Preparation method of ORR reaction catalyst

Abstract

The invention relates to the technical field of catalysts, and discloses a preparation method of an ORR reaction catalyst, which comprises the following steps: step 1, polydopamine coating of a carbon carrier; step 2, loading the active component of the carbon carrier; and 3, synthesizing the Pt-based intermetallic compound with the mosaic structure. Through ultrasonic dispersion and stirring, the surface of the activated carbon is uniformly coated with polydopamine, the surface modification degree of the activated carbon is increased, a larger surface area and higher active sites are provided for subsequent metal loading, the loading capacity of the polydopamine is confirmed through thermogravimetric analysis (TGA), the moderate coating amount is ensured, the activity of the catalyst can be improved, and the service life of the catalyst is prolonged. The mass and the volume of the material are not excessively increased, the catalytic activity of ORR reaction is improved, and the beneficial effect that the activity of the catalyst is higher is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and specifically to a preparation method of an ORR reaction catalyst. Background Art

[0002] Hydrogen fuel cells have the characteristics of environmental friendliness and high energy conversion efficiency, and are expected to be widely used in fields such as transportation, military, aerospace, etc. However, the platinum-based catalysts currently used in the ORR reaction of hydrogen fuel cells are relatively large in size and their electronic properties cannot be further regulated, resulting in low activity of the catalysts.

[0003] Compared with traditional internal combustion engines, hydrogen fuel cells are not restricted by the Carnot cycle, have a higher energy utilization rate, and their only product is water, causing almost no pollution to the environment. Compared with energy storage devices such as lithium batteries, their stack structure is simple and they operate more stably. However, the Pt / C catalyst used in hydrogen fuel cells on the market currently is expensive, and its catalytic performance needs to be further improved. Research has found that during the oxygen reduction process, oxygen-containing intermediates are strongly adsorbed to the Pt catalyst, occupying the active sites and greatly reducing the oxygen reduction reaction rate. Adding transition metals lowers the d-band center position of Pt, which helps with the removal of oxygen-containing intermediates and improves the catalyst performance. In terms of atomic structure, the Pt-Pt spacing on the surface of pure platinum is not ideal for the adsorption of O2. The adsorption of oxygen conforms to the Griffiths model, where the oxygen molecule is placed horizontally on one Pt atom and interacts with the empty dz2 orbital of Pt. The interaction between the d electrons of Pt and the π electrons of O2 weakens the O-O bond, which is beneficial to the four-electron reaction process to a certain extent. Different from the single-site adsorption mechanism of pure platinum, according to Vegard's rule, transition metals with smaller radii can reduce the Pt-Pt distance, making the Pt-Pt distance reach the ideal ORR double-site bridge adsorption distance. As a result, the oxygen molecule is placed flat on two Pt atoms, which is more conducive to the four-electron reaction of O2. Moreover, the addition of transition metals (such as Fe, Co, etc.) can also reduce the amount of Pt used and lower the catalyst cost. Therefore, the preparation of Pt-based intermetallic compound catalysts is of great significance. Currently, the preparation methods of Pt-based intermetallic compounds are mainly divided into thermal annealing method and wet chemical reduction method. Thermal annealing is to gradually heat the alloy of Pt and other transition metals from below the critical transition temperature from disorder to order in an inert gas or reducing gas to above this temperature and maintain it for a period of time. The wet chemical reduction method is to first obtain Pt metal seeds through pre-reduction and then grow other transition metals by diffusion on its periphery, and then simultaneously reduce the two metals with a reducing agent at a certain temperature. Compared with the latter, the thermal annealing method can achieve a specific stoichiometric ratio by adjusting the element ratio of the disordered alloy before annealing. Moreover, high temperature makes the order transformation easier. Therefore, the thermal annealing method is the most widely used method for preparing Pt-based intermetallic compounds. However, due to the thermal annealing method requiring a long time at a relatively high temperature, the nanoparticles usually undergo Ostwald ripening and sintering aggregation during this process, resulting in changes in the nanoparticle size and surface morphology, which inhibits the improvement of the catalytic activity of the catalyst. Summary of the Invention

[0004] Technical problems to be solved: Aiming at the deficiencies of the prior art, the present invention provides a preparation method for an ORR reaction catalyst, which has the advantages of higher activity and better catalytic performance of the catalyst, and solves the above technical problems.

[0005] Technical solution: To achieve the above object, the present invention provides the following technical solution: A preparation method of an ORR reaction catalyst, comprising the following steps: Step 1: Polydopamine coating of the carbon support: Activated carbon is dispersed in methanol by ultrasonic dispersion, coated with polydopamine, and after stirring, filtered and dried to obtain a polydopamine-coated carbon support; Step 2: Loading of the active components of the carbon support: Fe and Co transition metals are loaded by methods such as impregnation method, precipitation method, chemical reduction method, etc. through the polydopamine-coated support, and then the Pt catalyst is loaded to obtain a precursor; Step 3: Synthesis of the Pt-based intermetallic compound with an embedded structure: The precursor obtained above is pyrolyzed in an inert atmosphere to synthesize a Pt-based intermetallic compound with an embedded structure, and its degree of alloying is increased by high-temperature annealing.

[0006] Preferably, the first step further includes the following detailed steps: S1.1. Material preparation: Select mesoporous or macroporous activated carbon to ensure that its physical and chemical properties meet the catalytic requirements, and prepare a polydopamine solution with a concentration of 1-10 mg / mL; S1.2. Operating steps: Treat the activated carbon in an ultrasonic cleaner to ensure its full dispersion and avoid particle aggregation. During the reaction, control the temperature at room temperature and the time at 2-12 hours to ensure the uniformity of the coating. The dehydrated carbon support is dried at 60-80°C for 3-5 hours; S1.3. Characterization: Characterize the coated material, observe the surface structure using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and confirm the loading amount of polydopamine using thermogravimetric analysis (TGA).

[0007] Preferably, the second step further includes the following steps: S2.1. Selection of metal precursors: Select precursor compounds, including Fe(NO3)3·9H2O and Co(NO3)2·6H2O; S2.2. Loading technique: Use the impregnation method: Add the carbon support to the metal precursor solution, control the soaking time: 6-24 hours, and ensure full impregnation; S2.3. Washing and drying of the catalyst precursor: Wash the loaded material to remove the excess precursor, and then dry it at 60-100°C for 4-8 hours.

[0008] Preferably, the third step further includes the following steps: S3.1. Pyrolysis process: Select a pyrolysis temperature between 300-800°C and carry out the process in an inert atmosphere: argon or nitrogen to prevent oxidation, and set the pyrolysis time at 1-6 hours; S3.2, High-temperature annealing: Select an annealing temperature of 600 - 1000 °C and a time of 3 hours to increase the degree of platinum alloying and improve the catalytic performance. This process also needs to be carried out in an inert atmosphere to prevent re-oxidation of the material; S3.3, Post-treatment: Optionally perform pickling or washing after annealing to remove unreacted materials or impurities; S3.4, Characterization and testing: Characterize the final catalyst, and use X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX) to analyze the structure and composition. Conduct electrocatalytic tests to evaluate its catalytic activity and stability in the ORR reaction.

[0009] Preferably, the specific steps of the ultrasonic treatment of activated carbon in S1.2 are as follows: S1.2.1, Weigh the activated carbon: Weigh 5 - 20 grams of activated carbon. In a beaker, add 200 - 500 mL of methanol, and then add the weighed activated carbon to the methanol and stir to help disperse it; S1.2.2, Ultrasonic treatment: Place the beaker containing activated carbon and methanol in an ultrasonic cleaner, set the working time of the ultrasonic cleaner to 2 - 12 hours, and maintain the room temperature at 20 - 25 °C during the treatment; S1.2.3, Observe the dispersion situation: After the ultrasonic treatment is completed, observe the dispersion of the activated carbon to ensure that there is no obvious particle agglomeration. If there is still agglomeration, extend the ultrasonic treatment time by 10%; S1.2.4, In another beaker, prepare a polydopamine solution, dissolve an appropriate amount of polydopamine in methanol, and stir until it is completely dissolved; S1.2.4, Slowly add the ultrasonically treated activated carbon suspension to the polydopamine solution and gently stir to ensure uniform mixing; S1.2.5, Continue to stir the mixture at room temperature for 2 - 12 hours, and adjust the specific time according to the reaction rate of polydopamine; S1.2.6, Filter the mixture through a suction filtration device to remove the unreacted polydopamine solution and retain the coated activated carbon; S1.2.7, Transfer the washed activated carbon to an oven and dry it at 60 - 80 °C for 3 - 5 hours until it is completely dry.

[0010] Preferably, the reaction rate formula in S1.2.5 is calculated as:

[0011] Where: is the reaction rate constant, which is related to temperature and catalyst; is the concentration of the reactant, which is the concentration of polydopamine in this example; is the reaction order.

[0012] Preferably, the reaction time in S1.2.5 is calculated as follows: Considering the reaction rate, the required time is estimated using the following formula :

[0013] where: is the initial polydopamine concentration; is the concentration of polydopamine after the reaction.

[0014] Preferably, the impregnation treatment in S2.2 includes the following steps: S2.2.1. Select the metal precursor platinum chloride for platinum loading; S2.2.2. Take the metal precursor and dissolve it in deionized water to obtain a solution with the required concentration, with a concentration of 0.01 to 0.1 M; S2.2.3. Weigh the carbon support: Take 1 g of the carbon support, place the carbon support in a clean beaker, add the prepared metal precursor solution, ensure that the carbon support is completely immersed, stir the carbon support at room temperature, and set the soaking time to 6 to 24 hours, 6 hours for rapid loading; 12 hours for general requirements; 24 hours for maximum loading; S2.2.4. Stir once every 1 - 2 hours to ensure uniform penetration of the metal precursor; S2.2.5. After soaking, separate the impregnated carbon support and the unadsorbed metal precursor solution through a filtration device, rinse the carbon support with deionized water to wash away the unadsorbed metal precursor until there is no sign of metal ions in the washing liquid; S2.2.6. Transfer the filtered carbon support to an oven and dry it at 60 - 80 °C for 2 to 4 hours until it is completely dry.

[0015] Preferably, the pyrolysis process in S3.1 also includes the following steps: S3.1.1. Pyrolysis furnace setup: Ensure that the pyrolysis furnace is clean and free of residues, ensure stable control between 300 - 800 °C, check the gas cylinders of the inert gas to ensure sufficiency, connect the gas pipelines to ensure no leakage, and install a gas flow meter.

[0016] S3.1.2. Experimental parameter setting: Select the pyrolysis temperature according to the material properties, select 500 °C: suitable for materials with medium decomposition temperature, and set the pyrolysis time to 1 - 6 hours; S3.1.3. Pyrolysis process: Introduce an inert gas: argon or nitrogen into the pyrolysis furnace, and ensure that the gas flow rate is 50 - 100 mL / min; S3.1.4. Start the pyrolysis furnace and set the heating rate to 5 - 10 °C / min. Heat up to the set pyrolysis temperature. Once the set temperature is reached, maintain this temperature and start timing, and continue pyrolysis for 1 - 6 hours. S3.1.5. End the pyrolysis: After the pyrolysis time ends, turn off the heating source, continue to introduce inert gas, and let the pyrolysis furnace cool naturally to room temperature. Maintain the inert atmosphere to prevent oxidation. After cooling, open the pyrolysis furnace and take out the pyrolysis product.

[0017] Preferably, the pickling concentration in S3.3 is 0.5 - 1 M.

[0018] Compared with the prior art, the present invention provides a preparation method of an ORR reaction catalyst, having the following beneficial effects: 1. In the present invention, through ultrasonic dispersion and stirring, it is ensured that polydopamine is uniformly coated on the surface of activated carbon, increasing the degree of surface modification of activated carbon, providing a larger surface area and more active sites for subsequent metal loading. The loading amount of polydopamine is confirmed by thermogravimetric analysis (TGA) to ensure a moderate coating amount, which can not only improve the catalytic activity of the catalyst but also not excessively increase the mass and volume of the material. The Fe and Co transition metals are loaded onto the polydopamine-coated carbon support by the impregnation method to ensure that the metal precursors are evenly distributed on the surface of the carbon support, providing more reactive sites for the reaction. The soaking time is controlled to be 6 - 24 hours to ensure that the metal precursors are fully impregnated into the carbon support, maximizing the metal loading amount and activity of the catalyst. Pyrolysis is carried out under an inert atmosphere, with the temperature controlled at 300 - 800 °C and the time controlled at 1 - 6 hours. This pyrolysis process helps to form an inlaid Pt-based intermetallic compound, increasing the stability and activity of the catalyst. Annealing treatment is carried out at 600 - 1000 °C to increase the degree of alloying of Pt, improve the electronic structure and surface characteristics of the catalyst, and enhance the catalytic activity of the ORR reaction, achieving the beneficial effect of higher catalytic activity of the catalyst.

[0019] 2. In the present invention, by coating polydopamine on the surface of activated carbon, the hydrophilicity and chemical activity of the carbon support are increased, providing more active sites for subsequent metal loading. Through ultrasonic dispersion and stirring, it is ensured that polydopamine is uniformly coated on the surface of activated carbon, avoiding the problems of local agglomeration and uneven loading, achieving the beneficial effect of better catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] Please refer to Figure 1 , a preparation method of an ORR reaction catalyst, comprising the following steps: Step 1. Polydopamine coating of the carbon support: Activated carbon is dispersed in methanol by ultrasonic dispersion, coated with polydopamine, and after stirring, filtered and dried to obtain a polydopamine-coated carbon support; Step 2. Loading of the active components of the carbon support: Fe and Co transition metals are loaded by methods such as impregnation method, precipitation method, and chemical reduction method through the polydopamine-coated support, and then a Pt catalyst is loaded to obtain a precursor; Step 3. Synthesis of the Pt-based intermetallic compound with an inlaid structure: The precursor obtained above is pyrolyzed in an inert atmosphere to synthesize a Pt-based intermetallic compound with an inlaid structure, and its alloying degree is increased by high-temperature annealing.

[0023] Polydopamine-coated carbon support

[0024] Surface modification: The polydopamine coating on the surface of the activated carbon increases the hydrophilicity and chemical activity of the carbon support, providing more active sites for subsequent metal loading.

[0025] Uniform coating: Through ultrasonic dispersion and stirring, it is ensured that the polydopamine is uniformly coated on the surface of the activated carbon, avoiding problems of local agglomeration and non-uniform loading.

[0026] Loading of the active components of the carbon support

[0027] Multi-metal loading: Fe and Co transition metals are loaded on the polydopamine-coated carbon support by methods such as impregnation method, precipitation method, and chemical reduction method, increasing the multi-metal synergistic effect of the catalyst and improving the catalytic activity.

[0028] Controlling the loading amount: By controlling the impregnation time and the concentration of the metal precursor, it is ensured that the metal precursor is uniformly distributed on the surface of the carbon support, providing more reaction active sites and more uniform catalytic performance.

[0029] Synthesis of the Pt-based intermetallic compound with an inlaid structure

[0030] Pyrolysis process: Pyrolysis is carried out in an inert atmosphere, the temperature is controlled at 300 - 800 °C, and the time is controlled at 1 - 6 hours. This pyrolysis process helps to form a Pt-based intermetallic compound with an inlaid structure, increasing the stability and activity of the catalyst.

[0031] High-temperature annealing: Annealing is carried out at 600 - 1000 °C to increase the degree of alloying of Pt, improve the electronic structure and surface properties of the catalyst, and enhance the catalytic activity of the ORR reaction.

[0032] Post-treatment: Unreacted materials or impurities are removed by pickling or washing to ensure the purity and high activity of the final catalyst.

[0033] Preferably, step one further includes the following detailed steps: S1.1. Material preparation: Select mesoporous or macroporous activated carbon to ensure that its physical and chemical properties meet the catalytic requirements, and prepare a polydopamine solution with a concentration of 1 - 10 mg / mL; S1.2. Operating steps: Treat the activated carbon in an ultrasonic cleaner to ensure its full dispersion and avoid particle agglomeration. During the reaction, control the temperature at room temperature and the time for 2 - 12 hours to ensure uniform coating. The dehydrated carbon support is dried at 60 - 80 °C for 3 - 5 hours; S1.3. Characterization: Characterize the coated material, observe the surface structure using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and use thermogravimetric analysis (TGA) to confirm the loading amount of polydopamine.

[0034] Preferably, step two further includes the following steps: S2.1. Selection of metal precursors: Select precursor compounds including Fe(NO3)3·9H2O and Co(NO3)2·6H2O; S2.2. Loading technique: Use the impregnation method: Add the carbon support to the metal precursor solution and control the soaking time: 6 - 24 hours to ensure sufficient impregnation; S2.3. Washing and drying of the catalyst precursor: Wash the loaded material to remove excess precursors, and then dry it at 60 - 100 °C for 4 - 8 hours.

[0035] Preferably, step three further includes the following steps: S3.1. Pyrolysis process: Select a pyrolysis temperature between 300 - 800 °C and carry it out in an inert atmosphere: argon or nitrogen to prevent oxidation. Set the pyrolysis time at 1 - 6 hours; S3.2. High-temperature annealing: Select an annealing temperature of 600 - 1000 °C and a time of 3 hours to increase the degree of alloying of platinum and improve the catalytic performance. This process also needs to be carried out in an inert atmosphere to prevent re-oxidation of the material; S3.3. Post-treatment: Optionally carry out pickling or washing after annealing to remove unreacted materials or impurities; S3.4, Characterization and Testing: Characterize the final catalyst, and use X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDX) to analyze the structure and composition. Conduct electrocatalytic tests to evaluate its catalytic activity and stability in the ORR reaction.

[0036] Preferably, the specific steps of the ultrasonic treatment of activated carbon in S1.2 are as follows: S1.2.1, Weigh the activated carbon: Weigh 5 - 20 grams of activated carbon. In a beaker, add 200 - 500 mL of methanol, and then add the weighed activated carbon to the methanol and stir to help disperse it. S1.2.2, Ultrasonic treatment: Place the beaker containing the activated carbon and methanol in an ultrasonic cleaner, set the working time of the ultrasonic cleaner to 2 - 12 hours, and maintain the room temperature at 20 - 25 °C during the treatment. S1.2.3, Observe the dispersion: After the ultrasonic treatment is completed, observe the dispersion of the activated carbon to ensure that there is no obvious particle agglomeration. If there is still agglomeration, extend the ultrasonic treatment time by 10%. S1.2.4, In another beaker, prepare a polydopamine solution, dissolve an appropriate amount of polydopamine in methanol, and stir until it is completely dissolved. S1.2.4, Slowly add the ultrasonically treated activated carbon suspension to the polydopamine solution and gently stir to ensure uniform mixing. S1.2.5, Continue to stir the mixture, maintain the room temperature, and the time is 2 - 12 hours. The specific time is adjusted according to the reaction rate of polydopamine. S1.2.6, Filter the mixture through a suction filtration device to remove the unreacted polydopamine solution and retain the coated activated carbon. S1.2.7, Transfer the washed activated carbon to an oven and dry it at 60 - 80 °C for 3 - 5 hours until it is completely dry.

[0037] Preferably, the reaction rate formula in S1.2.5 is calculated as:

[0038] Where: is the reaction rate constant, which is related to temperature and catalyst; is the concentration of the reactant, which is the concentration of polydopamine in this example; is the reaction order.

[0039] Preferably, the reaction time in S1.2.5 is calculated: Considering the reaction rate, use the following formula to estimate the required time :

[0040] Wherein: is the initial polydopamine concentration; is the concentration of polydopamine after the reaction.

[0041] Preferably, the impregnation treatment in S2.2 includes the following steps: S2.2.1. Select the metal precursor platinum chloride for platinum loading; S2.2.2. Take the metal precursor and dissolve it in deionized water to obtain a solution with the required concentration, and the concentration is 0.01 to 0.1 M; S2.2.3. Weigh the carbon support: Take 1 gram of the carbon support, put the carbon support into a clean beaker, add the prepared metal precursor solution, ensure that the carbon support is completely immersed, stir the carbon support at room temperature, and set the soaking time to 6 to 24 hours, 6 hours for rapid loading; 12 hours for general requirements; 24 hours for maximum loading; S2.2.4. Stir once every 1 - 2 hours to ensure uniform penetration of the metal precursor; S2.2.5. After the soaking is completed, separate the impregnated carbon support and the unadsorbed metal precursor solution through a filtration device, wash the carbon support with deionized water to wash away the unadsorbed metal precursor until there is no sign of metal ions in the washing liquid; S2.2.6. Transfer the filtered carbon support to an oven and dry it at 60 - 80°C for 2 to 4 hours until it is completely dry.

[0042] Preferably, the pyrolysis process in S3.1 further includes the following steps: S3.1.1. Pyrolysis furnace setup: Ensure that the pyrolysis furnace is clean and residue - free, ensure stable control between 300 - 800°C, check the gas cylinder of the inert gas to ensure sufficiency, connect the gas pipeline to ensure no leakage, and install a gas flow meter.

[0043] S3.1.2. Experimental parameter setting: Select the pyrolysis temperature according to the material properties, select 500°C: suitable for materials with medium decomposition temperature, and set the pyrolysis time to 1 - 6 hours; S3.1.3. Pyrolysis process: Introduce an inert gas: argon or nitrogen into the pyrolysis furnace, and ensure that the gas flow rate is 50 - 100 mL / min; S3.1.4. Start the pyrolysis furnace, set the heating rate: 5 - 10°C / min, heat up to the set pyrolysis temperature, once the set temperature is reached, maintain this temperature and start timing, and continue pyrolysis for 1 - 6 hours; S3.1.5, End pyrolysis: After the pyrolysis time ends, turn off the heating source, continue to introduce inert gas, and let the pyrolysis furnace cool naturally to room temperature, maintaining an inert atmosphere to prevent oxidation. After cooling, open the pyrolysis furnace and take out the pyrolysis products.

[0044] Preferably, the pickling concentration in S3.3 is 0.5 - 1M.

[0045] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of an ORR reaction catalyst, characterized in that, It includes the following steps: Step 1. Polydopamine coating of the carbon support: Activated carbon is dispersed into methanol by ultrasonic dispersion, coated with polydopamine, filtered by suction and dried after stirring to obtain a polydopamine-coated carbon support; Step 2. Loading of the active components of the carbon support: Fe and Co transition metals are loaded by methods such as impregnation method, precipitation method, and chemical reduction method through the polydopamine-coated support, and then the Pt catalyst is loaded to obtain a precursor; Step 3. Synthesis of the Pt-based intermetallic compound with an embedded structure: The precursor obtained above is pyrolyzed under an inert atmosphere to synthesize the Pt-based intermetallic compound with an embedded structure, and its alloying degree is increased by high-temperature annealing.

2. The preparation method of an ORR reaction catalyst according to claim 1, wherein: The said Step 1 also includes the following detailed steps: S1.

1. Material preparation: Select mesoporous or macroporous activated carbon to ensure that its physical and chemical properties meet the catalytic requirements, and prepare a polydopamine solution with a concentration of 1-10 mg / mL; S1.

2. Operating steps: Treat the activated carbon in an ultrasonic cleaner to ensure its full dispersion and avoid particle agglomeration. During the reaction, control the temperature at room temperature and the time at 2-12 hours to ensure the uniformity of the coating. The dehydrated carbon support is dried at 60-80 °C for 3-5 hours; S1.

3. Characterization: Characterize the coated material, observe the surface structure using a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and confirm the loading amount of polydopamine using thermogravimetric analysis (TGA).

3. The preparation method of an ORR reaction catalyst according to claim 2, characterized in that: The said Step 2 also includes the following steps: S2.

1. Selection of metal precursors: Select precursor compounds, including Fe(NO3)3·9H2O and Co(NO3)2·6H2O; S2.

2. Loading technique: Use the impregnation method: Add the carbon support to the metal precursor solution, control the soaking time: 6-24 hours, and ensure sufficient impregnation; S2.

3. Washing and drying of the catalyst precursor: Wash the loaded material to remove the excess precursor, and then dry it at 60-100 °C for 4-8 hours.

4. The preparation method of an ORR reaction catalyst according to claim 3, wherein: The said Step 3 also includes the following steps: S3.

1. Pyrolysis process: Select a pyrolysis temperature between 300-800 °C and carry out the process in an inert atmosphere: argon or nitrogen to prevent oxidation, and set the pyrolysis time at 1-6 hours; S3.

2. High-temperature annealing: Select an annealing temperature of 600-1000 °C and a time of 3 hours to increase the alloying degree of platinum and improve the catalytic performance. This process also needs to be carried out in an inert atmosphere to prevent the material from re-oxidation; S3.

3. Post-treatment: Selectively carry out pickling or washing after annealing to remove unreacted materials or impurities; S3.

4. Characterization and testing: Characterize the final catalyst, analyze the structure and composition using X-ray diffraction (XRD), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDX), and carry out electrocatalytic testing to evaluate its catalytic activity and stability in the ORR reaction.

5. The preparation method of an ORR reaction catalyst according to claim 4, wherein: The specific steps of the ultrasonic treatment of the activated carbon in S1.2 are as follows: S1.2.

1. Weigh activated carbon: Weigh 5 - 20 grams of activated carbon. In a beaker, add 200 - 500 mL of methanol, and then add the weighed activated carbon to the methanol and stir to aid dispersion; S1.2.

2. Ultrasonic treatment: Place the beaker containing activated carbon and methanol into an ultrasonic cleaner. Set the working time of the ultrasonic cleaner to 2 - 12 hours. During the treatment, maintain the room temperature at 20 - 25 °C; S1.2.

3. Observe the dispersion: After the ultrasonic treatment ends, observe the dispersion of the activated carbon to ensure there is no obvious particle aggregation. If there is still aggregation, extend the ultrasonic treatment time by 10%; S1.2.

4. In another beaker, prepare a polydopamine solution. Dissolve an appropriate amount of polydopamine in methanol and stir until completely dissolved; S1.2.

4. Slowly add the ultrasonically treated activated carbon suspension to the polydopamine solution and gently stir to ensure uniform mixing; S1.2.

5. Continue to stir the mixture while maintaining the room temperature for 2 - 12 hours. The specific time is adjusted according to the reaction rate of polydopamine; S1.2.

6. Filter the mixture through a suction filtration device to remove the unreacted polydopamine solution and retain the coated activated carbon; S1.2.

7. Transfer the washed activated carbon to an oven and dry it at 60 - 80 °C for 3 - 5 hours until it is completely dry.

6. The preparation method of an ORR reaction catalyst according to claim 5, wherein: The reaction rate formula in S1.2.5 is calculated as: Wherein: is the reaction rate constant, which is related to temperature and catalyst; is the concentration of the reactant, which is the concentration of polydopamine in this example; is the reaction order.

7. The preparation method of an ORR reaction catalyst according to claim 6, characterized in that: Calculation of the reaction time in S1.2.5: Considering the reaction rate, the following formula is used to estimate the required time : Wherein: is the initial polydopamine concentration; is the concentration of polydopamine after the reaction.

8. The preparation method of an ORR reaction catalyst according to claim 7, characterized in that: The impregnation method treatment in S2.2 includes the following steps: S2.2.

1. Select the metal precursor platinum chloride for platinum loading; S2.2.

2. Take the metal precursor and dissolve it in deionized water to obtain a solution with the desired concentration, with a concentration of 0.01 to 0.1 M; S2.2.

3. Weigh the carbon support: Take 1 gram of the carbon support and place it in a clean beaker. Add the prepared metal precursor solution to ensure that the carbon support is completely immersed. Stir the carbon support at room temperature, and set the soaking time to 6 to 24 hours. 6 hours is for rapid loading; 12 hours is for general requirements; 24 hours is for maximum loading; S2.2.

4. Stir once every 1 - 2 hours to ensure uniform penetration of the metal precursor; S2.2.

5. After the soaking ends, separate the impregnated carbon support and the unadsorbed metal precursor solution through a filtration device. Rinse the carbon support with deionized water to wash away the unadsorbed metal precursor until there is no sign of metal ions in the washing liquid; S2.2.

6. Transfer the filtered carbon support to an oven and dry it at 60 - 80 °C for 2 to 4 hours until it is completely dry.

9. The preparation method of an ORR reaction catalyst according to claim 8, characterized in that: The pyrolysis process in S3.1 also includes the following steps: S3.1.

1. Pyrolysis furnace setup: Ensure that the pyrolysis furnace is clean and has no residues. Ensure stable control between 300 - 800 °C. Check the gas cylinder of the inert gas to ensure it is sufficient. Connect the gas pipeline to ensure there is no leakage, and install a gas flow meter; S3.1.

2. Experimental parameter setup: Select the pyrolysis temperature according to the material properties. Select 500 °C: suitable for materials with medium decomposition temperature. Set the pyrolysis time to 1 - 6 hours; S3.1.3, Pyrolysis process: Introduce an inert gas, argon or nitrogen, into the pyrolysis furnace to ensure a gas flow rate of 50 - 100 mL / min; S3.1.4, Start the pyrolysis furnace, set the heating rate at 5 - 10 °C / min, heat up to the set pyrolysis temperature. Once the set temperature is reached, maintain this temperature and start timing, and continue pyrolysis for 1 - 6 hours; S3.1.5, End pyrolysis: After the pyrolysis time ends, turn off the heating source, continue to introduce the inert gas, and let the pyrolysis furnace cool naturally to room temperature. Maintain the inert atmosphere to prevent oxidation. After cooling, open the pyrolysis furnace and take out the pyrolysis products.

10. The preparation method of an ORR reaction catalyst according to claim 9, characterized in that: The pickling concentration in S3.3 is 0.5 - 1 M.

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