of ​​the oxide support is 8m². 2 / g~100m 2 / g, for example 8m 2 / g, 10m2 / g、20m 2 / g, 50m 2 / g、80m 2 / g, 100m 2 / g etc.

[0043] In some embodiments, the oxide support includes at least one of titanium oxide, zirconium oxide, tungsten oxide, tin dioxide, cerium oxide, niobium pentoxide, tantalum pentoxide, or antimony tin oxide. Further, the oxide support may be undoped or doped titanium oxide. In some embodiments, the loading of iridium oxide particles is 55 wt% to 70 wt%. By way of example, the loading of iridium oxide particles can be any one of 55 wt%, 60 wt%, 65 wt%, 70 wt%, or a range between any two of these values.

[0044] In some embodiments, the ECSA measurement value of the supported iridium oxide catalyst is ≥40 m. 2 / g. As an example, the ECSA measurement for supported iridium oxide catalysts can be 40m. 2 / g, 50m 2 / g、60m 2 / g、70m 2 / g、80m 2 / g, 100m 2 / g etc.

[0045] Secondly, embodiments of this application provide a method for preparing the above-mentioned supported iridium oxide catalyst, comprising the following steps: S1: Dissolve the iridium precursor in a solvent according to the target loading to prepare a precursor solution.

[0046] In some embodiments, the concentration of the iridium precursor in the precursor solution is 0.01 mol / L to 0.05 mol / L. As an example, the concentration of the iridium precursor is any one value or a range between any two values ​​from 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, to 0.05 mol / L.

[0047] In some embodiments, the iridium precursor includes at least one of iridium trichloride (IrCl3), iridium chloroacetic acid (H2IrCl6), iridium nitrate (Ir(NO3)3), or iridium acetylacetonate.

[0048] In some embodiments, the solvent includes water and an alcohol solvent. The volume ratio of water to alcohol solvent is (1-2):1. Further, the alcohol solvent may include at least one selected from ethanol, n-propanol, isopropanol, and ethylene glycol.

[0049] In some embodiments, the precursor solution also includes a complexing agent, and the pH is 3-4. This can help reduce the hydrolysis or polymerization of iridium ions. Further, the complexing agent may include citric acid or ethylenediaminetetraacetic acid (EDTA), and the mass fraction in the precursor solution may be 0.1wt%-0.5wt%.

[0050] S2: The oxide support is impregnated in the precursor solution. After impregnation, it is separated and pre-dried in sequence. The impregnation is repeated multiple times. Finally, it is dried and calcined to obtain the supported iridium oxide catalyst.

[0051] In some embodiments, the immersion is repeated 2 to 6 times, for example 2, 3, 4, 5 or 6 times.

[0052] In some embodiments, the pre-drying temperature is 60°C to 80°C, and the time is 30 min to 60 min. As an example, the pre-drying temperature can be 60°C, 70°C, 80°C, etc.; and the time can be 30 min, 40 min, 50 min, 60 min, etc.

[0053] In some embodiments, the mass ratio of the oxide support to the precursor solution is 1:(10~20). As an example, the mass ratio of the oxide support to the precursor solution is any one of the following values, or a range between any two values: 1:10, 1:12, 1:15, 1:17, 1:20.

[0054] In some embodiments, the impregnation step is performed under stirring or ultrasonic conditions at a temperature of 25°C to 40°C for a time of 30 to 60 minutes. As examples, the impregnation temperature is 25°C, 30°C, 35°C, 40°C, etc.; and the impregnation time is 30 minutes, 40 minutes, 50 minutes, 60 minutes, etc.

[0055] Furthermore, before each impregnation, iridium precursor can be added to the precursor solution to maintain a constant concentration.

[0056] Furthermore, after impregnation, a static aging process of 1-2 hours may be included. This is beneficial for the stable adsorption of the iridium precursor on the oxide support surface.

[0057] In some embodiments, prior to the impregnation step, the process may further include pretreatment of the oxide support. For example, the oxide support may be dried to remove adsorbed moisture. The drying temperature may be 100°C to 120°C, and the drying time may be 2 hours to 4 hours.

[0058] Furthermore, before drying, the process may include: ultrasonically dispersing the oxide support in ethanol for 10 to 20 minutes to enhance surface cleanliness and wettability, and to maintain open pores on the support and full exposure of surface adsorption active sites.

[0059] In some embodiments, the temperature of the drying step is 80°C to 120°C, and the time is 10h to 12h. As examples, the temperature of the drying step is 80°C, 90°C, 100°C, 110°C, 120°C, etc.; and the time is 10h, 11h, 12h, etc.

[0060] In some embodiments, after the drying step, the process further includes: heating to 200°C to 250°C at a heating rate of 1°C / min to 3°C / min and holding at that temperature for 0.5h to 1h for decomposition pretreatment.

[0061] In some embodiments, the calcination step is performed at a temperature of 400°C to 500°C for 2 hours to 4 hours. As examples, the calcination step is performed at temperatures of 400°C, 420°C, 450°C, 470°C, 500°C, etc., and for times of 2 hours, 3 hours, 4 hours, etc.

[0062] Further, the calcination step includes: heating to 300°C ~ 350°C at a first heating rate, and then heating to 400°C ~ 500°C at a second heating rate; wherein the first heating rate is higher than the second heating rate, and the first heating rate and the second heating rate are each independently 1°C / min ~ 2°C / min.

[0063] As an example, the calcination step includes: heating from 200°C to 250°C to 300°C to 350°C at a rate of 2°C / min, then heating to 400°C to 500°C at a rate of 1°C / min, and holding at that temperature for 2 to 4 hours.

[0064] Thirdly, embodiments of this application also provide a water electrolysis hydrogen production membrane electrode, including a proton exchange membrane and an anode catalyst layer disposed on one side of the proton exchange membrane, wherein the anode catalyst layer includes the supported iridium oxide catalyst provided in the first aspect of this application.

[0065] In this embodiment, the "water electrolysis hydrogen production membrane electrode" typically includes a proton exchange membrane and an anode catalyst layer and a cathode catalyst layer located on opposite sides of the proton exchange membrane. The anode catalyst layer includes an oxygen evolution catalyst, responsible for the catalytic oxidation of water to produce oxygen, protons, and electrons (2H2O→O2↑+ 4H). + + 4e - The generated electrons migrate to the cathode through an external circuit, and protons migrate to the cathode through a proton exchange membrane. In the cathode catalyst layer, protons combine with electrons to undergo a reduction reaction, producing hydrogen gas (4H₂O). + + 4e- → 2H2↑).

[0066] In some embodiments, the proton exchange membrane may be any one of a perfluorosulfonic acid resin membrane, a modified perfluorosulfonic acid resin membrane, or a reinforced perfluorosulfonic acid resin membrane.

[0067] In some embodiments, the anode catalyst layer further includes an ionomer, and the mass ratio of the ionomer to the supported iridium oxide catalyst is (0.2~0.5):1, for example 0.25:1, 0.3:1, 0.4:1, etc.

[0068] Furthermore, the ionomer includes at least one of sulfonated polysulfone, sulfonated polyethersulfone, perfluorosulfonic acid resin (Nafion), sulfonated polyether ether ketone, sulfonated polyphenylene sulfide, perfluorocarboxylic acid resin or perfluorophosphate resin.

[0069] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0070] Example 1 This embodiment provides a supported iridium oxide catalyst, the preparation method of which includes the following steps: (1) Dissolve IrCl3·xH2O at a concentration of 0.03 mol / L in a mixed solvent of water / isopropanol (volume ratio 1:1), add 0.2 wt% citric acid, and prepare a precursor solution.

[0071] (2) Select particles with an average particle size of 60 nm and a specific surface area of ​​47 m². 2 / g of TiO2 support was added to the precursor solution at a mass ratio of oxide support to precursor solution of 1:15. The mixture was stirred at room temperature for 45 min, filtered, and pre-dried at 80°C for 30 min. The impregnation-pre-drying step was repeated 4 times to obtain the catalyst intermediate.

[0072] (3) The catalyst intermediate was first dried at 90°C for 11 h, then heated to 250°C at a heating rate of 2°C / min and held for 1 h, then heated from 200°C to 350°C at a heating rate of 2°C / min, then heated to 450°C at a heating rate of 1°C / min and held for 3 h, and then naturally cooled to room temperature to obtain the supported iridium oxide catalyst. The loading of iridium oxide particles was 60 wt%, and the average particle size was 3 nm.

[0073] Figure 1This is a TEM image of the supported iridium oxide catalyst provided in Example 1 of this application. It can be seen that the iridium oxide particles ( Figure 1 The small black particles are uniform in size and evenly distributed on the surface of the carrier.

[0074] Example 2 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (2), the immersion-pre-drying process is repeated twice.

[0075] Example 3 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (2), the mixture is stirred at room temperature for 55 minutes, and the impregnation-pre-drying process is repeated 6 times.

[0076] Example 4 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (2), the average particle size of the TiO2 support is 30 nm and the specific surface area is 89 m². 2 / g.

[0077] Example 5 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (2), the average particle size of the TiO2 support is 200 nm and the specific surface area is 17 m². 2 / g.

[0078] Example 6 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (2), the average particle size of the TiO2 support is 500 nm and the specific surface area is 11 m². 2 / g.

[0079] Example 7 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (1), the concentration of IrCl3·xH2O is 0.05 mol / L. Example 8 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (2), the mass ratio of oxide support to precursor solution is 1:10.

[0080] Example 9 This embodiment provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: Step (3) includes: first drying the catalyst intermediate at 90°C for 11 h, then heating it to 450°C at 3°C / min and holding it at that temperature for 4 h to obtain the supported iridium oxide catalyst. The iridium oxide particles are loaded with 60 wt% and have an average particle size of 7 nm.

[0081] Comparative Example 1 This comparative example provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: The immersion is performed once in step (2).

[0082] In the obtained supported iridium oxide catalyst, the loading of iridium oxide particles was 30 wt%, and the average particle size was 3 nm.

[0083] Comparative Example 2 This comparative example provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (3), the catalyst intermediate is first dried at 90°C for 11 h, and then heated to 450°C at 10°C / min and held for 4 h to obtain the supported iridium oxide catalyst. The loading of iridium oxide particles is 60 wt%, and the average particle size is 10 nm.

[0084] Comparative Example 3 This comparative example provides a supported iridium oxide catalyst, the preparation method of which differs from that of Example 1 in that: In step (2), the selected TiO2 support has an average particle size of 1 μm and a specific surface area of ​​5 m². 2 / g.

[0085] The preparation process parameters of the supported iridium oxide catalysts in Examples 1 to 9 and Comparative Examples 1 to 3 are shown in Table 1.

[0086] Table 1. Partial preparation process parameters of supported iridium oxide catalysts

[0087] Performance testing and results analysis 1. Supported iridium oxide catalyst (1) Load A precise mass m0 (accurate to 0.1 mg) of the obtained supported iridium oxide catalyst was weighed and placed in a polytetrafluoroethylene digestion vessel. An appropriate amount of aqua regia (HCl / HNO3 volume ratio = 3:1) was added, and digestion was carried out at 120℃ for 4 hours to ensure complete dissolution of the support and release of all metal elements into the solution. After cooling, the solution was brought to a fixed volume V. The mass concentration ρ of Ir in the solution was determined using inductively coupled plasma optical emission spectrometry (ICP-OES, following GB / T 223.71 or equivalent standard), and the mass fraction (loading) of iridium oxide was calculated.

[0088] (2) ECSA ECSA measurements were obtained using cyclic voltammetry (CV): 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 isopropanol, 100 mL water, and 0.31 g 5 wt% Nafion solution) was added to the centrifuge tube. The mixture was then ultrasonically dispersed in a cell disruptor for 20 min to obtain a homogeneous catalyst ink. 10 μL of the catalyst ink was then pipetted evenly onto a pre-polished and cleaned gold electrode (0.196 cm²). 2 The ink is spread evenly and without overflowing onto the electrode surface. After air drying to form a catalytic layer, the working electrode is obtained. A three-electrode system is formed using a Hydroflex hydrogen reference electrode (Gaskatel) as the reference electrode and a platinum wire coil as the counter electrode, placed in an electrolytic cell and connected to a CHI 600E (CHInstruments) electrochemical workstation. The electrolyte is an aqueous H2SO4 solution with a potential range of 1.2–1.6 vs RHE (0.544–0.944 vs Hg2SO4) and a scan rate of 50 mV / s. Before each test, saturated N2 is introduced for 60 min (in an oxygen-free environment), and the scan is performed at a rate of 100 mV / s until the CV curve stabilizes, allowing the catalyst to be fully activated and the re-desorption peak to stabilize. The electrochemical active area (ECSA) of the catalyst is calculated from the data of the last scan, thus obtaining the ECSA measurement value.

[0089] The theoretical ECSA value is calculated based on the catalyst's geometric surface area: Assuming the catalyst particles are of an ideal shape (e.g., spherical), the theoretical ECSA is calculated using the following formula: Theoretical ECSA = 4πr 2 Where: r is the radius of the catalyst particle, obtained by collecting the particle sizes of multiple particles (300) in the TEM, which is the average particle size; N is the number of particles in the catalyst. Assuming 1g of catalyst, N=1g / m (mass of one particle), m=ρV, where V is the volume of a single particle (V=4πr). 3 / 3), where ρ is the density of iridium oxide (taken as 11.6 g / cm³).

[0090] (3) Average particle size TEM tests were performed on the supported iridium oxide catalyst. The oxide support in the particles was analyzed by observing the TEM images and using ImageJ software. s and iridium oxide particles r a The particle sizes were statistically analyzed, with more than 100 statistical analyses performed. A normal distribution curve was then fitted to the statistical data to obtain the average particle size, and r was calculated. a / r s .

[0091] (4) Powder conductivity The PRCD3100 equipment of Xiamen Yuaneng Technology was used for testing. 1 g of the catalyst of each of the above embodiments and comparative examples was weighed with an electronic balance and added to the PEEK fixture. The fixture was placed in the test area, the test parameters were set, and a pressure change test was carried out. The pressure was 2 MPa to 30 MPa, the step was 2 MPa, and the pressure was held for 10 seconds. The test results were recorded.

[0092] 2. Water electrolysis hydrogen production membrane electrode The supported iridium oxide catalyst from the examples and comparative examples was mixed with perfluorosulfonic acid resin (Nafion D2020) and an aqueous alcohol solution (water and ethanol in a mass ratio of 3:1) at a mass ratio of 1:0.25:10 to prepare an anode catalyst slurry. The anode catalyst slurry was sprayed onto a transfer substrate and then dried in an oven 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 a transfer method, forming an anode catalyst layer with a total thickness of 10 μm on the anode side of the proton exchange membrane.

[0093] A cathode catalyst slurry was prepared by mixing a Pt / C catalyst (60% Pt loading), perfluorosulfonic acid resin, and a water-ethanol solution (water to ethanol mass ratio 3:1) at a mass ratio of 1:1:15. This slurry was then coated onto a transfer membrane using a slit-coating method and dried in an oven at 60°C to form a cathode catalyst layer on the transfer membrane. This cathode catalyst layer was then transferred onto a proton exchange membrane to obtain a water electrolysis hydrogen production membrane electrode.

[0094] (1) Polarization curve test The anode of the electrolytic cell is purged with 80℃ ultrapure water and connected to a Xinwei CT-8008-5V100A-NTFA power supply. Initially, a 4A / cm flow rate is applied. 2 Activation for 5 hours, followed by current scanning from 4 A / cm² in constant current mode. 2 Current density up to 0.01 A / cm 2 Each step lasts 2 minutes, and the current and voltage values ​​are recorded.

[0095] (2) Durability A square wave cyclic test was performed, with 1.45V held for 5 seconds and 2.00V held for 5 seconds, for 10,000 cycles. Afterwards, the polarization curve of the membrane electrode was measured at 3 A / cm. 2 The voltage attenuation was calculated based on the voltage value at the test point, and the test results are shown in Table 2.

[0096] Table 2 Performance test results of supported iridium oxide catalyst and water electrolysis hydrogen production membrane electrode

[0097] As can be seen from Tables 1 and 2, compared with Comparative Examples 1 to 3, the supported iridium oxide catalysts prepared in Examples 1 to 9 of this application meet the following requirements: iridium oxide particle loading ≥ 50 wt%, 0.4 ≤ ECSA measured value / ECSA theoretical value ≤ 0.8, and 0.004 ≤ r a / r s ≤0.15, and the ECSA measurement value of the supported iridium oxide catalyst is ≥40m. 2 / g, powder conductivity ≥0.6S / cm; corresponding to the prepared water electrolysis hydrogen production membrane electrode at 3A / cm 2 The battery voltage is ≤1.86V, and the voltage decay is ≤30mV after 10,000 acceleration durability tests, indicating that the supported iridium oxide catalyst in this application has high catalytic activity and long-term stability.

[0098] The performance test results of Example 1 and Comparative Example 1 show that the loading of iridium oxide particles in Comparative Example 1 is only 30 wt%, and the ECSA measurement value and powder conductivity of the catalyst are significantly reduced, failing to meet the requirement of 0.4 ≤ ECSA measurement value / ECSA theoretical value ≤ 0.8. The cell voltage of the membrane electrode and the voltage decay after the durability test are significantly increased. This indicates that by using multiple impregnations and adjusting the number of repeated impregnations, the loading, dispersion uniformity, and loading stability of iridium oxide particles in the catalyst can be effectively adjusted, thereby further improving the catalytic activity and long-term stability.

[0099] A comparison of the performance test results of Example 1 and Comparative Example 2 shows that the ECSA measured value of the catalyst in Comparative Example 2 does not meet the requirement of 0.4 ≤ ECSA measured value / ECSA theoretical value ≤ 0.8, and the powder voltage rate decreases significantly. Correspondingly, the cell voltage of the membrane electrode and the voltage decay after the durability test increase significantly. This may be due to the excessively rapid temperature rise leading to excessively rapid grain growth, resulting in large particle size and agglomeration, and uneven distribution on the support surface. This further illustrates that the average particle size of iridium oxide particles can be adjusted by regulating the temperature rise method, ultimately affecting the catalytic activity and long-term stability.

[0100] A comparison of the performance test results of Example 1 and Comparative Example 3 shows that the catalyst in Comparative Example 3 does not satisfy 0.4 ≤ ECSA measured value / ECSA theoretical value ≤ 0.8, and does not satisfy 0.004 ≤ r a / r s When the particle size ratio is ≤0.15, the powder conductivity of the catalyst decreases significantly, and the cell voltage of the corresponding membrane electrode and the voltage decay after the durability test increase significantly. This indicates that by controlling the particle size ratio of iridium oxide particles to the support within a suitable range, the ECSA measured value / ECSA theoretical value can be synergistically affected, thereby affecting the catalytic activity and stability of the catalyst.

[0101] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A supported iridium oxide catalyst, characterized in that, Includes an oxide support and iridium oxide particles supported on the oxide support; Wherein, the loading of the iridium oxide particles is ≥50wt%; The ratio of the ECSA measured value to the ECSA theoretical value of the supported iridium oxide catalyst satisfies the following condition: 0.4 ≤ ECSA measured value / ECSA theoretical value ≤ 0.8; The average particle size r of the iridium oxide particles a and the average particle size r of the oxide support s The ratio satisfies: 0.004 ≤ r a / r s ≤0.

15.

2. The supported iridium oxide catalyst according to claim 1, characterized in that, The average particle size r of the iridium oxide particles a The average particle size r of the oxide support is 2nm~5nm. s The range is 30nm to 500nm; And / or, the oxide support includes at least one of titanium oxide, zirconium oxide, tungsten oxide, tin dioxide, cerium oxide, niobium pentoxide, tantalum pentoxide, or antimony tin oxide.

3. The supported iridium oxide catalyst according to claim 1 or 2, characterized in that, The loading of the iridium oxide particles is 55wt%~70wt%; And / or, the ECSA measurement value of the supported iridium oxide catalyst is ≥40m. 2 / g.

4. A method for preparing a supported iridium oxide catalyst as described in any one of claims 1 to 3, characterized in that, Includes the following steps: According to the target loading, the iridium precursor is dissolved in a solvent to prepare a precursor solution; The oxide support is impregnated in the precursor solution, and after impregnation, it is separated and pre-dried in sequence. The impregnation is repeated multiple times, and finally dried and calcined to obtain the supported iridium oxide catalyst.

5. The preparation method according to claim 4, characterized in that, In the precursor solution, the concentration of the iridium precursor is 0.01 mol / L to 0.05 mol / L; And / or, the iridium precursor includes at least one of iridium trichloride, iridium chloroacetic acid, iridium nitrate, or iridium acetylacetonate.

6. The preparation method according to claim 4, characterized in that, The number of repeated impregnations is 2 to 6; And / or, the pre-drying temperature is 60℃~80℃, and the time is 30min~60min; And / or, the drying step is performed at a temperature of 80°C to 120°C for a time of 10 to 12 hours.

7. The preparation method according to claim 4, characterized in that, The mass ratio of the oxide support to the precursor solution is 1:(10~20). And / or, the impregnation step is carried out under stirring or ultrasonic conditions, at a temperature of 25°C to 40°C, for an impregnation time of 30 min to 60 min.

8. The preparation method according to claim 4, characterized in that, After the drying step, the process further includes: heating to 200°C to 250°C at a heating rate of 1°C / min to 3°C / min, and holding at that temperature for 0.5h to 1h.

9. The preparation method according to claim 4, characterized in that, The calcination step is performed at a temperature of 400℃~500℃ for 2h~4h. And / or, the calcination step includes: heating to 300°C ~ 350°C at a first heating rate, and then heating to 400°C ~ 500°C at a second heating rate; wherein the first heating rate is higher than the second heating rate, and the first heating rate and the second heating rate are each independently 1°C / min ~ 2°C / min.

10. A water electrolysis hydrogen production membrane electrode, characterized in that, It includes a proton exchange membrane and an anode catalyst layer disposed on one side of the proton exchange membrane, wherein the anode catalyst layer includes a supported iridium oxide catalyst as described in any one of claims 1 to 3.

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