Preparation method of fuel cell carbon-supported platinum catalyst, catalyst and application

Abstract

The invention relates to the technical field of fuel cells, and provides a preparation method of a fuel cell carbon-supported platinum catalyst, the catalyst and application, the preparation method comprises the following steps: S1, adding a platinum precursor solution and a carbon material into a solvent, dispersing, drying and grinding to obtain catalyst powder A; s2, performing primary microwave treatment on the catalyst powder A under inert gas to obtain catalyst powder B; and S3, mixing and grinding the catalyst powder B and the platinum precursor solid, and carrying out secondary microwave treatment under inert gas to obtain the carbon-supported platinum catalyst. The preparation method has the advantages that through two-step microwave treatment, the particle size of the platinum particles inside and outside the pores of the carbon carrier is accurately controlled under the condition that the high activity of the platinum particles is kept, so that the carbon-supported platinum catalyst has the advantages of high performance, high stability and durability, and meanwhile, the performance of the catalyst is not influenced under the low-humidity working condition.

Description

Technical Field

[0001] The present invention relates to the field of fuel cells, and more particularly, to a preparation method, a catalyst and an application of a platinum-carbon supported catalyst for fuel cells. Background Art

[0002] A proton exchange membrane fuel cell (PEMFC) is composed of a plurality of single cells connected in series. A single cell mainly consists of a membrane electrode assembly (MEA) and bipolar plates. The MEA mainly consists of a catalytic layer, a proton exchange membrane and a gas diffusion layer. The catalytic layer is the core of the MEA, which is not only the place for electrochemical reactions, but also the transfer channel for substances such as gas, water, electrons and protons.

[0003] The most important key material in the catalytic layer is the catalyst. Reactant gases, electrons and protons are transported to the surface of the catalyst to occur electrochemical reactions. The catalyst generally consists of a carbon support and metal particles. The specific surface area and pore structure of the support have an important impact on the mass transfer of gases and the distribution of metal particles. The mesoporous carbon supported catalyst is beneficial to gas circulation due to its unique carbon structure, reduces the mass transfer resistance, and promotes the performance improvement at high current densities. At the same time, the mesoporous structure is beneficial to the uniform distribution of platinum particles, and can effectively improve the performance of the membrane electrode at the cathode of the fuel cell.

[0004] The size of platinum particles in fuel cell catalysts has a great influence on performance and durability. Smaller-sized platinum particles have a large ECSA (effective electrochemical active area) and high activity, and usually show high performance on the membrane electrode; however, if the size is too small, the surface energy of the particles will be relatively large, and the crystal structure stability will be reduced, resulting in poor durability of the catalyst. Larger particles will reduce the utilization rate of platinum atoms and catalytic activity, but larger particles have strong stability and are not easily dissolved and migrated.

[0005] In addition to the influence of the size of platinum particles themselves, the deposition sites of platinum particles and the strength of the interaction with the support also affect the stability of the catalyst. When platinum particles are deposited in pores with a relatively small pore diameter of the carbon support, they often have high stability because the pores prevent the migration of platinum particles; therefore, even if the size of platinum particles is small, the platinum deposited in these pores can often be stable; this kind of catalyst has both good intrinsic activity and durability. The rich pore structure of the mesoporous support provides a large number of in-pore platinum deposition sites, which can deposit a large amount of platinum into the pores and maintain the stability of platinum particles even when the platinum particles are small; therefore, mesoporous support catalysts often have both high intrinsic activity and high catalyst durability.

[0006] However, in practical applications, the high intrinsic activity of the mesoporous support catalyst cannot be perfectly expressed under all operating conditions. Since the performance of a fuel cell depends on the three-phase interface, the catalysts in the pores, especially those deep in the pores, are far from the perfluorosulfonic acid resin, lacking the perfluorosulfonic acid resin-catalyst platinum particle interface. For such platinum to participate in the reaction, it requires high humidity conditions and relies on water to transfer protons. Therefore, the mesoporous support catalyst exhibits good performance expression at high humidity. However, once the operating humidity decreases, the catalysts deep in the pores cannot obtain protons and thus cannot participate in the reaction, often resulting in a performance decline. The platinum outside the pores has a complete perfluorosulfonic acid resin-platinum particle interface, and its mass transfer is basically unaffected at low humidity, enabling it to perform well at low humidity. As mentioned above, under the condition of the same platinum particle size, the durability of the platinum particles outside the pores is poor. Therefore, it is necessary to increase the particle size of the platinum particles outside the pores to improve the stability problem. Therefore, regulating the platinum particle sizes inside and outside the pores of the mesoporous platinum-carbon catalyst, depositing smaller platinum particles inside the mesopores to provide high intrinsic activity and stability, distributing larger platinum particles outside the pores to enhance the performance under dry operating conditions, and at the same time controlling the size of the platinum particles outside the catalyst pores not to be too large to improve stability, this is a catalyst design with high performance and high durability, which is crucial for improving the performance and durability of proton exchange membrane fuel cells.

[0007] When synthesizing the catalyst by the conventional impregnation reduction method, it often requires long-term continuous high-temperature treatment, which in turn causes excessive agglomeration and sintering of the catalyst platinum particles, an increase in the platinum particle size, a decrease in the atomic utilization rate, and low catalyst activity. Nowadays, advanced rapid annealing methods, pulse heating synthesis methods, etc., although they can synthesize platinum catalysts efficiently and rapidly and effectively solve the problem of particle sintering caused by long-term high temperature, it is difficult to precisely control the distribution of platinum particles inside and outside the pores. Therefore, it is difficult to prepare a catalyst that simultaneously possesses high performance and high durability. Summary of the Invention

[0008] The present invention aims to overcome at least one defect (shortcoming) of the above-mentioned prior art, and provides a preparation method, a catalyst and an application of a platinum-carbon catalyst for fuel cells, which can adjust the particle sizes of platinum particles inside and outside the carbon support pores and improve the activity and durability of the fuel cell cathode catalyst.

[0009] A preparation method of a platinum-carbon catalyst for fuel cells according to the present invention includes the following steps:

[0010] S1. Add a platinum precursor solution and a carbon material into a solvent, disperse, dry, and grind to obtain catalyst powder A;

[0011] S2. Perform a first microwave treatment on the catalyst powder A under an inert gas to obtain catalyst powder B;

[0012] S3. Mix and grind catalyst powder B with a platinum precursor solid, and then perform a secondary microwave treatment under an inert gas to obtain the platinum-carbon catalyst.

[0013] In step S1, the platinum precursor solution can be added to the solvent first, and then the carbon material can be added. Alternatively, the platinum precursor solution and the carbon material can be added to the solvent simultaneously. Or the carbon material can be added to the solvent first, and then the platinum precursor solution can be added. After the platinum precursor and the carbon material are added to the solvent and dispersed and mixed evenly, a platinum precursor impregnation solution is formed, and then drying and grinding are performed to form catalyst powder A, that is, catalyst powder A is the powder obtained after drying and grinding the platinum precursor impregnation solution. In step S2, the first microwave treatment is performed, and catalyst powder B is the powder obtained after the first platinum particle deposition. In step S3, the second microwave treatment is performed, and the obtained platinum-carbon catalyst is the catalyst powder obtained after the second platinum particle deposition. The carbon material is preferably a mesoporous carbon material.

[0014] In this solution, a two-step microwave method is adopted, which is divided into the first step of impregnation-microwave synthesis of small-sized nanoparticles, that is, steps S1 and S2, and the second step of solid-phase microwave-controlled synthesis, that is, step S3.

[0015] In the first step of microwave impregnation reduction, platinum particle deposition is carried out by high-power, fast, and efficient microwave treatment in an inert atmosphere, so that platinum particles are deposited inside and outside the pores of the mesoporous carbon carrier in a small size, which can effectively regulate the deposition of platinum inside and outside the carrier pores and keep it with high catalytic activity. In more than one embodiment of the present invention, in the catalyst powder B obtained by the first step of microwave impregnation reduction, the particle size range of platinum particles inside and outside the pores of the carbon carrier is 0.6 - 3 nm, and the smaller particle size is convenient for the microwave treatment in the second step to control the particle size of platinum particles.

[0016] In the second step of solid-phase microwave-controlled synthesis, a solid-phase platinum source is added to enrich and control platinum atoms on the surface of platinum particles, so that platinum atoms outside the pores migrate, and the particles grow and the crystal structure is stabilized; while for the platinum particles inside the pores and deep in the carrier, due to the blocking effect of the carrier structure and the difficulty of the solid-phase platinum source to agglomerate and sinter in the mesopores quickly and in a short time, the high catalytic activity is maintained, thus precisely controlling the atomic migration of platinum particles outside the pores and the growth of platinum particles. In more than one embodiment of the present invention, in the platinum-carbon catalyst obtained by the second step of solid-phase microwave-controlled synthesis, the particle size range of platinum particles outside the pores of the carbon carrier is 3.0 - 6 nm.

[0017] The two-step microwave synthesis method of this solution precisely controls the particle sizes of platinum particles inside and outside the pores of the carbon support. The platinum particles inside the pores are smaller, with a larger effective electrochemical active area and higher stability. The platinum particles outside the pores are larger, which can form a complete perfluorosulfonic acid resin-platinum particle interface, ensuring that the performance is not affected even at low humidity, and the larger particle size also guarantees the stability of the platinum particles outside the pores. In addition, the catalytic activity and stable crystal structure of the platinum particles are maintained in the two-step microwave synthesis method of this solution.

[0018] Therefore, under the premise that the high activity of platinum particles is maintained in both two-step microwave treatments of the preparation method of this solution, the platinum-carbon catalyst has the advantages of high performance, high stability and durability, and does not affect the catalyst performance under low-humidity working conditions.

[0019] Furthermore, the treatment time of the first microwave treatment is 8-10 min.

[0020] In this solution, proper control of the time is beneficial to avoiding the influence on the activity of platinum particles caused by too long time, or the inconvenience of particle size control of the second microwave due to too large platinum particles.

[0021] Furthermore, the treatment time of the second microwave treatment is 6-13 min.

[0022] In this solution, proper control of the time is beneficial to avoiding poor stability due to too small platinum particles outside the pores of the carbon support, and also avoiding low utilization rate and low activity due to too large platinum particles.

[0023] Furthermore, after the second microwave treatment under an inert gas, the following steps are also included: washing, centrifuging, drying and grinding to obtain the platinum-carbon catalyst. In this technical solution, the unreacted platinum precursor, impurities such as residual chlorides after the reaction, etc. can be washed away through washing.

[0024] Furthermore, the treatment conditions of both the first microwave treatment and the second microwave treatment are: the gas flow rate is 50-80 mL / min, and the treatment power is 500-800 W. In one or more embodiments of the present invention, the microwave frequency is 2450 MHz ± 15 Hz.

[0025] Furthermore, both the platinum precursor A and the platinum precursor B are selected from one or at least two combinations of chloroplatinic acid, platinum acetylacetonate, potassium chloroplatinate, potassium chloroplatinate or sodium chloroplatinate.

[0026] Furthermore, in step S1, the drying temperature is 55-65 °C, and the drying time is 8-15 h.

[0027] Another object of the present invention is to provide a carbon-supported platinum catalyst prepared by the preparation method of any one of the above. In the carbon-supported platinum catalyst, the particle size of platinum particles in the pores of the carbon support is 0.6 - 3 nm, and the particle size of platinum particles outside the pores of the carbon support is 3.0 - 6 nm.

[0028] Another object of the present invention is to provide an application of the above carbon-supported platinum catalyst in the preparation of a fuel cell catalyst slurry.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The present invention overcomes the problems of sintering and agglomeration of platinum particles in the traditional heat treatment impregnation reduction method. Through two-step microwave treatment, while maintaining the high activity of platinum particles, the particle sizes of platinum particles inside and outside the pores of the carbon support are accurately controlled, so that the carbon-supported platinum catalyst has the advantages of high performance, high stability and durability, and does not affect the catalyst performance under low humidity conditions. Description of the Drawings

[0031] Figure 1 It is the TEM particle size distribution diagram of platinum particles on the catalyst. Figure 1 (a - c): TEM particle size distribution diagrams of platinum particles of the catalysts prepared in Examples 1 - 3; Figure 1 (d): TEM particle size distribution diagram of platinum particles of the catalyst prepared in Comparative Example 1; Figure 1 (e): TEM particle size distribution diagram of platinum particles of the catalyst prepared in Comparative Example 2.

[0032] Figure 2 It is the polarization performance curve diagram of the membrane electrodes corresponding to Examples 1 - 3 and Comparative Examples 1 - 4.

[0033] Figure 3 It is the polarization performance curve diagram before and after the durability test of Example 1 and Comparative Example 1.

[0034] Figure 4 It is the cross-sectional structure schematic diagram of the carbon-supported platinum catalyst prepared by the preparation method of the present invention.

[0035] Reference numerals: carbon support 1, platinum particle 2. Detailed Embodiments

[0036] The drawings of the present invention are only for illustrative purposes and should not be construed as a limitation of the present invention. For better illustration of the following embodiments, some components in the drawings will be omitted, enlarged or reduced, which do not represent the dimensions of the actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0037] A preparation method of a fuel cell carbon-supported platinum catalyst of the present invention includes the following steps:

[0038] S1. Add a platinum precursor solution and a carbon material into a solvent, disperse, dry, and grind to obtain catalyst powder A;

[0039] S2. Perform a first microwave treatment on the catalyst powder A under an inert gas to obtain catalyst powder B;

[0040] S3. Mix and grind the catalyst powder B with a platinum precursor solid, and then perform a second microwave treatment under an inert gas to obtain the carbon-supported platinum catalyst.

[0041] The cross-section of the structure of the carbon-supported platinum catalyst prepared by the preparation method of the present invention is as Figure 4 shown. Platinum particles 2 are loaded on the carbon support 1. The carbon support 1 has a porous structure, and platinum particles 2 with smaller particle sizes are attached inside the pores, and platinum particles 2 with larger particle sizes are attached outside the pores.

[0042] Under the premise that the high activity of the platinum particles is maintained in both steps of the microwave treatment in the preparation method of this solution, the carbon-supported platinum catalyst has the advantages of high performance, high stability, and durability, and does not affect the catalyst performance under low-humidity working conditions.

[0043] Further, the treatment time of the first microwave treatment is 8 - 10 min.

[0044] Further, the treatment time of the second microwave treatment is 6 - 13 min.

[0045] Further, after the second microwave treatment under an inert gas, the following steps are also included: washing, centrifuging, drying, and grinding to obtain the carbon-supported platinum catalyst.

[0046] Further, the treatment conditions of both the first microwave treatment and the second microwave treatment are: the gas flow rate is 50 - 80 mL / min, and the treatment power is 500 - 800 W. In one or more embodiments of the present invention, the microwave frequency is 2450 MHz ± 15 Hz.

[0047] Further, both the platinum precursor A and the platinum precursor B are selected from one or at least two combinations of chloroplatinic acid, platinum acetylacetonate, potassium chloroplatinate, potassium chloroplatinate, or sodium chloroplatinate.

[0048] Further, in step S1, the drying temperature is 55 - 65 °C, and the drying time is 8 - 15 h.

[0049] Another object of the present invention is to provide a carbon-supported platinum catalyst prepared by the preparation method of any one of the above. In the carbon-supported platinum catalyst, the particle size of the platinum particles inside the pores of the carbon support is 1.8 - 3 nm, and the particle size of the platinum particles outside the pores of the carbon support is 3.0 - 5.5 nm.

[0050] Another object of the present invention is to provide an application of the above-mentioned platinum-carbon catalyst in the preparation of fuel cell catalyst slurry.

[0051] The following are specific embodiments.

[0052] Example 1

[0053] This example provides a method for preparing a fuel cell platinum-carbon catalyst, including:

[0054] S1. Take 10.25 mmol of chloroplatinic acid aqueous solution, 5.85 g of ECP-600JD carbon powder produced by KETJEN, and 50 ml of absolute ethanol, and perform ice bath ultrasonic treatment for 30 min in a beaker. After stirring for 6 h, a uniformly dispersed turbid liquid is obtained, which is transferred to an oven at 60 °C for drying for 12 h, and then the powder is ground.

[0055] S2. Fill the ground powder in a high-temperature and high-pressure resistant quartz reaction bottle filled with an argon atmosphere, and perform microwave treatment using a microwave reactor. The conditions inside the reactor are an argon atmosphere, a gas flow rate of 50 mL / min, a microwave frequency of 2.45 GHz, a treatment power of 800 W, and a treatment time of 8 min.

[0056] S3. After the powder treated in step S2 is completely cooled to room temperature, take out the powder and grind it evenly with 2.56 mmol of platinum acetylacetonate powder, and then perform microwave treatment again. The reaction conditions are an argon atmosphere, a gas flow rate of 50 mL / min, a microwave frequency of 2.45 GHz, a treatment power of 800 W, and a treatment time of 6 min. Wash the sample 4-5 times in an ethanol aqueous solution with an alcohol-water ratio of 2:8, centrifuge at 10000 rpm for 5 min, collect the sample, transfer it to an oven at 80 °C for drying for 12 h, and grind to obtain the platinum-carbon catalyst powder.

[0057] Example 2

[0058] This example provides a method for preparing a fuel cell platinum-carbon catalyst, which is different from Example 1 in that: in step S3, the treatment time of the microwave treatment is 8 min.

[0059] Example 3

[0060] This example provides a method for preparing a fuel cell platinum-carbon catalyst, which is different from Example 1 in that: in step S3, the treatment time of the microwave treatment is 10 min.

[0061] Comparative Example 1

[0062] This comparative example provides a platinum-carbon catalyst synthesized by a conventional thermal annealing method, including:

[0063] Weigh 12.8 mmol of aqueous chloroplatinic acid solution, 5.85 g of ECP-600JD carbon powder produced by KETJEN, and 50 ml of absolute ethanol. Place them in a beaker, perform ice bath ultrasonic treatment for 30 min, stir for 6 h to obtain a uniformly dispersed turbid liquid, transfer it to an oven at 60 °C and dry for 12 h, and then grind the powder. Place the ground powder in a crucible and perform thermal annealing treatment using a tube furnace. The reaction conditions in the tube furnace are an argon atmosphere, a gas flow rate of 50 mL / min, a heating rate of 5 °C / min. Heat from room temperature to 400 °C and keep it at a constant temperature for 2 h, and then naturally cool to room temperature. Wash the obtained powder 4 - 5 times in an ethanol aqueous solution with an alcohol-water ratio of 2:8, centrifuge at 10000 rpm for 5 min, collect the sample, transfer it to an oven at 80 °C and dry for 12 h, and then grind to obtain the platinum-carbon catalyst powder.

[0064] Comparative Example 2

[0065] This comparative example provides a preparation method of a platinum-carbon catalyst for a fuel cell, which only performs impregnation-microwave treatment, including:

[0066] Weigh 12.8 mmol of aqueous chloroplatinic acid solution, 5.85 g of ECP-600JD carbon powder produced by KETJEN, and 50 ml of absolute ethanol. Place them in a beaker, perform ice bath ultrasonic treatment for 30 min, stir for 6 h to obtain a uniformly dispersed turbid liquid, transfer it to an oven at 60 °C and dry for 12 h, and then grind the powder. Place the ground powder in a microwave reactor filled with an argon atmosphere. The conditions in the reactor are an argon atmosphere, a gas flow rate of 50 mL / min, a microwave frequency of 2.45 GHz, a treatment power of 800 W, and a treatment time of 17 min. Then naturally cool to room temperature. Wash the obtained powder 4 - 5 times in an ethanol aqueous solution with an alcohol-water ratio of 2:8, centrifuge at 10000 rpm for 5 min, collect the sample, transfer it to an oven at 80 °C and dry for 12 h, and then grind to obtain the platinum-carbon catalyst powder.

[0067] Comparative Example 3

[0068] This comparative example provides a preparation method of a platinum-carbon catalyst for a fuel cell. The steps S1 and S2 of this preparation method are the same as those in Example 1. The step S3 of this preparation method includes:

[0069] Wash the powder after the treatment in step S2 4-5 times in an ethanol aqueous solution with an ethanol-water ratio of 2:8, centrifuge at 10,000 rpm for 5 min, collect the sample, transfer it to an oven and dry at 80 °C for 12 h, grind it. Mix the ground powder with 2.56 mmol of chloroplatinic acid aqueous solution in 50 ml of absolute ethanol in a beaker, ultrasonically bath in ice for 30 min, stir for 6 h to obtain a uniformly dispersed turbid liquid, transfer it to an oven at 60 °C and dry for 12 h, grind the powder. Place the ground powder in a microwave reactor filled with an argon atmosphere. The conditions inside the reactor are an argon atmosphere, a gas flow rate of 50 mL / min, a microwave frequency of 2.45 GHz, a treatment power of 800 W, a treatment time of 6 min, and naturally cool to room temperature. Wash the obtained powder 4-5 times in an ethanol aqueous solution with an ethanol-water ratio of 2:8, centrifuge at 10,000 rpm for 5 min, collect the sample, transfer it to an oven and dry at 80 °C for 12 h, and grind to obtain the platinum-carbon catalyst powder.

[0070] Comparative Example 4

[0071] This comparative example provides a method for preparing a platinum-carbon catalyst for a fuel cell. The difference from Example 1 is that: in step S3, the treatment time of the microwave treatment is 14 min.

[0072] The platinum-carbon catalyst powders prepared by the preparation methods of Examples 1 to 3 and Comparative Examples 1 to 4 are respectively prepared into a cathode catalyst layer by the following method:

[0073] Weigh 8.08 g of the platinum-carbon catalyst powder, 18.17 g of a 20 wt% solid content M700 resin solution, 9.05 g of ethanol, and 64.70 g of ultrapure water. Slowly add the catalyst to the water and stir for 5 min, then add the resin solution and stir for 5 min, and then add ethanol and continue to stir for 5 min to complete the pre-dispersion of the slurry. Disperse the pre-dispersed slurry 2 times through a high-pressure homogenizer at a dispersion pressure of 4000 psi to obtain a catalyst slurry, coat it on one side of the proton exchange membrane by the slit coating method, and dry at 80 °C to obtain the cathode catalyst layer of the membrane electrode.

[0074] Test Example 1

[0075] Use XRD to measure and fit and calculate the particle size of platinum particles on the platinum-carbon catalysts prepared corresponding to Examples 1 to 3 and Comparative Examples 1 to 4. The results are shown in Table 1 and Table 2;

[0076] Table 1 Test results of the average particle size of platinum particles during the preparation of Examples 1 to 3 and Comparative Examples 1 to 4

[0077]

[0078]

[0079] Table 2 Test results of the average particle size of platinum particles of the carbon-supported platinum catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 4

[0080] Sample Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Particle Size (nm) 3.0 3.3 3.4 5.8 4.2 4.5 5.1

[0081] In addition, in Examples 1 to 3, the measured particle sizes of the platinum particles on the powder obtained by the treatment in Step S2 were all between 0.6 nm and 3 nm.

[0082] Test Example 2

[0083] The morphology of the catalyst was characterized by TEM, and the particle size distributions of the platinum particles in Examples 1 to 3 and Comparative Examples 1 to 2 were counted. The statistical results are as Figure 1 shown.

[0084] Test Example 3

[0085] The cathode catalyst layers corresponding to Examples 1 to 3 and Comparative Examples 1 to 4 were prepared into membrane electrodes, and the single-cell polarization performance curves of the membrane electrodes were tested using an 850e fuel cell test system. The test conditions were a cell temperature of 80 °C, a back pressure of 100 KPa, and a humidity of 100% RH. The test results are as Figure 2 shown.

[0086] Test Example 4

[0087] The cathode catalyst layers corresponding to Example 1 and Comparative Example 1 were prepared into membrane electrodes, and the platinum dissolution durability of the membrane electrodes was tested using an 850e fuel cell test system. The polarization performance curves before and after 30k voltage cycles were tested. The test results are as Figure 3 shown.

[0088] Comparative Example 1 is a catalyst sample synthesized by a conventional thermal annealing method. The results in Table 2 show that the average particle size of its platinum particles is 5.8 nm. At the same time, Figure 1 (a-c) and (d) show that the examples have a better platinum particle size distribution, and the maximum particle size does not exceed 6 nm, while in Comparative Example 1, most of the platinum particle size distributions are between 5 nm and 6 nm, and the maximum particle size reaches 8 nm, indicating that after the thermal annealing treatment at high temperature for a long time, the platinum particles are sintered and agglomerated due to the thermal effect, and the particles grow excessively. Figure 2 The test results show that the performance of Comparative Example 1 is the worst under the entire test conditions, while the fuel cell performances of Examples 1 to 3 are excellent. Figure 3 The test results show that after 30k voltage cycles of the catalyst in Example 1, the platinum dissolution durability is improved, indicating that the catalyst crystal structure synthesized by the two-step microwave is stable, exerting its high catalytic activity and improving the platinum durability of the fuel cell.

[0089] Comparative Example 2 is a catalyst sample synthesized by one-step impregnation-microwave. The results in Table 1 and Table 2 show that the particle size of the catalyst platinum particles increases to 4.2 nm. At the same time,Figure 1 (e) It is shown that most of the platinum particle sizes in Comparative Example 2 are distributed between 3.0 and 5.0 nm, indicating that the growth of particles inside and outside the pores will be caused only by extending the time of the first step, and the maximum particle size exceeds 6 nm, indicating that it is difficult to precisely control the particle size by only extending the impregnation microwave treatment time of the first step, and it is easy to cause the particle size of platinum particles outside the pores to be too large. Figure 2 The test results show that under high humidity conditions, the fuel cell performance of the catalyst in Comparative Example 2 is slightly improved compared with that in Comparative Example 1, but slightly worse than that in Examples 1 to 3, indicating that only by performing the first-step microwave treatment, the growth of particles inside and outside the pores will reduce the catalytic activity of the catalyst, and the relatively large particle size of platinum particles outside the pores will lead to a decrease in utilization rate, thereby reducing the activity.

[0090] Comparative Example 3 is a sample prepared by using the impregnation-microwave synthesis method for both the first step and the second step. The results in Table 1 and Table 2 show that the average particle size of the platinum particles of the catalyst increases to 4.5 nm, indicating that the growth of particles inside and outside the pores will also be caused by simple stepwise impregnation microwave reduction, and the particle size of platinum particles outside the pores is too large. Figure 2 The test results show that under high humidity conditions, the fuel cell performance of the catalyst in Comparative Example 2 is slightly improved compared with that in Comparative Example 1, but slightly worse than that in Examples 1 to 3, indicating that only by stepwise impregnation microwave treatment, the growth of particles inside and outside the pores will reduce the catalytic activity of the catalyst.

[0091] Comparative Example 4 is a sample synthesized by performing a long-time treatment during the second-step solid-phase microwave synthesis. The results in Table 1 and Table 2 show that the average particle size of the platinum particles of the catalyst increases to 5.1 nm, indicating that under long-time microwave treatment, the platinum particles are slightly sintered, and the migration of platinum atoms leads to overgrowth. Figure 2 The test results show that under high humidity conditions, the performance of the medium and low current densities of the catalyst in Comparative Example 3 decreases, indicating that the excessive growth of the platinum particle size, the decrease in specific surface area, the decrease in the utilization rate of platinum atoms, and the decrease in catalytic activity ultimately lead to the decrease in the performance of the membrane electrode.

[0092] Combining Examples 1 to 3 and Comparative Examples 1 to 4, it can be seen that through two-step moderate microwave impregnation and solid-phase microwave synthesis method, the growth and distribution of platinum particles inside and outside the pores of the mesoporous platinum-carbon catalyst can be effectively regulated, thereby optimizing the stability of platinum particles outside the pores of the carbon support, giving full play to the catalytic activity of platinum particles inside the pores, and improving the durability of platinum in the cathode of the fuel cell.

[0093] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly explaining the technical solutions of the present invention, rather than limitations on the specific implementation manners of the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the claims of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a carbon-supported platinum catalyst for a fuel cell, characterized in that, It includes the following steps: S1. Add a platinum precursor solution and a carbon material into a solvent, disperse, dry, and grind to obtain catalyst powder A; S2. Perform a first microwave treatment on the catalyst powder A under an inert gas to obtain catalyst powder B; S3. Mix and grind the catalyst powder B with a platinum precursor solid, and then perform a second microwave treatment under an inert gas to obtain the carbon-supported platinum catalyst.

2. The preparation method of the carbon-supported platinum catalyst for fuel cells according to claim 1, characterized in that, The treatment time of the first microwave treatment is 8 - 10 min.

3. The preparation method of the carbon-supported platinum catalyst for fuel cells according to claim 1, wherein, The treatment time of the second microwave treatment is 6 - 13 min.

4. The preparation method of the carbon-supported platinum catalyst for fuel cells according to claim 1, characterized in that, In the catalyst powder B, the particle size range of the platinum particles inside and outside the pores of the carbon support is 0.6 - 3 nm; in the carbon-supported platinum catalyst, the particle size range of the platinum particles outside the pores of the carbon support is 3.0 - 6 nm.

5. The preparation method of the carbon-supported platinum catalyst for fuel cells according to claim 1, wherein, In step S3, after performing the second microwave treatment under an inert gas, the following steps are further included: washing, centrifuging, drying, and grinding to obtain the carbon-supported platinum catalyst.

6. The preparation method of the carbon-supported platinum catalyst for fuel cells according to any one of claims 1 to 5, characterized in that, The treatment conditions of both the first microwave treatment and the second microwave treatment are: the gas flow rate is 50 - 80 mL / min, and the treatment power is 500 - 800 W.

7. The preparation method of the carbon-supported platinum catalyst for fuel cells according to any one of claims 1 to 5, characterized in that, The platinum precursor solution is selected from one or a combination of at least two of chloroplatinic acid solution, platinum acetylacetonate solution, potassium chloroplatinate solution, potassium chloroplatinate solution, and sodium chloroplatinate solution; The platinum precursor solid is selected from one or a combination of at least two of solid-phase chloroplatinic acid, platinum acetylacetonate, potassium chloroplatinate, potassium chloroplatinate, and sodium chloroplatinate.

8. The preparation method of the carbon-supported platinum catalyst for fuel cells according to any one of claims 1 to 5, characterized in that, In step S1, the drying temperature is 55 - 65 °C, and the drying time is 8 - 15 h.

9. A carbon-supported platinum catalyst prepared by the preparation method according to any one of claims 1 to 8, characterized in that, In the carbon-supported platinum catalyst, the particle size of the platinum particles inside the pores of the carbon support is 0.6 - 3 nm, and the particle size of the platinum particles outside the pores of the carbon support is 3.0 - 6 nm.

10. Use of the carbon-supported platinum catalyst according to claim 9 in the preparation of a fuel cell catalyst slurry.

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