Preparation method and application of biomass carbon-based catalyst based on synergistic activation of composting and joule flash evaporation

Abstract

This invention discloses a method for preparing a biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation. The steps are as follows: S1: Mix dried and pulverized rice husks with poultry and livestock manure after impurity removal, and adjust the moisture content of the mixture to 30-90% to obtain a mixed raw material; S2: Pile the mixed raw material into a self-prepared composting tank and seal it, and carry out composting and transformation under the action of microorganisms. The total composting time is 28-75 days until the material is mature and turns brownish-brown. After drying and pulverizing, compost powder is obtained as the basic catalyst; S3: Take 15g of the basic catalyst and place it in a pulse treatment device for Joule flash treatment and two-stage pulse discharge treatment; After the treatment, crude carbon material is obtained, namely, a biomass carbon-based non-metallic catalyst. By introducing Joule flash evaporation technology, the material is subjected to instantaneous ultra-high temperature treatment by controllable high-energy electrical pulses, achieving synergistic enhancement of carbon skeleton graphitization, defect engineering, and active sites.

Description

Technical Field

[0001] This invention relates to the field of catalysts, specifically to a method for preparing and applying a biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation. Technical Background

[0002] With the expanding applications of zinc-air batteries and proton exchange membrane fuel cells in the clean energy field, their high energy efficiency has attracted much attention. However, the high cost of their cathode catalysts limits their large-scale application. To replace platinum-based catalysts, transition metal catalysts have emerged, but they also suffer from problems such as low active site density, insufficient environmental friendliness, and inadequate mass transfer efficiency. In recent years, biomass-derived carbon-based non-metallic materials have become an important research direction for oxygen reduction reaction catalysts due to their high renewability and environmental friendliness.

[0003] Researchers have synthesized Fe-NC catalysts using silica as a template and soybeans as both carbon and nitrogen sources, introducing metallic iron. These catalysts exhibit high specific surface area and excellent oxygen reduction reaction (ORR) performance, providing a feasible route for developing low-cost, high-efficiency non-precious metal electrocatalysts based on economically sustainable biomass. However, this method still relies on metallic iron in its synthesis, not completely eliminating the use of metals, thus lacking environmental friendliness. Meanwhile, other researchers have successfully prepared a nitrogen-doped carbon-based non-metallic catalyst using enoki mushroom biomass as a precursor. This catalyst exhibits good catalytic activity in ORR, with a half-wave potential (approximately 0.81 V) slightly lower than that of commercial 20 wt% Pt / C catalysts, providing a new perspective for non-metallic catalyst design. However, enoki mushrooms are edible agricultural products, with high raw material costs and potential competition for food resources, resulting in poor economic viability.

[0004] Currently, existing biomass carbon catalyst preparation technologies suffer from more general limitations: most rely on the direct carbonization of lignocellulose or require the use of highly corrosive activators such as phosphoric acid or strong alkalis, resulting in waste of raw material components and high pollution and energy consumption. Some lack metallization research or rely on edible biomass, leading to insufficient economic viability, or improper pretreatment damages the natural porous structure of agricultural waste, failing to fully utilize the synergistic effect of its carbon skeleton and internal heteroatoms. Furthermore, traditional pyrolysis carbonization processes have relatively crude temperature and time control, making it difficult to achieve precise regulation of the electronic structure, defect concentration, and pore system of carbon materials, thus restricting further improvement of the intrinsic activity of the catalyst.

[0005] Recently, Joule flash evaporation, as an emerging ultrafast high-temperature processing method, has provided a new approach for the precise control of carbon materials. This technology uses instantaneous high-energy electrical pulses to heat materials to ultra-high temperatures within milliseconds to seconds, thereby inducing dramatic structural reorganization and atomic rearrangement. Its application in catalyst preparation holds promise for achieving high graphitization of the carbon framework in an extremely short time to improve conductivity, create high-density defects as active sites, and induce more stable doping configurations of heteroatoms, thus comprehensively improving ORR performance. However, how to combine such advanced energy field control technologies with low-cost, green biomass precursor pretreatment processes to build a synergistic and efficient complete technology chain remains an area that has not been fully explored.

[0006] Therefore, it is necessary to propose a method for preparing and applying a biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation, in order to overcome the problems of high raw material costs, environmental unfriendliness, insufficient catalytic activity, and high pollution and energy consumption in the preparation process of existing technologies. This invention combines innovative composting pretreatment with Joule flash evaporation technology, which not only fully utilizes low-cost, renewable resources such as agricultural waste like rice husks and livestock manure, avoiding competition for food resources, but also, through the microbial action during composting, initially achieves the natural enrichment and pre-distribution of carbon sources and heteroatoms such as nitrogen, phosphorus, and sulfur, providing an ideal raw material basis for subsequent Joule flash evaporation treatment. Summary of the Invention

[0007] The technical problem this invention aims to solve is to propose a method for preparing and applying a biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation, thus integrating "composting" and "Joule flash evaporation" into a composite process. This method eliminates the need for exogenous activators and metal elements, not only solving the resource utilization problem of agricultural waste but also achieving synergistic optimization and precise control of the catalyst's microstructure, electronic properties, and active sites through the organic combination of composting pretreatment and flash evaporation posttreatment. This provides a new pathway for preparing fuel cell cathode catalysts that combines low cost, high performance, and environmental friendliness, deeply aligning with the "dual carbon" goal and helping to overcome commercialization bottlenecks.

[0008] The first aspect of this invention is to provide a method for preparing a biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation, specifically comprising the following steps:

[0009] S1 Raw Material Pretreatment: The dried and crushed rice husks are mixed with the poultry and livestock manure after impurities have been removed by sieving, and the moisture content of the mixture is adjusted to 30-90% to obtain the mixed raw material;

[0010] S2 composting: The mixed raw materials are piled into a self-prepared composting bucket and sealed. Under the action of microorganisms, composting and transformation are carried out. The total composting time is 28-75 days until the material is mature and turns brownish-brown. After drying and crushing, compost powder is obtained as a basic catalyst.

[0011] S3 electro-pulse activation: 15g of basic catalyst was placed in a pulse treatment device and subjected to Joule flash evaporation and two-stage pulse discharge treatment. After the treatment was completed, crude carbon material was obtained, namely biomass carbon-based non-metallic catalyst.

[0012] By employing the above-mentioned technical solution, addressing the issues of high raw material costs and reliance on exogenous dopants and highly corrosive activators in existing non-metallic carbon-based catalysts, this invention uses rice husks and livestock manure compost as precursors. Through the composting process, nitrogen, phosphorus, and sulfur heteroatoms are in situ bonded to the carbon framework, and a pore template is constructed. The resulting material is then obtained through low-temperature pyrolysis carbonization. Furthermore, controlled Joule flash evaporation and multi-segment pulsed discharge treatment, using controlled high-energy electrical pulses to subject the material to instantaneous ultra-high temperature treatment, achieves synergistic enhancement of the carbon framework graphitization, defect engineering, and active sites. This method eliminates the need for exogenous activators and metal elements, not only solving the resource utilization problem of agricultural waste but also achieving synergistic optimization and precise control of the catalyst's microstructure, electronic properties, and active sites through the organic combination of composting pretreatment and flash evaporation posttreatment. This process is entirely metal-free and free of exogenous toxic reagents, with low raw material costs. The resulting catalyst exhibits excellent oxygen reduction activity, high stability, and rapid mass transfer capabilities, providing a novel green technology solution for the low-cost, high-performance commercialization of fuel cell cathode catalysts.

[0013] Preferably, the process further includes step S4, post-treatment purification: the crude carbon material obtained in step S3 is soaked in an alkaline solution, then washed with an acidic solution and deionized water until neutral, and dried to obtain the purified biomass carbon-based non-metallic catalyst.

[0014] Preferably, in step S4, the crude carbon material obtained in step S3 is soaked in 3M potassium hydroxide solution for 24 hours, then washed with 0.1M hydrochloric acid solution and deionized water until neutral, and dried to obtain the catalyst.

[0015] Preferably, the biomass carbon-based non-metallic catalyst comprises rice husks and poultry manure, wherein the relative total weight percentage of carbon is 88-95%, and the mass fraction of heteroatoms is 5-12%.

[0016] Preferably, the heteroatoms include nitrogen, phosphorus, and sulfur, wherein the total mass fraction of nitrogen is 8-11% of the total, the total mass fraction of phosphorus is 0.1-1.1% of the total, and the mass fraction of sulfur is 0.1-1.2%.

[0017] Preferably, in step S1, the mixing mass ratio of rice husks and livestock manure is 1:(0.5-1.5) to ensure that the moisture content of the pile is stable at 35-87%.

[0018] A further preferred method is to mix rice husks and livestock manure at a mass ratio of 1:(0.8-1.3) to ensure that the moisture content of the compost pile remains stable at 40-70%.

[0019] Preferably, the livestock and poultry manure includes at least one of chicken manure, pig manure, and duck manure.

[0020] Preferably, if two types of livestock and poultry manure are mixed, the mass ratio of the two types of livestock and poultry manure is (1-2):(1-2).

[0021] Preferably, the specific steps of Joule flash treatment and two-stage pulse discharge treatment in step S3 are as follows:

[0022] The conditions for the first pulse discharge are: voltage 10-60V, current 1-80A, discharge time 1-60s, and discharge times 1-5 times; the first Joule flash treatment causes the basic catalyst material to be instantly heated to 200-2000℃.

[0023] The conditions for the second stage of pulse discharge are: voltage 10-120V, current 10-240A, discharge time 1-1000ms, discharge times 1-10 times, and the second Joule flash treatment causes the catalyst material to be instantly heated to 200-3000℃.

[0024] Preferably, the specific steps of Joule flash treatment and two-stage pulse discharge treatment in step S3 are as follows:

[0025] The conditions for the first pulse discharge are: voltage 20-60V, current 3-80A, discharge time 5-60s, and discharge times 1-5 times; the first Joule flash treatment causes the basic catalyst material to be instantly heated to 200-1000℃.

[0026] The conditions for the second stage of pulse discharge are: voltage 20-120V, current 20-240A, discharge time 50-600ms, discharge times 1-10 times, and the second Joule flash treatment causes the catalyst material to be instantly heated to 200-2500℃.

[0027] Joule flash evaporation, the core technology of this invention, achieves instantaneous ultra-high temperature treatment and precise control of catalyst materials through a two-stage pulse discharge design. The first stage of pulse discharge initially opens the pore structure of carbon materials at a lower energy, promoting the initial doping of heteroatoms; while the second stage of pulse discharge further deepens the pore structure at a higher energy, increases the defect density, and induces heteroatoms to form a more stable doped configuration, thereby significantly improving the oxygen reduction reaction performance of the catalyst.

[0028] Preferably, in step S2, the height of the composting bucket is 0.3-1.5m, and the bottom diameter is 0.1-1m. The composting process includes a natural warming period of 3-15 days and a high-temperature stabilization period of 25-60 days, during which the internal temperature of the compost pile is maintained at 35-85℃ by opening the lid and turning the pile. When the temperature drops to ambient temperature and the rice husks turn brownish-brown, the compost is placed in an oven to dry, then crushed and sieved to obtain compost powder.

[0029] Further optimization involves using a composting barrel with a height of 0.4-1.0 m and a width of 0.2-0.8 m.

[0030] Preferably, in step S1, the rice husk drying temperature is 45-85℃ and the drying time is 2-12h to ensure that the moisture content of the rice husk is stable at 6-18%.

[0031] A further preferred method is to use a drying temperature of 55-60℃ and a drying time of 3-8 hours to ensure that the moisture content of the rice husk remains stable at 8-15%.

[0032] The second aspect of this invention provides the application of the biomass carbon-based non-metallic catalyst as described in the first aspect of this invention as a cathode catalyst in a zinc-air battery for fuel cell fabrication. The performance of the non-metallic catalyst is controlled by a rational formulation. The specific steps are as follows: 6.5 mg of catalyst is weighed and added to 150 μL of water, 750 μL of anhydrous ethanol, and 100 μL of Nafion solution. The mixture is ultrasonicated for 20-30 min to prepare an Ink solution. 35 μL of the Ink solution is then spin-drop coated onto the RRDE working electrode and air-dried at room temperature. The reaction performance is tested using 0.1 mol / L KOH (oxygenated for 30 min) at a rotation speed of 1600 rpm, a scan rate of 5 mV / s, and a scan range of 0-1.1 V (vsRHE). The performance of the zinc-air battery is tested using a polished 0.3 mm thick zinc sheet as the positive electrode, a mixed solution of 6 M KOH and 0.2 M Zn(Ac)₂ as the electrolyte, and a zinc-air battery cathode prepared with the same Ink formulation. The Ink is sprayed onto a 2*2 cm layer. 2 On the carbon cloth, the catalyst loading was 2 mg cm. -2 And at 5mA cm -2 Durability tests were conducted at a current density of 5 minutes of charging and 5 minutes of discharging.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) First, the composting process of rice husks and poultry manure is used to achieve in-situ fusion and doping of heteroatoms such as nitrogen, phosphorus, and sulfur. Then, a hierarchical porous template is constructed with the help of microorganisms. Finally, Joule flash evaporation technology is introduced to refine the structure and electronically regulate the material under an instantaneous ultra-high temperature field, thereby significantly improving the graphitization degree of the carbon skeleton, defect density, and intrinsic activity of active sites.

[0035] (2) This method not only utilizes rice husks and livestock manure as raw materials to achieve high-value utilization of waste, but more importantly, it innovatively combines "composting" pretreatment with "Joule flash" posttreatment. Through composting, in-situ doping of heteroatoms and construction of pore templates are achieved. Then, through controllable Joule flash and multi-segment pulse discharge, the structure of the precursor material is refined and activated in a very short time, forming a complete process with synergistic effects. This method aims to overcome the limitations of existing technologies, such as reliance on exogenous activators, high energy consumption, process pollution, and difficulty in precisely controlling the final structure of the catalyst.

[0036] (3) This method does not require precious metals or exogenous activators. The catalyst produced exhibits superior oxygen reduction activity and stability in alkaline electrolyte compared to conventional pyrolysis products. Moreover, the raw material cost is extremely low and the process is green and efficient, providing a novel and innovative path for the low-cost, high-performance and commercial application of fuel cell cathode catalysts. Attached Figure Description

[0037] Figure 1 This is a SEM image of Embodiment 1 of the present invention; from Figure 1 The morphology of the compost straw fibers in this embodiment can be seen.

[0038] Figure 2 The XRD pattern of Embodiment 1 of the present invention is shown below. Figure 2 It can be seen that a pure carbon-based non-metallic catalyst was prepared in Example 1;

[0039] Figure 3 The limiting current density of the catalyst was obtained from the linear sweep voltammogram of Example 1 of the present invention;

[0040] Figure 4 This is a peak power image of Embodiment 1 of the present invention;

[0041] Figure 5 These are images from a durability test of Embodiment 1 of the present invention. Detailed Implementation

[0042] The specific embodiments of the present invention will be described in detail below, but the present invention is not limited thereto.

[0043] Unless otherwise specified, the preparation methods and usage conditions used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0044] To avoid excessive and unnecessary detail, well-known structures or functions will not be described in detail in the following embodiments. The approximate language used in the following embodiments is for quantitative purposes, indicating that variations in quantity are permissible without altering the basic function. Unless otherwise defined, the technical and scientific terms used in the following embodiments have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0045] Example: The preparation method of this biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation specifically includes the following steps:

[0046] S1 Raw Material Pretreatment: The dried and crushed rice husks are mixed with the poultry and livestock manure after impurities have been removed by sieving, and the moisture content of the mixture is adjusted to 30-90% to obtain the mixed raw material;

[0047] In step S1, the mixing mass ratio of rice husks to livestock and poultry manure is 1:(0.5-1.5) to ensure that the moisture content of the compost pile remains stable at 35-87%.

[0048] In some specific embodiments, the mixing mass ratio of rice husks to livestock and poultry manure is 1:(0.8-1.3) to ensure that the moisture content of the pile is stable at 40-70%.

[0049] In some specific embodiments, the livestock and poultry manure includes at least one of chicken manure, pig manure, and duck manure.

[0050] In some specific embodiments, the livestock and poultry manure is a mixture of chicken manure and pig manure, with a mass ratio of 1:2 or 1:1.

[0051] In some specific embodiments, the livestock and poultry manure is a mixture of chicken manure and duck manure, with a mass ratio of 1:1 or 1:2.

[0052] In some specific embodiments, the livestock and poultry manure is a mixture of duck manure and pig manure, with a mass ratio of duck manure to pig manure of 1:1 or 1:2.

[0053] In step S1, the rice husk drying temperature is 45-85℃, and the drying time is 2-12 hours, ensuring that the moisture content of the rice husk remains stable at 6-18%.

[0054] In some specific embodiments, the preferred drying temperature is 55-60℃ and the drying time is 3-8h to ensure that the moisture content of the rice husk is stable at 8-15%.

[0055] S2 composting: The mixed raw materials are piled into a self-prepared composting bucket and sealed. Under the action of microorganisms, composting and transformation are carried out. The total composting time is 28-75 days until the material is mature and turns brownish-brown. After drying and crushing, compost powder is obtained as a basic catalyst.

[0056] In some specific embodiments, the height of the composting bucket in step S2 is 0.3-1.5m, and the bottom diameter is 0.1-1m. The composting process includes a natural warming period of 3-15 days and a high-temperature stabilization period of 25-60 days, during which the internal temperature of the compost pile is maintained at 35-85℃ by opening the lid and turning the pile. When the temperature drops to ambient temperature and the rice husks turn brownish-brown, the compost is placed in an oven to dry, then crushed and sieved to obtain compost powder.

[0057] In some specific embodiments, the height of the composting barrel is 0.4-1.0 m and the width is 0.2-0.8 m.

[0058] S3 electro-pulse activation: 15g of basic catalyst was placed in a pulse treatment device and subjected to Joule flash evaporation and two-stage pulse discharge treatment. After the treatment, crude carbon material was obtained, namely biomass carbon-based non-metallic catalyst.

[0059] The specific steps for Joule flash treatment and two-stage pulse discharge treatment in step S3 are as follows:

[0060] The conditions for the first pulse discharge are: voltage 10-60V, current 1-80A, discharge time 1-60s, and discharge times 1-5 times; the first Joule flash treatment causes the basic catalyst material to be instantly heated to 200-2000℃.

[0061] The conditions for the second stage of pulse discharge are: voltage 10-120V, current 10-240A, discharge time 1-1000ms, discharge times 1-10 times, and the second Joule flash treatment causes the catalyst material to be instantly heated to 200-3000℃.

[0062] S4 Post-treatment purification: The crude carbon material obtained in step S3 is soaked in an alkaline solution, then washed with an acidic solution and deionized water until neutral, and dried to obtain the purified biomass carbon-based non-metallic catalyst.

[0063] In some specific embodiments, the specific steps of performing Joule flash treatment and two-stage pulse discharge treatment in step S3 are as follows:

[0064] The conditions for the first pulse discharge are: voltage 20-60V, current 3-80A, discharge time 5-60s, and discharge times 1-5 times; the first Joule flash treatment causes the basic catalyst material to be instantly heated to 200-1000℃.

[0065] The conditions for the second stage of pulse discharge are: voltage 20-120V, current 20-240A, discharge time 50-600ms, discharge times 1-10 times, and the second Joule flash treatment causes the catalyst material to be instantly heated to 200-2500℃.

[0066] In some specific embodiments, in step S4, the crude carbon material obtained in step S3 is soaked in 3M potassium hydroxide solution for 24 hours, then washed with 0.1M hydrochloric acid solution and deionized water until neutral, and dried to obtain the catalyst.

[0067] In some specific embodiments, the biomass carbon-based non-metallic catalyst comprises rice husks and poultry manure, wherein the relative total weight percentage of carbon is 88-95%, and the mass fraction of heteroatoms is 5-12%.

[0068] In some specific embodiments, the heteroatoms include nitrogen, phosphorus, and sulfur, wherein the total mass fraction of nitrogen is 8-11% of the total, the total mass fraction of phosphorus is 0.1-1.1% of the total, and the mass fraction of sulfur is 0.1-1.2%.

[0069] The application of this biomass carbon-based non-metallic catalyst as a cathode catalyst in zinc-air batteries for fuel cell fabrication. The performance of the non-metallic catalyst was regulated by a rational formulation. The specific steps were as follows: 6.5 mg of catalyst was weighed and added to 150 μL of water, 750 μL of anhydrous ethanol, and 100 μL of Nafion solution. The mixture was sonicated for 20-30 min to prepare an Ink solution. 35 μL of the Ink solution was spin-drop coated onto the RRDE working electrode and allowed to air dry at room temperature. The reaction was tested using 0.1 mol / L KOH (oxygenated for 30 min) at a rotation speed of 1600 rpm, a scan rate of 5 mV / s, and a scan range of 0-1.1 V (vs RHE). The reaction performance was recorded. The performance of the zinc-air battery was tested using a polished 0.3 mm thick zinc sheet as the positive electrode and a mixed solution of 6 M KOH and 0.2 M Zn(Ac)₂ as the electrolyte. The cathode of the zinc-air battery was prepared using the same Ink formulation, and the Ink was sprayed onto a 2*2 cm layer. 2 On the carbon cloth, the catalyst loading was 2 mg cm. -2 And at 5mAcm -2 Durability tests were conducted at a current density of 5 minutes of charging and 5 minutes of discharging.

[0070] The following detailed description is based on several specific embodiments.

[0071] Example 1: The preparation method of this biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation specifically includes the following steps:

[0072] S1 Raw Material Pretreatment: Take rice husks, crush them, and dry them in a drying oven at 60 ℃ for 8 hours to ensure that the moisture content of the rice husks is 9-10%; take chicken manure, sieve it to remove impurities, and mix the rice husks and manure at a mass ratio of 1:1.2 to adjust the moisture content of the pile to 60-65%;

[0073] S2 composting: The mixed raw materials are loaded into a cylindrical container with a height of 0.9 m and a diameter of 0.6 m, covered with breathable non-woven fabric, and allowed to heat up naturally for 11 days in the first stage and then for 45 days in the second stage. During this period, the composting temperature is kept at 55 ℃. When the temperature drops to the ambient temperature and the rice husks turn brownish-brown, the container is placed in an oven to dry, and then crushed and sieved to obtain compost powder.

[0074] S3 Electro-Pulse Activation: 15g of the basic catalyst was placed in a pulse treatment device and subjected to Joule flash evaporation and two-stage pulse discharge. The conditions for the first stage pulse discharge were: voltage 35 V, current 55 A, discharge time 50 s, discharge times 2, and peak temperature 600 ℃. The conditions for the second stage pulse discharge were: voltage 100 V, current 200 A, discharge time 300 ms, discharge times 6, and peak temperature 1800 ℃. After the treatment, the biomass carbon-based non-metallic catalyst was obtained.

[0075] S4 Post-treatment Purification: The crude carbon material was soaked in 3M potassium hydroxide solution for 24 hours, then washed with 0.1M hydrochloric acid solution and deionized water until neutral, and dried to obtain the catalyst. The catalyst has a total nitrogen content of 2.5% by mass, a total phosphorus content of 1.5% by mass, a sulfur content of 0.6% by mass, and a specific surface area of ​​2609 m². 2 / g;

[0076] S5 catalyst evaluation: 6.5 mg of catalyst was weighed and added to 150 μL of water, 750 μL of anhydrous ethanol, and 100 μL of Nafion solution. The mixture was sonicated for 20-30 min to prepare an Ink solution. 35 μL of the Ink solution was spin-dropped onto the RRDE working electrode and allowed to air dry at room temperature. The electrode was tested with 0.1 mol / L KOH (oxygenated for 30 min) at a spin speed of 1600 rpm, a scan rate of 5 mV / s, and a scan range of 0-1.1 V (vsRHE). The limiting current density was 5.9 mA cm⁻¹ after subtracting the current density under a nitrogen atmosphere. -2 The half-wave potential was 0.85 V; and a zinc-air cell cathode catalyst was prepared using the same Ink formulation, yielding a peak voltage of 253 mW / cm². -2 Its stability is 1200 h.

[0077] like Figure 1 The image shown is a SEM image of Example 1; from Figure 1It can be seen that the compost straw fiber morphology in this embodiment is micron-sized particles;

[0078] Figure 2 The XRD pattern of Example 1 is shown below. Figure 2 It can be seen that a pure carbon-based non-metallic catalyst was prepared in Example 1.

[0079] Figure 3 The linear sweep voltammogram for Example 1 shows that the limiting current density of the catalyst was determined to be 5.9 mA / cm². -2 The half-wave potential is 0.85 V, indicating that the catalyst has high activity and selectivity in the oxygen reduction reaction.

[0080] Figure 4 The image shown is the peak power image for Example 1, demonstrating that when this catalyst is used as the cathode catalyst in a zinc-air battery, the peak power density of the battery reaches 253 mW / cm². -2 This demonstrates its excellent electrochemical performance.

[0081] Figure 5 These are images from the durability test of Example 1, taken at 5 mA cm. -2 Cyclic tests were conducted at a current density of 5 minutes for charging and 5 minutes for discharging. The results showed that the catalyst exhibited good stability and could run continuously for more than 1200 hours, providing a strong guarantee for the long-term stable operation of fuel cells.

[0082] Example 2: The preparation method of this biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation specifically includes the following steps:

[0083] S1 Raw Material Pretreatment: Take rice husks, crush them, and dry them in a drying oven at 60 ℃ for 7 h to ensure that the moisture content of the rice husks is 9-10%; take chicken manure and duck manure (mass ratio of 1:1), sieve to remove impurities, mix rice husks and manure at a mass ratio of 1:1.1, and adjust the moisture content of the pile to 55%;

[0084] S2 composting: The mixed raw materials are piled into a cylindrical container with a height of 0.77 m and a diameter of 1.53 m, covered with breathable non-woven fabric, and the initial stage is naturally heated and maintained for 10 days, followed by 42 days. During this period, the composting temperature is maintained at 52 ℃. When the temperature drops to the ambient temperature and the rice husks turn brownish-brown, they are placed in an oven to dry, crushed and sieved to obtain compost powder.

[0085] S3 Electro-Pulse Activation: 15g of the basic catalyst was placed in a pulse treatment device and subjected to Joule flash evaporation and two-stage pulse discharge. The conditions for the first stage pulse discharge were: voltage 32 V, current 50 A, discharge time 45 s, discharge times 2, and peak current 550 °C. The conditions for the second stage pulse discharge were: voltage 95 V, current 180 A, discharge time 280 ms, discharge times 5, and peak current 1600 °C. After the treatment, the biomass carbon-based non-metallic catalyst was obtained.

[0086] S4 Post-treatment Purification: The crude carbon material was soaked in 3M potassium hydroxide solution for 24 hours, then washed with 0.1M hydrochloric acid solution and deionized water until neutral, and dried to obtain the catalyst. The catalyst has a total nitrogen content of 2.2% by mass, a total phosphorus content of 1.3% by mass, a sulfur content of 0.5% by mass, and a specific surface area of ​​2320 m². 2 / g.

[0087] S5 catalyst evaluation: 6.5 mg of catalyst was weighed and added to 150 μL of water, 750 μL of anhydrous ethanol, and 100 μL of Nafion solution. The mixture was sonicated for 20–30 min to prepare an Ink solution. 35 μL of the Ink solution was spin-dropped onto the RRDE working electrode and allowed to air dry at room temperature. The electrode was tested using 0.1 mol / L KOH (oxygenated for 30 min) at a spin speed of 1600 rpm, a scan rate of 5 mV / s, and a scan range of 0–1.1 V (vs RHE). The limiting current density was determined to be 5.4 mA cm⁻¹ after subtracting the current density under a nitrogen atmosphere. -2， The half-wave potential was 0.81 V; and a zinc-air cell cathode catalyst was prepared using the same Ink formulation, yielding a peak voltage of 172 mW / cm². -2 Its stability is 680 h.

[0088] Example 3: The preparation method of this biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation specifically includes the following steps:

[0089] S1 Raw Material Pretreatment: Take rice husks, crush them, and dry them in a drying oven at 58 ℃ for 6 h to ensure that the moisture content of the rice husks is 9-10%; take chicken manure and duck manure (mass ratio of 1:1), sieve to remove impurities, mix rice husks and manure at a mass ratio of 1:1.3, and adjust the moisture content of the pile to 61%;

[0090] S2 composting: The mixed raw materials are piled into a cylindrical container with a height of 1.1 m and a diameter of 0.7 m, covered with breathable non-woven fabric, and the initial stage is naturally heated and maintained for 10 days, followed by 48 days. During this period, the composting temperature is maintained at 58 ℃. When the temperature drops to the ambient temperature and the rice husks turn brownish-brown, they are placed in an oven to dry, crushed and sieved to obtain compost powder.

[0091] S3 Electro-Pulse Activation: 15g of the basic catalyst was placed in a pulse treatment device and subjected to Joule flash evaporation and two-stage pulse discharge. The conditions for the first stage pulse discharge were: voltage 38 V, current 60 A, discharge time 55 s, discharge times 3, and peak current 650 °C. The conditions for the second stage pulse discharge were: voltage 105 V, current 210 A, discharge time 320 ms, discharge times 7, and peak current 1900 °C. After the treatment, the biomass carbon-based non-metallic catalyst was obtained.

[0092] S4 Post-treatment Purification: The crude carbon material was soaked in 3M potassium hydroxide solution for 24 hours, then washed with 0.1M hydrochloric acid solution and deionized water until neutral, and dried to obtain the catalyst. The catalyst has a total nitrogen content of 2.8%, a total phosphorus content of 1.6%, a sulfur content of 0.7%, and a specific surface area of ​​2640 m². 2 / g.

[0093] S5 catalyst evaluation: 6.5 mg of catalyst was weighed and added to 150 μL of water, 750 μL of anhydrous ethanol, and 100 μL of Nafion solution. The mixture was sonicated for 20-30 min to prepare an Ink solution. 35 μL of the Ink solution was spin-dropped onto the RRDE working electrode and allowed to air dry at room temperature. The electrode was tested using 0.1 mol / L KOH (oxygenated for 30 min) at a spin speed of 1600 rpm, a scan rate of 5 mV / s, and a scan range of 0-1.1 V (vsRHE). The limiting current density was determined to be 4.5 mA cm⁻¹ after subtracting the current density under a nitrogen atmosphere. -2 The half-wave potential was 0.74 V; and a zinc-air cell cathode catalyst was prepared using the same Ink formulation, with a peak voltage of 198 mW / cm². -2 Its stability is 820 h.

[0094] Comparative Example 1: Comparative Example 1 differs from Specific Example 1 in that it omits the "composting" step, while all other steps remain the same. The limiting current density of the resulting biomass carbon-based non-metallic catalyst is 3.2 mA / cm². 2 The half-wave potential is 0.65V, and the peak current density is 96mW / cm². -2 The durability was 210 h, which is much less than that of Example 1. The limiting current density of the catalyst without composting was significantly lower than that of the catalyst treated with composting. This indicates that composting can achieve in-situ doping of heteroatoms and optimize the pore structure of rice husks through microbial action, thereby improving catalytic mass transfer efficiency and activity.

[0095] Comparative Example 2: Comparative Example 2 is compared with Specific Example 1, except that the flash Joule method is not used. Instead, a conventional tube furnace is used for heating at a rate of 5°C / min to 600°C. After cooling to room temperature, it is then heated to 1800°C at a rate of 5°C / min, and subsequently cooled to room temperature to mimic the Joule flash process. The limiting current density of the resulting biomass carbon-based non-metallic catalyst is 4.9 mA / cm². 2 The half-wave potential is 0.75V, and the peak current density is 125mW / cm². -2 The durability was 235 h, which is far less than that of Example 1. This proves the necessity of the flash joule method, which can revolutionize the basic carbon material obtained from composting by injecting ultra-high energy in an instantaneous (millisecond and second-level) manner.

[0096] Example 4-24:

[0097] The different parameter conditions in steps S1, S2 and S3 are discussed separately. The biomass carbon-based non-metallic catalyst is prepared under the conditions in Tables 1-4. The steps in the implementation plan are followed to obtain the catalyst characterization and ORR performance in Table 5.

[0098] Table 1. Raw material pretreatment conditions in different steps S1

[0099] Example Drying temperature (°C) Drying time (h) Moisture content of rice husks (%) Mixed mass ratio of poultry and livestock manure (1:X) Manure type Moisture content of the heap (%) 4 57 5 10-12 1.1 duck droppings 54-56 5 56 4 11-13 1.0 pig manure 49-51 6 55 3 14-16 1.3 Duck manure : Pig manure (1:1) 69-71 7 60 7 8-10 0.85 chicken manure 41-43 8 59 6 9-11 0.95 duck droppings 47-49 9 58 5 10-12 1.05 pig manure 51-53 10 57 4 11-13 1.15 Chicken manure : Duck manure (2:1) 57-59 11 56 3 13-15 1.25 Chicken manure : Pig manure (2:1) 61-63 12 60 8 7-9 0.82 duck droppings 43-45 13 59 7 8-10 0.92 pig manure 45-47 14 58 6 9-11 1.02 chicken manure 53-55 15 57 5 10-12 1.12 Duck manure : Pig manure (2:1) 64-66 16 56 4 11-13 1.22 chicken manure 67-69 17 55 3 14-16 1.3 duck droppings 40-42 18 60 7 8-10 0.88 pig manure 48-50 19 59 6 9-11 0.98 Chicken manure : Duck manure (1:2) 50-52 20 58 5 10-12 1.08 Chicken manure : Pig manure (1:2) 58-60 21 57 4 11-13 1.18 duck droppings 62-64 22 56 3 13-15 1.28 pig manure 65-67 23 60 8 7-9 0.83 chicken manure 42-44 24 59 7 8-10 0.93 duck droppings 52-54 25 58 6 9-11 1.03 pig manure 55-57 26 57 5 10-12 1.23 Chicken manure : Duck manure (1:1) 63-65 27 56 4 11-13 1.3 Chicken manure : Pig manure (1:1) 46-48 28 55 3 13-15 0.95 Duck manure : Pig manure (1:1) 47-49 29 60 8 7-9 0.97 chicken manure 66-68 30 59 7 8-10 0.85 duck droppings 41-43

[0100] Table 2 Composting conditions in different steps S2

[0101] Example Cylinder height (m) Cylinder diameter (m) A while ago (days) In the coming period (days) temperature of compost pile (°C) 4 0.8 1.5 10 42 50-54 5 0.7 1.4 9 40 48-52 6 1.0 1.8 14 55 58-62 7 0.55 1.1 8 32 44-48 8 0.65 1.3 9 38 47-51 9 0.75 1.45 10 41 49-53 10 0.85 1.7 12 48 54-58 11 0.95 1.75 13 50 56-60 12 0.52 1.05 7 31 45-49 13 0.62 1.25 8 36 48-52 14 0.72 1.55 9 43 51-55 15 0.82 1.65 11 46 55-59 16 0.92 1.78 13 52 57-61 17 0.58 1.15 8 33 43-47 18 0.68 1.35 9 39 47-51 19 0.78 1.48 10 44 50-54 20 0.88 1.68 12 49 54-58 21 0.98 1.72 14 53 56-60 22 0.53 1.08 7 34 44-48 23 0.63 1.22 8 37 46-50 24 0.73 1.52 9 45 49-53 25 0.83 1.62 10 47 52-56 26 0.57 1.12 8 38 47-51 27 0.67 1.38 9 40 48-52 28 0.65 1.3 9 38 47-51 29 0.87 1.67 12 54 57-61 30 0.55 1.1 8 32 44-48

[0102] Table 3. Activation conditions of the first electrical pulse in different steps S3.

[0103] Example First pulse voltage (V) First pulse current (A) First discharge time (s) Number of discharges in the first stage (times) First peak temperature (°C) 4 28 45 35 2 450 5 42 65 60 3 700 6 36 58 48 2 580 7 39 62 52 3 630 8 30 48 40 2 500 9 40 68 56 3 680 10 25 40 30 2 400 11 45 72 58 3 750 12 37 56 51 2 610 13 33 52 46 2 560 14 39 63 53 3 640 15 29 46 38 2 480 16 41 66 57 3 690 17 34 53 47 2 570 18 38 61 54 3 660 19 27 43 32 2 430 20 43 70 59 3 720 21 31 51 42 2 520 22 36 57 49 2 590 23 28 47 36 2 470 24 39 64 53 3 640 25 32 50 44 2 540 26 37 59 50 3 620 27 35 55 48 2 590 28 44 71 58 3 730 29 26 42 31 2 410 30 36 56 49 2 580

[0104] Table 4. Activation conditions for the second electrical pulse in different steps S3

[0105] Example Second pulse voltage (V) Second pulse current (A) Second discharge duration (ms) Number of discharges in the second stage (times) Second peak temperature (°C) 4 85 160 220 2 1400 5 110 220 350 3 2100 6 98 190 290 2 1750 7 102 205 60 3 1850 8 90 170 250 2 1500 9 108 215 80 3 2000 10 80 150 200 2 1300 11 115 230 140 3 2200 12 101 195 300 2 1800 13 96 185 120 2 1650 14 103 208 315 3 1880 15 88 165 240 2 1450 16 107 218 340 3 2050 17 97 188 285 2 1700 18 104 202 65 3 1920 19 83 158 210 2 1380 20 112 225 360 3 2150 21 92 175 260 2 1550 22 99 192 90 2 1780 23 86 162 230 2 1420 24 103 206 80 3 1860 25 94 178 275 2 1580 26 100 198 305 3 1820 27 98 190 290 2 1760 28 113 228 90 3 2180 29 81 155 205 2 1320 30 99 191 294 2 1770

[0106] Table 5 Performance of the catalysts obtained in Examples 4-24

[0107] Example Nitrogen content (%) Phosphorus content (%) Sulfur content (%) Current density (mA·cm⁻²) Half-wave potential (V) Peak power (mW·cm⁻²) Stability (h) 4 1.8 1 0.4 3.5 0.66 156 550 5 3.2 1.8 0.8 4.8 0.76 215 880 6 2.4 1.4 0.55 4.1 0.71 182 720 7 2.7 1.55 0.65 4.4 0.73 192 790 8 2 1.1 0.45 3.7 0.68 164 620 9 3 1.7 0.75 4.6 0.75 205 850 10 1.5 0.8 0.35 3.2 0.64 148 480 11 3.5 1.9 0.9 5 0.78 228 920 12 2.6 1.45 0.62 4.3 0.72 189 760 13 2.3 1.35 0.52 4 0.71 176 700 14 2.75 1.58 0.68 4.45 0.73 195 800 15 1.9 1.05 0.48 3.6 0.67 160 580 16 3.1 1.75 0.78 4.7 0.76 208 860 17 2.35 1.38 0.58 4 0.7 178 710 18 2.85 1.62 0.72 4.55 0.74 200 810 19 1.75 0.95 0.42 3.4 0.65 152 530 20 3.3 1.85 0.85 4.9 0.77 222 900 21 2.1 1.2 0.5 3.8 0.69 168 650 22 2.5 1.42 0.6 4.2 0.72 185 740 23 1.85 1.02 0.46 3.6 0.67 158 570 24 2.7 1.56 0.67 4.4 0.73 194 790 25 2.2 1.28 0.53 3.9 0.7 170 670 26 2.6 1.5 0.65 4.3 0.72 188 770 27 2.45 1.4 0.58 4.1 0.71 181 730 28 3.4 1.88 0.88 4.95 0.77 225 910 29 1.6 0.85 0.38 3.3 0.64 150 500 30 2.48 1.41 0.59 4.15 0.715 184 735

[0108] As can be seen from the above, the carbon materials processed using this technical solution exhibit excellent electrochemical performance. For example, in Example 5, the peak power reached 229 kW, and the stable operation lasted for 920 hours. This is because the "composting" process during preparation was conducted under suitable conditions, with a suitable temperature in the first stage of the "Joule flash" process and a higher temperature in the second stage, resulting in a greater incorporation of nitrogen into the material, leading to higher material activity and excellent stability. Furthermore, the stability of Examples 20 and 28 also reached 900 hours. In contrast, the "Joule flash" process temperatures in Examples 10 and 29 were relatively mild, with less nitrogen incorporation, resulting in poorer material performance.

[0109] In this technical solution, through the sequential synergistic effect of "composting" and "Joule flash evaporation," multi-level optimization and refinement of catalyst performance are achieved from atomic doping and structural construction to final electronic state regulation. Firstly, the composting process is the pre-construction and activation stage of the precursor. During this stage, microbial metabolism converts the organic nitrogen and phosphorus macromolecules in livestock manure into active small molecules such as amino, amide, and phosphate groups. These molecules react with oxygen-containing functional groups on the surface of the rice husk carbon skeleton during the high-temperature period of the compost pile, achieving in-situ and uniform anchoring of heteroatoms such as N, P, and S, laying the material basis for the active components of the catalyst. Simultaneously, the enzymes secreted by microorganisms degrade the rice husk fibers, forming pre-etched channels. Their metabolic gases escape during subsequent pyrolysis, leaving behind abundant mesopores and micropores, thus constructing a interconnected multi-level porous template, effectively shortening the oxygen molecule diffusion path. In addition, the silicon in rice husks and potassium, calcium and other elements in manure form soluble substances in the weakly acidic environment of compost. During pyrolysis, these substances can act as "self-activators" to produce a mild pore-forming effect and coordinate with doped heteroatoms, thus initially enhancing the stability of active sites.

[0110] However, traditional pyrolysis has limited depth of control over the electronic structure of the carbon framework. Therefore, this scheme innovatively introduces Joule flash evaporation as a decisive post-processing step. This process, through instantaneous (millisecond to second-level) ultra-high energy injection, performs disruptive structural refinement and electronic rearrangement on the basic carbon material obtained from composting-pyrolysis: the instantaneous ultra-high temperature forces the carbon network to undergo rapid rearrangement, significantly improving the degree of graphitization and crystallinity, and greatly enhancing the overall conductivity. At the same time, the extremely rapid thermal shock creates a large number of topological defects and edge sites in the carbon framework, and strongly synergizes with the N, P, and S atoms pre-doped in the composting stage, jointly modulating the local electron density of the carbon framework, causing the Fermi level to shift further towards the conduction band, and significantly reducing charge transfer resistance. The high-energy environment of the flash evaporation process can promote the transformation of some doped nitrogen atoms to a more catalytically active configuration, and may enable heteroatoms such as N, P, and S to form more stable chemical bonds with the carbon framework, thereby further improving the intrinsic activity and durability of active sites.

[0111] In summary, composting completes the green synthesis process of implanting active components and constructing biological templates, while Joule flash evaporation represents a high-energy reshaping of this precursor, achieving deep synergistic optimization from atomic and electronic structure to macroscopic pore network. The organic combination of these two processes significantly reduces the rate-determining energy barrier of the oxygen reduction reaction, thereby comprehensively improving the catalyst's activity, stability, and mass transfer efficiency.

[0112] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0113] For those skilled in the art, the specific embodiments are merely illustrative descriptions of the present invention. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the inventive concept and technical solution, such as changing the mass of a substance or a reaction parameter, or directly applying the inventive concept and technical solution to other situations without modification, are all within the protection scope of the present invention.

Claims

1. A method for preparing a biomass carbon-based catalyst based on the synergistic activation of composting and Joule flash evaporation, characterized in that, Specifically, the following steps are included: S1 Raw Material Pretreatment: The dried and crushed rice husks are mixed with the poultry and livestock manure after impurities have been removed by sieving, and the moisture content of the mixture is adjusted to 30-90% to obtain the mixed raw material; S2 composting: The mixed raw materials are piled into a composting bucket and sealed. Under the action of microorganisms, composting and transformation take place. The total composting time is 28-75 days until the material is mature and turns brown. After drying and crushing, compost powder is obtained as a basic catalyst. S3 electro-pulse activation: The base catalyst is placed in a pulse processing device and subjected to Joule flash evaporation and two-stage pulse discharge treatment. After processing, crude carbon material is obtained, namely biomass carbon-based non-metallic catalyst.

2. The method according to claim 1, characterized in that, The process also includes step S4, which involves post-treatment purification: soaking the crude carbon material obtained in step S3 in an alkaline solution, then washing it with an acidic solution and deionized water until it is neutral, and finally drying it to obtain the purified biomass carbon-based non-metallic catalyst.

3. The method according to claim 1, characterized in that, The biomass carbon-based non-metallic catalyst comprises rice husks and poultry manure, wherein the relative total weight percentage of carbon is 88-95%, and the mass fraction of heteroatoms is 5-12%.

4. The method according to claim 3, characterized in that, The heteroatoms include nitrogen, phosphorus, and sulfur, with the total mass fraction of nitrogen being 8-11%, the total mass fraction of phosphorus being 0.1-1.1%, and the mass fraction of sulfur being 0.1-1.2%.

5. The method according to claim 1, characterized in that, In step S1, the mixing mass ratio of rice husks and livestock manure is 1:(0.5-1.5) to ensure that the moisture content of the pile is stable at 35-87%.

6. The method according to claim 1, characterized in that, The specific steps for Joule flash treatment and two-stage pulse discharge treatment in step S3 are as follows: The conditions for the first pulse discharge are: voltage 10-60V, current 1-80A, discharge time 1-60s, and discharge times 1-5 times; the first Joule flash treatment causes the basic catalyst material to be instantly heated to 200-2000℃. The conditions for the second stage of pulse discharge are: voltage 10-120V, current 10-240A, discharge time 1-1000ms, discharge times 1-10 times, and the second Joule flash treatment causes the catalyst material to be instantly heated to 200-3000℃.

7. The method according to claim 6, characterized in that, The specific steps for Joule flash treatment and two-stage pulse discharge treatment in step S3 are as follows: The conditions for the first pulse discharge are: voltage 20-60V, current 3-80A, discharge time 5-60s, and discharge times 1-5 times; the first Joule flash treatment causes the basic catalyst material to be instantly heated to 200-1000℃. The conditions for the second stage of pulse discharge are: voltage 20-120V, current 20-240A, discharge time 50-600ms, discharge times 1-10 times, and the second Joule flash treatment causes the catalyst material to be instantly heated to 200-2500℃.

8. The method according to claim 5, characterized in that, In step S2, the height of the composting bucket is 0.3-1.5m and the bottom diameter is 0.1-1m. The composting process includes a natural warming period of 3-15 days and a high-temperature stabilization period of 25-60 days. The internal temperature of the compost pile is maintained at 35-85℃ by opening the lid and turning the pile.

9. The method according to claim 1, characterized in that, In step S1, the rice husk drying temperature is 45-85℃ and the drying time is 2-12h to ensure that the moisture content of the rice husk is stable at 6-18%.

10. The application of a biomass carbon-based nonmetallic catalyst as described in any one of claims 1-9 as a zinc-air battery cathode catalyst in the preparation of fuel cells.

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