Multi-element-doped hierarchical porous biomass carbon material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of biomass carbon materials, and particularly relates to a multi-element-doped hierarchical pore biomass carbon material as well as a preparation method and application thereof. According to the preparation method of the multi-element doped hierarchical pore biomass carbon material provided by the invention, mixed molten salt pore-forming agents including a micropore pore-forming agent, a mesopore pore-forming agent and a macropore pore-forming agent and compounds including nonmetal, metal and transition metal are introduced in the preparation process; the prepared biomass carbon material has rich doping components and conductive active sites on one hand, and also has a hierarchical pore structure including micropores, mesopores and macropores on the other hand, and the biomass carbon material is purified and stripped through post-treatment; the biomass carbon material has excellent electrochemical performance, ion transmission performance and catalytic performance and is a high-performance biomass carbon material, and the technical problem that the performance of the biomass carbon material prepared at present is low is solved.

Description

Technical Field

[0001] This application belongs to the field of biomass carbon material technology, and in particular relates to a multi-element doped hierarchical porous biomass carbon material, its preparation method and application. Background Technology

[0002] Traditional carbon materials such as graphite and carbon black mainly rely on non-renewable mineral resources, and their extraction process easily causes environmental damage. In contrast, emerging carbon materials, such as biomass carbon materials, are mainly obtained by carbonizing agricultural and forestry waste and kitchen residues such as rice husks, straw, fallen leaves, fruit peels, and fish bones. During the carbonization process, volatile substances in the biomass raw materials are removed, forming biomass carbon materials with a porous carbon framework. Due to their high specific surface area, high porosity, chemical stability, good conductivity and usability, as well as low cost, sustainability and renewability, biomass carbon materials are often used in electrochemical energy storage and catalysis fields such as lithium-ion batteries, supercapacitors, and electrocatalysts, and are one of the important energy functional materials.

[0003] The performance of biomass carbon materials is related to their microstructure, chemical composition, and conductive active sites. If the selected biomass raw materials are high in cellulose, lignin, and have a dense structure and high ash content, the microporous structure formed after carbonization will not be obvious, or the chemical composition and conductive active sites will not be abundant enough, which will lead to a decrease in the electrochemical and catalytic performance of the biomass carbon materials. At the same time, if the carbonization temperature is too high during the carbonization process, the carbon skeleton structure may be damaged, or a large amount of chemical composition and conductive active sites may be lost, which will also lead to a decrease in the electrochemical and catalytic performance of the biomass carbon materials. At present, the research on the preparation process of biomass carbon materials is not in-depth enough, and the prepared biomass carbon materials lack rich microporous structures and are not rich in chemical composition and conductive active sites, resulting in low performance. Therefore, it is necessary to develop a new generation of preparation processes to prepare high-performance biomass carbon materials to meet the ever-expanding needs of energy storage and catalysis. Summary of the Invention

[0004] In view of this, this application provides a multi-element doped hierarchical porous biomass carbon material, its preparation method, and its application, in order to solve the technical problem of low performance of biomass carbon materials prepared in the prior art.

[0005] The first aspect of this application provides a method for preparing multi-element-doped hierarchical porous biomass carbon materials, the method comprising the following steps:

[0006] Pretreatment steps for biomass raw materials: The biomass raw materials are crushed, washed, dried and ground in sequence to obtain pretreated biomass raw materials;

[0007] The mixing steps of the precursor mixture are as follows: pretreated biomass raw materials, microporous pore-forming agents, mesoporous pore-forming agents, macroporous pore-forming agents, non-metallic compounds, metallic compounds and transition metal compounds are mixed evenly to obtain a precursor mixture;

[0008] Carbonization steps of precursor mixture: The precursor mixture is subjected to a low-temperature carbonization reaction to obtain biomass carbon materials;

[0009] Post-processing steps of carbonization reactants: The biomass carbon material is washed alternately with acid solution and deionized water, ultrasonically exfoliated, and dried to obtain multi-element-doped hierarchical porous biomass carbon material.

[0010] Preferably, in the pretreatment step of biomass raw materials, the biomass raw materials used are selected from at least one of leaves, fish bones, and seed shells.

[0011] Preferably, in the pretreatment step of biomass raw materials, the mixed solvent used for cleaning is any two of chloroform, isopropanol, and acetone, with a volume ratio of 1:1.

[0012] Preferably, in the mixing step of the precursor mixture, the microporous pore-forming agent used is selected from lithium chloride and / or potassium chloride, the mesoporous pore-forming agent is selected from potassium carbonate and / or sodium carbonate, and the macroporous pore-forming agent is selected from zinc chloride.

[0013] Preferably, in the mixing step of the precursor mixture, the non-metallic compound used is selected from at least one of silicon compounds, phosphorus compounds, tellurium compounds, sulfur compounds, and nitrogen compounds; the metallic compound is selected from aluminum compounds and / or tin compounds; and the transition metal compound is selected from at least one of cobalt compounds, nickel compounds, chromium compounds, and silver compounds.

[0014] Preferably, in the mixing step of the precursor mixture, the process of uniform mixing includes: adding the pretreated biomass raw material, microporous pore-forming agent, mesoporous pore-forming agent, macroporous pore-forming agent, non-metallic compound, metallic compound and transition metal compound to a low-boiling-point mixed organic solvent for stirring and dispersion, and then rotary evaporating and vacuum drying at a temperature of 50~70°C to obtain the precursor mixture; the low-boiling-point mixed organic solvent is any two of chloroform, isopropanol and acetone in a volume ratio of 1:1.

[0015] Preferably, in the carbonization step of the precursor mixture, the low-temperature carbonization process includes: heating to 400-550°C at a heating rate of 2-4°C / min and holding at that temperature for 4-8 hours for low-temperature carbonization.

[0016] Preferably, in the post-treatment step of the carbonized reactants, the acid solution used is at least one of hydrochloric acid, nitric acid, and sulfuric acid at a concentration of 1-2 mol / L, and ultrasonic stripping is performed in deionized water.

[0017] Preferably, in the mixing step of the precursor mixture, the mass ratio of the biomass raw material to the sum of the masses of the microporous pore-forming agent, the mesoporous pore-forming agent, and the macroporous pore-forming agent to the sum of the masses of the non-metallic compound, the metallic compound, and the transition metal compound is 1:15 to 20:3.

[0018] Preferably, the mass ratio of microporous pore-forming agent, mesoporous pore-forming agent and macroporous pore-forming agent is 0.4~0.55:0.4~0.5:1, and the mass ratio of non-metallic compound, metallic compound and transition metal compound is 1:1:1.

[0019] The second aspect of this application provides a multi-element-doped hierarchical porous biomass carbon material, which is prepared by the preparation method described in the first aspect.

[0020] The third aspect of this application provides the application of a multi-element doped hierarchical porous biomass carbon material as described in the second aspect in the field of electrochemical energy storage or catalysis.

[0021] The fourth aspect of this application provides a lithium-ion battery anode, wherein the current collector of the lithium-ion battery anode is loaded with a multi-element-doped hierarchical porous biomass carbon material as described in the second aspect.

[0022] The fifth aspect of this application provides an electrocatalyst, wherein the support or catalytically active material of the electrocatalyst includes the multi-element-doped hierarchical porous biomass carbon material described in the second aspect.

[0023] Compared with the prior art, the method for preparing multi-element-doped hierarchical porous biomass carbon materials provided in this application has at least the following beneficial effects:

[0024] 1. In the preparation method of multi-element doped hierarchical porous biomass carbon material provided in this application, by introducing a mixed molten salt pore-forming agent, biomass raw materials such as fish bones can be carbonized to form a biomass carbon material with hierarchical pores. By introducing non-metals, metals and metal compounds, the prepared biomass carbon material has abundant chemical doping elements and conductive active sites, and has a hierarchical pore structure such as micropores, mesopores and macropores, thereby providing a biomass carbon material with excellent electrochemical performance, ion transport performance and catalytic performance.

[0025] 2. In the preparation method of multi-element doped hierarchical porous biomass carbon material provided in this application, the post-processing after carbonization uses alternating washing with acid solution / water and ultrasonic exfoliation to effectively remove inorganic mineral ash, break up the agglomeration of biomass carbon material, disperse the biomass carbon material, and obtain biomass carbon material with good dispersibility, high specific surface area and more open pore structure, thereby improving the electrochemical activity and conductivity of biomass carbon material.

[0026] 3. In the preparation method of multi-element doped hierarchical porous biomass carbon material provided in this application, since the provided biomass carbon material has excellent electrochemical performance, ion transport performance and catalytic performance, it can be used as a catalytic material or anode material for energy storage and catalysis. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0028] Figure 1 Scanning electron microscope image of the multi-element-doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 1 of this application;

[0029] Figure 2 Scanning electron microscope image of the multi-element-doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 3 of this application;

[0030] Figure 3 Scanning electron microscope image of the multi-element-doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 6 of this application;

[0031] Figure 4 The attached figure shows the nitrogen adsorption and desorption of the multi-element-doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 6 of this application;

[0032] Figure 5 X-ray photoelectron spectrum of the multi-element-doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 6 of this application;

[0033] Figure 6 The graph shows the cycle performance test results of a lithium-ion battery assembled using the multi-element doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 6 of this application as the negative electrode active material of a lithium-ion battery.

[0034] Figure 7 The graph shows the rate performance test results of a lithium-ion battery assembled using the multi-element doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 6 of this application as the negative electrode active material of a lithium-ion battery.

[0035] Figure 8 The current-time chronoamperometry response diagram of the multi-element-doped hierarchical porous biomass carbon material prepared by the preparation method provided in Example 6 of this application as an electrocatalyst. Detailed Implementation

[0036] This application provides a multi-element doped hierarchical porous biomass carbon material, its preparation method, and its application, which addresses the technical problem of low performance of biomass carbon materials prepared in the prior art.

[0037] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] Given the current lack of in-depth research on the preparation process of biomass carbon materials, the prepared biomass carbon materials lack rich microporous structures, and the chemical composition and conductive active sites are also insufficient, resulting in low performance of the prepared biomass carbon materials. This application provides a method for preparing multi-element doped hierarchical porous biomass carbon materials. The preparation method includes: firstly, crushing, washing, drying, and grinding biomass raw materials sequentially to obtain pretreated biomass raw materials; then, mixing the pretreated biomass raw materials, microporous pore-forming agents, mesoporous pore-forming agents, macroporous pore-forming agents, non-metallic compounds, metallic compounds, and transition metal compounds uniformly to obtain a precursor mixture; next, subjecting the precursor mixture to a low-temperature carbonization reaction to obtain biomass carbon materials; subsequently, washing the biomass carbon materials alternately with acid solution and deionized water, ultrasonically exfoliating, and drying to obtain multi-element doped hierarchical porous biomass carbon materials.

[0039] The method for preparing multi-element doped hierarchical porous biomass carbon materials provided in this application introduces a mixed molten salt pore-forming agent, including microporous, mesoporous, and macroporous agents, to give the prepared biomass carbon material a hierarchical porous structure. For example, for high-density biomass such as fish bones, the doping with the mixed molten salt pore-forming agent can also form a hierarchical porous structure through carbonization. The formation of the hierarchical porous structure utilizes micropores to provide a higher specific surface area, mesopores to promote mass transfer, and macropores to serve as fast mass transfer channels and provide buffer space. Thus, the hierarchical porous structure can improve electrical conductivity. The volume change caused by ion insertion / extraction during cyclic charging and discharging stabilizes the structure, improves the cycle performance of lithium-ion batteries, maintains high capacity retention, and effectively enhances the conductivity of biomass carbon materials, promoting ion / electron transport efficiency and reaction kinetics. Furthermore, the introduction of non-metallic, metallic, and transition metal compounds provides biomass carbon materials with abundant chemical components and conductive active sites. The synergistic interaction between non-metallic elements such as phosphorus, sulfur, nitrogen, cobalt, and chromium, as well as metallic and transition metal elements, effectively improves the conductive network and electrochemical performance of biomass carbon materials, significantly enhancing their electrochemical activity and catalytic efficiency. Additionally, a low-temperature carbonization process preserves some of the structure, surface functional groups, and chemical components of the biomass raw materials. For example, plant fibers in leaves and seed shells retain some fibrous morphology after low-temperature carbonization, improving the structural stability of the biomass carbon materials and ensuring long-term performance stability during cyclic charging and discharging or electrocatalysis. Finally, after carbonizing the biomass raw materials, this application also uses acid solution washing and ultrasonic exfoliation. Acid solution washing removes residual inorganic minerals from the carbonized biomass raw materials. Ash removal reduces the impact of impurities, resulting in higher purity, more active sites, and stronger electrochemical activity and conductivity in biomass carbon materials. In addition, during carbonization, some biomass may cross-link / shrink, causing the biomass carbon materials to stick together and stack, forming large agglomerates, reducing surface area and obscuring active sites. By using ultrasonic exfoliation, the energy of ultrasound can break up the agglomerates of biomass carbon materials, disperse them, and obtain biomass carbon materials with good dispersibility, high specific surface area, and more open pore structure, thus improving the electrochemical activity and ion transport performance of biomass carbon materials.

[0040] Preferably, in the preparation method of multi-element doped hierarchical porous biomass carbon material provided in this application, the biomass raw material used is selected from at least one of leaves, fish bones, and seed shells. Biomass naturally has various 0D to 3D microstructures, and the 3D microstructures of biomass such as leaves, fish bones, and seed shells used in this application can retain the original pore structure even at high carbonization temperatures. This can effectively shorten the ion transport distance and provide the position and transport efficiency for ions to enter and exit during energy storage. At the same time, the chemical components and functional groups contained in the leaves, fish bones, and seed shells can also be used as doping components to improve the electrochemical activity and conductivity of the biomass carbon material.

[0041] Preferably, in the preparation method of the multi-element doped hierarchical porous biomass carbon material provided in this application, the non-metallic compounds introduced can be selected from nitrogen sources such as lithium nitrate, urea, and melamine as nitrogen compounds, phosphorus sources such as phytic acid and phosphoric acid as phosphorus compounds, sulfur sources such as ferrous sulfate, ferrous sulfate, and potassium sulfate as sulfur compounds, silicon sources such as sodium silicate and silicic acid as silicon compounds, and telluric acid as telluric compounds. For metallic compounds, aluminum sources such as aluminum chloride and aluminum sulfate can be selected as aluminum compounds, and tin sources such as tin dioxide and tin chloride as tin compounds. As for transition metal compounds, cobalt sources such as cobalt nitrate and cobalt carbonate can be selected as cobalt compounds, chromium sources such as chromium nitrate and chromium carbonate as chromium compounds, nickel sources such as nickel sulfate and nickel chloride as nickel compounds, and silver sources such as silver nitrate and silver chloride as silver compounds.

[0042] As a preferred embodiment, in the preparation method of multi-element doped hierarchical porous biomass carbon material provided in this application, the temperature and time for low-temperature carbonization are 400~550℃ and 4~8h.

[0043] Preferably, the multi-element-doped hierarchical porous biomass carbon material prepared by the method of this application can be applied to electrochemical energy storage or catalysis fields such as lithium-ion battery anodes, supercapacitors, and electrocatalysts. As for specific application scenarios, it can be selected as an anode active material loaded onto the current collector of the lithium-ion battery anode, or used as a catalyst support material or catalytic active material.

[0044] The following section will provide a detailed description of the multi-element-doped hierarchical porous biomass carbon material provided in this application, combining the preparation process and performance testing of the multi-element-doped hierarchical porous biomass carbon material.

[0045] Example 1

[0046] This embodiment provides a method for preparing multi-element doped hierarchical porous biomass carbon materials. The preparation method includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0047] Preprocessing steps include:

[0048] First, 10g of biomass raw material leaves are crushed. Then, the crushed leaves are added to an appropriate amount of chloroform-isopropanol solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw material is obtained.

[0049] The mixing steps include:

[0050] Weigh 4g of potassium carbonate, 4g of sodium carbonate, 5.5g of potassium chloride and 10g of zinc chloride according to a mass ratio of 0.4:0.4:0.55:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0051] Weigh 1g of nitrogen compound melamine, 1g of aluminum compound aluminum chloride, and 1g of cobalt compound cobalt nitrate according to a mass ratio of 1:1:1.

[0052] According to the mass ratio of 1:15:1:1:1, 1g of pretreated biomass raw material, 15g of mixed molten salt pore-forming agent, 1g of nitrogen compound, 1g of aluminum compound, and 1g of cobalt compound were added to an appropriate amount of chloroform-isopropanol solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then rotary evaporated and vacuum dried at 50°C to obtain a precursor mixture.

[0053] The carbonization process includes:

[0054] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was placed back into the tube furnace and carbonized at a rate of 2°C / min. The temperature was raised to 400°C and held for 4 hours to carry out the carbonization reaction. After cooling to room temperature, the biomass carbon material was obtained.

[0055] Post-processing steps include:

[0056] The biomass carbon material was washed alternately with 1 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, multi-element-doped hierarchical porous biomass carbon material was obtained. This multi-element-doped hierarchical porous biomass carbon material is a leaf-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with elements such as nitrogen, aluminum and cobalt.

[0057] Example 2

[0058] This embodiment provides a method for preparing multi-element doped hierarchical porous biomass carbon materials. The preparation method includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0059] Preprocessing steps include:

[0060] First, 10g of biomass raw material leaves are crushed. Then, the crushed leaves are added to an appropriate amount of chloroform-isopropanol solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw material is obtained.

[0061] The mixing steps include:

[0062] Weigh 4g of potassium carbonate, 5.5g of potassium chloride, 5.5g of lithium chloride and 10g of zinc chloride according to a mass ratio of 0.4:0.55:0.55:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0063] Weigh 1g of phosphoric acid (a phosphorus compound), 1g of aluminum chloride (an aluminum compound), and 1g of chromium nitrate (a chromium compound) according to a mass ratio of 1:1:1.

[0064] According to the mass ratio of 1:15:1:1:1, 1g of pretreated biomass raw material, 15g of mixed molten salt pore-forming agent, 1g of phosphorus compound, 1g of aluminum compound, and 1g of chromium compound were added to an appropriate amount of chloroform-isopropanol solvent with a volume ratio of 1:1 and stirred to disperse. The mixture was then rotary evaporated and vacuum dried at 50°C to obtain a precursor mixture.

[0065] The carbonization process includes:

[0066] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was placed back into the tube furnace and carbonized at a rate of 2°C / min. The temperature was raised to 400°C and held for 4 hours to carry out the carbonization reaction. After cooling to room temperature, the biomass carbon material was obtained.

[0067] Post-processing steps include:

[0068] The biomass carbon material was washed alternately with 1 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, multi-element-doped hierarchical porous biomass carbon material was obtained. This multi-element-doped hierarchical porous biomass carbon material is a leaf-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with elements such as phosphorus, aluminum and chromium.

[0069] Example 3

[0070] This embodiment provides a method for preparing multi-element doped hierarchical porous biomass carbon materials. The preparation method includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0071] The preprocessing steps include:

[0072] First, 10g of biomass raw material fish bones are crushed. Then, the crushed fish bones are added to an appropriate amount of chloroform-acetone solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw material is obtained.

[0073] The mixing steps include:

[0074] Weigh 4g of potassium carbonate, 4g of sodium carbonate, 5g of potassium chloride and 10g of zinc chloride according to a mass ratio of 0.4:0.4:0.5:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0075] Weigh 1g of nitrogen compound urea, 1g of aluminum compound aluminum chloride, and 1g of chromium compound chromium nitrate according to a mass ratio of 1:1:1.

[0076] According to the mass ratio of 1:18:1:1:1, 1g of pretreated biomass raw material, 18g of mixed molten salt pore-forming agent, 1g of nitrogen compound, 1g of aluminum compound, and 1g of chromium compound were added to an appropriate amount of chloroform-acetone solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then rotary evaporated and vacuum dried at 60°C to obtain a precursor mixture.

[0077] The carbonization process includes:

[0078] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was put back into the tube furnace and carbonized at a rate of 3°C / min, heated to 500°C and held for 6 hours for carbonization. After cooling to room temperature, the biomass carbon material was obtained.

[0079] Post-processing steps include:

[0080] The biomass carbon material was washed alternately with 1.5 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, multi-element-doped hierarchical porous biomass carbon material was obtained. This multi-element-doped hierarchical porous biomass carbon material is a fishbone-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with elements such as nitrogen, aluminum and chromium.

[0081] Example 4

[0082] This embodiment provides a method for preparing multi-element doped hierarchical porous biomass carbon materials. The preparation method includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0083] The preprocessing steps include:

[0084] First, 10g of biomass raw material fish bones are crushed. Then, the crushed fish bones are added to an appropriate amount of chloroform-acetone solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw material is obtained.

[0085] The mixing steps include:

[0086] Weigh 4g of sodium carbonate, 5g of lithium chloride, 5g of potassium chloride and 10g of zinc chloride according to a mass ratio of 0.4:0.5:0.5:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0087] Weigh 1g of ferric sulfate (a sulfur compound), 1g of aluminum chloride (an aluminum compound), and 1g of cobalt nitrate (a cobalt compound) according to a mass ratio of 1:1:1.

[0088] According to the mass ratio of 1:18:1:1:1, 1g of pretreated biomass raw material, 18g of mixed molten salt pore-forming agent, 1g of nitrogen compound, 1g of aluminum compound, and 1g of cobalt compound were added to an appropriate amount of chloroform-acetone solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then rotary evaporated and vacuum dried at 60°C to obtain a precursor mixture.

[0089] The carbonization process includes:

[0090] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was put back into the tube furnace and carbonized at a rate of 3°C / min, heated to 500°C and held for 6 hours for carbonization. After cooling to room temperature, the biomass carbon material was obtained.

[0091] Post-processing steps include:

[0092] The biomass carbon material was washed alternately with 1.5 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, multi-element-doped hierarchical porous biomass carbon material was obtained. This multi-element-doped hierarchical porous biomass carbon material is a fishbone-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with elements such as sulfur, aluminum and cobalt.

[0093] Example 5

[0094] This embodiment provides a method for preparing multi-element doped hierarchical porous biomass carbon materials. The preparation method includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0095] The preprocessing steps include:

[0096] First, 10g of biomass raw material seed shells are crushed. Then, the crushed seed shells are added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw materials are obtained.

[0097] The mixing steps include:

[0098] Weigh 5g of potassium carbonate, 5g of sodium carbonate, 4g of lithium chloride and 10g of zinc chloride according to a mass ratio of 0.5:0.5:0.4:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0099] Weigh 1g of phosphoric acid (a phosphorus compound), 1g of aluminum chloride (an aluminum compound), and 1g of chromium carbonate (a chromium compound) according to a mass ratio of 1:1:1.

[0100] According to the mass ratio of 1:20:1:1:1, 1g of pretreated biomass raw material, 20g of mixed molten salt pore-forming agent, 1g of phosphorus compound, 1g of aluminum compound, and 1g of chromium compound were added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then rotary evaporated and vacuum dried at 70°C to obtain a precursor mixture.

[0101] The carbonization process includes:

[0102] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was put back into the tube furnace and carbonized at a rate of 4°C / min. The temperature was raised to 550°C and held for 8 hours for carbonization. After cooling to room temperature, the biomass carbon material was obtained.

[0103] Post-processing steps include:

[0104] The biomass carbon material was washed alternately with 2 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, multi-element-doped hierarchical porous biomass carbon material was obtained. This multi-element-doped hierarchical porous biomass carbon material is a seed shell-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with elements such as phosphorus, aluminum and chromium.

[0105] Example 6

[0106] This embodiment provides a method for preparing multi-element doped hierarchical porous biomass carbon materials. The preparation method includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0107] The preprocessing steps include:

[0108] First, 10g of biomass raw material seed shells are crushed. Then, the crushed seed shells are added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw materials are obtained.

[0109] The mixing steps include:

[0110] Weigh 5g of potassium carbonate, 4g of lithium chloride, 4g of potassium chloride and 10g of zinc chloride according to a mass ratio of 0.5:0.4:0.4:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0111] Weigh 1g of ferric sulfate (a sulfur compound), 1g of aluminum chloride (an aluminum compound), and 1g of cobalt carbonate (a cobalt compound) according to a mass ratio of 1:1:1.

[0112] According to the mass ratio of 1:20:1:1:1, 1g of pretreated biomass raw material, 20g of mixed molten salt pore-forming agent, 1g of sulfur compound, 1g of aluminum compound, and 1g of cobalt compound were added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then rotary evaporated and vacuum dried at 70°C to obtain a precursor mixture.

[0113] The carbonization process includes:

[0114] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was put back into the tube furnace and carbonized at a rate of 4°C / min. The temperature was raised to 550°C and held for 8 hours for carbonization. After cooling to room temperature, the biomass carbon material was obtained.

[0115] Post-processing steps include:

[0116] The biomass carbon material was washed alternately with 2 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, multi-element-doped hierarchical porous biomass carbon material was obtained. This multi-element-doped hierarchical porous biomass carbon material is a seed shell-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with elements such as sulfur, aluminum and cobalt.

[0117] Comparative Example 1

[0118] This comparative example provides a method for preparing hierarchical porous biomass carbon materials, which includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0119] The preprocessing steps include:

[0120] First, 10g of biomass raw material seed shells are crushed. Then, the crushed seed shells are added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw materials are obtained.

[0121] The mixing steps include:

[0122] Weigh 5g of potassium carbonate, 4g of lithium chloride, 4g of potassium chloride and 10g of zinc chloride according to a mass ratio of 0.5:0.4:0.4:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0123] Weigh 1.5g of ferric sulfate (a sulfur compound) and 1.5g of cobalt carbonate (a cobalt compound) at a mass ratio of 1:1.

[0124] According to the mass ratio of 1:20:1.5:1.5, 1g of pretreated biomass raw material, 20g of mixed molten salt pore-forming agent, 1.5g of sulfur compound and 1.5g of cobalt compound were added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then rotary evaporated and vacuum dried at 70°C to obtain a precursor mixture.

[0125] The carbonization process includes:

[0126] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was put back into the tube furnace and carbonized at a rate of 4°C / min. The temperature was raised to 550°C and held for 8 hours for carbonization. After cooling to room temperature, the biomass carbon material was obtained.

[0127] Post-processing steps include:

[0128] The biomass carbon material was washed alternately with 2 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, a multi-level porous biomass carbon material was obtained. This multi-level porous biomass carbon material is a seed shell-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with elements such as sulfur and cobalt.

[0129] Comparative Example 2

[0130] This comparative example provides a method for preparing hierarchical porous biomass carbon materials, which includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0131] The preprocessing steps include:

[0132] First, 10g of biomass raw material seed shells are crushed. Then, the crushed seed shells are added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw materials are obtained.

[0133] The mixing steps include:

[0134] Weigh 5g of potassium carbonate, 4g of lithium chloride, 4g of potassium chloride and 10g of zinc chloride according to a mass ratio of 0.5:0.4:0.4:1, and mix them evenly to obtain a mixed molten salt pore-forming agent.

[0135] Weigh 3g of ferric sulfate, a sulfur compound;

[0136] According to the mass ratio of 1:20:3, 1g of pretreated biomass raw material, 20g of mixed molten salt pore-forming agent and 3g of sulfur compound were added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then mixed evenly by rotary evaporation and vacuum drying at 70°C to obtain a precursor mixture.

[0137] The carbonization process includes:

[0138] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was put back into the tube furnace and carbonized at a rate of 4°C / min. The temperature was raised to 550°C and held for 8 hours for carbonization. After cooling to room temperature, the biomass carbon material was obtained.

[0139] Post-processing steps include:

[0140] The biomass carbon material was washed alternately with 2 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, a multi-level porous biomass carbon material was obtained. This multi-level porous biomass carbon material is a seed shell-based biomass carbon material with multi-level pores such as micropores, mesopores and macropores, and is doped with sulfur.

[0141] Comparative Example 3

[0142] This comparative example provides a method for preparing biomass carbon materials doped with multiple elements. The preparation method includes a pretreatment step, a mixing step, a carbonization step, and a post-treatment step.

[0143] The preprocessing steps include:

[0144] First, 10g of biomass raw material seed shells are crushed. Then, the crushed seed shells are added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 for ultrasonic cleaning. After drying and grinding in a vacuum environment, pretreated biomass raw materials are obtained.

[0145] The mixing steps include:

[0146] Weigh 10g of potassium carbonate, 8g of lithium chloride, and 8g of potassium chloride according to a mass ratio of 0.5:0.4:0.4, mix them evenly to obtain a mixed molten salt pore-forming agent, and take 20g of the mixed molten salt pore-forming agent for later use.

[0147] Weigh 1g of ferric sulfate (a sulfur compound), 1g of aluminum chloride (an aluminum compound), and 1g of cobalt carbonate (a cobalt compound) according to a mass ratio of 1:1:1.

[0148] According to the mass ratio of 1:20:1:1:1, 1g of pretreated biomass raw material, 20g of mixed molten salt pore-forming agent, 1g of sulfur compound, 1g of aluminum compound, and 1g of cobalt compound were added to an appropriate amount of isopropanol-acetone solvent with a volume ratio of 1:1 and stirred and dispersed. The mixture was then rotary evaporated and vacuum dried at 70°C to obtain a precursor mixture.

[0149] The carbonization process includes:

[0150] The precursor mixture was transferred to a vacuum tube furnace, where argon gas was introduced and the temperature was raised to remove excess moisture. After being removed from the tube furnace and repeatedly ground, the precursor mixture powder was put back into the tube furnace and carbonized at a rate of 4°C / min. The temperature was raised to 550°C and held for 8 hours for carbonization. After cooling to room temperature, the biomass carbon material was obtained.

[0151] Post-processing steps include:

[0152] The biomass carbon material was washed alternately with 2 mol / L hydrochloric acid and deionized water 1 to 5 times, and then ultrasonically exfoliated in deionized water. After vacuum drying, multi-element doped biomass carbon material was obtained. This multi-element doped biomass carbon material is a seed shell-based biomass carbon material, doped with elements such as sulfur, aluminum, and cobalt, and has a porous structure with micropores and mesopores.

[0153] Experimental Example 1

[0154] This experiment characterizes the structure and properties of the multi-element doped hierarchical porous biomass carbon materials prepared in Examples 1, 3 and 6, the multi-element doped biomass carbon materials provided in Comparative Examples 1-2, and the multi-element doped biomass carbon material provided in Comparative Example 3.

[0155] Structural characterization was performed using scanning electron microscopy, nitrogen adsorption-desorption, and X-ray photoelectron spectroscopy. The test results are as follows: Figure 1-3 , Figure 4 and Figure 5 As shown; from Figure 1-3 The provided scanning electron microscope images, Figure 4 The attached diagram shows nitrogen adsorption and desorption. Figure 5 As shown in the X-ray photoelectron spectroscopy spectrum, the multi-element doped hierarchical porous biomass carbon material prepared in Example 6 has a porous structure with an average pore size of 4-60 nm and an average specific surface area of ​​800-2600 m². 2 / g; The porous structure includes micropores, mesopores, and macropores of different pore sizes. In particular, for biomass with high density, such as fish bones, the mixed molten salt pore-forming agent penetrates into the carbon skeleton to form micropores, mesopores, and macropores, promoting an increase in specific surface area. This results in a complex hierarchical porous structure with high porosity and a robust carbon skeleton. This hierarchical porous, high-porosity, and robust carbon skeleton structure in biomass carbon materials can provide a higher specific surface area through micropores, promote mass transfer through mesopores, and serve as a fast mass transfer channel. Macropores also support the structure, improving structural stability. This enhances the electrical conductivity, ion / electron transport efficiency, reaction kinetics, and cycling performance of biomass carbon materials. The C1s spectrum shows a C=C bond main peak at 284.8 eV, with a significant C=C characteristic peak at its high binding energy side (approximately 286.2 eV), and peaks at 287.8 eV and 288.9 eV. The presence of characteristic peaks for CO and OC=O functional groups at eV indicates the simultaneous presence of sp² hybrid carbon structures and oxygen-containing functional groups on the material surface. This combination of characteristic peaks confirms that the material is a carbon-based material with a specific degree of oxidation, and its unique carbon chemical state distribution is key to achieving the superior performance of this invention.

[0156] Since the seed shells provided in Example 6 are biomass raw materials, the average pore size of the multi-element-doped hierarchical porous biomass carbon material is about 26 nm, and the average specific surface area is 1154 m². 2 With a density of approximately / g and a good microstructure, the multi-element doped hierarchical porous biomass carbon material provided in Example 6 was used for performance testing. The performance characterization tests included cycle stability, rate performance, and catalytic performance tests. At the same time, the multi-element doped biomass carbon materials provided in Examples 1-2 and the multi-element doped biomass carbon material provided in Example 3 were also subjected to cycle performance tests.

[0157] The testing process for cycle stability in performance characterization testing includes:

[0158] The multi-element doped hierarchical porous biomass carbon material provided in Example 6, the multi-element doped biomass carbon material provided in Comparative Examples 1-2, and the multi-element doped biomass carbon material (90 wt.%), Super P (5 wt.%), and sodium alginate (5 wt.%) provided in Comparative Example 3 were mixed with deionized water and ground into a uniform slurry; then the slurry was heated at 1.5 mg / cm³. 2 The loading amount is coated on the current collector copper foil and then stamped into a lithium-ion battery negative electrode sheet with a diameter of 12 mm after drying. Subsequently, the prepared lithium-ion battery negative electrode sheet is assembled with lithium foil positive electrode, EC / DMC / EMC electrolyte (volume ratio of 1:1:1, 1.0M LiPF6) and Celgard 2500 separator to form a CR2032 type coin cell.

[0159] The assembled CR2032 coin cell was subjected to cycle performance testing using a battery testing system at a current density of 1 A / g within a potential range of 0.01 to 1.5 V. Simultaneously, the CR2032 coin cell assembled from the multi-element doped hierarchical porous biomass carbon material provided in Example 6 was subjected to rate performance testing at 0.2 A / g, 0.5 A / g, 1 A / g, 2 A / g, and 5 A / g, respectively. The test results are as follows: Figure 6 and Figure 7 As shown; from Figure 6 It can be seen that when the negative electrode of a lithium-ion battery is loaded with the multi-element-doped hierarchical porous biomass carbon material provided in Example 6 of this application, it can provide better cycle stability and a charge-discharge specific capacity of 300.4 mAh / g after 50 cycles. This cycle performance is higher than that of lithium-ion batteries loaded with the multi-element-doped biomass carbon material provided in Comparative Examples 1-2, or the lithium-ion battery loaded with the multi-element-doped biomass carbon material provided in Comparative Example 3. Figure 7 It can be seen that when the negative electrode of the lithium-ion battery is loaded with the multi-element-doped hierarchical porous biomass carbon material provided in Example 6 of this application, it can still provide a capacity recovery rate of 97% after cycling at a high current density.

[0160] The catalytic performance testing process includes:

[0161] Two mg of the multi-element-doped hierarchical porous biomass carbon material provided in Example 6 was used as an electrocatalyst and mixed with 20 μL of Nafion solution (5 wt.%), 780 μL of ethanol, and 200 μL of deionized water. The catalyst ink was then ultrasonically treated to produce a uniform catalyst dispersion. Two μL of the catalyst dispersion was then dropped onto a rotating ring electrode and allowed to stand at room temperature for 1 h, resulting in a loading mass of 0.2 mg / cm³. 2 The working electrode was obtained; subsequently, 0.1M KOH was selected as the electrolyte. To test the long-term durability of the catalyst, a 20,000-s current-time chronocurrent response test was conducted at 0.5V. The test results are as follows. Figure 8 As shown, from Figure 8 It can be seen that when the multi-element doped hierarchical porous biomass carbon material provided in Example 6 of this application is used as an electrocatalyst, it can provide long-term catalytic stability. The multi-element doped hierarchical porous biomass carbon material is not prone to problems such as loss of active sites, structural collapse and surface contamination, and has excellent electrocatalytic activity.

[0162] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a multi-element-doped hierarchical porous biomass carbon material, characterized in that, Includes the following steps: Pretreatment steps for biomass raw materials: The biomass raw materials are crushed, washed, dried and ground in sequence to obtain pretreated biomass raw materials; The mixing steps of the precursor mixture are as follows: pretreated biomass raw materials, microporous pore-forming agents, mesoporous pore-forming agents, macroporous pore-forming agents, non-metallic compounds, metallic compounds and transition metal compounds are mixed evenly to obtain a precursor mixture; Carbonization steps of precursor mixture: The precursor mixture is subjected to a low-temperature carbonization reaction to obtain biomass carbon materials; Post-processing steps of carbonization reactants: The biomass carbon material is washed alternately with acid solution and deionized water, ultrasonically exfoliated, and dried to obtain multi-element-doped hierarchical porous biomass carbon material.

2. The method for preparing a multi-element-doped hierarchical porous biomass carbon material according to claim 1, characterized in that, In the mixing step of the precursor mixture, the microporous pore-forming agent used is selected from lithium chloride and / or potassium chloride, the mesoporous pore-forming agent is selected from potassium carbonate and / or sodium carbonate, and the macroporous pore-forming agent is selected from zinc chloride.

3. The method for preparing a multi-element-doped hierarchical porous biomass carbon material according to claim 1, characterized in that, In the mixing step of the precursor mixture, the non-metallic compound used is selected from at least one of silicon compounds, phosphorus compounds, tellurium compounds, sulfur compounds, and nitrogen compounds; the metallic compound is selected from aluminum compounds and / or tin compounds; and the transition metal compound is selected from at least one of cobalt compounds, nickel compounds, chromium compounds, and silver compounds.

4. The method for preparing a multi-element-doped hierarchical porous biomass carbon material according to claim 1, characterized in that, In the carbonization step of the precursor mixture, the low-temperature carbonization process includes: holding at 400~550℃ for 4~8h for low-temperature carbonization.

5. The method for preparing a multi-element-doped hierarchical porous biomass carbon material according to claim 1, characterized in that, In the post-processing steps of the carbonized reactants, the acid solution used is at least one of hydrochloric acid, nitric acid, and sulfuric acid at a concentration of 1-2 mol / L, and ultrasonic stripping is carried out in deionized water.

6. The method for preparing a multi-element-doped hierarchical porous biomass carbon material according to claim 1, characterized in that, In the mixing step of the precursor mixture, the mass ratio of biomass raw material to the sum of the masses of microporous pore-forming agent, mesoporous pore-forming agent and macroporous pore-forming agent to the sum of the masses of non-metallic compound, metallic compound and transition metal compound is 1:15~20:

3.

7. A multi-element-doped hierarchical porous biomass carbon material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The application of the multi-element doped hierarchical porous biomass carbon material as described in claim 7 in the field of electrochemical energy storage or catalysis.

9. A lithium-ion battery negative electrode, characterized in that, The current collector of the lithium-ion battery negative electrode is loaded with a multi-element doped hierarchical porous biomass carbon material as described in claim 7.

10. An electrocatalyst, characterized in that, The support or catalytically active material of the electrocatalyst includes the multi-element-doped hierarchical porous biomass carbon material as described in claim 7.

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