Preparation and application method of coal-based porous carbon-supported low-platinum catalyst for hydrogen evolution in water electrolysis

Abstract

This invention discloses a method for preparing and applying a coal-based porous carbon-supported low-platinum catalyst for hydrogen evolution in water electrolysis, relating to the fields of nanomaterials and electrochemistry. It addresses the problems of existing hydrogen evolution catalysts for water electrolysis, such as high noble metal loading, high raw material costs, insufficient activity of single metals, and poor long-term stability. The coal-based porous carbon electrode is prepared from bituminous coal through coal sample treatment, precursor preparation, multi-metal loading, Pt loading, and coating molding steps. The specific preparation steps are as follows: Step 1, coal sample pretreatment; Step 2, preparation of bituminous coal-derived porous carbon; Step 3, loading Ni and Co metals onto BPC to prepare NiCo / BPC; Step 4, loading Pt metal onto NiCo / BPC to prepare PtNiCo / BPC. This invention effectively increases the number of active sites on the catalyst and reduces the interfacial charge transfer resistance through the high specific surface area characteristics of the porous carbon support and the synergistic catalytic effect of Ni, Co, and Pt multi-metals, significantly improving the catalytic activity and long-term stability of the hydrogen evolution reaction in water electrolysis.

Description

Technical Field

[0001] This invention relates to the fields of nanomaterials and electrochemistry, specifically to a method for preparing and applying a coal-based carbon-supported Pt, Ni, and Co catalyst for hydrogen evolution through water electrolysis. Background Technology

[0002] Electrolysis of water is currently the most promising route for producing green hydrogen, with its core reactions including the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. Among various electrolyte systems, alkaline electrolytes have become the mainstream choice for industrial hydrogen production through water electrolysis due to their low raw material cost, low equipment corrosivity, and high safety. However, the catalytic efficiency of the HER reaction at the cathode and the cost of the electrode directly determine the commercial feasibility of water electrolysis for hydrogen production. Currently, commercial HER catalytic electrodes mainly rely on precious metal materials such as Pt, but their scarcity and high price severely limit the large-scale application of water electrolysis for hydrogen production. Therefore, developing low-cost, highly active, and long-term stable low-precious-metal-supported HER electrode materials has become a research hotspot and a core challenge in this field.

[0003] Chinese patent document (CN114892185A) discloses the application of a porous carbon-confined metal oxide-supported platinum-based catalyst in alkaline water electrolysis for hydrogen evolution. This technology involves loading a metal oxide precursor salt onto porous carbon, followed by heat treatment in air to obtain a porous carbon-confined metal oxide composite support, and then loading platinum-based nanoparticles onto the surface of the composite support. In this scheme, the metal oxide in the porous carbon can promote the dissociation process of water molecules, accelerating the catalytic rate of alkaline water electrolysis by the platinum-based catalyst. However, the carbon support used in this technology is a commercially available porous carbon material, resulting in high raw material costs, and the simultaneous loading of metal oxide and platinum makes it difficult to achieve an ordered distribution and strong interaction between the metal components.

[0004] Chinese patent document (CN117552042A) discloses a bifunctional catalyst for water electrolysis and its preparation method. The catalyst comprises a carbon support, a NiCuP catalyst, and a nickel-iron hydroxide. By loading the NiCuP catalyst and nickel-iron hydroxide onto the carbon support as the active components, it exhibits excellent hydrogen evolution and oxygen evolution performance under alkaline conditions. In this scheme, the strong electronic interaction between the nickel-iron hydroxide and NiCuP provides more effective active sites. However, the carbon support used in this technology is also a traditional carbon material, failing to effectively reduce the support cost, and the design of the bifunctional catalyst limits the optimization space for hydrogen evolution performance.

[0005] Furthermore, transition metals (such as Ni and Co) are widely used in the research and development of HER electrode materials due to their abundant reserves, low cost, and certain catalytic activity. Meanwhile, carbon materials, with their high specific surface area, good conductivity, and chemical stability, are often used as supports for metal active components. Constructing composite catalytic systems by loading metal active sites can effectively improve the catalytic performance of the electrode. Coal, as an abundant and extremely low-cost carbonaceous raw material, offers porous carbon materials derived from it. These materials not only possess the inherent advantages of carbon materials but also allow for the control of pore structure and surface properties through simple activation processes, providing ample loading sites and good electron transport channels for metal active components. This makes them an ideal choice for preparing low-cost HER electrode supports.

[0006] However, coal-based porous carbon-based HER catalysts still face several challenges: First, insufficient pore structure control on the coal-based carbon support leads to poor dispersion and inadequate exposure of the metal active components. Second, the catalytic activity of a single metal support is limited, making it difficult to meet the high current density requirements of industrial water electrolysis. Third, the interaction between the metal active components and the carbon support is weak, making them prone to detachment and aggregation during long-term electrolysis, resulting in decreased electrode stability. Therefore, developing coal-based porous carbon-based HER catalysts with high catalytic activity, high stability, and low cost through rational design of the preparation process, optimization of metal component combinations, and enhancement of the interaction between active sites and the support is of great significance for promoting the industrial application of water electrolysis for hydrogen production. Summary of the Invention

[0007] To address the above problems, this invention proposes a method for preparing and applying a coal-based porous carbon-supported low-platinum catalyst for hydrogen evolution through water electrolysis, thereby solving the problems of high precious metal loading, high raw material cost, insufficient single metal activity, and poor long-term stability of existing hydrogen evolution catalysts for water electrolysis.

[0008] The technical solution of this invention is as follows: the coal-based porous carbon electrode is prepared using bituminous coal as raw material through coal sample processing, precursor preparation, multi-metal loading, Pt loading, and coating molding steps. The specific preparation steps are as follows: Step 1, Coal Sample Pretreatment: The bituminous coal is ground using a ball mill and then sieved to below 200 mesh. Step 2: Preparation of porous carbon derived from bituminous coal: Take an appropriate amount of the treated bituminous coal from step 1, mix it with KOH and grind it into powder. Place the mixed powder in a Ni boat, put it in a tube furnace and activate it under certain conditions to obtain bituminous coal-derived porous carbon. Step 3: Load metals Ni and Co onto BPC to prepare NiCo / BPC: Take an appropriate amount of BPC obtained in step 2, mix it with nickel salt, cobalt salt, polyvinylpyrrolidone and 1 mL of deionized water, disperse it by ultrasonication, freeze and dry it, and then place the dried product in a tube furnace for annealing to obtain NiCo / BPC. Step 4: Load metal Pt onto NiCo / BPC to prepare PtNiCo / BPC: Add an appropriate amount of NiCo / BPC obtained in step 3 and an appropriate amount of chloroplatinic acid hexahydrate to deionized water and disperse by ultrasonication. After ultrasonication, filter, wash with water and dry. Use a certain concentration of NaBH4 solution and slowly add it dropwise to the catalyst solution that is being vigorously stirred. After the reduction reaction is complete and no more bubbles are generated, continue stirring for a period of time, then filter and dry the product in a vacuum drying oven.

[0009] Furthermore, in step 2, the mass ratio of bituminous coal to KOH is 1:3; during activation, the tubular furnace is heated to 800℃ at a heating rate of 5℃ / min and held at that temperature for 2 hours.

[0010] Furthermore, the mass of BPC used in step 3 is 0.5g; the nickel salt used is nickel nitrate, the cobalt salt used is cobalt nitrate, the total amount of nickel nitrate and cobalt nitrate added is 0.2155mmol, and the molar ratio of nickel nitrate to cobalt nitrate is 1:1; the ultrasonic time is 30min. In step 3, the vacuum drying time is 24 hours; the annealing conditions are: under pure N2 gas flow protection, heating to 800℃ at a heating rate of 5℃ / min, and holding at that temperature for 2 hours.

[0011] Furthermore, in step 4, the amount of NiCo / BPC used is 36 mg, the volume of chloroplatinic acid hexahydrate used is 20 µL, and the volume of deionized water used is 10 mL; the sonication time is 1 h, divided into 3 times, with a 5 min break after each 15 min sonication. The concentration of NaBH4 used in step 4 is 0.1M; the catalyst solution is 36mg of catalyst dissolved in 20mL of deionized water; the stirring time is 1h after no bubbles are generated; the drying temperature of the vacuum drying oven is 60~80℃.

[0012] Application methods of the prepared coal-based porous carbon-supported low-platinum catalyst: PtNiCo / BPC was prepared into a slurry and coated to prepare electrodes for HER: Take an appropriate amount of PtNiCo / BPC obtained in step 4, dissolve it in Nafion solution, ethanol and deionized water, sonicate it, and then use a pipette to measure an appropriate amount of the sonicated solution. Apply it to carbon paper under infrared lamp irradiation to obtain the HER electrode.

[0013] The mass of the catalyst used was 5 mg; the volumes of Nafion solution, ethanol, and deionized water used were 50 µL, 850 µL, and 100 µL, respectively; the ultrasonic time was 10 min. The carbon paper is 1cm×2cm in size, the coating is 1cm×1cm in size, the volume of each pipette is 25uL, and the coating is applied 4 times on each side; the infrared lamp irradiation intensity is 50~100W, and the coating drying temperature is controlled at 40~60℃.

[0014] This invention aims to develop a HER catalyst that is inexpensive and readily available, has a simple preparation process, high catalytic activity, and strong long-term stability, thereby reducing the industrial cost of hydrogen production through water electrolysis and promoting the large-scale application of green hydrogen technology. The specific process involves: grinding and sieving bituminous coal and mixing it with KOH, followed by high-temperature activation under a nitrogen atmosphere to obtain a bituminous coal-derived porous carbon precursor; subsequently, Ni and Co metal components are loaded onto the porous carbon support through ultrasonic dispersion, freeze-drying, and high-temperature annealing; then, a Pt-modified phase is introduced using a combination of chloroplatinic acid impregnation and NaBH4 reduction, and finally, an electrode is fabricated using a coating process. This invention effectively increases the number of active sites on the catalyst and reduces the interfacial charge transfer resistance by leveraging the high specific surface area of ​​the porous carbon support and the synergistic catalytic effect of Ni, Co, and Pt, significantly improving the catalytic activity and long-term stability of the hydrogen evolution reaction through water electrolysis. The electrode preparation process is simple and the raw material cost is low. It exhibits excellent HER performance in a 1M KOH alkaline electrolyte, providing a new path for the development of low-cost, high-efficiency electrode materials for hydrogen production through water electrolysis, and has broad prospects for industrial application.

[0015] Compared with the prior art, the present invention has the following beneficial effects: First, the raw material cost is significantly reduced. Using bituminous coal as the carbon source, the raw material cost is reduced by more than 80% compared with traditional commercial porous carbon. At the same time, the Pt content is reduced to below 2wt% through Ni-Co alloy synergistic catalysis, which is more than 90% lower than the precious metal content of commercial Pt / C catalysts.

[0016] Second, it exhibits excellent catalytic activity. The high specific surface area of ​​the porous carbon support combined with the synergistic effect of Ni-Co-Pt multimetals gives the electrode abundant exposed active sites and rapid charge transfer capability, resulting in superior HER performance compared with noble metal Pt / C electrodes in 1M KOH electrolyte.

[0017] Third, it has strong long-term stability. The strong interaction between the metal active component and the carbon support and the spatial confinement effect of the porous structure effectively inhibit the aggregation and shedding of the active component. The electrode can operate stably for a long time under high current density electrolysis conditions. It can operate under constant current for 24 hours at a current density of 100 mA / cm² with voltage fluctuation of less than 0.02V and no obvious performance degradation.

[0018] Fourth, the preparation process is simple and controllable. It adopts a process route of bituminous coal activation and pore formation, Ni-Co stepwise loading to form an alloy, Pt reduction modification, and electrode coating. It does not require harsh conditions or steps such as high temperature and high pressure. It has low energy consumption and is easy to industrialize and mass-produce, providing a new technical path for the large-scale application of low-cost and high-efficiency water electrolysis hydrogen production technology. Attached Figure Description

[0019] Figure 1 This invention relates to a method for preparing a coal-based porous carbon electrode.

[0020] Figure 2 This is a TEM image of PtNiCo / BPC obtained in Example 1 of the present invention.

[0021] Figure 3 This is a SEM image of PtNiCo / BPC obtained in Example 1 of the present invention.

[0022] Figure 4 This is the X-ray diffraction pattern of PtNiCo / BPC obtained in Example 1 of the present invention.

[0023] Figure 5 The PtNiCo / BPC obtained in Example 1 of this invention, compared with Comparative Examples 1 and 2, and Pt / C under alkaline conditions of 1M KOH, exhibits: (a) a comparison of HER polarization curves; (b) current densities of 10, 100, and 250 mA cm⁻¹. -2 The following is a comparison chart of HER bars.

[0024] Figure 6 The PtNiCo / BPC obtained in Example 1 of this invention at 100 mA cm⁻¹ -2 HER stability test graph under current density. Detailed Implementation

[0025] To clearly illustrate the technical features of the present invention, the present invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings.

[0026] All raw materials used in the following embodiments of the present invention are commercially available.

[0027] Example 1, Step 1: Coal Sample Pretreatment: Weigh 5g of bituminous coal, grind it using a ball mill, and sieve it to below 200 mesh. After sieving, bituminous coal powder with a particle size of less than or equal to 75 micrometers is obtained. The purpose of grinding the bituminous coal to a fine particle size is to increase the contact area between the bituminous coal and the alkali metal hydroxide, ensuring that the subsequent activation reaction proceeds fully. Excessively large particle size will lead to uneven activation and irregular porous carbon structure; excessively small particle size will increase the risk of dust dispersion and place higher demands on the ball mill equipment.

[0028] Step 2: Preparation of Bituminous Coal-Derived Porous Carbon (BPC): Weigh 8g of bituminous coal powder treated in Step 1 and mix it with 24g of potassium hydroxide to form a powder. Weigh 4g of the powder and place it in a Ni boat in a tube furnace. Under pure N2 gas protection, heat to 800℃ at a heating rate of 5℃ / min and hold at that temperature for 2 hours to obtain bituminous coal-derived porous carbon. During the activation process, potassium hydroxide undergoes a redox reaction with the carbon in the bituminous coal. The oxygen atoms produced by the decomposition of potassium hydroxide attack the carbon-carbon bonds in the carbon skeleton, causing partial breakage of the carbon skeleton and forming micropores and mesopores. At the same time, the molten state of potassium hydroxide (melting point of about 406 degrees Celsius) promotes its penetration and diffusion inside the carbon matrix, further etching the carbon layer and forming a macroporous structure.

[0029] The activation temperature of 800 degrees Celsius was chosen based on the following considerations: below 700 degrees Celsius, the activation effect of potassium hydroxide is weak, resulting in insufficient pore structure and low specific surface area; above 900 degrees Celsius, the graphitization degree of the carbon framework increases, the pore structure collapses, and the specific surface area decreases. A constant temperature time of 2 hours ensures the activation reaction proceeds fully; too short a time leads to incomplete activation, while too long a time increases energy consumption and has limited improvement on the pore structure. After activation, heating is stopped, and the mixture is allowed to cool naturally to room temperature.

[0030] Step 3: NiCo / BPC is prepared by loading Ni and Co onto BPC: 0.1 g BPC, 0.0314 g nickel nitrate hexahydrate, 0.0313 g cobalt nitrate hexahydrate, and 0.01 g polyvinylpyrrolidone are mixed with 1 mL deionized water and sonicated for 30 min. After freeze-drying for 24 h, the mixture is placed in a tube furnace and heated to 800 °C at a rate of 5 °C / min under pure N2 gas protection, and held at that temperature for 2 hours to obtain NiCo / BPC. The role of polyvinylpyrrolidone is to enhance the dispersibility of the metal salts in aqueous solution, prevent the aggregation of metal ions during loading, and ensure a uniform distribution of the metal components on the carbon support surface. Freeze-drying aims to remove moisture through sublimation, avoiding the migration and aggregation of metal salts during traditional drying processes, and maintaining a uniform distribution of the metal components.

[0031] Step 4: Prepare PtNiCo / BPC by loading Pt onto NiCo / BPC: Disperse 36 mg of NiCo / BPC and 20 µL of a chloroplatinic acid hexahydrate solution in 10 ml of deionized water using ultrasonication for 1 hour (ultrasonication for 15 min, pause for 5 min). After completion, filter, wash with water, and dry. Dissolve the dried PtNiCo / BPC in 20 ml of deionized water to prepare a solution, and slowly add 0.1 M NaBH4 to the catalyst solution while stirring at 500 rpm. After no more bubbles are generated, continue stirring for 1 hour, filter, and dry in a 60℃ drying oven for 12 hours. Sodium borohydride is a strong reducing agent; it decomposes in aqueous solution to release hydrogen gas and provide hydride anions. These hydride anions reduce tetravalent platinum ions to zero-valent platinum metal. Slowly add the sodium borohydride solution to the vigorously stirred catalyst suspension through a constant-pressure dropping funnel. During the addition process, a large number of bubbles are generated in the solution; these bubbles are the hydrogen gas released by the decomposition of sodium borohydride. When the production of bubbles stops, it indicates that the reduction reaction is basically complete.

[0032] The choice of a sodium borohydride concentration of 0.1 mol / L is based on the following considerations: too low a concentration will result in a slow reduction reaction rate and a prolonged reaction time; too high a concentration will result in an excessively fast decomposition rate of sodium borohydride, generating a large number of hydrogen bubbles, which will affect the uniform distribution of platinum nanoparticles.

[0033] like Figure 2 As shown, the transmission electron microscope (TEM) images of PtNiCo / BPC reveal the microstructure of the catalyst. From... Figure 2 As can be seen, platinum nanoparticles and nickel-cobalt alloy particles are uniformly dispersed on the surface of the coal-based porous carbon support, with particle sizes ranging from 5 to 10 nanometers. High-resolution transmission electron microscopy images show clear lattice fringes, confirming the crystallinity of the platinum nanoparticles. A tight interfacial contact exists between the nickel-cobalt alloy particles and the carbon support, indicating a strong interaction between the metal and the support.

[0034] like Figure 3 As shown, the scanning electron microscope images of PtNiCo / BPC reveal the macroscopic morphology of the catalyst. From Figure 3 As can be seen, the catalyst exhibits a distinct porous structure with pore sizes ranging from 1 to 3 micrometers. The formation of this porous structure originates from the etching effect of bituminous coal after activation with potassium hydroxide. The pores are interconnected, and the porous structure provides abundant specific surface area and sufficient space for active sites to be exposed, which is beneficial for electrolyte penetration and proton transport, thereby improving the electrochemical activity of the catalyst.

[0035] like Figure 4 As shown, the X-ray diffraction pattern of PtNiCo / BPC characterizes the crystal structure of the catalyst. From... Figure 4 It can be seen that there are two obvious diffraction peaks.

[0036] The schematic diagram and microstructure of the PtNiCo / BPC prepared in this embodiment based on bituminous coal-derived porous carbon are attached. Figure 1 , 2 As shown in Figures 3 and 4.

[0037] Comparative Example 1 differs from Example 1 only in that it does not undergo the Pt impregnation process in step 4, and is denoted as NiCo / BPC.

[0038] Comparative Example 2 differs from Example 1 only in that the Ni and Co loading in step 3 is omitted, and is denoted as Pt / BPC.

[0039] Comparative Example 3 differs from Example 1 in that it uses commercially available Pt / C.

[0040] Application Example 1, the specific implementation process of the PtNiCo / BPC water electrolysis hydrogen evolution (HER) experiment is as follows: To prepare the 1M KOH electrolyte: Weigh 29.5315g of KOH and dissolve it in a beaker. After cooling to room temperature, transfer it to a 500mL volumetric flask and make up to volume.

[0041] Electrochemical testing: Tests were conducted using a standard three-electrode system on a CS Studio6 electrochemical workstation. A saturated Hg / HgO electrode with a double salt bridge was used as the reference electrode, and a carbon rod as the counter electrode. The prepared PtNiCo / BPC electrode material, after being coated, was used as the working electrode. The working electrode, immersed in the electrolyte, was 1 cm × 1 cm in size. The electrolyte was 1 M KOH, and approximately 60 mL of electrolyte was used for each test. When using this electrode material for the first time, a CV test should be performed to activate the active sites. HER testing was performed with 95% iR compensation, and all measured potentials were converted to reversible hydrogen electrode polarization for comparison. The HER polarization curves are shown below. Figure 5 As shown in (a), the figure demonstrates that at the same current density, the overpotential required for PtNiCo / BPC is significantly lower than that of other electrodes, exhibiting superior performance even compared to Pt / C under high current. Figure 5 (b) It can be seen that at current densities of 0, 100 and 250 mA m -2 At that time, the overpotentials of PtNiCo / BPC were 23.1, 91.6, and 154.4 mV, respectively; like Figure 6 As shown, at 100 mA cm -2 At current density, the voltage of PtNiCo / BPC as the working electrode shows almost no fluctuation and remains stable within 0.02V, and can operate stably for at least 24 hours, indicating that this electrode has excellent stability for HER and is very promising for industrial applications.

[0042] There are many specific ways to implement this invention. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A method for preparing a coal-based porous carbon-supported low-platinum catalyst, characterized in that, The specific preparation steps are as follows: Step 1, Coal Sample Pretreatment: The bituminous coal is ground using a ball mill and then sieved to below 200 mesh. Step 2: Preparation of porous carbon derived from bituminous coal: Take an appropriate amount of the treated bituminous coal from step 1, mix it with KOH and grind it into powder. Place the mixed powder in a Ni boat, put it in a tube furnace and activate it under certain conditions to obtain bituminous coal-derived porous carbon. Step 3: Load metals Ni and Co onto BPC to prepare NiCo / BPC: Take an appropriate amount of BPC obtained in step 2, mix it with nickel salt, cobalt salt, polyvinylpyrrolidone and 1 mL of deionized water, disperse it by ultrasonication, freeze and dry it, and then place the dried product in a tube furnace for annealing to obtain NiCo / BPC. Step 4: Load metal Pt onto NiCo / BPC to prepare PtNiCo / BPC: Add an appropriate amount of NiCo / BPC obtained in step 3 and an appropriate amount of chloroplatinic acid hexahydrate to deionized water and disperse by ultrasonication. After ultrasonication, filter, wash with water and dry. Use a certain concentration of NaBH4 solution and slowly add it dropwise to the catalyst solution that is being vigorously stirred. After the reduction reaction is complete and no more bubbles are generated, continue stirring for a period of time, then filter and dry the product in a vacuum drying oven.

2. The method for preparing a coal-based porous carbon-supported low-platinum catalyst according to claim 1, characterized in that, In step 2, the mass ratio of bituminous coal to KOH is 1:3; during activation, the tubular furnace is heated to 800℃ at a heating rate of 5℃ / min and held at that temperature for 2 hours.

3. The method for preparing a coal-based porous carbon-supported low-platinum catalyst according to claim 1, characterized in that, The mass of BPC used in step 3 is 0.5g; the nickel salt used is nickel nitrate, the cobalt salt used is cobalt nitrate, the total amount of nickel nitrate and cobalt nitrate added is 0.2155mmol, and the molar ratio of nickel nitrate to cobalt nitrate is 1:1; the ultrasonic time is 30min. In step 3, the vacuum drying time is 24 hours; the annealing conditions are: under pure N2 gas flow protection, heating to 800℃ at a heating rate of 5℃ / min, and holding at that temperature for 2 hours.

4. The method for preparing a coal-based porous carbon-supported low-platinum catalyst according to claim 1, characterized in that, The amount of NiCo / BPC used in step 4 is 36 mg, the volume of chloroplatinic acid hexahydrate is 20 µL, and the volume of deionized water is 10 mL; the sonication time is 1 h, divided into 3 times, with a 5 min break after each 15 min sonication. The concentration of NaBH4 used in step 4 is 0.1M; the catalyst solution is 36mg of catalyst dissolved in 20mL of deionized water; the stirring time is 1h after no bubbles are generated; the drying temperature of the vacuum drying oven is 60~80℃.

5. A method for applying the coal-based porous carbon-supported low-platinum catalyst prepared according to claim 1, characterized in that, PtNiCo / BPC was prepared into a slurry and coated to prepare electrodes for HER: Take an appropriate amount of PtNiCo / BPC obtained in step 4, dissolve it in Nafion solution, ethanol and deionized water, sonicate it, and then use a pipette to measure an appropriate amount of the sonicated solution. Apply it to carbon paper under infrared lamp irradiation to obtain the HER electrode.

6. The application method of the coal-based porous carbon-supported low-platinum catalyst according to claim 5, characterized in that, The mass of the catalyst used was 5 mg; the volumes of Nafion solution, ethanol, and deionized water used were 50 µL, 850 µL, and 100 µL, respectively; the ultrasonic time was 10 min. The carbon paper is 1cm×2cm in size, the coating is 1cm×1cm in size, the volume of each pipette is 25uL, and the coating is applied 4 times on each side; the infrared lamp irradiation intensity is 50~100W, and the coating drying temperature is controlled at 40~60℃.

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