Biomass carbon-based non-metallic catalysts, methods of making, and use in fuel cell cathodes

Abstract

The application discloses a biomass carbon-based non-metallic catalyst, a preparation method thereof and application of the catalyst in a fuel cell cathode, and relates to the technical field of biomass carbon-based non-metallic catalysts. The biomass carbon-based non-metallic catalyst comprises a biomass carbon base and non-metallic heteroatoms, wherein the mass fraction of the total amount of the biomass carbon base is 88-96%, and the mass fraction of the total amount of the non-metallic heteroatoms is 4-12%. A small amount of non-metallic exogenous activator is added to the biomass carbon base, so that full-component high-efficiency utilization of straw can be realized, and preparation energy consumption and pollutant emission can be significantly reduced. The prepared catalyst has excellent activity and stability in an oxygen reduction reaction, does not use metal elements, meets international environmental protection standards, and provides a sustainable solution for low-cost commercialization of fuel cells.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to the application of a biomass carbon-based non-metallic catalyst and its preparation method in the cathode of a fuel cell. Background Technology

[0002] With the rapid development of fuel cell technology, proton exchange membrane fuel cells (PEMFCs) have become a research focus in the clean energy field due to their high energy efficiency and zero-emission characteristics. However, their cathode oxygen reduction reaction is highly dependent on platinum-based catalysts, resulting in high system costs. As of 2025, platinum catalyst costs still account for more than 40% of the total cost of fuel cells, and the global scarcity of platinum resources further exacerbates the commercialization bottleneck. Although non-precious metal catalysts such as transition metal-nitrogen-carbon (MNC) materials have shown potential for substitution, problems such as low active site density, insufficient stability in acidic environments, and limited mass transfer have not yet been overcome. In recent years, biomass-derived carbon materials have attracted much attention and developed rapidly due to their renewability and structural tunability.

[0003] Waste peanut shells can be used as carbon precursors to synthesize porous carbon materials through pyrolysis and other methods. Current researchers have used peanut shells as carbon precursors to obtain Co- and S co-doped carbon materials with microporous structures via CO2 reduction and high-temperature pyrolysis strategies. Due to the unique layered three-dimensional open-pore structure of this material, the active sites of the catalyst are increased, giving it significant ORR catalytic activity. As a natural lignocellulose material, coconut shells are also suitable for preparing porous carbon materials. Researchers have used coconut shell residue as a carbon precursor, phosphoric acid as an activator, and urea as a nitrogen source to prepare N- and P-doped porous carbon via a chemical activation method. The catalyst prepared by this method has a large number of mesopores, and the addition of phosphate prevents shrinkage and collapse during the high-temperature process, so the final biochar catalyst has good long-term stability. Other researchers have cleverly prepared N- and F-doped porous carbon from green coconut shells using an economical and environmentally friendly strategy. The microporous structure of this catalyst and the synergistic effect of N and F elements give it excellent ORR activity and stability.

[0004] Chinese patent document CN 105375042 A discloses a biomass carbon-based catalyst, its preparation method, and its application. The catalyst precursor is composed of biomass and metal salts. The biomass includes one or more of the following: corn stalks, corn cobs, rice stalks, cotton stalks, peanut stalks, peanut shells, wheat husks, rice husks, wood, sawdust, bamboo, and weeds. By controlling the addition of different amounts of metal salts, adjusting the precursor impregnation concentration and reaction temperature, as well as the carbonization and nitriding treatment temperature, a biomass carbon-based catalyst with controllable and tunable pore structure and specific surface area is prepared. This technical solution uses metal salts to modify the biomass carbon-based material and employs an impregnation method for preparation. The metal ions in the metal salts typically possess a certain charge and radius, enabling them to interact with functional groups on the surface of the biomass carbon-based material to varying degrees, such as electrostatic attraction and coordination. After doping, the metal ions may enter the lattice structure of the carbon-based material or form nanoparticles on the surface, thereby altering the electronic and crystal structures of the carbon-based material. For example, when iron salts are doped into biomass carbon-based materials, iron ions may form chemical bonds with hydroxyl and carboxyl groups on the carbon-based surface, affecting the conductivity and chemical stability of the carbon-based material. At the same time, the doping of metal salts may cause environmental pollution.

[0005] Chinese patent document CN 106881138 A discloses a method for preparing a nitrogen-phosphorus co-doped porous biomass carbon catalyst. The method uses biomass chitosan as both a carbon and nitrogen source, and triphenylphosphine as a phosphorus source. It involves pyrolysis of a metal salt to create pores, followed by removal of the metal using hydrochloric acid. While this method utilizes the coordination ability of chitosan's amino groups to form complexes with metal ions, the metal salts may not be completely removed by the hydrochloric acid. Furthermore, the use of triphenylphosphine in the reaction process poses safety risks, and the disposal of waste reaction liquid is costly.

[0006] Chinese patent document CN 110854395 A discloses a method for preparing biomass chitosan with doped porous carbon and its application. By controlling the reaction temperature, time, and atmosphere, the performance of the catalyst can be adjusted. The catalyst prepared by this method has a more developed pore structure and a higher specific surface area, thus improving the catalyst's ORR performance. However, this method introduces few types of heteroatoms, relying solely on the nitrogen element of chitosan itself for nitrogen doping, without introducing other heteroatoms such as sulfur, phosphorus, and boron, making it difficult to form a synergistic effect of multiple heteroatoms.

[0007] Existing technologies are mostly limited to the direct carbonization of lignocellulose or rely on highly corrosive activators, which not only wastes components but also faces the dilemma of high pollution and high energy consumption. Although agricultural waste, represented by corn stalks, is abundant, traditional treatment methods are difficult to effectively utilize its natural hierarchical pores and inherent mineral activity due to the destruction of vascular bundle structure and disordered distribution of silicon and potassium minerals caused by mechanical crushing.

[0008] Meanwhile, fuel cell cathode catalysts currently rely on precious metals and biomass-derived carbon materials, and their preparation process suffers from problems such as high pollution and high energy consumption, as well as high cost.

[0009] Therefore, it is necessary to develop a biomass carbon-based non-metallic catalyst, its preparation method, and its application in fuel cell cathodes, using non-metals to replace precious metals or metals, effectively reducing costs while being environmentally friendly. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a biomass carbon-based non-metallic catalyst that effectively reduces costs by using non-metals instead of precious metals or metals, while being environmentally friendly.

[0011] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is that the biomass carbon-based non-metallic catalyst includes biomass carbon-based and non-metallic heteroatoms, wherein the total mass fraction of the biomass carbon-based is 88-96%, and the total mass fraction of the non-metallic heteroatoms is 4-12%.

[0012] By employing the above technical solution, addressing the dependence of existing technologies on precious metal catalysts and the pollution and high energy consumption issues in the biomass conversion process, a small amount of non-metallic exogenous activator is added to the biomass carbon-based catalyst. This enables the efficient utilization of all components of straw, significantly reducing energy consumption and pollutant emissions during production. The resulting catalyst exhibits excellent activity and stability in the oxygen reduction reaction, does not use any metal elements, meets international environmental standards, and provides a sustainable solution for the low-cost commercialization of fuel cells.

[0013] As a preferred embodiment of the present invention, the biomass carbon base is corn stalk; the non-metallic heteroatoms are nitrogen and phosphorus elements.

[0014] As a preferred embodiment of the present invention, the total mass fraction of nitrogen in the biomass carbon-based non-metallic catalyst is 4-11%; the total mass fraction of phosphorus is 0.1-1.1%; and the total mass fraction of carbon is 88-96%.

[0015] The technical problem to be solved by this invention is to provide a method for preparing a biomass carbon-based non-metallic catalyst, which uses waste straw as raw material to realize the high value of waste agricultural products and overcome the defects of pore collapse and low heteroatom loading rate in the preparation of existing biomass carbon catalysts.

[0016] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is a method for preparing the biomass carbon-based non-metallic catalyst, comprising the following steps:

[0017] S1 Crushed Carbon Base: The biomass carbon base is pulverized multiple times using a pulverizer to collect 50-120 mesh powder, ensuring the integrity of its fiber bundles, and thus obtaining powder.

[0018] S2 Steam Micro-Explosion Modification: Weigh the powder from step S1 according to the ratio and put it into a high-pressure reactor. Add deionized water and then add nitrogen source according to the ratio. Raise the temperature to 120-190℃ at a heating rate of 1-5℃ / min and maintain it for 1-6h. Then release the pressure of the solenoid valve instantly and collect the expanded fluffy fiber.

[0019] S3 High-Temperature Carbonization: The fluffy fibers obtained in step S2 are placed in a tube furnace with a nitrogen source atmosphere and heated to 600-1200℃ at a heating rate of 2-6℃ / min, and held for 2-5 hours to obtain the catalyst. The catalyst is then soaked in an alkaline solution for 2-8 hours, washed with deionized water, and dried in an oven at 80℃ for 24 hours.

[0020] As a preferred embodiment of the present invention, the biomass carbon base in step S1 is corn stalk, and the number of cyclic crushing times is 2-5 times.

[0021] Using the above-mentioned technical solution, the natural vascular bundle structure of corn stalks is directionally regulated through steam micro-explosion technology, combined with the self-activation characteristics of its ash minerals, to construct a hierarchical porous carbon support and form highly active sites. Utilizing the self-activation mechanism of specific minerals in corn stalk ash, such as the synergistic effect of potassium and calcium compounds, and combining micro-steam explosion technology to directionally regulate its natural vascular bundle structure, carbon materials with a hierarchical porous network and high-density active sites are prepared without exogenous activators. After introducing heteroatoms, these heteroatoms reconstruct the electronic structure of the carbon-based material, construct highly active sites, optimize mass transfer pathways, and enhance stability, achieving a comprehensive improvement in ORR performance. This overcomes the defects of pore collapse and low heteroatom loading rates in existing biomass carbon catalyst preparation. This method requires only a small amount of exogenous activator, achieves efficient utilization of all components of the straw, and significantly reduces preparation energy consumption and pollutant emissions. The resulting catalyst exhibits excellent activity and stability in the oxygen reduction reaction, does not use metal elements, meets international environmental standards, and provides a sustainable solution for the low-cost commercialization of fuel cells.

[0022] As a preferred embodiment of the present invention, the nitrogen source in step S2 is one of melamine, urea, and dicyandiamide.

[0023] As a preferred embodiment of the present invention, in step S2, deionized water is injected into the high-pressure reactor until the solid-liquid ratio is 1:6; the temperature is raised to 135-190°C at a heating rate of 3-5°C / min and then maintained for 2-5 hours.

[0024] As a preferred embodiment of the present invention, in step S3, the tube furnace is heated to a temperature of 800-1200°C at a heating rate of 3-6°C / min and then held for 2-5 hours; the nitrogen source atmosphere introduced into the tube furnace is nitrogen or ammonia; the alkaline solution is NaOH solution or KOH solution with a concentration of 2-5M.

[0025] As a preferred embodiment of the present invention, the nitrogen source in step S2 is melamine; the nitrogen source atmosphere introduced into the tube furnace in step S3 is ammonia; and the alkaline solution is NaOH solution with a concentration of 3M.

[0026] Another technical problem to be solved by the present invention is to provide an application of a biomass carbon-based non-metallic catalyst.

[0027] To address the aforementioned technical problems, the present invention employs the application of this biomass carbon-based non-metallic catalyst in the cathode catalyst of a fuel cell. The biomass carbon-based non-metallic catalyst is applied to a high-efficiency system for testing oxygen reduction catalysts at the fuel cell cathode, and the performance of the non-metallic catalyst is controlled through a rational formulation.

[0028] The specific testing method is as follows: Prepare an Ink mixed solution by mixing 6.5 mg of the prepared catalyst, 150 μL of deionized water, 750 μL of ethanol solution, and 100 μL of Nafion solution. Transfer 12 μL of this solution to a rotating disk electrode using a pipette. The test is performed using a rotating disk electrode with a 0.1 M KOH solution as the electrolyte. The rotation speed is 1600 rpm, the scan rate is 10 mV / s, and the scan range is 0-1.1 V relative to the hydrogen electrode. The main component of the Nafion solution is perfluorosulfonic acid-polytetrafluoroethylene copolymer.

[0029] Compared with existing technologies, the beneficial effects of the technical solution of this invention are as follows: Utilizing the self-activation mechanism of specific minerals in corn straw ash, such as the synergistic effect of potassium and calcium compounds, and combining micro-steam explosion technology to directionally regulate its natural vascular bundle structure, a carbon material with a hierarchical porous network and high-density active sites is prepared under conditions without external activators. The performance is further enhanced after the additional introduction of heteroatoms. The doping of non-metallic salts improves the chemical stability of the biomass carbon-based catalyst, enhancing its corrosion and oxidation resistance in harsh environments. The straw component in this biomass carbon-based non-metallic catalyst achieves full utilization, significantly reducing preparation energy consumption. The prepared biomass carbon-based non-metallic catalyst exhibits excellent oxygen reduction activity and stability in alkaline electrolytes, meeting international environmental standards and biomass energy technical specifications, providing an innovative solution for the low-cost commercialization of fuel cells. Attached Figure Description

[0030] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings:

[0031] Figure 1 This is a SEM image of the biomass carbon-based non-metallic catalyst of Specific Embodiment 1 of the present invention;

[0032] Figure 2 This is the XRD pattern of the biomass carbon-based nonmetallic catalyst of Specific Embodiment 1 of the present invention;

[0033] Figure 3 The limiting current density of the catalyst was obtained from the linear scanning voltammogram of a specific embodiment of the present invention. Detailed Implementation

[0034] Example: This biomass carbon-based non-metallic catalyst comprises biomass carbon and non-metallic heteroatoms, wherein the total mass fraction of the biomass carbon is 88-96%, and the total mass fraction of the non-metallic heteroatoms is 4-11%; the biomass carbon is corn straw; and the non-metallic heteroatoms are nitrogen and phosphorus. In this biomass carbon-based non-metallic catalyst, the total mass fraction of nitrogen is 4-8%; the total mass fraction of phosphorus is 0.1-1.1%; and the total mass fraction of carbon is 88-96%.

[0035] The preparation method of this biomass carbon-based non-metallic catalyst includes the following steps:

[0036] S1 Crushing of Carbon Base: The biomass carbon base is pulverized multiple times using a pulverizer to collect 50-120 mesh powder, ensuring the integrity of its fiber bundles, and thus obtaining powder; the biomass carbon base in step S1 is corn stalks, and the pulverization cycle is 2-5 times.

[0037] S2 Steam Micro-Explosion Modification: Weigh the powder from step S1 according to the formula and put it into a high-pressure reactor. Add deionized water and then add a nitrogen source according to the formula. Raise the temperature to 120-190℃ at a heating rate of 1-5℃ / min and maintain it for 1-6 hours. Then, release the pressure instantly through the solenoid valve and collect the expanded fluffy fibers. The nitrogen source in step S2 is one of melamine, urea, and dicyandiamide. Melamine is preferred as the nitrogen source in step S2. In step S2, deionized water is injected into the high-pressure reactor until the solid-liquid ratio is 1:6. Raise the temperature to 135-190℃ at a heating rate of 3-5℃ / min and maintain it for 2-5 hours.

[0038] S3 High-temperature carbonization: The fluffy fiber obtained in step S2 is placed in a tube furnace with a nitrogen source atmosphere and heated to 600-1200℃ at a heating rate of 2-6℃ / min and held for 2-5 hours. After obtaining the catalyst, it is soaked in an alkaline solution for 2-8 hours and then washed with deionized water. It is then dried in an 80℃ oven for 24 hours to obtain the catalyst.

[0039] In step S3, the tube furnace is heated to 800-1200℃ at a heating rate of 3-6℃ / min and then held for 2-5 hours. The nitrogen source atmosphere introduced into the tube furnace is nitrogen or ammonia; preferably, it is ammonia. The alkaline solution is NaOH or KOH solution with a concentration of 2-5M. NaOH solution is preferred.

[0040] In the following specific examples 1 to 7, melamine was used as the nitrogen source to explore the effects of different modification temperatures and times on the performance of the prepared catalysts.

[0041] Specific Example 1: The preparation method of this biomass carbon-based non-metallic catalyst includes the following steps:

[0042] S1 Crushed Carbon-Based: Take corn stalks, use a crusher to crush them three times in a cycle, collect 50-120 mesh powder, ensuring that the fiber bundles are intact, and obtain powder;

[0043] S2 steam micro-explosion modification: Weigh 15g of powder according to the ratio and put it into a high-pressure reactor. Add deionized water until the solid-liquid ratio is 1:6. Then add 5g of melamine according to the ratio. Raise the temperature to 170℃ at a heating rate of 3℃ / min and keep it for 5h. Then release the pressure of the solenoid valve instantly and collect the expanded fluffy fiber.

[0044] S3 High-Temperature Carbonization: The fluffy fibers obtained in step S2 were placed in a tube furnace with a nitrogen source atmosphere and heated to 1100℃ at a heating rate of 3℃ / min, and held for 3 hours. After obtaining the catalyst, it was soaked in a 3M KOH solution for 3 hours, then washed with deionized water, and dried in an 80℃ oven for 24 hours to obtain the catalyst. The catalyst obtained had a total nitrogen content of 7.9% and a total phosphorus content of 0.9%, and a specific surface area of ​​1439 m². 2 / g.

[0045] like Figure 1 The image shown is a SEM image of this biomass carbon-based nonmetallic catalyst. Figure 1 It can be seen that the straw fiber morphology of this specific embodiment 1 is that it is a strip of uniform size with exposed rough carbon edges.

[0046] like Figure 2 The image shows the XRD pattern of this biomass carbon-based nonmetallic catalyst. Figure 2 The diffraction peaks at 23.7° and 42.1° can be seen, proving that the straw fiber has been completely carbonized.

[0047] The performance of the catalyst prepared in Specific Example 1 was evaluated using the following steps: 6.5 mg of the prepared catalyst, 150 μL of deionized water, 750 μL of ethanol solution, and 100 μL of Nafion solution were mixed to prepare an Ink solution. 12 μL of this solution was transferred to a rotating disk electrode using a pipette. The rotating disk electrode was used for testing. The electrolyte was a 0.1 M KOH solution. The rotation speed was 1600 rpm, the scan rate was 10 mV / s, the scan range was 0-1.1 V relative to the hydrogen electrode, and the limiting current density was 5.4 mA / cm². 2 ,like Figure 3 As shown.

[0048] The differences between Specific Examples 2 to 7 and Specific Example 1 lie in the amount of nitrogen source melamine added, as well as the conditions for steam micro-explosion modification and high-temperature carbonization. Specific differences are shown in Table 1. The characterization and ORR performance of the prepared catalysts are shown in Table 2.

[0049] Table 1. Different addition amounts and steam micro-explosion modification and high-temperature carbonization conditions of specific examples 1-7

[0050]

[0051] Table 2 Characterization and ORR performance of the catalysts prepared in Specific Examples 1-7

[0052]

[0053] As can be seen from Tables 1 and 2, the nitrogen content can be positively correlated based on the total amount of nitrogen source added. At the same time, the phosphorus content will also change differently depending on the heating rate and the temperature maintained. Furthermore, phosphorus content and specific surface area are not the main influencing factors; the performance of ORR is mainly affected by nitrogen content.

[0054] In the following specific examples 8 to 16, dicyandiamide was used as the nitrogen source to explore the effects of different modification temperatures and times on the performance of the prepared catalysts.

[0055] Specific Example 8: The preparation method of this biomass carbon-based non-metallic catalyst includes the following steps:

[0056] S1 Crushed Carbon-Based: Take corn stalks, use a crusher to crush them three times in a cycle, collect 50-120 mesh powder, ensuring that the fiber bundles are intact, and obtain powder;

[0057] S2 steam micro-explosion modification: Weigh 15g of powder according to the ratio and put it into a high-pressure reactor. Add deionized water until the solid-liquid ratio is 1:6. Then add 5g of dicyandiamide according to the ratio. Raise the temperature to 140℃ at a heating rate of 4℃ / min and keep it for 3h. Then release the pressure of the solenoid valve instantly and collect the expanded fluffy fiber.

[0058] S3 High-Temperature Carbonization: The fluffy fibers obtained in step S2 were placed in a tube furnace with a nitrogen source atmosphere and heated to 800℃ at a heating rate of 4℃ / min, and held for 4 hours. After obtaining the catalyst, it was soaked in a 3M NaOH solution for 3 hours, then washed with deionized water, and dried in an 80℃ oven for 24 hours to obtain the catalyst. The catalyst obtained had a total nitrogen content of 4.1% by mass, a total phosphorus content of 0.7% by mass, and a specific surface area of ​​957 m². 2 / g.

[0059] The performance of the catalyst prepared in Specific Example 8 was evaluated. The specific steps were as follows: 6.5 mg of the prepared catalyst, 150 μL of deionized water, 750 μL of ethanol solution, and 100 μL of Nafion solution were mixed to prepare an Ink solution. 12 μL of this solution was transferred to a rotating disk electrode using a pipette. The rotating disk electrode was used for testing. The electrolyte was a 0.1 M KOH solution. The rotation speed was 1600 rpm, the scan rate was 10 mV / s, the scan range was 0-1.1 V relative to the hydrogen electrode, and the limiting current density was 3.1 mA / cm². 2 .

[0060] The difference between Specific Examples 9 to Specific Examples 16 and Specific Example 8 lies in the amount of dicyandiamide added as a nitrogen source, as well as the conditions for steam micro-explosion modification and high-temperature carbonization. The specific differences are shown in Table 3. The characterization and ORR performance of the prepared catalyst are shown in Table 4.

[0061] Table 3. Different addition amounts and steam micro-explosion modification and high-temperature carbonization conditions of specific examples 8-16

[0062]

[0063] Table 4. Characterization and ORR performance of the catalysts prepared in Specific Examples 8-16

[0064]

[0065]

[0066] Tables 3 and 4 show that when dicyandiamide is used as a nitrogen source, a positive correlation in nitrogen content can be obtained. At the same time, the phosphorus content will also change differently depending on the heating rate and the temperature maintained. Furthermore, phosphorus content and specific surface area are not the main influencing factors; the performance of ORR is mainly affected by nitrogen content.

[0067] In the following specific examples 17 to 24, dicyandiamide was used as the nitrogen source to explore the effects of different modification temperatures and times on the prepared catalysts.

[0068] Specific Example 17: The preparation method of this biomass carbon-based non-metallic catalyst includes the following steps:

[0069] S1 Crushed Carbon-Based: Take corn stalks, use a crusher to crush them three times in a cycle, collect 50-120 mesh powder, ensuring that the fiber bundles are intact, and obtain powder;

[0070] S2 steam micro-explosion modification: Weigh 15g of powder according to the ratio and put it into a high-pressure reactor. Add deionized water until the solid-liquid ratio is 1:6. Then add 4.7g of urea according to the ratio. Raise the temperature to 150℃ at a heating rate of 5℃ / min and keep it for 4h. Then release the pressure of the solenoid valve instantly and collect the expanded fluffy fiber.

[0071] S3 High-Temperature Carbonization: The fluffy fibers obtained in step S2 were placed in a tube furnace with a nitrogen source atmosphere and heated to 900℃ at a heating rate of 5℃ / min, and held for 4 hours. After obtaining the catalyst, it was soaked in a 3M NaOH solution for 3 hours, then washed with deionized water, and dried in an 80℃ oven for 24 hours to obtain the catalyst. The obtained catalyst had a total nitrogen content of 5.2% by mass, a total phosphorus content of 0.3% by mass, and a specific surface area of ​​1124 m². 2 / g.

[0072] The performance of the catalyst prepared in Specific Example 17 was evaluated. The specific steps were as follows: 6.5 mg of the prepared catalyst, 150 μL of deionized water, 750 μL of ethanol solution, and 100 μL of Nafion solution were mixed to prepare an Ink solution. 12 μL of this solution was transferred to a rotating ring electrode using a pipette. The rotating ring electrode was used for testing. The electrolyte was a 0.1 M KOH solution, the rotation speed was 1600 rpm, the scan rate was 10 mV / s, the scan range was 0-1.1 V relative to the hydrogen electrode, and the limiting current density was 3.8 mA / cm². 2 .

[0073] The differences between Specific Examples 18-24 and Specific Example 17 lie in the amount of nitrogen source urea added, the conditions for steam micro-explosion modification, and the high-temperature carbonization conditions, as shown in Table 5. The characterization and ORR performance of the prepared catalyst are shown in Table 6.

[0074] Table 5. Different addition amounts and steam micro-explosion modification and high-temperature carbonization conditions of specific examples 17-24

[0075]

[0076]

[0077] Table 6 Characterization and ORR performance of the catalysts prepared in specific Examples 17-24

[0078]

[0079] Tables 5 and 6 show that the amount of urea added affects the nitrogen content, exhibiting a positive correlation. Simultaneously, the phosphorus content varies with different heating rates and maintained temperatures. Furthermore, phosphorus content and specific surface area are not the primary influencing factors; nitrogen content is the main factor affecting ORR performance. When comparing all the results, melamine, with its high nitrogen content, controllable pyrolysis characteristics, and ability to directionally regulate the carbon framework structure, significantly improves the nitrogen doping efficiency and active site quality of the catalyst, ultimately achieving higher ORR performance than the dicyandiamide and urea systems.

[0080] In this technical solution, biomass carbon-based materials undergo micro-explosion modification to form a multi-level porous structure and expose abundant edge defect sites. Non-metallic element doping induces the reconstruction of the electronic structure of the carbon skeleton—nitrogen atoms introduce lone pairs of electrons in the form of pyridine / graphitic nitrogen to form charge donors, while phosphorus atoms act as electron acceptors. The two work together to construct electron transfer channels, causing the Fermi level to shift towards the conduction band. At the same time, the inherent oxygen-containing functional groups of biomass form coordination bonds with heteroatoms, enhancing the stability of active sites. The interconnected mesopores of the porous carbon matrix shorten the diffusion path of oxygen molecules, and the micropores anchor heteroatoms to form a conjugated system, synergistically reducing the rate-determining energy barrier of the oxygen reduction reaction and improving ORR performance.

[0081] Compared to other catalysts:

[0082] Comparative Example 1: Comparative Example 1 is compared with Specific Example 1, except that it does not use the steam micro-explosion modified fiber technology in step S2. All other steps are the same, and the limiting current density of the resulting biomass carbon-based non-metallic catalyst is 3.1 mA / cm². 2 The limiting current density of the biomass carbon-based non-metallic catalyst prepared in Specific Example 1 is 5.4 mA / cm². 2This demonstrates that the limiting current density of the biomass carbon-based non-metallic catalyst prepared without the steam micro-explosion modified fiber technology in step S2 is significantly lower than that prepared using the same technology. In other words, the catalyst using micro-explosion fiber technology exhibits superior performance compared to catalysts without this technology.

[0083] Comparative Example 2: Comparative Example 2 differs from Specific Example 1 in that no additional nitrogen source was introduced in step S2; all other steps were the same, and the resulting limiting current density was 2.9 mA / cm². 2 The limiting current density of the biomass carbon-based non-metallic catalyst prepared in Specific Example 1 is 5.4 mA / cm². 2 This demonstrates that catalysts with added nitrogen exhibit superior performance compared to catalysts without added nitrogen.

[0084] Finally, it should be noted that the above examples are merely a few specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and many variations are possible, such as using other nitrogen sources or simply changing the preparation conditions. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of this invention should be considered within the scope of protection of this invention.

Claims

1. A biomass carbon-based non-metallic catalyst, characterized in that, The biomass carbon-based non-metallic catalyst comprises biomass carbon-based material and non-metallic heteroatoms, wherein the total mass fraction of the biomass carbon-based material is 88-96%, and the total mass fraction of the non-metallic heteroatoms is 4-12%. The preparation method of the biomass carbon-based non-metallic catalyst includes the following steps: S1 Crushed Carbon Base: The biomass carbon base is pulverized multiple times using a pulverizer to collect 50-120 mesh powder, ensuring the integrity of its fiber bundles, and thus obtaining powder. S2 Steam Micro-Explosion Modification: Weigh the powder from step S1 according to the ratio and put it into a high-pressure reactor. Add deionized water and then add nitrogen source according to the ratio. Raise the temperature to 120-190℃ at a heating rate of 1-5℃ / min and maintain it for 1-6h. Then release the pressure of the solenoid valve instantly and collect the expanded fluffy fiber. S3 High-temperature carbonization: The fluffy fiber obtained in step S2 is placed in a tube furnace with a nitrogen source atmosphere and heated to 600-1200℃ at a heating rate of 2-6℃ / min and held for 2-5 hours. After obtaining the catalyst, it is soaked in an alkaline solution for 2-8 hours and then washed with deionized water. It is then dried in an oven to obtain the catalyst.

2. The biomass carbon-based non-metallic catalyst according to claim 1, characterized in that, The biomass carbon base is corn stalk; the non-metallic heteroatoms are nitrogen and phosphorus.

3. The biomass carbon-based non-metallic catalyst according to claim 1, characterized in that, The total mass fraction of nitrogen in this biomass carbon-based non-metallic catalyst is 4-8%; the total mass fraction of phosphorus is 0.1-1.1%; and the total mass fraction of carbon is 88-95%.

4. The biomass carbon-based non-metallic catalyst according to claim 2, characterized in that, The biomass carbon base in step S1 is corn stalks, and the shredding cycle is 2-5 times.

5. The biomass carbon-based non-metallic catalyst according to claim 4, characterized in that, In step S2, the nitrogen source is one of melamine, urea, or dicyandiamide.

6. The biomass carbon-based non-metallic catalyst according to claim 5, characterized in that, In step S2, deionized water is injected into the high-pressure reactor until the solid-liquid ratio is 1:6; the temperature is then raised to 135-190℃ at a rate of 3-5℃ / min and maintained for 2-5 hours.

7. The biomass carbon-based non-metallic catalyst according to claim 6, characterized in that, In step S3, the tube furnace is heated to 800-1200℃ at a heating rate of 3-6℃ / min and then held for 2-5 hours. The nitrogen source atmosphere introduced into the tube furnace is nitrogen or ammonia. The alkaline solution is NaOH or KOH solution with a concentration of 2-5M.

8. The biomass carbon-based non-metallic catalyst according to claim 7, characterized in that, The nitrogen source in step S2 is melamine; the nitrogen source atmosphere introduced into the tube furnace in step S3 is ammonia; the alkaline solution is NaOH solution with a concentration of 3M.

9. The application of a biomass carbon-based nonmetallic catalyst as described in any one of claims 1-8, characterized in that, Application of this biomass carbon-based non-metallic catalyst in the cathode catalyst of fuel cells.

Images