Platinum-based high-entropy alloy fuel cell catalyst and preparation method and application thereof

Abstract

The invention relates to a platinum-based high-entropy alloy fuel cell catalyst and a preparation method and application thereof.The preparation method comprises the steps that a platinum source, non-platinum transition metal mixed salt, a carbon carrier and a solvent are evenly mixed, an obtained platinum-based high-entropy alloy precursor is subjected to microwave sintering, and the platinum-based high-entropy alloy fuel cell catalyst is obtained; the non-platinum transition metal mixed salt includes a combination of at least four non-platinum transition metal salts. According to the microwave sintering method, the heating and cooling speed is high, the needed sintering time is shorter, the particle growth time is shortened, the temperature field is uniform in the sintering process, particles grow uniformly, and due to rapid cooling, crystal lattices easily form a large number of surface vacancies, dislocations and other structural defects under thermal shock, and the crystal lattices become efficient active sites. The platinum-based high-entropy alloy nanoparticles in the obtained platinum-based high-entropy alloy fuel cell catalyst are small in particle size, uniform in active site distribution and high in electronic structure regulation and control capability, have high oxygen reduction activity and relatively high stability, and can meet the requirements of long-life fuel cells.

Description

Technical Field

[0001] This invention relates to the field of fuel cell catalyst preparation technology, and in particular to a platinum-based high-entropy alloy fuel cell catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean, efficient, and sustainable energy source, is one of the important channels for achieving low-carbon goals. Proton exchange membrane fuel cells (PEMFCs) are the core device for realizing hydrogen energy utilization, a zero-carbon emission power generation device that converts chemical energy into electrical energy. This process relies heavily on precious metal platinum-based catalysts, which are considered to have excellent oxygen reduction reaction performance. However, common binary / ternary platinum-based alloy fuel cell catalysts have simple compositions and limited electronic structure control capabilities. They are often prone to reduced active sites due to elemental segregation during long-term operation, and their activity and stability cannot meet the requirements of long-life fuel cells. For example, CN113113621A discloses an ordered low-platinum alloy catalyst, a binary platinum-cobalt alloy catalyst. Performance testing revealed low ORR electrocatalytic activity; after half-wave potential and 5000 cycles of accelerated voltammetry testing, the half-wave potential of the platinum-cobalt alloy catalyst decreased by as much as 20 mV, indicating a significant reduction in activity.

[0003] In light of this, platinum-based high-entropy alloy fuel cell catalysts are gradually replacing common binary / ternary platinum-based alloy fuel cell catalysts. These catalysts possess strong electronic structure control capabilities, resulting in higher oxygen reduction activity and stability. Currently, most common preparation methods for platinum-based high-entropy alloy fuel cell catalysts employ calcination. For example, CN114094129A discloses a carbon-supported high-entropy alloy oxygen reduction electrocatalyst. First, a coating layer adsorbing metal ions is formed on the surface of platinum-carbon, which is then immersed in a metal salt solution. Calcination allows the metal ions to diffuse into platinum nanoparticles through thermal diffusion, thus forming a high-entropy alloy. At high temperatures, the coating layer not only inhibits the migration of platinum particles but also acts as a reducing agent, enabling the reduction of metal ions. The carbonized coating layer exhibits strong metal-carrier interaction with the platinum particles, stabilizing them. However, even with the formation of a metal ion coating layer on the platinum-carbon surface, the half-wave potential and mass-to-area ratio activity remain relatively low to facilitate metal ion loading. This may be attributed to uneven heating of the material during calcination and the relatively long calcination time, resulting in larger high-entropy alloy nanoparticle sizes, agglomeration, and component segregation.

[0004] Therefore, how to provide a method for preparing platinum-based high-entropy alloy fuel cell catalysts that can meet the requirements of long-term operation and long lifespan while improving the drawbacks of traditional sintering in catalyst preparation, and thus have better oxygen reduction performance, has become an urgent technical problem to be solved. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a platinum-based high-entropy alloy fuel cell catalyst, its preparation method, and its applications. This invention employs a solution impregnation combined with microwave sintering. Microwave sintering offers faster heating and cooling rates and requires less sintering time, resulting in a shorter overall reaction time and significantly shortening particle growth time. The uniform temperature field during sintering ensures uniform particle growth, avoiding abnormal particle growth caused by uneven heating and localized high temperatures. Rapid cooling allows the crystal lattice to easily form numerous surface vacancies and dislocations under thermal shock, making them highly efficient active sites for the ORR reaction. The platinum-based high-entropy alloy fuel cell catalyst prepared by this invention features small-sized platinum-based high-entropy alloy nanoparticles with uniformly distributed active sites, strong electronic structure control capabilities, high oxygen reduction activity, and high stability, meeting the requirements of long-life fuel cells.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst, the method comprising the following steps:

[0008] A platinum source, a non-platinum transition metal mixed salt, a carbon support, and a solvent are mixed uniformly to obtain a platinum-based high-entropy alloy precursor; the platinum-based high-entropy alloy precursor is then subjected to microwave sintering to obtain a platinum-based high-entropy alloy fuel cell catalyst.

[0009] The non-platinum transition metal mixed salt comprises a combination of at least four non-platinum transition metal salts.

[0010] The platinum-based high-entropy alloy fuel cell catalyst of this invention is prepared by solution impregnation combined with microwave sintering. The process is simple and time-saving. In particular, compared with the traditional sintering furnace method, microwave sintering can directly convert energy through dipole vibration or ion conduction inside the material to achieve rapid heating. The heating rate can reach 20~500℃ / min (far higher than the 5~20℃ / min of traditional sintering furnace sintering). Rapid heating can reach the required sintering temperature in a short time, and the sintering process can be completed in a shorter sintering holding time. The overall reaction time is shorter (heating time plus holding time), which reduces the particle growth time. Particle growth (such as Ostwald ripening) depends on atomic diffusion time. Therefore, short-term high temperature will significantly shorten the particle coarsening window caused by atomic diffusion, preventing the particles from growing excessively. In addition, the rapid cooling after sintering makes the lattice prone to forming a large number of surface vacancies and dislocations under thermal shock. These structural defects also become highly efficient active sites for the ORR reaction.

[0011] Furthermore, compared to traditional sintering using a sintering furnace, microwave sintering produces a more uniform temperature field, which avoids localized overheating. In the traditional sintering furnace process, the outer layer of the sample is heated first, while the internal temperature lags behind, easily forming a "higher outside, lower inside" temperature gradient. This causes the outer layer particles to grow first and inhibits internal diffusion. However, during microwave heating, the sample's interior and exterior absorb energy simultaneously, resulting in a more uniform temperature distribution. This avoids the problem of abnormal particle growth caused by uneven heating and localized high temperatures. The uniformity of the temperature field promotes the formation of a single solid solution in platinum-based high-entropy alloys, avoiding elemental segregation and ensuring a uniform distribution of active sites.

[0012] As a preferred technical solution of the present invention, the sintering atmosphere of the microwave sintering includes an inert atmosphere.

[0013] Preferably, the gas used in the inert atmosphere includes any one or a combination of at least two of argon, nitrogen, or helium.

[0014] Preferably, the holding temperature for microwave sintering is 600℃~900℃, such as 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃.

[0015] Preferably, the holding time for microwave sintering is 10 min to 50 min, for example, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, or 50 min. In this invention, the holding temperature for microwave sintering is controlled to be 600℃ to 900℃, and the holding time is 10 min to 50 min. Within the above temperature and time range, the obtained platinum-based high-entropy alloy fuel cell catalyst exhibits high oxygen reduction activity and high stability. Specifically, when the low temperature is held for a long time (e.g., a sintering temperature of 600℃ to 700℃ combined with a holding time of 30 min to 50 min), excessive grain growth can be effectively suppressed, which is beneficial to obtaining a fine and uniform microstructure, thereby improving the mechanical properties and catalytic activity stability of the alloy. It can also reduce platinum loss, ensuring the platinum content and the number of catalytic active sites in the alloy, thus helping to maintain the performance of the hydrogen fuel cell; when the medium temperature is held for a medium time (e.g., a sintering temperature of 700℃ to 800℃ combined with a holding time of 20 min to 30 min), the excessive grain growth can be effectively suppressed, which is beneficial to obtaining a fine and uniform microstructure, thereby improving the mechanical properties and catalytic activity stability of the alloy. Furthermore, it can reduce platinum loss, ensuring the platinum content and the number of catalytic active sites in the alloy, thus helping to maintain the performance of the hydrogen fuel cell. High temperature and short holding time (e.g., sintering temperature of 800℃~900℃ with a holding time of 10min~20min) can fully sinter the alloy, achieving a certain degree of densification and catalytic activity, while taking into account grain size and energy consumption. It also helps to form an active site structure that is beneficial to ORR, improving the catalytic activity and stability of platinum-based high-entropy alloys for the ORR of hydrogen fuel cells. When high temperature is held for a short time (e.g., sintering temperature of 800℃~900℃ with a holding time of 10min~20min), atoms have enough energy to diffuse and migrate, promoting the densification of the alloy. This allows the alloy powder to achieve densification in a shorter time, improving production efficiency and reducing energy consumption.

[0016] Preferably, the total heating and holding time for microwave sintering is 15 min to 70 min, for example, 15 min, 25 min, 35 min, 45 min, 55 min, 65 min, or 70 min.

[0017] As a preferred embodiment of the present invention, the non-platinum transition metal mixed salt includes a combination of at least four of the following: iron salt, cobalt salt, nickel salt, palladium salt, copper salt, zinc salt, manganese salt, or chromium salt, preferably a combination of iron salt, cobalt salt, nickel salt, and palladium salt.

[0018] As a preferred technical solution of the present invention, the types of salts corresponding to the non-platinum transition metal mixed salts include any one or a combination of at least two of nitrates, chlorides, or sulfates.

[0019] Preferably, the platinum source includes any one or a combination of at least two of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, platinum nitrate, sodium chloroplatinate, potassium chloroplatinate, tetraammineplatinum nitrate, or potassium chloroplatinate.

[0020] Preferably, the carbon support comprises any one or a combination of at least two of mesoporous carbon, carbon nanotubes, activated carbon, graphene, or carbon nanofibers.

[0021] As a preferred embodiment of the present invention, the solvent comprises a mixed solution of organic polycarboxylic acids and polyols.

[0022] In this invention, the organic polycarboxylic acid plays the following roles: first, as a microwave absorption enhancer, it promotes uniform heating of the material and avoids local high temperatures; second, as a complexing stabilizer for metal ions, it inhibits precursor aggregation; and third, as a carbon source precursor and dispersing aid, it optimizes the carrier-active component interface.

[0023] Preferably, the organic polycarboxylic acid includes any one or a combination of at least two of citric acid, tartaric acid, malic acid, ethylenediaminetetraacetic acid, or hydantoin, and more preferably any one or a combination of at least two of citric acid, tartaric acid, or malic acid.

[0024] Preferably, the ratio of the molar amount of the organic polycarboxylic acid to the total molar amount of the metal elements in the platinum source and the non-platinum transition metal mixed salt is (2~3):1, for example, 2:1, 2.2:1, 2.5:1, 2.8:1 or 3:1, etc.

[0025] Preferably, the polyol includes any one or a combination of at least two of ethylene glycol, glycerol, 1,2-propanediol, or an ethanol-polyethylene glycol mixed solution.

[0026] Preferably, the ratio of the volume of the polyol to the total mass of the platinum source and the non-platinum transition metal mixed salt is (0.5 mL to 1 mL): 1 mg, for example, 0.5 mL: 1 mg, 0.6 mL: 1 mg, 0.7 mL: 1 mg, 0.8 mL: 1 mg, 0.9 mL: 1 mg, or 1 mL: 1 mg, etc.

[0027] As a preferred embodiment of the present invention, the mixing includes ultrasonic dispersion.

[0028] Preferably, the mixing time is 1 hour to 2 hours, such as 1 hour, 1.5 hours, or 2 hours.

[0029] Preferably, the mixing process further includes a solvent removal step.

[0030] Preferably, the solvent removal method includes rotary evaporation.

[0031] As a preferred technical solution of the present invention, the preparation method includes the following steps:

[0032] A platinum source, a non-platinum transition metal mixed salt, a carbon support, and a solvent are mixed and ultrasonically dispersed for 1-2 hours to achieve uniform mixing. The solvent is then removed by rotary evaporation to obtain a platinum-based high-entropy alloy precursor. The platinum-based high-entropy alloy precursor is then microwave sintered at 600-900℃ for 10-50 minutes under an inert atmosphere, with a total heating and holding time of 15-70 minutes, to obtain a platinum-based high-entropy alloy fuel cell catalyst.

[0033] The non-platinum transition metal mixed salt comprises a combination of at least four non-platinum transition metal salts; the solvent comprises a mixed solution of organic polycarboxylic acids and polyols; the molar ratio of the organic polycarboxylic acid to the total molar ratio of the metal elements in the platinum source and the non-platinum transition metal mixed salt is (2~3):1; the volume ratio of the polyol to the total mass of the platinum source and the non-platinum transition metal mixed salt is (0.5mL~1mL):1mg.

[0034] In a second aspect, the present invention also provides a platinum-based high-entropy alloy fuel cell catalyst, which is prepared according to the preparation method described in the first aspect.

[0035] As a preferred embodiment of the present invention, the platinum-based high-entropy alloy fuel cell catalyst comprises platinum-based high-entropy alloy nanoparticles and a carbon support.

[0036] Preferably, based on the total mass of the platinum-based high-entropy alloy fuel cell catalyst being 100wt%, the mass of the platinum-based high-entropy alloy nanoparticles is 20wt%~40wt%, for example, 20wt%, 22wt%, 25wt%, 28wt%, 30wt%, 32wt%, 35wt%, 38wt%, or 40wt%, with the remainder being a carbon support.

[0037] Preferably, the platinum-based high-entropy alloy nanoparticles comprise platinum atoms and non-platinum transition metal atoms.

[0038] Preferably, the non-platinum transition metal atoms include a combination of at least four of the following: iron atoms, cobalt atoms, nickel atoms, palladium atoms, copper atoms, zinc atoms, manganese atoms, or chromium atoms, and more preferably a combination of iron atoms, cobalt atoms, nickel atoms, and palladium atoms.

[0039] Preferably, in the platinum-based high-entropy alloy nanoparticles, the atomic percentage of platinum atoms in the total metal atoms is 20at% to 70at, for example, 20at%, 21at%, 25at%, 30at%, 32at%, 45at%, 56at%, 60at%, 62at% or 70at%, etc., preferably 45at% to 55at.

[0040] Preferably, in the platinum-based high-entropy alloy nanoparticles, the atomic percentage of non-platinum transition metal atoms in the total metal atoms is 30at% to 80at, for example, 30at%, 35at%, 41at%, 53at%, 65at%, 70at%, 74at% or 80at%, etc., preferably 45at% to 55at.

[0041] As a preferred embodiment of the present invention, the average particle size of the platinum-based high-entropy alloy nanoparticles is 3nm~8nm, such as 3nm, 4nm, 5nm, 6nm, 7nm or 8nm, preferably 3nm~6nm.

[0042] Thirdly, the present invention also provides an application of a platinum-based high-entropy alloy fuel cell catalyst, wherein the platinum-based high-entropy alloy fuel cell catalyst prepared by the preparation method described in the first aspect, or the platinum-based high-entropy alloy fuel cell catalyst described in the second aspect, is applied to a hydrogen fuel cell.

[0043] Compared with the prior art, the present invention has at least the following beneficial effects:

[0044] 1) This invention uses a solution impregnation combined with microwave sintering method, which is simple to prepare, easy to operate, short in time, and low in reaction temperature. The resulting platinum-based high-entropy alloy fuel cell catalyst has small platinum-based high-entropy alloy nanoparticles with uniform distribution of active sites. Compared with binary / ternary alloy fuel cell catalysts, it has stronger electronic structure regulation capability and can still maintain uniform element distribution even in long-term operation. It has high oxygen reduction activity and high stability, which can meet the requirements of long-life fuel cells.

[0045] 2) Compared with traditional sintering furnace sintering, the microwave sintering method used in this invention has a faster heating and cooling rate and a shorter sintering time, resulting in a shorter overall reaction time and greatly shortening the particle growth time. The temperature field is uniform during sintering, which makes the particles grow uniformly and avoids the problem of abnormal particle growth caused by uneven heating of the material and local high temperature. The rapid cooling makes it easy for the crystal lattice to form a large number of surface vacancies and dislocations under thermal shock, making them highly efficient active sites for the ORR reaction.

[0046] 3) The PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided by this invention, after 30,000 cycles of accelerated decay test, has a half-wave potential decay of ≤25mV and a mass-to-activity decay of ≤24.9%, which is far higher than the requirements of DOE2025. Attached Figure Description

[0047] Figure 1 This is a TEM image of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of the present invention.

[0048] Figure 2 This is the XRD pattern of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of this invention.

[0049] Figure 3 This is a comparison chart of the activities of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of the present invention, the commercial platinum-carbon catalyst provided in Comparative Example 3, and the commercial platinum-cobalt alloy catalyst provided in Comparative Example 4.

[0050] Figure 4 The ORR positive scan polarization curves of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of this invention are the initial and 30,000-cycle accelerated decay test results in an O2-saturated 0.1M HClO4 solution.

[0051] Figure 5 These are the cyclic voltammetry curves of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of this invention, both initially and after 30,000 cycles of accelerated decay testing. Detailed Implementation

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0053] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0054] Example 1

[0055] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst, the preparation method comprising the following steps:

[0056] Chloroplatinic acid, palladium chloride, ferric chloride, cobalt chloride, and nickel chloride were dissolved in a citric acid-ethylene glycol mixed solution according to the atomic ratio of Pt, Pd, Fe, Co, and Ni of 5:1.5:1:1.5:1. Mesoporous carbon was added, and the mixture was ultrasonically dispersed for 1 hour and then mixed evenly. The solvent was removed by rotary evaporation to form the PtPdFeCoNi / C precursor.

[0057] The PtPdFeCoNi / C precursor was placed in a microwave sintering furnace and held at 800℃ for 20 min in an Ar atmosphere. The total time for heating and holding was 30 min, and the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst was obtained.

[0058] The PtPdFeCoNi / C high-entropy alloy fuel cell catalyst contains PtPdFeCoNi high-entropy alloy nanoparticles and support mesoporous carbon, with the mass percentage of PtPdFeCoNi high-entropy alloy nanoparticles being 40 wt% and the remainder being support mesoporous carbon.

[0059] In PtPdFeCoNi high-entropy alloy nanoparticles, Pt atoms account for 50 at%, Pd atoms 15 at%, Fe atoms 10 at%, Co atoms 15 at%, and Ni atoms 10 at%.

[0060] Figure 1 The TEM image of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of the present invention is shown. As can be seen from the figure, the PtPdFeCoNi high-entropy alloy nanoparticles are uniformly dispersed on the carbon support, with an average particle size of 3.2 nm. The particles have high dispersion and uniformity.

[0061] X-ray diffraction (XRD) was performed on the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1. The powder sample was uniformly flattened in a quartz plate groove and placed in the testing instrument. The tube voltage and tube current of the instrument were adjusted to 40 kV and 15 mA, respectively. The test angle was 30°~90° and the scanning speed was 5°·min. -1 .

[0062] Figure 2 The XRD pattern of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of the present invention is shown. As can be seen from the figure, the obtained material is a PtPdFeCoNi high-entropy alloy, which is a standard intermetallic ordered alloy.

[0063] Example 2

[0064] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this method and that of Example 1 is that the raw materials are added in an atomic ratio of Pt, Pd, Fe, Co, and Ni of 5:1:1:1.7:1.3, while the rest of the preparation method and parameters remain the same as in Example 1.

[0065] The PtPdFeCoNi / C high-entropy alloy fuel cell catalyst contains PtPdFeCoNi high-entropy alloy nanoparticles and support mesoporous carbon, with the mass percentage of PtPdFeCoNi high-entropy alloy nanoparticles being 40 wt% and the remainder being support mesoporous carbon.

[0066] In PtPdFeCoNi high-entropy alloy nanoparticles, Pt atoms account for 50 at%, Pd atoms 10 at%, Fe atoms 10 at%, Ni atoms 17 at%, and Co atoms 13 at%.

[0067] Example 3

[0068] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this method and that of Example 1 is that mesoporous carbon is replaced with an equal amount of carbon nanotubes, while the rest of the preparation methods and parameters remain the same as in Example 1.

[0069] Example 4

[0070] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this method and that of Example 1 is that the microwave sintering holding time is 50 min, and the total heating and holding time is 60 min. The remaining preparation methods and parameters are the same as those of Example 1.

[0071] Example 5

[0072] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this method and that of Example 1 is that the microwave sintering temperature is 600℃ and the sintering time is 50 min. The remaining preparation methods and parameters are the same as those of Example 1.

[0073] Example 6

[0074] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst, the preparation method comprising the following steps:

[0075] Chloroplatinic acid, palladium chloride, ferric chloride, cobalt chloride, and nickel chloride were dissolved in a citric acid-1,2-propanediol mixed solution according to the atomic ratio of Pt, Pd, Fe, Co, and Ni of 5.5:1:1.1:1.2:1.2. Activated carbon was added, and the mixture was ultrasonically dispersed for 2 hours and then mixed evenly. The solvent was removed by rotary evaporation to form the PtPdFeCoNi / C precursor.

[0076] The PtPdFeCoNi / C precursor was placed in a microwave sintering furnace and held at 900℃ for 10 min in an Ar atmosphere. The total time for heating and holding was 30 min, and the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst was obtained.

[0077] The PtPdFeCoNi / C high-entropy alloy fuel cell catalyst contains PtPdFeCoNi high-entropy alloy nanoparticles and mesoporous carbon support. The mass percentage of PtPdFeCoNi high-entropy alloy nanoparticles is 20 wt%, with the remainder being mesoporous carbon support.

[0078] In PtPdFeCoNi high-entropy alloy nanoparticles, Pt atoms account for 55 at%, Pd atoms 10 at%, Fe atoms 11 at%, Co atoms 12 at%, and Ni atoms 12 at%.

[0079] Example 7

[0080] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this method and Example 1 is that the microwave sintering holding time is 60 min, and the total heating and holding time is 70 min. The remaining preparation methods and parameters are the same as in Example 1.

[0081] Example 8

[0082] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this method and Example 1 is that the microwave sintering temperature is 1000℃, the holding time is 20min, and the total time for heating and holding is 30min. The remaining preparation methods and parameters are the same as in Example 1.

[0083] Example 9

[0084] This embodiment provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this method and Example 1 is that the citric acid-ethylene glycol mixed solution is replaced with a tartaric acid-ethylene glycol mixed solution, ensuring that the ratio of the molar amount of the organic polycarboxylic acid to the total molar amount of the metal elements in the platinum source and the non-platinum transition metal mixed salt is consistent with that in Example 1. The remaining preparation methods and parameters are consistent with those in Example 1.

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing a platinum-based high-entropy alloy fuel cell catalyst. The difference between this preparation method and Example 1 is that the PtPdFeCoNi / C precursor is placed in a muffle furnace and heated to 800°C at a heating rate of 5°C / min under an Ar atmosphere, and held for 300 min. The total heating and holding time is 454 min. The remaining preparation methods and parameters are the same as in Example 1.

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing a platinum-based ternary alloy fuel cell catalyst, the method comprising the following steps:

[0089] Chloroplatinic acid, palladium chloride, and ferric chloride were dissolved in a citric acid-ethylene glycol mixed solution according to an atomic ratio of Pt, Pd, and Fe of 5:1:1. Mesoporous carbon was added, and the mixture was ultrasonically dispersed for 1 hour and then mixed evenly. The solvent was removed by rotary evaporation to form the PtPdFe / C precursor.

[0090] The PtPdFe / C precursor was placed in a microwave sintering furnace and held at 800℃ for 20 min in an Ar atmosphere. The total time for heating and holding was 30 min, and the PtPdFe / C ternary alloy fuel cell catalyst was obtained.

[0091] The PtPdFe / C ternary alloy fuel cell catalyst contains PtPdFe ternary alloy nanoparticles and support mesoporous carbon, with PtPdFe ternary alloy nanoparticles accounting for 40 wt% of the mass and the remainder being support mesoporous carbon.

[0092] In PtPdFe ternary alloy nanoparticles, Pt atoms account for 71.4 at%, Pt atoms account for 14.3 at%, and Fe atoms account for 14.3 at%.

[0093] Comparative Example 3

[0094] This comparative example provides a commercial platinum-carbon catalyst (Pt / C).

[0095] Comparative Example 4

[0096] This comparative example provides a commercial platinum-cobalt alloy catalyst (PtCo / C).

[0097] The average particle size of the alloy nanoparticles was tested for the PtPdFeCoNi / C high-entropy alloy fuel cell catalysts provided in Examples 1-9 and Comparative Example 1, and the PtPdFe / C ternary alloy fuel cell catalyst provided in Comparative Example 2. The specific test results are shown in Table 1.

[0098] The catalysts provided in Examples 1-9 and Comparative Examples 1-4 were subjected to rotating disk electrode (RDE) tests. The specific test method is as follows: 3 mg of catalyst was dispersed in a mixture of 780 μL isopropanol and 200 μL deionized water, and 20 μL of 5% Nafion solution was added. The mixture was sonicated for 1 h. A portion of the dispersed ink was drop-coated onto a disk (0.2475 cm²). 2 The electrodes are thoroughly dried under a heat lamp to produce 40ug. Pt ·cm -2 The catalyst loading electrode was used for testing. Specific electrochemical characterization tests were performed in a standard three-electrode system, with a carbon rod as the counter electrode and a saturated calomel electrode as the reference electrode. Tests were conducted at room temperature. ORR polarization curves were measured in O2-saturated 0.1M HClO4 electrolyte, and background CV curves were measured in N2-saturated 0.1M HClO4 electrolyte. The specific scan potentials ranged from 0.1 to 1.1 V. RHE The scan rate was 10 mV·s. -1 The initial (first lap) half-wave potential and mass ratio activity were tested, and the half-wave potential and mass ratio activity were tested after 30,000 laps of accelerated decay test. The specific test data are shown in Table 1.

[0099] Figure 3 The diagram shows a comparison of the activities of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of this invention, the commercial platinum-carbon catalyst provided in Comparative Example 3, and the commercial platinum-cobalt alloy catalyst provided in Comparative Example 4. As can be seen from the diagram, the electrochemical activity of the PtPdFeCoNi / C high-entropy alloy is far superior to that of the commercial platinum-carbon and commercial platinum-cobalt alloy catalysts. The PtPdFeCoNi high-entropy alloy of this invention exhibits a multi-principal-element synergistic regulation of its electronic structure. The orbital hybridization between multi-element atoms (such as dd orbital overlap) further optimizes the electron cloud distribution of the active sites, enhancing the activation ability for O2 and improving the intrinsic activity of the active sites. In contrast, the commercial platinum-carbon and commercial platinum-cobalt alloys are only regulated by Pt or Pt combined with a single element (Co), and the d-band center of Pt is difficult to precisely match the optimal reaction requirements.

[0100] Figure 4The ORR positive scanning polarization curves of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of the present invention are shown in the initial and 30,000-cycle accelerated decay test in O2-saturated 0.1M HClO4 solution. As can be seen from the figure, the initial ORR half-wave potential is 0.95V, and after 30,000-cycle accelerated decay test, the half-wave potential only decreases by 8mV.

[0101] Figure 5 The cyclic voltammograms of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 of this invention are shown, both initially and after 30,000 accelerated decay cycles. As can be seen from the figure, after 30,000 accelerated decay cycles, the specific activity is 0.92 A·mg. Pt -1 The mass-specific activity decay rate of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst is only 12.4%.

[0102] Table 1

[0103]

[0104] The test results show that:

[0105] (1) As can be seen from Examples 1-6 and 9, the high-entropy alloy catalyst prepared by solution impregnation combined with microwave sintering does not exhibit excessive agglomeration, and therefore does not significantly affect the ORR stability. This is due to the small particle size and uniform crystal nuclei of PtPdFeCoNi high-entropy alloy nanoparticles brought about by microwave sintering. Through the rapid heating of microwave sintering, elemental segregation can be suppressed, and the synergistic effect between various metal elements can be promoted. At the same time, microwave sintering can also achieve rapid cooling. Under thermal shock, the crystal lattice is prone to form a large number of surface vacancies and dislocations and other defect structures. These defect structures also become highly efficient active sites for the ORR reaction.

[0106] Specifically, after 30,000 accelerated degradation cycles, the half-wave potential of the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst decreased by only ≤25mV, and the specific activity decreased by ≤24.9%. In particular, the PtPdFeCoNi / C high-entropy alloy fuel cell catalyst provided in Example 1 had an initial ORR half-wave potential of 0.95V, which decreased by only 8mV after 30,000 accelerated degradation cycles, and the specific activity decreased from the initial 1.05A·mg... Pt -1 Decreased to 0.92 A·mg Pt -1 The degradation was 12.4%, and the tested area-specific activity decreased from 2.2 mA·cm⁻¹. -2 Reduced to 1.9 mA·cm -2The attenuation was 13.6%, far exceeding the requirements of the DOE2025 target.

[0107] (2) As can be seen from Examples 1, 7 and 8, the present invention controls the holding temperature of microwave sintering to be 600℃~900℃ and the holding time to be 10min~50min. By matching the holding temperature and time of microwave sintering, the resulting platinum-based high-entropy alloy fuel cell catalyst has high oxygen reduction activity and high stability. In Example 7, the holding time of microwave sintering was too long (60min) and in Example 8, the holding temperature was too high (1000℃), which will further aggravate agglomeration, increase the average particle size of high-entropy alloy particles, and reduce the initial mass specific activity of platinum-based high-entropy alloy fuel cell catalyst. After 30,000 cycles of accelerated decay test, the half-wave potential decay and the mass specific activity decay rate are significantly reduced, and the catalytic activity and stability of ORR are reduced.

[0108] (3) As can be seen from Example 1 and Comparative Example 1, the average particle size of the high-entropy alloy nanoparticles prepared by conventional tube furnace sintering is 10.4 nm, which is much larger than the average particle size of the high-entropy alloy nanoparticles prepared by microwave sintering under the same conditions (3.2 nm). At the same time, the catalytic activity and stability of ORR in Example 1 are also much better than those in Comparative Example 1. This indicates that the traditional calcination method has a slow heating and cooling rate, which makes it easier to cause uneven growth rate of crystal nuclei, resulting in a larger average particle size of high-entropy alloy nanoparticles. At the same time, the diffusion rates of each metal element are different, which easily leads to the formation of segregated phases, thereby destroying the synergistic effect between metals, resulting in a decrease in the ORR catalytic activity and stability of the catalyst.

[0109] (4) As can be seen from Example 1 and Comparative Example 2, the PtPdFeCoNi high-entropy alloy of the present invention has a multi-principal element synergistic regulation of electronic structure. The orbital hybridization between multi-element atoms (such as dd orbital overlap) further optimizes the electron cloud distribution of active sites, enhances the activation ability of O2, and improves the intrinsic activity of active sites. As a result, the obtained platinum-based high-entropy alloy fuel cell catalyst has good ORR catalytic performance.

[0110] In summary, this invention employs a solution impregnation combined with microwave sintering. Microwave sintering offers faster heating and cooling rates and requires less sintering time, resulting in a shorter overall reaction time and significantly reduced particle growth time. The uniform temperature field during sintering ensures uniform particle growth, avoiding abnormal particle growth caused by uneven heating and localized high temperatures. Rapid cooling allows for the formation of numerous surface vacancies and dislocations under thermal shock, creating highly efficient active sites for the ORR reaction. The platinum-based high-entropy alloy fuel cell catalyst prepared by this invention features small-sized platinum-based high-entropy alloy nanoparticles with uniformly distributed active sites, strong electronic structure control capabilities, high oxygen reduction activity, and high stability, meeting the requirements for long-life fuel cells.

[0111] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a platinum-based high-entropy alloy fuel cell catalyst, characterized in that, The preparation method includes the following steps: A platinum source, a non-platinum transition metal mixed salt, a carbon support, and a solvent are mixed uniformly to obtain a platinum-based high-entropy alloy precursor; the platinum-based high-entropy alloy precursor is then subjected to microwave sintering to obtain a platinum-based high-entropy alloy fuel cell catalyst. The non-platinum transition metal mixed salt comprises a combination of at least four non-platinum transition metal salts.

2. The preparation method according to claim 1, characterized in that, The sintering atmosphere of the microwave sintering includes an inert atmosphere; Preferably, the gas used in the inert atmosphere includes any one or a combination of at least two of argon, nitrogen, or helium; Preferably, the holding temperature for microwave sintering is 600℃~900℃; Preferably, the holding time for microwave sintering is 10 min to 50 min; Preferably, the total heating and holding time for microwave sintering is 15 min to 70 min.

3. The preparation method according to claim 1 or 2, characterized in that, The non-platinum transition metal mixed salt includes a combination of at least four of the following: iron salt, cobalt salt, nickel salt, palladium salt, copper salt, zinc salt, manganese salt, or chromium salt, preferably a combination of iron salt, cobalt salt, nickel salt, and palladium salt.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The types of salts corresponding to the non-platinum transition metal mixed salts include any one or a combination of at least two of nitrates, chlorides, or sulfates. Preferably, the platinum source includes any one or a combination of at least two of chloroplatinic acid, sodium chloroplatinate, potassium chloroplatinate, platinum nitrate, sodium chloroplatinate, potassium chloroplatinate, tetraammineplatinum nitrate, or potassium chloroplatinate. Preferably, the carbon support comprises any one or a combination of at least two of mesoporous carbon, carbon nanotubes, activated carbon, graphene, or carbon nanofibers.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The solvent includes a mixed solution of organic polycarboxylic acids and polyols; Preferably, the organic polycarboxylic acid includes any one or a combination of at least two of citric acid, tartaric acid, malic acid, ethylenediaminetetraacetic acid, or hydantoin, and more preferably any one or a combination of at least two of citric acid, tartaric acid, or malic acid. Preferably, the ratio of the molar amount of the organic polycarboxylic acid to the total molar amount of metal elements in the platinum source and the non-platinum transition metal mixed salt is (2~3):1; Preferably, the polyol includes any one or a combination of at least two of ethylene glycol, glycerol, 1,2-propanediol, or an ethanol-polyethylene glycol mixed solution; Preferably, the ratio of the volume of the polyol to the total mass of the platinum source and the non-platinum transition metal mixed salt is (0.5 mL ~ 1 mL): 1 mg.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The mixing includes ultrasonic dispersion; Preferably, the mixing time is 1 hour to 2 hours; Preferably, the mixing process further includes a solvent removal step; Preferably, the solvent removal method includes rotary evaporation.

7. A platinum-based high-entropy alloy fuel cell catalyst, characterized in that, The platinum-based high-entropy alloy fuel cell catalyst is prepared according to any one of claims 1 to 6.

8. The platinum-based high-entropy alloy fuel cell catalyst according to claim 7, characterized in that, The platinum-based high-entropy alloy fuel cell catalyst comprises platinum-based high-entropy alloy nanoparticles and a carbon support; Preferably, based on the total mass of the platinum-based high-entropy alloy fuel cell catalyst being 100wt%, the mass of the platinum-based high-entropy alloy nanoparticles is 20wt%~40wt%, with the remainder being a carbon support; Preferably, the platinum-based high-entropy alloy nanoparticles comprise platinum atoms and non-platinum transition metal atoms; Preferably, the non-platinum transition metal atoms include a combination of at least four of the following: iron atoms, cobalt atoms, nickel atoms, palladium atoms, copper atoms, zinc atoms, manganese atoms, or chromium atoms, and more preferably a combination of iron atoms, cobalt atoms, nickel atoms, and palladium atoms. Preferably, in the platinum-based high-entropy alloy nanoparticles, the atomic percentage of platinum atoms in the total metal atoms is 20 at% to 70 at%, more preferably 45 at% to 55 at%; Preferably, in the platinum-based high-entropy alloy nanoparticles, the atomic percentage of non-platinum transition metal atoms in the total metal atoms is 30 at% to 80 at, more preferably 45 at% to 55 at.

9. The platinum-based high-entropy alloy fuel cell catalyst according to claim 7 or 8, characterized in that, The average particle size of the platinum-based high-entropy alloy nanoparticles is 3nm~8nm, preferably 3nm~6nm.

10. The application of a platinum-based high-entropy alloy fuel cell catalyst, characterized in that, The platinum-based high-entropy alloy fuel cell catalyst prepared by the preparation method according to any one of claims 1 to 6, or the platinum-based high-entropy alloy fuel cell catalyst according to any one of claims 7 to 9, is applied to a hydrogen fuel cell.

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