Hydrogen fuel cell catalyst carrier and preparation method thereof

Abstract

The invention discloses a preparation method of a hydrogen fuel cell catalyst carrier. The preparation method comprises the following steps: 1) preparing a nitrogen-doped porous carbon core layer; 2) coating a CeO2 shell layer with the nitrogen-doped porous carbon core layer prepared in the step 1) to obtain a nitrogen-doped porous carbon CeO2 core-shell carrier; and 3) loading a Pt catalyst on the nitrogen-doped porous carbon CeO2 core-shell carrier in the step 2) to obtain the hydrogen fuel cell catalyst carrier. Through the collaborative design of nitrogen-doped porous carbon core layer anchoring, CeO2 shell layer blocking and mild hydrogen reduction loading, the Pt particle size is stably controlled within the range of 2-3 nm, Pt particle aggregation and curing are remarkably inhibited, the long-term activity stability of the catalyst is greatly improved, the particle size increase amount after 1000-hour operation and the 1000-hour activity attenuation rate (%) are remarkably reduced, and the catalyst has good application prospects. The technical problems that a traditional carbon-based carrier Pt is poor in dispersity and rapid in activity attenuation are solved.

Description

Technical Field

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

[0002] Hydrogen fuel cells, as a highly efficient and clean energy conversion technology, rely heavily on a catalyst layer as one of their core components. The catalyst support, as a key material for supporting and dispersing active metal nanoparticles, directly impacts the catalyst's stability, activity, and overall battery performance and cost. Currently, carbon-based catalyst support systems have become the mainstream choice for the commercial application of hydrogen fuel cells, particularly proton exchange membrane fuel cells (PEMFCs), due to their excellent conductivity, high specific surface area, tunable pore structure, and relatively mature fabrication processes.

[0003] From a system perspective, catalyst supports do not exist in isolation; their technological development is closely linked to the overall needs of fuel cells. In hydrogen fuel cell stacks, the oxygen reduction reaction kinetics at the three-phase interface of the catalyst layer are slow, requiring the extensive use of precious metal catalysts such as platinum (Pt) to maintain sufficient power output. The core function of the support is to maximize the utilization and durability of precious metals: firstly, to provide a high specific surface area to support highly dispersed nano-platinum particles, preventing agglomeration and increasing active sites; secondly, to construct a continuous electron conduction network to ensure efficient electron transport in the reaction; thirdly, to form a suitable porous structure to promote mass transfer between reactant gases and product water; and fourthly, to maintain physical and electrochemical stability in the harsh operating environment of fuel cells—characterized by strong acidity, high potential, high temperature, and humidity—preventing platinum particle shedding, agglomeration, or loss due to support corrosion, which is crucial to battery life.

[0004] Carbon black supports are widely used due to their low cost. The core technology lies in introducing oxygen-containing functional groups (such as -COOH and -OH) onto the surface of carbon black particles through pretreatment such as concentrated nitric acid oxidation. This not only improves hydrophilicity, facilitating the impregnation and distribution of subsequent platinum salt precursors, but also enhances the anchoring effect between the support and platinum particles. However, existing carbon black supports easily lead to Pt agglomeration into large particles, resulting in low exposure of active sites; and they cannot suppress Ostwald ripening of Pt during battery operation. After 1000 hours of operation, the Pt particle size significantly increases, accelerating activity decay. Summary of the Invention

[0005] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the main objective of this invention is to provide a hydrogen fuel cell catalyst support and a method for preparing the same.

[0006] The objective of this invention is achieved through the following technical solution: A method for preparing a catalyst support for a hydrogen fuel cell includes the following steps: 1) Preparation of nitrogen-doped porous carbon core layer; 2) Coat the nitrogen-doped porous carbon core layer obtained in step 1) with a CeO2 shell layer to obtain a nitrogen-doped porous carbon CeO2 core-shell support; 3) Load the Pt catalyst onto the nitrogen-doped porous carbon CeO2 core-shell support from step 2) to obtain the hydrogen fuel cell catalyst support.

[0007] In some specific embodiments, the nitrogen-doped porous carbon core layer described in step 1) is prepared using the following method: 1a) Add the carbon source, nitrogen source and pore-forming agent to deionized water, stir evenly, and prepare a slurry; 1b) The slurry obtained in step 1a) is subjected to hydrothermal carbonization and cooled to obtain a hydrothermal carbon precursor; 1c) The hydrothermal carbon precursor obtained in step 1c) is subjected to high-temperature carbonization to obtain a nitrogen-doped carbon / pore-forming agent composite. 1d) The nitrogen-doped carbon / pore-forming agent composite obtained in step 1d) is subjected to pore-forming and purification to obtain a nitrogen-doped porous carbon core layer.

[0008] In some specific embodiments, the mass ratio of the carbon source, nitrogen source, and pore-forming agent is (3-6):(2-4):(1-3); the carbon source is glucose, the nitrogen source is urea, and the pore-forming agent is zinc oxide; wherein glucose is a renewable carbon source, and after carbonization, it forms a graphite-like structure to ensure conductivity; urea decomposes into NH3 and CN at high temperature. - This provides a source for nitrogen doping; ZnO, after carbonization, can be dissolved by hydrochloric acid, providing technical support for the subsequent formation of mesopores.

[0009] Furthermore, the solid-liquid ratio of the slurry is (0.5-2):(3-10) (g:ml); In some specific embodiments, the hydrothermal carbonization process conditions in step 1c) are: constant temperature reaction at 150-200℃ for 6-10 hours.

[0010] In some specific embodiments, the high-temperature carbonization process conditions described in step 1d) are as follows: in a nitrogen atmosphere, the temperature is increased to 700-900℃ at a rate of 5±1℃ / min and held for 1.5-2.5h.

[0011] In some specific embodiments, the pore-forming and purification process specifically involves: adding the nitrogen-doped carbon / pore-forming agent complex to a hydrochloric acid solution (solid-liquid ratio 1:20, g:mL), stirring at room temperature for 3-5 hours, filtering, washing with deionized water until the filtrate pH reaches 6-7, and vacuum drying at 80±5℃ for 4±0.5 hours to obtain a nitrogen-doped porous carbon core layer.

[0012] In some specific embodiments, the method for coating the CeO2 shell in step 2) is as follows: 2a) Add cerium nitrate solution to nitrogen-doped porous carbon core layer and disperse by ultrasonication to obtain dispersion; 2b) Ammonia water was added dropwise to the dispersion prepared in step 2a) to carry out a deposition reaction, resulting in Ce(OH)3 / carbon core complex; 2c) The Ce(OH)3 / carbon core composite obtained in step 2c) is calcined and crystallized to obtain nitrogen-doped porous carbon CeO2 core-shell support.

[0013] In some specific embodiments, the ammonia solution is added at a rate of 1-2 ml / min in step 2b). In some specific embodiments, the process conditions for the deposition reaction in step 2b) are: at a temperature of 25-35°C and a pH of 9-10, with continuous stirring at a speed of 300-500 rpm for 1.5-2.5 hours. In some specific embodiments, the calcination crystallization process conditions in step 2c are as follows: drying at 70-90℃ for 1.5-2.5h, then placing it in a muffle furnace, heating it to 250-350℃ at 5±1℃ / min in an air atmosphere, and holding it at that temperature for 1.5-2.5h.

[0014] In some specific embodiments, the method for loading the Pt catalyst in step 3) is as follows: 3a) Nitrogen-doped porous carbon CeO2 core-shell support was added to chloroplatinic acid solution and stirred evenly at room temperature to obtain an adsorption solution; 3b) The adsorbent in step 3a) is reduced with hydrogen, then dried and purified to obtain the catalyst support for the hydrogen fuel cell.

[0015] In some specific embodiments, the hydrogen reduction in step 3b) specifically involves: transferring the adsorbent liquid to a high-pressure reactor, introducing hydrogen to replace the air 3-5 times, maintaining the hydrogen pressure at 0.1-0.2 MPa, raising the temperature to 75-85°C, and holding the temperature for 1.5-2.5 hours.

[0016] As part of the same inventive concept, this invention provides a hydrogen fuel cell catalyst support prepared by the aforementioned preparation method.

[0017] Compared with the prior art, the present invention has at least the following advantages: The preparation method of this invention, through the synergistic design of "nitrogen-doped porous carbon core layer anchoring + CeO2 shell layer barrier + mild hydrogen reduction loading", stably controls the Pt particle size in the range of 2-3 nm, significantly inhibits Pt particle agglomeration and ripening, greatly improves the long-term activity stability of the catalyst, and significantly reduces the particle size growth and the activity decay rate (%) after 1000 h of operation, thus solving the technical pain points of poor Pt dispersion and rapid activity decay of traditional carbon-based supports. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0019] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0020] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0021] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0022] In the following examples, the glucose and urea were analytical grade and purchased from Anaiji Chemical; the hydrochloric acid concentration was 0.5 mol / L; the cerium nitrate solution concentration was 0.1 mol / L; the ammonia concentration was 0.5 mol / L; and the chloroplatinic acid solution was prepared from chloroplatinic(IV) acid hexahydrate with a concentration of 0.01 mol / L.

[0023] Example 1 1) Preparation of nitrogen-doped porous carbon core layer 1a) Weigh 20g of glucose (analytical grade), 15g of urea (analytical grade), and 10g of zinc oxide (particle size 50nm) in a mass ratio of 4:3:2, add 150mL of deionized water, place in an ultrasonic instrument and sonicate at 400W power for 30min to obtain a uniform slurry. 1b) Transfer the slurry obtained in step 1a) to a 200 mL hydrothermal reactor, react at a constant temperature of 180 °C for 8 h, and after naturally cooling to room temperature, filter and collect the black precipitate. Wash with deionized water until the filtrate is colorless to obtain a brownish-brown hydrothermal carbon precursor. 1c) The hydrothermal carbon precursor obtained in step 1b) is placed in a tube furnace and nitrogen gas (purity 99.999%, flow rate 50 mL / min) is introduced. The temperature is increased to 800℃ at 5℃ / min and held for 2 hours for high-temperature carbonization. After cooling, nitrogen-doped carbon / ZnO composite carbon core is obtained. 1d) Add the composite carbon core prepared in step 1c) to 100 mL of 2 mol / L hydrochloric acid solution, stir at 60 °C for 2 h to dissolve zinc oxide, filter, wash with deionized water until pH=7, and vacuum dry at 80 °C for 4 h to obtain nitrogen-doped porous carbon core layer. 2) CeO2 shell coating 2a) Take 10g of the nitrogen-doped porous carbon core layer prepared in step 1d), add 49.3mL of 0.1mol / L cerium nitrate solution (Ce(NO3)3·6H2O), and sonicate at 400W for 30min to obtain a dispersion; 2b) Place the dispersion obtained in step 2a) in a constant temperature water bath, heat it to 30°C, adjust the pH to 9.5 with 2 mol / L sodium hydroxide solution, add 60 mL of 0.5 mol / L ammonia solution dropwise at a rate of 2 mL / min (30 min), and continue stirring until the white precipitate no longer increases, and continue to keep the reaction at the temperature for 1.5 h; 2c) Filter and collect the precipitate, wash with deionized water until pH=7, place in a muffle furnace, heat to 300℃ at 3℃ / min in air atmosphere, keep at the temperature for 2h to crystallize, and obtain the "carbon core-CeO2 shell" carrier.

[0024] 3) Support of Pt catalyst 3a) Weigh 0.8 g of chloroplatinic acid hexahydrate, dissolve it in deionized water and make up to 100 mL to prepare chloroplatinic acid solution; 3b) Add 5g of the “carbon core-CeO2 shell” support obtained in step 2) to the above chloroplatinic acid solution, stir at room temperature for 2h for adsorption, and obtain an adsorption mixture; 3c) The adsorption mixture was transferred to a high-pressure reactor, hydrogen gas was introduced to 0.15 MPa, and the mixture was reduced at 80°C for 2 hours. After cooling, the mixture was filtered, washed, and vacuum dried at 60°C for 2 hours to obtain the target catalyst, i.e., the catalyst support for hydrogen fuel cells.

[0025] Example 2 This embodiment provides a method for preparing a catalyst support for a hydrogen fuel cell, which is basically the same as that in Example 1, except that the CeO2 shell loading is adjusted. The rest of the process is the same as in Example 1; specifically, it includes the following steps: 1) Preparation of nitrogen-doped porous carbon core layer (Same as step 1 in Example 1) Take 10g of the prepared nitrogen-doped porous carbon core layer for later use.

[0026] 2) CeO2 shell coating (10% loading) 2a) Take 10g of the nitrogen-doped porous carbon core layer prepared in step 1d), add 123mL of 0.1mol / L cerium nitrate solution (Ce(NO3)3·6H2O), and sonicate at 400W for 30min to obtain a dispersion; 2b) Place the dispersion obtained in step 2a) in a constant temperature water bath, heat it to 30°C, adjust the pH to 9.5 with 2 mol / L sodium hydroxide solution, add 110 mL of 0.5 mol / L ammonia solution dropwise at a rate of 2 mL / min (55 min), and continue stirring until the white precipitate no longer increases, and continue to keep the reaction at the temperature for 1.5 h; 2c) Filter and collect the precipitate, wash with deionized water until pH=7, place in a muffle furnace, heat to 300℃ at 3℃ / min in air atmosphere, keep at the temperature for 2h to crystallize, and obtain the "carbon core-CeO2 shell" carrier.

[0027] 3) Pt loading and subsequent processes Following the same procedure as in step 3 of Example 1, the target catalyst, namely the catalyst support for the hydrogen fuel cell, is finally obtained.

[0028] Comparative Example 1 This comparative example provides a method for preparing a conventional hydrogen fuel cell catalyst support, which includes the following steps: 1) Oxidation pretreatment of carbon black carrier 1a) Take commercial Vulcan XC-72 carbon black (particle size 20-40nm, specific surface area 254m²) 2 10g of the mixture was added to 200mL of 68% concentrated nitric acid (analytical grade) at a solid-liquid ratio of 1:20 and placed in a 500mL three-necked flask. 1b) Oxidation at 80℃ and 300rpm with magnetic stirring for 4 hours, with auxiliary stirring every 30 minutes; 1c) After the reaction is complete, cool to room temperature, centrifuge at 3000 rpm for 10 min, and discard the supernatant; 1d) Wash with deionized water until the filtrate pH=6-7, and vacuum dry at 80℃ for 4h to obtain the oxidized modified carbon black carrier.

[0029] 2) Impregnation method for supporting Pt catalysts 2a) Take 5g of carbon black carrier; weigh 0.8g of chloroplatinic acid hexahydrate, dissolve and dilute to 100mL; 2b) Add carbon black oxide to 100 mL of chloroplatinic acid solution and stir at 250 rpm at room temperature for 2 h for adsorption; 2c) Add 5 mL of 80% hydrazine hydrate (5% of the volume of chloroplatinic acid solution) dropwise at 1 mL / min, and stir at 250 rpm for 1.5 h until the solution turns black; 2d) Centrifuge at 3000 rpm for 10 min, collect the solid, wash three times with deionized water, and dry under vacuum at 60℃ for 2 h to obtain the catalyst.

[0030] Comparative Example 2 This comparative example provides a method for preparing a catalyst support for a hydrogen fuel cell, which is basically the same as that in Example 1, except that a CeO2 shell is not applied (i.e., step 2 is omitted). Specifically, it includes the following steps: 1) Preparation of nitrogen-doped porous carbon core layer Completely identical to step 1 of Example 1, a nitrogen-doped porous carbon core layer is obtained; 2) Direct support of Pt catalyst 3) Take 5g of nitrogen-doped porous carbon core layer and replace the "carbon core-CeO2 shell" support with nitrogen-doped porous carbon core layer. Other steps are the same as step 3 in Example 1.

[0031] Comparative Example 3 This comparative example provides a method for preparing a catalyst support for a hydrogen fuel cell, which is basically the same as that in Example 1, except that CeO2 particles are mixed in instead of being coated with a shell. Specifically, it includes the following steps: 1) Preparation of nitrogen-doped porous carbon core layer; Completely identical to step 1 of Example 1, a nitrogen-doped porous carbon core layer is obtained; 2) The 10g nitrogen-doped porous carbon core layer prepared in step 1) was mechanically mixed with CeO2 particles at a mass ratio of 9:1 at 300 rpm for 2 hours to obtain nitrogen-doped porous carbon-CeO2 particle support. 3) Load the Pt catalyst onto the 5g nitrogen-doped porous carbon-CeO2 particle support from step 2) to obtain the hydrogen fuel cell catalyst support. The nitrogen-doped porous carbon-CeO2 particle support replaces the "carbon core-CeO2 shell" support. Other steps are the same as step 3 in Example 1.

[0032] Test column This application conducts performance tests on the hydrogen fuel cell catalyst supports prepared in Examples 1, 2, 1, 2, and 3, specifically as follows: 1) Testing Method The standard for testing the initial Pt particle size and the Pt particle size after 1000 hours is GB / T 20042.4-2009 "Proton Exchange Membrane Fuel Cells - Part 4: Electrocatalyst Test Methods". 1000h Activity decay rate (%): T / CAAMTB 12—2020 "Test Method for Membrane Electrode of Proton Exchange Membrane Fuel Cell"; 2) Test Results The performance of the hydrogen fuel cell catalyst supports prepared in Examples 1 and 2, and Comparative Examples 1, 2 and 3, was tested according to the aforementioned test methods. The results are shown in Table 1. Table 1. Performance test results of catalysts in each embodiment and comparative example. According to the data in Table 1, compared with Comparative Example 1 (traditional carbon black process), the initial Pt particle size in Comparative Example 1 was 7.8 nm (3.5 times), and after 1000 h it was 12.5 nm (4.2 times), with a decay rate of 38.0% (5.1 times). Example 1 verified the feasibility of the new process, while Comparative Example 1 highlighted its advantages in optimizing Pt dispersion and suppressing agglomeration.

[0033] Comparison of Example 1 and Comparative Example 2 (without CeO2 shell): Comparative Example 2 Pt initial particle size 4.5 nm, 8.8 nm after 1000 h, attenuation rate 26.5%. Example 1 demonstrates the necessity of core-shell structure integrity, while Comparative Example 2 reversely verifies the key role of CeO2 shell.

[0034] Comparison of Example 1 and Comparative Example 3 (without CeO2 shell): The initial Pt particle size of Comparative Example 3 was 4.0 nm, and after 1000 h it was 6.6 nm with a decay rate of 14.8%, indicating that the "carbon core-CeO2 shell" is more advantageous than the "nitrogen-doped porous carbon-CeO2 particles" in optimizing Pt dispersion and suppressing agglomeration.

[0035] Comparison of Example 1 and Example 2 (high CeO2 loading): Example 2 Pt initial particle size 2.4nm, 3.5nm after 1000h, decay rate 10.2%; Example 1 provides a basic reference, and Example 2 illustrates that the CeO2 loading is not necessarily better the higher it is, and the former has better stability with standard loading.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for preparing a catalyst support for a hydrogen fuel cell, characterized in that, Includes the following steps: 1) Preparation of nitrogen-doped porous carbon core layer; 2) Coat the nitrogen-doped porous carbon core layer obtained in step 1) with a CeO2 shell layer to obtain a nitrogen-doped porous carbon CeO2 core-shell support; 3) Load the Pt catalyst onto the nitrogen-doped porous carbon CeO2 core-shell support from step 2) to obtain the hydrogen fuel cell catalyst support.

2. The method for preparing the hydrogen fuel cell catalyst support according to claim 1, characterized in that, The specific preparation method of the nitrogen-doped porous carbon core layer mentioned in step 1) is as follows: 1a) Add the carbon source, nitrogen source and pore-forming agent to deionized water, stir evenly, and prepare a slurry; 1b) The slurry obtained in step 1a) is subjected to hydrothermal carbonization and cooled to obtain a hydrothermal carbon precursor; 1c) The hydrothermal carbon precursor obtained in step 1c) is subjected to high-temperature carbonization to obtain a nitrogen-doped carbon / pore-forming agent composite. 1d) The nitrogen-doped carbon / pore-forming agent composite obtained in step 1d) is subjected to pore-forming and purification to obtain a nitrogen-doped porous carbon core layer.

3. The method for preparing the hydrogen fuel cell catalyst support according to claim 2, characterized in that, The mass ratio of the carbon source, nitrogen source and pore-forming agent is (3-6):(2-4):(1-3); the carbon source is glucose, the nitrogen source is urea, and the pore-forming agent is zinc oxide.

4. The method for preparing a hydrogen fuel cell catalyst support according to claim 2, characterized in that, The hydrothermal carbonization process conditions described in step 1c) are: constant temperature reaction at 150-200℃ for 6-10 hours.

5. The method for preparing a hydrogen fuel cell catalyst support according to claim 2, characterized in that, The high-temperature carbonization process conditions described in step 1d) are as follows: in a nitrogen atmosphere, the temperature is increased to 700-900℃ at a rate of 5±1℃ / min and held for 1.5-2.5h.

6. The method for preparing a hydrogen fuel cell catalyst support according to claim 2, characterized in that, The method for coating the CeO2 shell in step 2) is as follows: 2a) Add cerium nitrate solution to nitrogen-doped porous carbon core layer and disperse by ultrasonication to obtain dispersion; 2b) Ammonia water was added dropwise to the dispersion prepared in step 2a) to carry out a deposition reaction, resulting in Ce(OH)3 / carbon core complex; 2c) The Ce(OH)3 / carbon core composite obtained in step 2c) is calcined and crystallized to obtain nitrogen-doped porous carbon CeO2 core-shell support.

7. The method for preparing a hydrogen fuel cell catalyst support according to claim 6, characterized in that, The ammonia water is added at a rate of 1-2 ml / min in step 2b); the deposition reaction process conditions are: at a temperature of 25-35℃ and a pH of 9-10, stirred continuously at a speed of 300-500 rpm for 1.5-2.5 h; the calcination crystallization process conditions in step 2c are: drying at 70-90℃ for 1.5-2.5 h, then placing it in a muffle furnace and heating it to 250-350℃ at a rate of 5±1℃ / min in an air atmosphere, and holding it at that temperature for 1.5-2.5 h.

8. The method for preparing a hydrogen fuel cell catalyst support according to claim 1, characterized in that, The method for loading the Pt catalyst in step 3) is as follows: 3a) Nitrogen-doped porous carbon CeO2 core-shell support was added to chloroplatinic acid solution and stirred evenly at room temperature to obtain an adsorption solution; 3b) The adsorbent in step 3a) is reduced with hydrogen, then dried and purified to obtain the catalyst support for the hydrogen fuel cell.

9. The method for preparing a hydrogen fuel cell catalyst support according to claim 4, characterized in that, The hydrogen reduction described in step 3b) specifically involves: transferring the adsorbent liquid to a high-pressure reactor, introducing hydrogen to replace the air 3-5 times, maintaining the hydrogen pressure at 0.1-0.2 MPa, raising the temperature to 75-85°C, and holding the temperature for 1.5-2.5 hours.

10. A hydrogen fuel cell catalyst support prepared according to any one of claims 1-9.

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