A hydrogen fuel cell catalyst and its preparation method, and a hydrogen fuel cell

Abstract

This invention provides a hydrogen fuel cell catalyst, its preparation method, and a hydrogen fuel cell. The method includes: preparing an aqueous dispersion of a support material, an aqueous solution of a platinum-based precursor, an aqueous dispersion of a dopant precursor, and a dispersion of an additive; mixing and reacting the aqueous dispersion of the support material, the aqueous solution of the platinum-based precursor, and the aqueous dispersion of the dopant precursor, followed by adding the dispersion of the additive and continuing the reaction to obtain a catalyst slurry; spray-drying the catalyst slurry to obtain a powdered precursor; subjecting the powdered precursor to reduction heat treatment under a reducing atmosphere; subjecting the reduction-heat-treated powdered precursor to high-temperature densification treatment under an inert atmosphere; and washing and drying the product after high-temperature densification treatment to obtain the hydrogen fuel cell catalyst. The hydrogen fuel cell catalyst of this invention exhibits good catalytic activity and strong cycle stability.

Description

Technical Field

[0001] This invention relates to the field of fuel cell materials technology, specifically to a hydrogen fuel cell catalyst, its preparation method, and a hydrogen fuel cell. Background Technology

[0002] Hydrogen fuel cells, as a highly efficient and clean new energy conversion device, directly convert chemical energy into electrical energy through the electrochemical reaction of hydrogen and oxygen. They possess significant advantages such as high energy density, fast start-up speed, and zero emissions, and are widely used in various fields including new energy vehicles, stationary energy storage, and portable power supplies. They represent one of the core directions for the future development of the new energy industry. Catalysts, as a core component of hydrogen fuel cells, directly determine the cell's electrocatalytic performance, lifespan, and cost control. The oxygen reduction reaction (ORR), a key reaction at the cathode of hydrogen fuel cells, is a slow-moving kinetic process requiring a highly efficient catalyst to accelerate its reaction. Therefore, developing high-performance, long-life, and low-cost hydrogen fuel cell catalysts has become a key bottleneck in promoting their commercial application.

[0003] Currently, platinum-based catalysts are the most widely used in hydrogen fuel cells due to their excellent oxygen reduction catalytic activity, making them the best-performing catalyst system in existing technology. However, existing platinum-based catalysts still suffer from several technical drawbacks: Firstly, platinum nanoparticles are prone to agglomeration, leading to a reduction in catalytic active sites and active surface area, resulting in low platinum utilization. Secondly, during long-term operation of fuel cells, especially during start-up / shutdown, the local interface potential at the cathode can reach 1.6V, accelerating carbon support corrosion. The presence of platinum further exacerbates the carbon corrosion rate, causing rapid degradation of catalyst activity and insufficient stability. Furthermore, impurities such as CO in the hydrogen feedstock can poison platinum-based catalysts, further reducing catalytic activity and lifespan. These issues limit the practical application of existing platinum-based catalysts.

[0004] To address the aforementioned issues, existing technologies primarily focus on improvements in support modification, elemental doping, and process optimization. As a crucial component of platinum-based catalysts, the support must possess high specific surface area, good conductivity, and stability to achieve uniform dispersion of platinum nanoparticles and reduce agglomeration. Commonly used supports in existing technologies include conductive carbon black, carbon nanotubes, and graphene. Among these, carbon nanotubes exhibit excellent conductivity and a one-dimensional nanostructure, while graphene possesses an ultra-large specific surface area and good mechanical properties. Combining these two can achieve complementary performance. However, existing composite supports often lack precise modification or employ inappropriate modification methods, resulting in weak interactions between the support and the platinum-based active components, and persistent problems such as platinum particle agglomeration and insufficient corrosion resistance. Some technologies employ heteroatom doping to modify the support, introducing heteroatoms such as nitrogen, sulfur, phosphorus, and boron to regulate the electronic structure of the support and enhance catalytic activity. However, existing doping techniques often use single heteroatoms or random proportions of multiple heteroatoms, making it difficult to achieve synergistic effects between heteroatoms. Furthermore, the binding mode of the doping elements is difficult to control, resulting in limited improvement in catalytic performance. Additionally, these technologies are unsuitable for the acidic operating environment of proton exchange membrane fuel cells.

[0005] Regarding elemental doping, existing technologies mostly employ single doping or co-doping with two heteroatoms, such as sulfur-nitrogen co-doping or phosphorus-boron co-doping. However, single doping has limited effect on regulating catalyst performance, while co-doping with two heteroatoms is difficult to achieve a synergistic effect, failing to effectively optimize the electronic structure and catalytic active sites of platinum-based catalysts. Furthermore, the selection and ratio of existing doping precursors lack precise design, resulting in poor doping uniformity and difficulty in achieving uniform distribution of heteroatoms on the support surface, further affecting the stability of catalytic performance.

[0006] In terms of preparation processes, existing methods for preparing platinum-based catalysts mainly include chemical reduction, impregnation, and spray drying. Chemical reduction is simple, but results in uneven dispersion of platinum nanoparticles and low utilization. Impregnation easily leads to platinum particle agglomeration, reducing active sites. While spray drying can reduce particle agglomeration to some extent, existing processes lack precise control over spray drying parameters, reduction heat treatment, and high-temperature densification conditions, and do not adequately incorporate auxiliary agents, resulting in insufficient catalyst densification, conductivity, and stability. Furthermore, existing preparation processes exhibit poor synergy between support modification, platinum-based precursor preparation, doping, and auxiliary agent addition, failing to form a systematic process system and hindering comprehensive optimization of catalyst performance.

[0007] In summary, current platinum-based catalysts for hydrogen fuel cells and their preparation methods still suffer from low platinum utilization, insufficient catalytic activity, poor stability, and weak resistance to poisoning. Furthermore, their preparation processes are complex and costly, making it difficult to meet the demands of large-scale commercial applications of hydrogen fuel cells. Therefore, developing a hydrogen fuel cell catalyst and its preparation method that can overcome these technical shortcomings and achieve comprehensive optimization of catalytic activity, stability, and economics has significant practical importance and application value. Summary of the Invention

[0008] Based on the technical problems described above, the purpose of this invention is to overcome the defects of existing platinum-based catalysts for hydrogen fuel cells, such as low platinum utilization, insufficient catalytic activity, poor stability, and weak resistance to CO poisoning. It also addresses the problems of inaccurate support modification, poor heteroatom doping synergy, and insufficient process synergy in existing preparation processes, while simultaneously reducing catalyst costs. By controlling the support composite and modification, heteroatom doping ratio, additive formulation, and preparation process parameters, this invention provides a hydrogen fuel cell catalyst with high catalytic activity, strong stability, and excellent resistance to poisoning, as well as its preparation method. Furthermore, it provides a high-performance and cost-effective hydrogen fuel cell containing this catalyst, thereby promoting the commercial application of hydrogen fuel cells.

[0009] Specifically, according to one aspect of the present invention, a method for preparing a hydrogen fuel cell catalyst is provided, comprising the following steps:

[0010] (1) Prepare aqueous dispersions of carrier raw materials, aqueous solutions of platinum-based precursors, aqueous dispersions of dopant precursors, and dispersions of additives, respectively, wherein: the carrier raw material is a mixture of carbon nanotubes and graphene; the dopant precursor is a mixture of thiourea, ammonium dihydrogen phosphate, and boric acid; and the additive is a mixture of heteropolyacid salts, semiconductor nanoparticles, and polytetrafluoroethylene particles.

[0011] (2) Mix the aqueous dispersion of the carrier raw material, the aqueous solution of the platinum-based precursor and the aqueous dispersion of the doped element precursor and stir at 40-60℃ for 2-12 hours. Then add the dispersion of the additive and continue to react for 20-30 minutes to obtain the catalyst slurry.

[0012] (3) The catalyst slurry was spray-dried to obtain a powder precursor;

[0013] (4) The powder precursor is kept at 300-400℃ for 1-2 hours in a reducing atmosphere for reduction heat treatment;

[0014] (5) The powder precursor that has undergone reduction heat treatment is kept at 600-700℃ for 2-3 hours in an inert atmosphere to carry out high-temperature densification treatment;

[0015] (6) The product subjected to high-temperature densification treatment is washed and dried to obtain a hydrogen fuel cell catalyst, wherein:

[0016] Based on the total weight of the carrier raw material, platinum-based precursor, doped element precursor and additives as 100%, the carrier raw material accounts for 60-85%, the platinum-based precursor accounts for 5-20%, the doped element precursor accounts for 2-8%, and the additives account for 3-12%.

[0017] According to certain preferred embodiments of the present invention, the carrier material is a mixture of carbon nanotubes and graphene in a weight ratio of 5:1 to 2:1.

[0018] According to certain preferred embodiments of the present invention, based on the total weight of the doped element precursors as 100%, thiourea accounts for 40-60%, ammonium dihydrogen phosphate accounts for 20-40%, and boric acid accounts for 10%-20%.

[0019] According to certain preferred embodiments of the present invention, based on the total weight of the additives as 100%, the heteropolyacid salt accounts for 70-80%, the semiconductor nanoparticles account for 10-20%, and the polytetrafluoroethylene particles account for 10-20%.

[0020] According to certain preferred embodiments of the present invention, the aqueous solution of the platinum-based precursor is prepared by the following steps:

[0021] Dissolve platinum salts and transition metal salts in water, add a complexing agent and adjust the pH to 3.0-4.0, wherein the total weight of platinum salts and transition metal salts is 100%, platinum salts account for 40-70% and transition metal salts account for 30-60%.

[0022] According to certain preferred embodiments of the present invention, the platinum salt is platinum nitrate, the transition metal salt is cobalt chloride, and the complexing agent is citric acid.

[0023] According to certain preferred embodiments of the present invention, the total concentration of all metal ions in the aqueous solution of the platinum-based precursor is 2.5-15% by weight.

[0024] According to certain preferred embodiments of the invention, the complexing agent is 15-25% of the total weight of all metal salts.

[0025] According to certain preferred embodiments of the present invention, the heteropolyacid salt is selected from one or more of cesium hydrogen phosphomolybdate, cesium hydrogen phosphotungstate, and cesium molybdate silylate.

[0026] According to certain preferred embodiments of the present invention, the aqueous dispersion of the carrier material is a mixture of the carrier material and deionized water in a weight ratio of 1:10 to 1:5.

[0027] According to certain preferred embodiments of the present invention, the aqueous dispersion of the carrier raw material is prepared by the following steps:

[0028] (a) Add the carrier raw material to the reaction vessel, add a mixture of concentrated nitric acid and concentrated sulfuric acid, stir and react at 60-80℃ for 2-4 hours, wash until neutral and then centrifuge to obtain the oxidized carrier;

[0029] (b) The oxidized modified support is mixed with a nitrogen source, an aqueous solution of ethanol is added, the mixture is ultrasonically dispersed and dried, and the dried product is calcined at 700-800℃ for 2-3 hours under an inert atmosphere, and then ground to obtain a nitrogen-doped modified support.

[0030] (c) Disperse the nitrogen-doped modified support in deionized water.

[0031] According to certain preferred embodiments of the present invention, the nitrogen source is selected from one or more of melamine, urea and ethylenediamine.

[0032] According to certain preferred embodiments of the present invention, in step (b), the weight ratio of the oxidative modified support to the nitrogen source is 1:5 to 1:10.

[0033] According to certain preferred embodiments of the present invention, the semiconductor nanoparticles are P-type semiconductor nanoparticles or N-type semiconductor nanoparticles.

[0034] According to certain preferred embodiments of the present invention, the semiconductor nanoparticles are selected from one or more of copper oxide nanoparticles, nickel oxide nanoparticles, titanium dioxide nanoparticles, and zinc oxide nanoparticles.

[0035] According to certain preferred embodiments of the present invention, the average particle size of the semiconductor nanoparticles is in the range of 10-50 nm.

[0036] According to certain preferred embodiments of the present invention, the average particle size of the polytetrafluoroethylene particles is in the range of 200 nm to 5 μm.

[0037] According to certain preferred embodiments of the present invention, the dopant precursor accounts for 0.2-3% by weight of the aqueous dispersion of the dopant precursor.

[0038] According to certain preferred embodiments of the present invention, the total weight of the heteropolyacid salt, semiconductor nanoparticles and polytetrafluoroethylene particles accounts for 5-10% by weight of the dispersion of the adjuvant.

[0039] According to certain preferred embodiments of the present invention, the dispersion medium of the dispersion of the additive is a mixture of isopropanol and water in a volume ratio of 3:2 to 4:1.

[0040] According to certain preferred embodiments of the present invention, the aqueous dispersion of the dopant precursor is prepared by dissolving thiourea, ammonium dihydrogen phosphate and boric acid in deionized water.

[0041] According to certain preferred embodiments of the present invention, in step (3), the inlet temperature of the spray dryer is 180-200°C and the outlet temperature is 80-100°C.

[0042] According to certain preferred embodiments of the present invention, in step (4), the reducing atmosphere is a mixture of hydrogen and nitrogen in a volume ratio of 1:20 to 1:5 and a gas flow rate of 50-80 mL / min.

[0043] According to certain preferred embodiments of the present invention, in step (5), the inert atmosphere is nitrogen.

[0044] According to another aspect of the present invention, a hydrogen fuel cell catalyst is provided, which is prepared according to the method described above.

[0045] According to certain preferred embodiments of the present invention, the oxygen reduction reaction half-wave potential of the hydrogen fuel cell catalyst is greater than or equal to 0.88 V vs RHE, and the specific active area is 60-80 m². 2 / g.

[0046] According to certain preferred embodiments of the present invention, the electrochemical active area retention rate of the hydrogen fuel cell catalyst is greater than or equal to 85% after 10,000 cycles.

[0047] According to certain preferred embodiments of the present invention, the hydrogen fuel cell catalyst retains a catalytic activity of greater than or equal to 90% after operating for 200 hours in an atmosphere containing 100 ppm CO.

[0048] According to another aspect of the present invention, a hydrogen fuel cell is provided, the hydrogen fuel cell comprising a membrane electrode assembly, the membrane electrode assembly comprising an anode catalyst layer, a cathode catalyst layer and a proton exchange membrane, wherein the anode catalyst layer and / or the cathode catalyst layer comprises the hydrogen fuel cell catalyst described above.

[0049] According to certain preferred embodiments of the present invention, the catalyst loading in the anode catalyst layer is 0.1-0.2 mg / cm³. 2 Furthermore, the catalyst loading in the cathode catalyst layer is 0.15-0.25 mg / cm³. 2 .

[0050] According to certain preferred embodiments of the present invention, the membrane electrode is prepared by mixing the catalyst with an ionomer solution to form a slurry, coating it onto the surface of a proton exchange membrane or a gas diffusion layer, and then hot-pressing it.

[0051] According to certain preferred embodiments of the present invention, the hydrogen fuel cell is a proton exchange membrane fuel cell or an alkaline fuel cell.

[0052] Compared with existing technologies, the beneficial effects of this invention are as follows: First, the catalytic performance is significantly improved. By precisely proportioning carbon nanotubes and graphene composite supports and modifying them with nitrogen doping, combined with a specific ratio of sulfur, phosphorus, and boron multi-heteroatom synergistic doping, platinum particle agglomeration is effectively suppressed, the active specific area is increased, and the oxygen reduction reaction half-wave potential is greater than or equal to 0.88V vs RHE, resulting in catalytic activity exceeding that of existing catalysts. Second, the stability and anti-poisoning ability are greatly optimized. The rational combination of heteropolyacid salts, semiconductor nanoparticles, and polytetrafluoroethylene particles, combined with reduction and densification processes, enhances the catalyst's resistance to carbon corrosion. After 10,000 cycles, the electrochemical active area retention rate is greater than or equal to 85%, and the resistance to CO poisoning is excellent. After 200 hours of operation in an atmosphere containing 100ppm CO, the catalytic activity retention rate is greater than or equal to 90%. Third, the cost is reduced and the economic efficiency is improved. By optimizing the platinum-based precursor ratio and preparation process, the platinum utilization rate is improved, the catalyst loading is reduced, and the preparation process is simplified, achieving synergistic optimization of the process and balancing performance and cost. Fourth, it has strong adaptability. The hydrogen fuel cell catalyst according to the present invention can be applied to proton exchange membranes, alkaline hydrogen fuel cells, etc., effectively improving the overall performance of the battery. Attached Figure Description

[0053] The accompanying drawings are provided in this specification to more clearly explain the technical solutions of the present invention; however, the art is not limited thereto.

[0054] Figure 1 A flowchart illustrating the preparation process of a hydrogen fuel cell catalyst according to the present invention is shown.

[0055] Figure 2 A transmission electron microscope (TEM) image of the hydrogen fuel cell catalyst 1 prepared in Example 1 is shown. Detailed Implementation

[0056] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It will be understood that other embodiments may be implemented without departing from the scope or spirit of the invention. Therefore, the following detailed description is non-limiting.

[0057] Unless otherwise specified, all figures used in this specification to represent characteristic dimensions, quantities, and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters listed in the foregoing specification are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired properties using the teachings disclosed herein.

[0058] As mentioned above, existing platinum-based catalysts for hydrogen fuel cells suffer from numerous defects and inadequate preparation processes. For example, platinum particles are prone to agglomeration, leading to low utilization, limited catalytic activity, and a low oxygen reduction half-wave potential; they also exhibit poor stability, weak resistance to carbon corrosion and CO poisoning, and short service life; and the preparation process costs are relatively high, making it difficult to meet the performance and cost requirements for large-scale commercial applications of hydrogen fuel cells. This invention aims to solve one or more of the above-mentioned technical problems.

[0059] Specifically, according to one aspect of the present invention, a method for preparing a hydrogen fuel cell catalyst is provided, the method comprising the following steps:

[0060] (1) Prepare aqueous dispersions of carrier raw materials, aqueous solutions of platinum-based precursors, aqueous dispersions of dopant precursors, and dispersions of additives, respectively, wherein: the carrier raw material is a mixture of carbon nanotubes and graphene; the dopant precursor is a mixture of thiourea, ammonium dihydrogen phosphate, and boric acid; and the additive is a mixture of heteropolyacid salts, semiconductor nanoparticles, and polytetrafluoroethylene particles.

[0061] (2) Mix the aqueous dispersion of the carrier raw material, the aqueous solution of the platinum-based precursor and the aqueous dispersion of the doped element precursor and stir at 40-60℃ for 2-12 hours. Then add the dispersion of the additive and continue to react for 20-30 minutes to obtain the catalyst slurry.

[0062] (3) The catalyst slurry was spray-dried to obtain a powder precursor;

[0063] (4) The powder precursor is kept at 300-400℃ for 1-2 hours in a reducing atmosphere for reduction heat treatment;

[0064] (5) The powder precursor that has undergone reduction heat treatment is kept at 600-700℃ for 2-3 hours in an inert atmosphere to carry out high-temperature densification treatment;

[0065] (6) The product subjected to high-temperature densification treatment is washed and dried to obtain a hydrogen fuel cell catalyst, wherein:

[0066] Based on the total weight of the carrier raw material, platinum-based precursor, doped element precursor and additives as 100%, the carrier raw material accounts for 60-85%, the platinum-based precursor accounts for 5-20%, the doped element precursor accounts for 2-8%, and the additives account for 3-12%.

[0067] Specifically, this invention addresses the technical shortcomings of existing platinum-based catalysts for hydrogen fuel cells, such as insufficient catalytic activity, poor cycle stability, and weak resistance to CO poisoning. It provides a method for preparing a hydrogen fuel cell catalyst. This method achieves multiphase synergistic effects among the support, platinum-based active components, dopant elements, and additives by designing the support composition, doping system, and additive formulation, as well as controlling process parameters such as reaction temperature and heat treatment conditions. This fundamentally solves the pain points of existing technologies. Furthermore, this invention also provides a hydrogen fuel cell catalyst prepared by this method, and a hydrogen fuel cell containing this catalyst.

[0068] Figure 1 A flowchart illustrating the preparation process of a hydrogen fuel cell catalyst according to the present invention is shown, specifically including:

[0069] (1) Prepare aqueous dispersions of carrier raw materials, aqueous solutions of platinum-based precursors, aqueous dispersions of doped element precursors, and dispersions of additives.

[0070] (2) Mix and react the aqueous dispersion of the carrier raw material, the aqueous solution of the platinum-based precursor and the aqueous dispersion of the doped element precursor, then add the dispersion of the additive and continue the reaction to obtain the catalyst slurry.

[0071] (3) The catalyst slurry was spray-dried to obtain a powder precursor;

[0072] (4) The powder precursor is subjected to reduction heat treatment in a reducing atmosphere;

[0073] (5) The powder precursor that has undergone reduction heat treatment is subjected to high-temperature densification treatment under an inert atmosphere;

[0074] (6) The product that has undergone high-temperature densification treatment is washed and dried to obtain a hydrogen fuel cell catalyst.

[0075] The technical solution of the present invention will be described in detail below.

[0076] I. Preparation methods of hydrogen fuel cell catalysts

[0077] (1) Preparation of each dispersion / aqueous solution

[0078] In step (1), an aqueous dispersion of the carrier raw material, an aqueous solution of the platinum-based precursor, an aqueous dispersion of the doped element precursor, and a dispersion of the additive are prepared respectively.

[0079] Regarding the preparation of aqueous dispersions of carrier raw materials, the carrier, as the loading substrate for platinum-based active components, must simultaneously possess high specific surface area, excellent conductivity, good structural stability, and strong interaction with the active components. This invention uses a mixture of carbon nanotubes and graphene as the carrier raw material. Carbon nanotubes, with their one-dimensional nanotube structure, exhibit excellent conductivity and high mechanical strength, providing a rapid electron transport channel for electrochemical reactions. Graphene, with its two-dimensional sheet structure and ultra-large specific surface area, effectively disperses platinum-based nanoparticles, preventing their aggregation. The combination of these two materials achieves complementary performance, constructing a three-dimensional hierarchical porous carrier substrate that provides ample active sites for catalytic reactions.

[0080] There are no particular limitations on the specific types of carbon nanotubes and graphene that can be used in this invention; selection can be made from carbon nanotube and graphene materials commonly used in hydrogen fuel cell catalysts.

[0081] This invention preferably uses carbon nanotubes and graphene in a weight ratio of 5:1 to 2:1 as the carrier material. Within this range, carbon nanotubes can effectively support graphene sheets, preventing them from stacking and agglomerating. Simultaneously, the graphene sheets can uniformly encapsulate the carbon nanotubes, forming a continuous conductive network. If the proportion of carbon nanotubes is too high, the carrier surface area is insufficient, and platinum-based particles are prone to agglomeration. If the proportion of graphene is too high, sheet stacking is likely to occur, leading to blockage of carrier pores and a decrease in electron transport efficiency.

[0082] To further enhance the interaction between the carrier and the platinum-based active components and improve the corrosion resistance of the carrier, according to certain preferred embodiments of the present invention, the carrier raw material undergoes a two-step modification process of oxidation modification and nitrogen doping modification, rather than directly dispersing the carrier raw material in water. The specific modification and dispersion steps are as follows: First, the carrier raw material is stirred and reacted with a mixture of concentrated nitric acid and concentrated sulfuric acid at 60-80°C for 2-4 hours. Concentrated nitric acid is a strong oxidant, and concentrated sulfuric acid is a dehydrating agent; their synergistic effect introduces oxygen-containing functional groups such as carboxyl and hydroxyl groups onto the carrier surface, increasing the hydrophilicity and active sites of the carrier, providing binding sites for subsequent nitrogen doping and platinum-based particle loading. After the reaction is complete, the carrier is washed until neutral and centrifuged to obtain the oxidized carrier. Then, the oxidized carrier is mixed with a nitrogen source at a weight ratio of 1:5-1:10, an aqueous solution of ethanol is added, and the mixture is ultrasonically dispersed and dried. Finally, it is calcined at 700-800°C for 2-3 hours under an inert atmosphere to achieve nitrogen doping modification. The nitrogen source is preferably one or more of melamine, urea, and ethylenediamine. This type of nitrogen source has a high nitrogen content and easily decomposes into nitrogen-containing free radicals during calcination. These free radicals react with oxygen-containing functional groups on the support surface to form doped structures such as pyridine nitrogen, pyrrole nitrogen, and graphitic nitrogen, thereby regulating the electronic structure of the support and enhancing the oxygen reduction catalytic activity of the platinum-based catalyst. The preferred weight ratio of the oxidized modified support to the nitrogen source is 1:5 to 1:10. Finally, the nitrogen-doped modified support is mixed with deionized water at a weight ratio of 1:10 to 1:5 and ultrasonically dispersed to obtain an aqueous dispersion of the support raw material.

[0083] Regarding the preparation of aqueous solutions of platinum-based precursors, where the platinum-based precursors are the source of the active components of the catalyst, some preferred embodiments of this invention combine platinum salts with transition metal salts instead of using a single platinum salt. By doping with transition metals, the electronic structure of platinum is controlled, reducing the amount of platinum used and improving its utilization rate. Specifically, the preparation method involves dissolving the platinum salt and the transition metal salt in water, adding a complexing agent, and adjusting the pH to 3.0-4.0. Platinum nitrate is preferred as the platinum salt, cobalt chloride as the transition metal salt, and citric acid as the complexing agent. Platinum nitrate has good water solubility, a moderate decomposition temperature, and can form uniformly sized platinum nanoparticles after reduction. Cobalt ions in cobalt chloride can form a platinum-cobalt alloy with platinum ions, controlling the d-band center of platinum, lowering the energy barrier of the oxygen reduction reaction, and enhancing catalytic activity. Citric acid is a multidentate complexing agent that can form stable complexes with platinum and cobalt ions, preventing premature precipitation of metal ions in subsequent reactions and ensuring uniform dispersion of metal ions.

[0084] According to certain preferred embodiments of the present invention, based on the total weight of platinum salt and transition metal salt (100%), the platinum salt accounts for 40-70%, and the transition metal salt accounts for 30-60%, which may form a homogeneous platinum-cobalt alloy phase. The complexing agent accounts for 15-25% of the total weight of all metal salts. Simultaneously, the pH of the solution is adjusted to 3.0-4.0; this acidic environment ensures the stability of the complex and prevents the hydrolysis and precipitation of metal ions. The final aqueous solution of the platinum-based precursor has a total concentration of all metal ions of 2.5-15% by weight.

[0085] Regarding the preparation of aqueous dispersions of doped element precursors, according to certain preferred embodiments of the present invention, sulfur, phosphorus, and boron heteroatoms are further introduced for co-doping. Through the synergistic effect of multiple heteroatoms, the electronic structure of the platinum-based catalyst is further optimized, enhancing its catalytic activity and resistance to poisoning. The doped element precursor is a mixture of thiourea (sulfur source), ammonium dihydrogen phosphate (phosphorus source), and boric acid (boron source). This type of precursor has good water solubility, a moderate decomposition temperature, and can uniformly release heteroatoms in subsequent reactions, forming a stable bond with platinum-based particles and the support.

[0086] Preferably, based on the total weight of the doped element precursors (100%), thiourea accounts for 40-60%, ammonium dihydrogen phosphate for 20-40%, and boric acid for 10-20%. This ratio is the optimal ratio for sulfur, phosphorus, and boron co-doping. Sulfur atoms can form Pt-S bonds with platinum, reducing the adsorption energy of CO at platinum sites and enhancing resistance to CO poisoning. Phosphorus atoms can regulate the electronic structure of platinum, enhancing oxygen reduction catalytic activity. Boron atoms can enhance the interaction between the support and platinum-based particles, preventing platinum particle detachment. The synergistic effect of these three heteroatoms in this ratio can simultaneously improve catalytic activity, stability, and resistance to poisoning.

[0087] The aqueous dispersion of the dopant precursor is prepared by directly dissolving the three precursors mentioned above in deionized water. Preferably, the dopant precursor accounts for 0.2-3% by weight of the dispersion. This concentration ensures that the dopant is uniformly dispersed in subsequent reactions and fully combined with the platinum-based particles and the support.

[0088] Regarding the preparation of the dispersion of the additive, according to the technical solution of the present invention, the additive is an important component for improving the overall performance of the catalyst. The present invention uses a mixture of heteropolyacid salts, semiconductor nanoparticles, and polytetrafluoroethylene particles as the additive. The three work synergistically to improve the catalyst performance in terms of catalytic activity, anti-poisoning ability, and structural stability. Preferably, the heteropolyacid salt is one or more of cesium hydrogen phosphomolybdate, cesium hydrogen phosphotungstate, and cesium molybdate silylate. These heteropolyacid salts have strong redox properties and proton conductivity, and can act as a co-catalyst to accelerate the oxygen reduction reaction while inhibiting the growth of platinum particles. Preferably, the semiconductor nanoparticles are p-type or n-type, preferably one or more of copper oxide nanoparticles, nickel oxide nanoparticles, titanium dioxide nanoparticles, and zinc oxide nanoparticles, with an average particle size in the range of 10-50 nm. The semiconductor nanoparticles can form heterojunctions with platinum-based particles, reducing CO adsorption at platinum sites and improving anti-CO poisoning ability. The particle size of the semiconductor nanoparticles in the range of 10-50 nm ensures their uniform dispersion in the catalyst. Preferably, the average particle size of the polytetrafluoroethylene particles is in the range of 200 nm to 5 μm. They have excellent hydrophobicity and chemical stability, and can form a hydrophobic layer on the catalyst surface to prevent water generated during the reaction from clogging the active sites. At the same time, they enhance the structural stability of the catalyst and improve its corrosion resistance.

[0089] According to certain preferred embodiments of the present invention, based on the total weight of the additives (100%), heteropolyacid salts account for 70-80%, semiconductor nanoparticles account for 10-20%, and polytetrafluoroethylene particles account for 10-20%. Under this ratio, the synergistic effect of the three is optimal, with heteropolyacid salts being the main additive and having the highest proportion, ensuring the improvement of catalytic activity; semiconductor nanoparticles and polytetrafluoroethylene particles are auxiliary additives with a moderate proportion, achieving both anti-poisoning and structural stability effects without covering platinum-based active sites.

[0090] According to certain preferred embodiments of the present invention, the dispersion of the additive uses a mixture of isopropanol and water in a volume ratio of 3:2 to 4:1 as the dispersion medium. Isopropanol is an organic solvent with good wetting properties, which can ensure the uniform dispersion of the additive. Water is the dispersed phase. The mixing of the two in this ratio can balance the dispersibility of the additive and its compatibility with subsequent aqueous slurries. Preferably, the total weight of the heteropolyacid salt, semiconductor nanoparticles, and polytetrafluoroethylene particles accounts for 5-10% by weight of the additive dispersion. This concentration can ensure that the additive is uniformly dispersed in the catalyst during subsequent reactions.

[0091] (2) Preparation of catalyst slurry by mixed reaction

[0092] Step (2) is the composite reaction step of each component. In this step, the aqueous dispersion of the carrier raw material, the aqueous solution of the platinum-based precursor, and the aqueous dispersion of the dopant precursor are first mixed and reacted, and then the dispersion of the additive is added to continue the reaction. Allowing the carrier raw material, platinum-based precursor, and dopant precursor to react fully first can achieve uniform loading of platinum-based metal ions on the carrier surface. At the same time, the dopant forms a preliminary bond with the carrier and platinum-based ions. If the additive is added first, the additive will preferentially adsorb on the carrier surface and occupy the active sites, resulting in uneven loading of platinum-based ions and ineffective binding of the dopant.

[0093] The specific reaction conditions are as follows: After mixing the three dispersions, stir and react at 40-60℃ for 2-12 hours. 40-60℃ is a mild reaction temperature, ensuring that platinum-based metal ions are slowly and uniformly adsorbed onto the active sites on the support surface, while the heteroatoms of the dopant elements gradually coordinate with the support and platinum-based ions. A reaction time of 2-12 hours ensures sufficient bonding of the components. If the temperature is too high, the reaction rate is too fast, and platinum-based ions easily aggregate locally on the support surface, forming large particles; if the temperature is too low, the reaction rate is too slow, resulting in low production efficiency. After the main reaction is complete, add the dispersion of the additives and continue the reaction for 20-30 minutes. A short stirring time ensures that the additives are uniformly dispersed in the slurry, forming a loose bond with the support loaded with platinum-based and dopant elements, thus maximizing the effect of the additives without disrupting the already formed platinum-support-doped element composite structure. If the reaction time is too long, the additives are easily over-adsorbed, covering the active sites; if too short, the additives are not evenly dispersed.

[0094] (3) Spray drying to prepare powder precursors

[0095] This invention uses spray drying to convert catalyst slurry into powder precursor. Compared with existing methods such as oven drying and freeze drying, spray drying can dry the slurry into spherical powder with uniform particle size in an instant, avoiding particle agglomeration caused by the slow rate of oven drying. Meanwhile, freeze drying is too expensive and not suitable for industrial production.

[0096] The present invention preferably uses an inlet temperature of 180-200℃ and an outlet temperature of 80-100℃ for spray drying. The inlet temperature is the temperature of hot air, which can ensure that the droplets of the slurry are heated and dried quickly. The outlet temperature is the temperature of the exhaust gas after drying, which reflects the degree of drying of the powder. This temperature range can ensure that the powder precursor is fully dried and will not cause excessive decomposition of the organic components in the precursor.

[0097] (4) Reduction heat treatment

[0098] The purpose of reduction heat treatment is to reduce metal ions in the platinum-based precursor into nanoscale platinum-cobalt alloy particles, while simultaneously allowing the heteroatoms of the dopant elements to form a stable bond with the support and the platinum-based alloy. According to the technical solution of this invention, the process involves holding at 300-400℃ for 1-2 hours in a reducing atmosphere. Preferably, the reducing atmosphere is a mixture of hydrogen and nitrogen in a volume ratio of 1:20 to 1:5, with a gas flow rate of 50-80 mL / min. The reduction temperature of 300-400℃ for 1-2 hours is the optimal temperature for platinum-cobalt alloy particle formation, yielding ultrafine platinum-cobalt alloy particles with a diameter of 2-5 nm, exhibiting uniform particle size and high activity.

[0099] (5) High-temperature densification treatment

[0100] After reduction heat treatment, the structure of the powder precursor is relatively loose, and the bonding strength between the platinum-based alloy particles and the support is insufficient. During long-term operation of the fuel cell, problems such as platinum particle shedding and support structure damage are likely to occur. Therefore, this invention adds a high-temperature densification treatment step after reduction heat treatment, which is an important step to improve the stability of the catalyst.

[0101] The specific processing conditions are as follows: Hold at 600-700℃ for 2-3 hours under an inert atmosphere. Nitrogen is preferred as the inert atmosphere to prevent catalyst oxidation at high temperatures. The high temperature of 600-700℃ allows for stronger metal-support interactions between the platinum alloy particles and the support. Simultaneously, the carbon skeleton of the support undergoes slight graphitization, improving the structural stability and corrosion resistance of the support, and achieving catalyst densification. If the temperature is too high, excessive graphitization of the support occurs, resulting in a significant decrease in specific surface area, easy agglomeration of platinum particles, and removal of heteroatoms from the catalyst, thus losing the doping effect. If the temperature is too low, the densification effect is poor, the bonding strength between the platinum particles and the support is insufficient, and they are still prone to detachment. Holding at this temperature for 2-3 hours ensures the complete densification reaction and the formation of a stable catalyst structure.

[0102] (6) Washing and drying to prepare the finished catalyst

[0103] After high-temperature densification, a small amount of inorganic salts, unreacted precursors, and other impurities remain in the product. These impurities adhere to the catalyst surface, blocking active sites and reducing catalytic activity. Therefore, the product needs to be washed, preferably multiple times with deionized water, which can effectively remove water-soluble impurities. After washing, drying is performed. The preferred drying temperature is 80-100℃. A gentle drying temperature ensures thorough drying of the catalyst without damaging the already formed stable structure, ultimately yielding the hydrogen fuel cell catalyst of this invention.

[0104] According to the technical solution of this invention, based on the total weight of the support raw material, platinum-based precursor, doped element precursor, and additives as 100%, the support raw material accounts for 60-85%, the platinum-based precursor accounts for 5-20%, the doped element precursor accounts for 2-8%, and the additives account for 3-12%. The support raw material is the main component, accounting for the highest proportion, providing a sufficient loading substrate for the active components. If the proportion is too low, platinum-based particles cannot be effectively loaded, and they are prone to agglomeration; if the proportion is too high, the content of active components and additives is insufficient, resulting in low catalytic activity. The platinum-based precursor is the core active component, accounting for 5-20%, which can ensure the catalytic activity of the catalyst. If the proportion is too high, the cost increases significantly, and platinum particles are prone to agglomeration; if the proportion is too low, there are insufficient active sites, resulting in poor catalytic activity. The doped element precursor accounts for 2-8%. A small amount of dopant can achieve effective control of the electronic structure; if the proportion is too high, it easily covers the active sites; if the proportion is too low, the synergistic effect is not obvious. Additives, accounting for 3-12%, can effectively improve the stability and anti-poisoning ability of catalysts. If the proportion is too high, it will block the active sites; if the proportion is too low, the improvement effect will be limited.

[0105] II. Hydrogen Fuel Cell Catalysts

[0106] In another aspect of the invention, a hydrogen fuel cell catalyst prepared by the above-described method is provided. This catalyst is a quaternary composite system formed by a support, a platinum-cobalt active component, sulfur / phosphorus / boron heteroatoms, heteropolyacid salts-semiconductor nanoparticles, and a polytetrafluoroethylene (PTFE) additive. Each component forms a stable three-dimensional structure. The platinum-cobalt ultrafine nanoparticles are supported on the surface of a nitrogen-doped carbon nanotube-graphene composite support. Sulfur / phosphorus / boron heteroatoms are distributed at the interface between the support and the platinum-cobalt alloy particles. The additive is attached to the surface of the composite structure, forming a catalytic system characterized by "sufficient active sites, rapid electron transport, structural stability, and strong resistance to poisoning."

[0107] The hydrogen fuel cell catalyst of this invention possesses excellent comprehensive performance, with all performance indicators reaching a relatively high level in the industry. Specific performance parameters are as follows:

[0108] 1. The half-wave potential of the oxygen reduction reaction is greater than or equal to 0.88 V vs RHE, and the specific active area is 60-80 m². 2 / g. The catalyst half-wave potential of this invention is higher than that of existing platinum-based catalysts (the half-wave potential of existing catalysts is generally ≤0.85 V vsRHE);

[0109] 2. After 10,000 cycles, the electrochemical active area retention rate is greater than or equal to 85%. The catalyst of this invention can still maintain more than 85% of the electrochemical active area after 10,000 accelerated cycle aging tests, which is much higher than that of existing catalysts (the retention rate of existing catalysts is generally ≤70%). This is due to the stable structure formed by high-temperature densification treatment, as well as the inhibition of platinum particle shedding and support corrosion by the additives;

[0110] 3. After operating for 200 hours in an atmosphere containing 100 ppm CO, the catalytic activity retention rate is greater than or equal to 90%. The catalyst of this invention significantly reduces the adsorption energy of CO at platinum sites through the Pt-S bond formed between sulfur atoms and platinum, and the heterojunction formed between semiconductor nanoparticles and platinum-based particles, preventing CO from occupying the active sites. Therefore, it can still maintain more than 90% of the catalytic activity after operating for 200 hours in an atmosphere containing 100 ppm CO, and its resistance to CO poisoning is significantly better than that of the prior art.

[0111] The catalyst of this invention exhibits good reproducibility, with fluctuations in various performance indicators within ±2% in different preparation batches, making it suitable for large-scale industrial production.

[0112] III. Hydrogen Fuel Cells

[0113] In another aspect of the invention, a hydrogen fuel cell is provided, comprising a membrane electrode assembly (MEA) consisting of an anode catalyst layer, a cathode catalyst layer, and a proton exchange membrane. The anode catalyst layer and / or the cathode catalyst layer contains the hydrogen fuel cell catalyst of the present invention described above. The oxygen reduction reaction occurs at the cathode of a hydrogen fuel cell, a slow kinetic process that is crucial to the cell's performance. Therefore, applying the catalyst of the present invention to the cathode catalyst layer can maximize the cell's catalytic efficiency and stability. Simultaneously, applying it to the anode catalyst layer can effectively suppress CO poisoning at the anode, further enhancing the overall performance of the cell.

[0114] Preferably, the catalyst loading in the anode catalyst layer is 0.1-0.2 mg / cm³. 2 The catalyst loading in the cathode catalyst layer is 0.15-0.25 mg / cm³. 2 This loading is lower than the catalyst loading of existing hydrogen fuel cells (the cathode loading in existing technology is generally ≥0.4 mg / cm³). 2 This is due to the high catalytic activity of the catalyst of this invention. The low loading can significantly reduce the production cost of the battery without causing a decline in battery performance.

[0115] The membrane electrode is prepared by a conventional coating-hot pressing method: the catalyst of the present invention is mixed with an ionomer solution to form a slurry, the slurry is coated on the surface of a proton exchange membrane or a gas diffusion layer, and then hot-pressed. The preferred hot-pressing conditions are 130-150°C, 2-4 MPa, and 3-5 minutes. These conditions can ensure a tight bond between the catalyst layer and the proton exchange membrane / gas diffusion layer, forming a good interfacial contact and improving the electron and proton transport efficiency.

[0116] The hydrogen fuel cell according to the present invention is preferably a proton exchange membrane fuel cell or an alkaline fuel cell. The catalyst of the present invention maintains excellent catalytic activity, stability and anti-poisoning ability in both acidic and alkaline environments, and is compatible with both mainstream hydrogen fuel cell systems. Compared with existing catalysts that are only applicable to a single system, it has stronger adaptability and a wider range of applications.

[0117] The hydrogen fuel cell catalyst and its preparation method of this invention, as well as the hydrogen fuel cell itself, achieve multiple optimizations in performance, cost, and adaptability compared to existing technologies. Specifically: First, through triple electronic regulation of composite support nitrogen doping, multi-heteroatom co-doping, and platinum-cobalt, catalytic performance is significantly improved, with oxygen reduction half-wave potential and active specific area both superior to existing platinum-based catalysts, thus increasing battery output power. Second, by combining high-temperature densification treatment and compounded additives, catalyst stability and resistance to CO poisoning are significantly enhanced, solving the pain points of easy degradation and poisoning in existing products and extending battery life. Third, by reducing platinum consumption at the raw material end and simplifying the industrial process at the process end, production costs are reduced by more than 40%, improving economic efficiency. Fourth, the catalyst is adaptable to acidic and alkaline environments and can be applied to two mainstream fuel cells without the need for additional CO removal devices, making its application range wide.

[0118] The present invention will now be described in more detail with reference to embodiments. It should be noted that these descriptions and embodiments are intended to facilitate understanding of the present invention and are not intended to limit the invention.

[0119] Example

[0120] In this invention, unless otherwise specified, all reagents used are commercially available products and are used directly without further purification. Furthermore, "%" refers to "weight %" and "parts" refers to "parts by weight".

[0121] Table 1 below lists specific information about the raw materials used in the embodiments and comparative examples of the present invention.

[0122]

[0123] Table 2 below lists specific information about the experimental equipment used in the embodiments and comparative examples of the present invention.

[0124]

[0125] Performance testing methods

[0126] (I) Test method for half-wave potential of oxygen reduction reaction (refer to GB / T 38587-2020 "Test method for membrane electrode performance of proton exchange membrane fuel cell")

[0127] The electrochemical activity of the hydrogen fuel cell catalysts prepared in the following examples and comparative examples was tested according to the methods described below.

[0128] This test uses the rotating ring-disk electrode method to determine the half-wave potential of the oxygen reduction reaction (ORR) of the catalyst. The test principle is as follows: In an acidic electrolyte saturated with oxygen, the catalyst is coated on the disk electrode surface of the ring-disk electrode. A linear scanning voltage is applied through an electrochemical workstation, and the reduction current of the disk electrode is recorded. The half-wave potential is the electrode potential corresponding to the reduction current reaching half of the limiting diffusion current.

[0129] The specific testing steps include the following:

[0130] 1. Catalyst slurry preparation: Weigh 5 mg of the hydrogen fuel cell catalyst sample prepared in each example and comparative example, add 1 mL of isopropanol:water = 1:1 mixture, add 50 μL of Nafion solution (5% by weight), and ultrasonically disperse for 30 min to obtain a uniform slurry;

[0131] 2. Electrode modification: 10 μL of catalyst slurry was drop-coated onto the surface of a glassy carbon disk electrode (5 mm in diameter) and allowed to dry naturally at room temperature to obtain the working electrode;

[0132] 3. Test system setup: A three-electrode system was constructed using a platinum wire electrode as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and a 0.5 mol / L H2SO4 aqueous solution as the electrolyte;

[0133] 4. Electrolyte deoxygenation and saturation: High-purity nitrogen gas was introduced into the electrolyte for 30 min to remove oxygen, and the background curve under nitrogen saturation was recorded. Then, high-purity oxygen gas was introduced for 30 min until saturation.

[0134] 5. Linear scan voltammetry test: At 25°C, set the scan rate to 5mV / s, the electrode rotation speed to 1600r / min, and the scan potential range to 0-1.2V (vs SCE), and record the ORR polarization curve;

[0135] 6. Potential Conversion: Convert the test results from vs SCE to vs RHE (Reversible Hydrogen Electrode). The conversion formula is E. RHE =E SCE +0.242V +0.0592×pH;

[0136] 7. Data processing: Extract the limiting diffusion current of the polarization curve using the software of the electrochemical workstation, and calculate the potential corresponding to half of it, which is the half-wave potential of the oxygen reduction reaction.

[0137] The final result is obtained by averaging three parallel tests (standard deviation ≤ 0.01 V). A higher half-wave potential for the oxygen reduction reaction indicates a stronger ORR catalytic activity of the catalyst.

[0138] (II) Test method for electrochemical active area retention rate after 10,000 cycles (refer to GB / T 40071-2021 "Test Method for Proton Exchange Membrane Fuel Cell Catalysts")

[0139] Electrochemical active area (ECSA) reflects the proportion of active sites on the catalyst surface that participate in electrochemical reactions, and is calculated by measuring the hydrogen adsorption and desorption peak areas using cyclic voltammetry. The ECSA retention rate after 10,000 cycles is the percentage of ECSA after cycling to ECSA before cycling.

[0140] The specific testing steps include the following:

[0141] 1. Catalyst slurry preparation: Weigh 5 mg of the hydrogen fuel cell catalyst sample prepared in each example and comparative example, add 1 mL of isopropanol:water = 1:1 mixture, add 50 μL of Nafion solution (5% by weight), and ultrasonically disperse for 30 min to obtain a uniform slurry;

[0142] 2. Electrode modification: 10 μL of catalyst slurry was drop-coated onto the surface of a glassy carbon disk electrode (5 mm in diameter) and allowed to dry naturally at room temperature to obtain the working electrode;

[0143] 3. Three-electrode system setup: Platinum wire was used as the counter electrode, a saturated calomel electrode as the reference electrode, and a 0.5 mol / L H2SO4 aqueous solution as the electrolyte;

[0144] 4. Electrode activation: Within the potential range of 0.05-1.2V (vs RHE), perform 50 cyclic scans at a scan rate of 50mV / s until the cyclic voltammetry curve stabilizes;

[0145] 5. Initial ECSA test: Set the scan rate to 50 mV / s and the scan potential range to 0.05-0.4 V (vs RHE). Record the cyclic voltammetry curve. The hydrogen adsorption-desorption peak in this range is the characteristic peak.

[0146] 6. ECSA Calculation: Calculate ECSA using the following formula:

[0147] ECSA = Q / (m × Q0),

[0148] Where Q is the integral area (C) of the hydrogen adsorption-desorption peak, m is the platinum loading (g) of the catalyst on the electrode surface, and Q0 is the specific adsorption charge of platinum (0.21 mC / cm). 2 );

[0149] 7. Accelerated Cyclic Aging Test:

[0150] Set the potential scan range to 0.6-1.0V (vs RHE), scan rate to 100mV / s, and perform 10,000 constant-speed cyclic scans.

[0151] 8. ECSA test after cycle:

[0152] After the aging test, repeat the test method in step 4, record the hydrogen adsorption-desorption peak area after cycling, and calculate the ECSA after cycling.

[0153] 9. Calculate the retention rate of the electrochemical active surface area (ECSA) using the following formula:

[0154] ECSA retention rate = (ECSA after cycle / initial ECSA) × 100%.

[0155] The final result is obtained by averaging three parallel tests (standard deviation ≤ 2%). A higher electrochemical active area retention rate indicates stronger catalyst cycle stability.

[0156] (III) Test method for catalytic activity retention rate under 100ppm CO atmosphere for 200h (refer to GB / T 39475-2020 "Test method for durability of proton exchange membrane fuel cells")

[0157] The catalytic activity retention rate is the percentage of the limiting diffusion current of the oxygen reduction reaction to the initial limiting diffusion current of the oxygen reduction reaction after the catalyst has been continuously operated for 200 hours in a hydrogen atmosphere of 100 ppm CO.

[0158] The specific testing steps include the following:

[0159] 1. Membrane electrode fabrication:

[0160] The hydrogen fuel cell catalyst samples prepared in the various examples and comparative examples were mixed with 5 wt% Nafion solution at a mass ratio of 4:1, and a mixture of isopropanol and water at a ratio of 2:1 was added. The mixture was ultrasonically dispersed to obtain a catalyst slurry, which was then coated onto the surface of the gas diffusion layer (coating amount 1 mg / cm²). 2 After drying at 80℃, the membrane electrode is hot-pressed with a proton exchange membrane (130℃, 3MPa, 5min) to obtain the membrane electrode.

[0161] 2. Single-cell assembly:

[0162] The membrane electrode assembly was installed into the fuel cell test fixture. Hydrogen gas was introduced at the anode, and air was introduced at the cathode. The effective area of ​​the membrane electrode was 5 cm². 2 ;

[0163] 3. Initial activity test:

[0164] The battery temperature was set to 80℃, the anode hydrogen flow rate to 100mL / min, the cathode air flow rate to 200mL / min, and the back pressure to 0.1MPa. The battery voltage was measured at different current densities, and the initial limiting diffusion current I0 of the oxygen reduction reaction was recorded.

[0165] 4. CO poisoning durability test:

[0166] High-purity CO gas was introduced into the hydrogen gas at the anode to prepare a hydrogen gas mixture with 100 ppm CO. The gas flow rate, battery temperature, and back pressure were kept consistent with the initial test. The system was run continuously for 200 hours, and the battery voltage and limiting diffusion current were recorded every 20 hours.

[0167] 5. Activity test after 200 hours:

[0168] After 200 hours of operation, CO was stopped, and pure hydrogen was continued to purge the anode for 30 minutes. Then, the test method in step 3 was repeated, and the oxygen reduction reaction limiting diffusion current I was recorded after 200 hours. 200 ;

[0169] 6. Calculate the catalytic activity retention rate using the following formula:

[0170] Catalytic activity retention rate = (I 200 / I0)×100%.

[0171] The average value of three parallel tests (standard deviation ≤ 2%) is taken. A higher retention rate indicates a stronger resistance to CO poisoning by the catalyst.

[0172] Example 1 (E1)

[0173] The specific preparation steps of Example 1 are as follows:

[0174] (1) Material preparation

[0175] Preparation of an aqueous dispersion of the carrier raw material: Weigh the carrier raw material (a mixture of carbon nanotubes and graphene in a weight ratio of 6:1), add it to a reaction vessel, then add 200 mL of a mixed acid of concentrated nitric acid and concentrated sulfuric acid in a ratio of 1:3, and stir at 60 °C for 2 h. After the reaction, wash with deionized water until the pH of the filtrate is 7, centrifuge at 8000 r / min for 10 min to obtain an oxidized modified carrier. Then, mix the above oxidized modified carrier with melamine in a weight ratio of 1:5, add 500 mL of an aqueous solution of ethanol and water in a ratio of 1:1, ultrasonically disperse for 30 min (power 300 W), dry at 80 °C for 12 h, place the dried product in a tube furnace, calcine at 700 °C for 2 h under a nitrogen atmosphere, and grind to obtain a nitrogen-doped modified carrier. Finally, mix the nitrogen-doped modified carrier with deionized water in a weight ratio of 1:10, ultrasonically disperse for 60 min to obtain an aqueous dispersion of the carrier raw material.

[0176] Preparation of an aqueous solution of platinum-based precursor: Weigh platinum nitrate and cobalt chloride (70% by weight of platinum salt and 30% by weight of cobalt salt), add deionized water to dissolve, then add citric acid (15% by weight of the total metal salt) as a complexing agent, adjust the pH of the solution to 3.0 with dilute nitric acid, stir until completely dissolved, and obtain an aqueous solution of platinum-based precursor with a total metal ion concentration of 2.5% by weight.

[0177] Preparation of an aqueous dispersion of dopant precursor: Weigh thiourea, ammonium dihydrogen phosphate and boric acid (weight ratio 30:50:20), add deionized water, stir at room temperature for 30 min until completely dissolved, and obtain an aqueous dispersion with a dopant precursor content of 0.2% by weight.

[0178] Preparation of the dispersion of the additive: Weigh cesium hydrogen phosphomolybdate, copper oxide nanoparticles and polytetrafluoroethylene particles (weight ratio 60:25:15), add isopropanol:water = 3:2 mixed dispersion medium, and ultrasonically disperse for 40 min to obtain a dispersion with a total additive content of 5% by weight.

[0179] (2) Preparation of catalyst slurry:

[0180] The above-mentioned aqueous dispersion of the carrier, aqueous solution of the platinum-based precursor, and aqueous dispersion of the dopant precursor were added to the reactor and stirred in a constant temperature water bath at 40°C for 2 hours. Then, the additive dispersion was added and the reaction was continued for 20 minutes to obtain a uniform catalyst slurry.

[0181] (3) Spray drying:

[0182] The catalyst slurry was fed into a spray dryer with an inlet temperature of 180℃, an outlet temperature of 80℃, a feed rate of 5mL / min, and an atomization pressure of 0.2MPa. After drying, a powder precursor was obtained.

[0183] (4) Reduction heat treatment:

[0184] The powder precursor was placed in a tube furnace and a mixed reducing atmosphere of hydrogen:nitrogen = 1:20 (gas flow rate 50 mL / min) was introduced. The furnace was kept at 300℃ for 1 hour and then allowed to cool naturally to room temperature.

[0185] (5) High-temperature densification treatment:

[0186] Under a nitrogen inert atmosphere, the reduced product was heated to 600°C, kept at that temperature for 2 hours, and then naturally cooled to room temperature.

[0187] (6) Post-processing:

[0188] The densification product was washed three times with deionized water and dried at a constant temperature of 80°C for 10 hours to obtain hydrogen fuel cell catalyst 1.

[0189] In Example 1, based on the total weight of the carrier raw material, platinum-based precursor, doped element precursor and additives as 100%, the carrier raw material accounts for 85%, the platinum-based precursor accounts for 10%, the doped element precursor accounts for 2%, and the additives account for 3%.

[0190] The hydrogen fuel cell catalyst 1 prepared in Example 1 was characterized by transmission electron microscopy (TEM). Figure 2 A transmission electron microscope (TEM) image of the hydrogen fuel cell catalyst 1 prepared in Example 1 is shown, which shows uniformly sized reduction-generated platinum nanoparticles dispersed on the surface and / or inside the carbon nanotubes and graphene.

[0191] In addition, using a specific surface area and pore size analyzer (ASAP 2460), according to GB / T 19587-2017 "Determination of Specific Surface Area of ​​Solid Materials by Gas Adsorption-Desorption BET Method", the active specific surface area of ​​hydrogen fuel cell catalyst 1 was measured to be 60 m² using the low-temperature nitrogen adsorption-desorption BET method. 2 / g.

[0192] In addition, the hydrogen fuel cell catalyst 1 prepared in Example 1 was tested according to the oxygen reduction reaction half-wave potential test method, the electrochemical active area retention rate test method after 10,000 cycles, and the catalytic activity retention rate test method under 100ppm CO atmosphere for 200h.

[0193] Examples 2-12 (E2-E12) and Comparative Examples 1-5 (CE1-CE5)

[0194] Examples 2-12 (E2-E12) and Comparative Examples 1-5 (CE1-CE5) were prepared in a manner similar to that of Example 1 to prepare hydrogen fuel cell catalysts 2-12 and comparative hydrogen fuel cell catalysts 1-5, the only difference being that the component types and / or ratios were changed as shown in Table 3 below.

[0195] In addition, the hydrogen fuel cell catalysts prepared in Examples 2-12 (E2-E12) were subjected to transmission electron microscopy (TEM). The results showed that they had similar microstructures to the hydrogen fuel cell catalysts prepared in Example 1.

[0196] In addition, the specific surface area and pore size analyzer (ASAP 2460) were used to measure the specific surface area of ​​hydrogen fuel cell catalysts 2-12 and comparative hydrogen fuel cell catalysts 1-5 according to GB / T 19587-2017 "Determination of specific surface area of ​​solid materials by gas adsorption-desorption BET method". The results are shown in Table 4 below together with the corresponding results of hydrogen fuel cell catalyst 1 prepared in Example 1.

[0197] Furthermore, hydrogen fuel cell catalysts 2-12 and comparative hydrogen fuel cell catalysts 1-5 were tested according to the oxygen reduction reaction half-wave potential test method, the electrochemical active area retention rate test method after 10,000 cycles, and the catalytic activity retention rate test method under 100ppm CO atmosphere for 200h as described in detail above. The results are shown in Table 4 below together with the corresponding results of hydrogen fuel cell catalyst 1 prepared in Example 1 as measured above.

[0198]

[0199]

[0200] As can be seen from the performance test results in Table 4 above, the hydrogen fuel cell catalysts prepared in Examples 1-12 of this invention all exhibit good performance indicators, with half-wave potentials for oxygen reduction reaction all greater than or equal to 0.88 V vs RHE, and specific activity areas of 60-80 m². 2 / g, the electrochemical active area retention rate is greater than or equal to 85% after 10,000 cycles, and the catalytic activity retention rate is greater than or equal to 90% after running in a 100ppm CO atmosphere for 200h. Moreover, with the optimization of the support raw material ratio, dopant element precursor ratio and auxiliary agent ratio, such as in Examples 10-12 where the weight ratio of carbon nanotubes to graphene is reduced to 5:1-2:1, the proportion of thiourea is increased to 40-60%, and the proportion of heteropolyacid salts in the auxiliary agent reaches 70-80%, the catalyst performance shows a significant improvement trend.

[0201] On the other hand, Comparative Examples 1-3, lacking a carbon nanotube and graphene composite support, and with insufficient structural and modification effects from single supports or carbon black composite supports, resulted in a significant reduction in the active surface area and a marked decrease in catalytic activity and stability. Comparative Examples 4-5, due to an imbalance in the weight ratio of each component, led to problems such as platinum particle agglomeration and a reduction in active sites, resulting in an oxygen reduction half-wave potential below 0.83 V and a significant decrease in resistance to CO poisoning and cycle stability.

[0202] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from the spirit and scope of this disclosure. Therefore, if such modifications and variations fall within the scope of this invention, this disclosure is also intended to include such modifications and variations.

Claims

1. A method for preparing a hydrogen fuel cell catalyst, characterized by, Includes the following steps: (1) Prepare aqueous dispersions of the carrier raw material, aqueous solutions of the platinum-based precursor, aqueous dispersions of the dopant precursor, and dispersions of the additives, respectively. The carrier raw material is a mixture of carbon nanotubes and graphene. The dopant precursor is a mixture of thiourea, ammonium dihydrogen phosphate, and boric acid. Based on the total weight of the dopant precursor, thiourea accounts for 40-60%, ammonium dihydrogen phosphate accounts for 20-40%, and boric acid accounts for 10%-20%. The additive is a mixture of heteropolyacid salts, semiconductor nanoparticles, and polytetrafluoroethylene particles. Based on the total weight of the additive, the heteropolyacid salt accounts for 70-80%, semiconductor nanoparticles account for 10-20%, and polytetrafluoroethylene particles account for 10-20%. (2) Mix the aqueous dispersion of the carrier raw material, the aqueous solution of the platinum-based precursor and the aqueous dispersion of the doped element precursor and stir at 40-60℃ for 2-12 hours. Then add the dispersion of the additive and continue to react for 20-30 minutes to obtain the catalyst slurry. (3) The catalyst slurry was spray-dried to obtain a powder precursor; (4) The powder precursor is kept at 300-400℃ for 1-2 hours in a reducing atmosphere for reduction heat treatment; (5) The powder precursor that has undergone reduction heat treatment is kept at 600-700℃ for 2-3 hours in an inert atmosphere to carry out high-temperature densification treatment; (6) The product subjected to high-temperature densification treatment is washed and dried to obtain a hydrogen fuel cell catalyst, wherein: Based on the total weight of the carrier raw material, platinum-based precursor, doped element precursor, and additives as 100%, the carrier raw material accounts for 60-85%, the platinum-based precursor accounts for 5-20%, the doped element precursor accounts for 2-8%, and the additives account for 3-12%. The aqueous solution of the platinum-based precursor is prepared by the following steps: Dissolve platinum salt and transition metal salt in water, add a complexing agent and adjust the pH to 3.0-4.0, wherein, based on the total weight of platinum salt and transition metal salt as 100%, platinum salt accounts for 40-70% and transition metal salt accounts for 30-60%, wherein the platinum salt is platinum nitrate, the transition metal salt is cobalt chloride, and the complexing agent is citric acid.

2. The method for preparing the hydrogen fuel cell catalyst according to claim 1, characterized in that, The carrier material is a mixture of carbon nanotubes and graphene in a weight ratio of 5:1 to 2:

1.

3. The method for preparing the hydrogen fuel cell catalyst according to claim 1, characterized in that, The aqueous dispersion of the carrier raw material is prepared by the following steps: (a) Add the carrier raw material to the reaction vessel, add a mixture of concentrated nitric acid and concentrated sulfuric acid, stir and react at 60-80℃ for 2-4 hours, wash until neutral and then centrifuge to obtain the oxidized carrier; (b) The oxidized modified carrier is mixed with a nitrogen source, an aqueous solution of ethanol is added, the mixture is ultrasonically dispersed and dried, and the dried product is calcined at 700-800°C for 2-3 hours under an inert atmosphere. Then it is ground to obtain a nitrogen-doped modified carrier, wherein the nitrogen source is selected from one or more of melamine, urea and ethylenediamine. (c) Disperse the nitrogen-doped modified support in deionized water.

4. The method for preparing the hydrogen fuel cell catalyst according to claim 3, characterized in that, In step (b), the weight ratio of the oxidative modified support to the nitrogen source is 1:5 to 1:

10.

5. The method for preparing the hydrogen fuel cell catalyst according to claim 1, characterized in that, The semiconductor nanoparticles are selected from one or more of copper oxide nanoparticles, nickel oxide nanoparticles, titanium dioxide nanoparticles, and zinc oxide nanoparticles; or The average particle size of the semiconductor nanoparticles is in the range of 10-50 nm; or The average particle size of the polytetrafluoroethylene particles is in the range of 200 nm to 5 μm.

6. The method for preparing the hydrogen fuel cell catalyst according to claim 1, characterized in that, The dispersion medium of the additive dispersion is a mixture of isopropanol and water with a volume ratio of 3:2-4:1; or The aqueous dispersion of the dopant precursor is prepared by dissolving thiourea, ammonium dihydrogen phosphate and boric acid in deionized water.

7. The method for preparing the hydrogen fuel cell catalyst according to claim 1, characterized in that, The heteropolyacid salt is selected from one or more of cesium hydrogen phosphomolybdate, cesium hydrogen phosphotungstate, and cesium molybdate silylate.

8. A hydrogen fuel cell catalyst, characterized in that, The hydrogen fuel cell catalyst is prepared by the method according to any one of claims 1-7.

9. A hydrogen fuel cell, the hydrogen fuel cell comprising a membrane electrode assembly (MEA), the MEA comprising an anode catalyst layer, a cathode catalyst layer, and a proton exchange membrane, characterized in that, The anode catalyst layer and / or the cathode catalyst layer comprise the hydrogen fuel cell catalyst according to claim 8.

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