A high-platinum-supported fuel cell catalyst, its preparation method and application

Abstract

This invention belongs to the field of fuel cell technology, specifically relating to a high-platinum-loaded fuel cell catalyst, its preparation method, and its application. By optimizing the heat treatment and reduction processes of the support, this invention achieves a uniform distribution of platinum on the support, resulting in a highly efficient, stable, and high-performance high-platinum-loaded fuel cell catalyst. This improves the catalyst's activity and membrane electrode performance while reducing production costs.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a high platinum-loaded fuel cell catalyst, its preparation method, and its application. Background Technology

[0002] As a highly efficient and clean energy conversion device, the performance of fuel cells largely depends on the activity and stability of the catalyst. Platinum (Pt) is currently the most commonly used fuel cell catalyst material due to its excellent catalytic activity and chemical stability. However, the high cost and scarcity of platinum limit its large-scale application.

[0003] Existing technologies and traditional methods for preparing platinum catalysts suffer from problems such as uneven platinum distribution, low activity, and poor stability, making it difficult to meet practical application requirements. Therefore, developing a method for preparing highly platinum-supported catalysts that are uniformly loaded, highly active, and easily scalable is of great significance. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a method for preparing a highly efficient, stable, and high-performance platinum-loaded fuel cell catalyst. By optimizing the heat treatment and reduction processes of the support, a uniform distribution of platinum on the support is achieved, thereby improving the catalyst's activity and membrane electrode performance while reducing production costs.

[0005] The technical solution of the present invention:

[0006] In a first aspect, the present invention provides a method for preparing a high-platinum-supported fuel cell catalyst, comprising the following steps:

[0007] (1) The carbon support is subjected to stepwise gradient heat treatment under inert gas protection;

[0008] (2) The treated carbon support is dispersed in a homogeneous platinum precursor solution formed by dissolving platinum salt in deionized water, and then stirred and sonicated.

[0009] (3) Dry the sample obtained in step (2) under vacuum conditions;

[0010] (4) The dried sample was subjected to high-temperature reduction in a hydrogen or inert gas-hydrogen mixed atmosphere;

[0011] (5) The reduced sample was cooled to room temperature under an inert atmosphere to obtain a high platinum-loaded fuel cell catalyst precursor;

[0012] (6) Repeat steps (2)-(5) once or multiple times using the obtained high platinum-loaded fuel cell catalyst precursor as a new reaction support to obtain the high platinum-loaded fuel cell catalyst.

[0013] In some implementation schemes, the carbon carrier is one or more of carbon black, Cabo carbon, activated carbon, biomass carbon, and Ketjen black carbon.

[0014] In some embodiments, the stepwise gradient heat treatment includes heat treatment at 200-350°C, 400-550°C and 600-750°C respectively, for 2-3 hours each.

[0015] In some embodiments, the platinum salt is one or more of chloroplatinic acid, platinum nitrate, platinum tetrachloride, ammonium chloroplatinate, and platinum acetylacetonate.

[0016] In some embodiments, the stirring and sonication treatment includes stirring for 30-40 minutes, followed by sonication for 20-30 minutes, and optionally repeated multiple times, for example, three times.

[0017] In some implementations, the high-temperature reduction is carried out at a temperature of 250-350°C for 2-3 hours.

[0018] As used herein, the term "inert gas" is not an inert gas in the strict chemical definition, but refers to any gas that does not chemically react with the platinum metal and carbon support used in this invention, which may include, for example, nitrogen or argon, helium, etc.

[0019] This invention has discovered that a multi-step high-temperature reduction process on a platinum-supported carbon support can ensure uniform nucleation and distribution of platinum particles, thereby improving the catalyst's activity, chemical stability, and durability. Those skilled in the art will understand that two or more high-temperature reduction processes can be performed, all achieving the technical effects discovered in this invention. Therefore, in some embodiments, steps (2)-(5) can be repeated 1, 2, 3, 4, 5, or more times. Preferably, they are repeated once or twice.

[0020] Those skilled in the art will understand that, during a multi-step high-temperature reduction process, the carrier can be dispersed in a homogeneous platinum precursor solution formed by dissolving the same or different platinum salts in deionized water, or in platinum precursor solutions of the same or different volumes, as long as the platinum precursor solution is a homogeneous dispersion and no platinum salt precipitation occurs.

[0021] In the preparation method of the present invention, the amounts of carbon support and platinum salt are generally not limited. In general, the total amount of platinum salt is sufficient to ensure the target catalyst loading on the carbon support after multiple impregnations. For example, when the carbon support is impregnated with platinum salt solution twice, that is, when steps (2)-(5) are repeated once, the amount of platinum salt used in each impregnation can be half of the amount required to ensure the target catalyst loading; when the carbon support is impregnated with platinum salt solution three times, that is, when steps (2)-(5) are repeated twice, the amount of platinum salt used in each impregnation can be one-third of the amount required to ensure the target catalyst loading; and so on.

[0022] In some embodiments, the high platinum-loaded fuel cell catalyst prepared by the present invention has a platinum loading of 50-70% and an average particle size of 2-3 nm.

[0023] In a second aspect, the present invention provides a high platinum-loaded fuel cell catalyst prepared by the methods described herein.

[0024] In some embodiments, the high platinum-loaded fuel cell catalyst has a platinum loading of 50-70% and an average particle size of 2-3 nm.

[0025] In a third aspect, the present invention provides the application of high platinum-supported fuel cell catalysts as described herein in membrane electrodes for fuel cells.

[0026] Compared with the prior art, the present invention has the following significant advantages:

[0027] 1. High Dispersion: The carbon support surface is more uniform and stable after stepwise heating treatment, which is beneficial for the uniform loading and anchoring of platinum particles. The multiple stirring and ultrasonic treatments of the carbon support increase its dispersibility, which is beneficial for the uniform adsorption of platinum salts and promotes further uniform loading of platinum particles.

[0028] 2. High activity and high stability: A two-step high-temperature reduction process is adopted to ensure uniform nucleation and distribution of platinum particles, thereby improving the activity, chemical stability and durability of the catalyst.

[0029] 3. High loading: The stepwise carbon support treatment, stepwise carbon support dispersion and stepwise high-temperature reduction process provided by this invention work synergistically to achieve high loading of Pt particles on the platinum-carbon catalyst. Attached Figure Description

[0030] Figure 1 This is a TEM image of the high platinum-loaded fuel cell catalyst prepared in Example 2.

[0031] Figure 2 The images show the XRD patterns of the high platinum-loaded fuel cell catalysts prepared in Examples 2, 3, and Comparative Example 2.

[0032] Figure 3 ORR polarization curves of the high platinum-supported fuel cell catalysts prepared in Example 2 and Comparative Example 2 in 0.1 M perchloric acid solution.

[0033] Figure 4 The 25cm high-platinum-supported fuel cell catalyst prepared for Example 2 and Comparative Example 2 was used to prepare the catalyst. 2 Polarization curves of membrane electrodes.

[0034] Figure 5 This is a TEM image of the high platinum-supported fuel cell catalyst prepared in Example 3.

[0035] Figure 6 The 25cm sample prepared from the high platinum-supported fuel cell catalyst obtained in Example 3 2 Polarization curves of membrane electrodes. Detailed Implementation

[0036] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0037] Example 1

[0038] 2.73 g of chloroplatinic acid hexahydrate was dissolved in 200 mL of deionized water to form a homogeneous platinum precursor solution. 0.95 g of carbon black support was subjected to stepwise gradient heat treatment under argon protection at temperatures of 200℃, 400℃, and 600℃, with each treatment lasting 2.5 hours. The heat-treated carbon black support was dispersed in 100 mL of the platinum precursor solution, stirred for 35 minutes, and then sonicated for 25 minutes, repeated three times to obtain sample A. The dispersed sample A was dried in a vacuum drying oven for 8 hours. Under a hydrogen atmosphere, the dried sample A was reduced at 300℃ for 2.5 hours. The reduced sample A was cooled to room temperature under an argon atmosphere to obtain a high-platinum-supported fuel cell catalyst precursor. The other half of the 100 mL platinum precursor solution was stirred for 30 minutes to redisperse it uniformly. The high-platinum fuel cell catalyst precursor was dispersed in the other half of the platinum precursor solution, stirred for 35 minutes, and then sonicated for 25 minutes, repeated three times to obtain sample B. After the dispersed sample B underwent the same processing steps as sample A, a high platinum-loaded fuel cell catalyst was obtained, with an ICP test result showing a Pt loading of 50%.

[0039] Example 2

[0040] 1.35 g of platinum nitrate was dissolved in 150 mL of deionized water to form a homogeneous platinum precursor solution. 0.5 g of activated carbon support was subjected to stepwise gradient heat treatment under nitrogen protection at temperatures of 300℃, 500℃, and 700℃, with each treatment lasting 2.5 hours. The heat-treated activated carbon support was dispersed in 75 mL of the platinum precursor solution, stirred for 30 minutes, and then sonicated for 20 minutes. This process was repeated three times to obtain sample A. The dispersed sample A was dried in a vacuum drying oven for 8 hours. Under an argon-hydrogen mixed atmosphere, the dried sample A was reduced at 250℃ for 3 hours. The reduced sample A was cooled to room temperature under a nitrogen atmosphere to obtain a high-platinum-supported fuel cell catalyst precursor. The other half of the 75 mL platinum precursor solution was stirred for 30 minutes to redisperse it homogeneously. The high-platinum fuel cell catalyst precursor was then dispersed in the other half of the platinum precursor solution, stirred for 30 minutes, and then sonicated for 20 minutes. This process was repeated three times to obtain sample B. After undergoing the same processing steps as sample A, dispersed sample B yielded a high-platinum-supported fuel cell catalyst, as shown in the TEM image. Figure 1 As shown. The ICP test results indicate that the Pt loading of the catalyst is 60%, which is obtained through... Figure 2 The average particle size was calculated to be 2.2 nm from the XRD pattern.

[0041] Example 3

[0042] 2.23 g of platinum tetrachloride was dissolved in 180 mL of deionized water to form a homogeneous platinum precursor solution. 0.5 g of Ketjen black carbon support was subjected to stepwise gradient heat treatment under argon protection at temperatures of 350 °C, 550 °C, and 750 °C, with each treatment lasting 3 hours. The heat-treated Ketjen black carbon support was dispersed in 90 mL of the platinum precursor solution, stirred for 40 minutes, and then sonicated for 30 minutes. This process was repeated three times to obtain sample A. The dispersed sample A was dried in a vacuum drying oven for 8 hours. Under an argon-hydrogen mixed atmosphere, the dried sample A was subjected to high-temperature reduction at 350 °C for 2 hours. The reduced sample A was cooled to room temperature under an argon atmosphere to obtain a high-platinum-supported fuel cell catalyst precursor. The other half of the 90 mL platinum precursor solution was stirred for 30 minutes to redisperse it homogeneously. The high-platinum fuel cell catalyst precursor was then dispersed in the other half of the platinum precursor solution, stirred for 40 minutes, and then sonicated for 30 minutes. This process was repeated three times to obtain sample B. After undergoing the same processing steps as sample A, dispersed sample B yielded a high-platinum-supported fuel cell catalyst, as shown in the TEM image. Figure 5 As shown. The ICP test results showed that the Pt loading of the catalyst was 70%, and the calculated average particle size from the XRD pattern was 2.4 nm. Figure 2 ).like Figure 6 As shown, the membrane electrode performance prepared by the catalyst in Example 3 is 0.643V@50A.

[0043] Comparative Example 1

[0044] The catalyst was prepared using the same method as in Example 1. The difference was that the carbon black support underwent a single-step heat treatment under argon protection at a temperature of 700°C for 5 hours. The resulting catalyst showed a platinum loading of 45% according to ICP testing. The carbon black support without multiple heat treatments had limited platinum adsorption capacity and could not completely adsorb all platinum ions. Therefore, multi-step heat treatment of the carbon support is a crucial step in synthesizing high platinum loading fuel cell catalysts.

[0045] Comparative Example 2

[0046] The same procedure as in Example 2 was used for preparation. The difference was that 150 mL of platinum precursor solution was mixed with 0.5 g of activated carbon in a single step. After drying, the dried sample was subjected to high-temperature reduction at 250 °C for 3 hours under an argon-hydrogen mixed atmosphere; this was a single-step high-temperature reduction method. The ICP test results of the obtained catalyst showed a Pt loading of 60%, according to... Figure 2 XRD plot calculations show that the particle size of the high-platinum-supported fuel cell catalyst obtained through a single-step high-temperature reduction process increased to 3.0 nm. The ORR test results for Example 2 and Comparative Example 2 are as follows: Figure 3 As shown, the catalyst's mass activity decreased from 0.21 A / mg in the two-step high-temperature reduction to 0.18 A / mg in the single-step high-temperature reduction. Figure 4 The membrane electrode assembly (MEA) prepared with the catalyst in Example 2 showed a performance of 0.635 V@50 A, while the MEA prepared with the catalyst in Comparative Example 2 showed a performance of 0.619 V@50 A. Therefore, the two-step high-temperature reduction method helps to obtain high-platinum fuel cell catalysts with smaller particle sizes and is beneficial for improving the ORR performance of the catalyst and the MEA performance.

[0047] It should be noted that while the preferred embodiments of the present invention are given in the specification and accompanying drawings, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of the present invention specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a high-platinum-supported fuel cell catalyst, characterized in that, Includes the following steps: (1) The carbon support is subjected to stepwise gradient heat treatment under inert gas protection. The stepwise gradient heat treatment includes heat treatment at 200-350℃, 400-550℃ and 600-750℃ respectively, for 2-3 hours each. (2) The treated carbon support is dispersed in a homogeneous platinum precursor solution formed by dissolving platinum salt in deionized water, and then stirred and sonicated. (3) Dry the sample obtained in step (2) under vacuum conditions; (4) The dried sample was subjected to high-temperature reduction in a hydrogen or inert gas-hydrogen mixed atmosphere; (5) The reduced sample was cooled to room temperature under an inert atmosphere to obtain a high platinum-loaded fuel cell catalyst precursor; (6) Repeat steps (2)-(5) once or multiple times using the obtained high-platinum-supported fuel cell catalyst precursor as a new reaction support to obtain the high-platinum-supported fuel cell catalyst. The high-platinum-loaded fuel cell catalyst has a platinum loading of 50-70% and an average particle size of 2-3 nm.

2. The preparation method according to claim 1, characterized in that, The carbon carrier is carbon black or activated carbon.

3. The preparation method according to claim 2, characterized in that, The carbon black is selected from Cabo carbon and Ketjen black carbon.

4. The preparation method according to claim 1, characterized in that, The platinum salt is one or more of chloroplatinic acid, platinum nitrate, platinum tetrachloride, ammonium chloroplatinate, and platinum acetylacetonate.

5. The preparation method according to claim 1, characterized in that, The stirring and sonication process includes stirring for 30-40 minutes, followed by sonication for 20-30 minutes, and optionally repeated multiple times.

6. The preparation method according to claim 1, characterized in that, The high-temperature reduction is carried out at a temperature of 250-350℃ for 2-3 hours.

7. The preparation method according to claim 1, characterized in that, In step (6), the obtained high platinum-loaded fuel cell catalyst precursor is used as a new reaction support and steps (2)-(5) are repeated once or twice.

8. The preparation method according to claim 1, characterized in that, The inert gas is nitrogen or argon.

9. A high-platinum-supported fuel cell catalyst, characterized in that, Prepared by the method according to any one of claims 1-8.

10. The application of the high platinum-supported fuel cell catalyst as described in claim 9 in a membrane electrode assembly for a fuel cell.

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