A nitrogen-sulfur co-doped functional porous carbon material, its preparation method and application

Abstract

This invention belongs to the field of porous carbon technology, specifically relating to a nitrogen-sulfur co-doped functional porous carbon material, its preparation method, and its application. A method for preparing a nitrogen-sulfur co-doped functional porous carbon material includes the following steps: S1, pretreatment of biomass raw materials; S2, mixing the pretreated biomass raw materials, aminosulfonic acid, and water, and carrying out a hydrothermal reaction; after the reaction, solid-liquid separation is performed, and the resulting solid portion is vacuum dried to obtain hydrothermal carbon; S3, pyrolysis activation: mixing the hydrothermal carbon and an activator, grinding, and pyrolyzing to obtain carbon powder; washing and drying the carbon powder to obtain the nitrogen-sulfur co-doped functional porous carbon material. The nitrogen-sulfur co-doped functional porous carbon material prepared by the method of this invention has a rich porous structure. When applied to supercapacitors, it exhibits high specific capacitance and good stability, effectively overcoming the problems of poor specific capacitance and stability of existing porous carbon materials.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon technology, specifically relating to a nitrogen-sulfur co-doped functional porous carbon material, its preparation method, and its application. Background Technology

[0002] Porous carbon mainly refers to carbon materials with well-developed pores and ultra-high specific surface area prepared through certain chemical or physical activation methods. Due to its good electrical conductivity, stable chemical properties, large specific surface area, abundant raw material sources, and low cost, porous carbon is the earliest and most widely used adsorbent material and supercapacitor electrode material.

[0003] The raw materials that can be used to prepare porous carbon are very extensive, and can be broadly divided into fossil raw materials and biomass raw materials. Fossil raw materials mainly include bitumen, tar, and coal. Biomass raw materials mainly include agricultural waste (straw, corn cobs, rice husks, etc.), fruit shells, leaves, and wood. Faced with the gradual depletion of fossil energy and the vigorous development of renewable energy, how to store and release these energy sources has become an important research direction, and the research on preparing porous carbon materials from biomass has become a hot research area. Biomass raw materials are characterized by their wide availability, infinite renewability, and the fact that they are usually waste materials. Using them as raw materials to prepare porous carbon not only benefits environmental protection but also brings additional economic benefits. However, the structure and properties of biomass porous carbon materials are affected not only by the carbonization and activation processes used but also by the natural structure of the selected biomass raw materials.

[0004] Supercapacitors, due to their rapid charging and discharging capabilities and high power and energy densities, have become a hot research topic and are widely used in the military, transportation, and electronics industries. Among these, carbon-based electrode materials have gained favor among researchers due to their excellent physical, chemical, and electrochemical properties, and have become the most widely used material in commercial supercapacitor applications. However, existing porous carbon materials used in supercapacitors suffer from poor specific capacitance and stability. Therefore, there is an urgent need to develop a porous carbon material that can effectively improve specific capacitance and stability. Summary of the Invention

[0005] This invention aims to provide a nitrogen-sulfur co-doped functional porous carbon material, its preparation method, and its application. The nitrogen-sulfur co-doped functional porous carbon material prepared by the method of this invention has abundant void structures. When applied to supercapacitors, it exhibits high specific capacitance and good stability, effectively overcoming the problems of poor specific capacitance and stability of porous carbon materials in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing nitrogen-sulfur co-doped functional porous carbon materials, comprising the following steps: S1. Biomass raw material pretreatment; S2. The pretreated biomass raw material, aminosulfonic acid and water are mixed and subjected to hydrothermal reaction. After the reaction is completed, the solid and liquid are separated and the obtained solid part is vacuum dried to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0007] In the preparation method of this invention, during the aminosulfonic acid-assisted hydrothermal reaction treatment, aminosulfonic acid provides acidic H protons to preferentially hydrolyze hemicellulose in biomass raw materials, disrupting the bonds between these three major components. With increasing hydrothermal reaction time, active hydrogen protons hydrolyze cellulose under temperature-driven conditions. Simultaneously, its sulfonic acid groups can combine with glucose monosaccharides or xylose monosaccharides from cellulose or hemicellulose hydrolysis, as well as hydroxyl groups on lignin residues, achieving nitrogen-sulfur co-doping of both liquid and solid components. There is a synergistic effect between the nitrogen and sulfur elements doped in the material. The dual doping of nitrogen and sulfur can regulate the edge strain and electron distribution within the carbon framework, thereby stabilizing the chemical environment of the doped region. After pyrolysis activation, the prepared hydrothermal carbon can significantly increase the number of microporous structures in the material, effectively improving the storage capacitance of the prepared nitrogen-sulfur co-doped functional porous carbon material. Furthermore, the specific distribution structure of nitrogen and sulfur elements in the material further enhances the stability of the prepared porous carbon material. When applied to supercapacitors, it can maintain a high capacitance retention rate even after 5000 cycles.

[0008] As one embodiment of the preparation method of the present invention, the mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:(1~3).

[0009] In the preparation method of the nitrogen-sulfur co-doped functional porous carbon material of this invention, the introduction of excessive aminosulfonic acid not only fails to improve the doping efficiency of N and S elements but also leads to a decrease in the N and S doping efficiency. This is attributed to the possibility of hydrolysis of sulfonate groups under excessive acid concentration, resulting in unstable sulfur doping and consequently a decline in the performance of the final porous carbon material. When the amount of aminosulfonic acid introduced is too small, on the one hand, the nitrogen and sulfur doping amount will be smaller, resulting in poor performance; on the other hand, the acidity is too low, leading to incomplete hydrolysis of biomass, low carbonization rate, and increased doping difficulty, ultimately resulting in a smaller doping amount and poorer electrochemical performance of the prepared porous carbon material.

[0010] In a preferred embodiment of the preparation method described in this invention, the mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:2.

[0011] In the preparation method of this invention, when the mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:2, the nitrogen content in the resulting hydrothermal carbon increases from 0.11% to 1.87%, and the sulfur content increases from 0.09% to 1.36%. The main nitrogen configuration changes from C=N to CN, and the sulfur configuration is mainly C-SOx-C sulfoxide. This yields activated carbon with the highest nitrogen and sulfur co-doping content and the most developed microporous structure, achieving a surface area of ​​2987.81 m². 2 / g, with a micropore ratio of 36.2%, achieving the dual functions of heteroatom doping and structural regulation.

[0012] In one embodiment of the preparation method described in this invention, the amount of water added is 10 to 30 times the mass of the pretreated biomass raw material.

[0013] As one embodiment of the preparation method described in this invention, the hydrothermal reaction conditions are: continuous reaction for 1-5 hours in a vacuum drying oven at 200°C.

[0014] In one embodiment of the preparation method described in this invention, the vacuum drying temperature is 100~110℃.

[0015] As one embodiment of the preparation method described in this invention, the biomass raw material includes at least one of poplar wood, sugarcane bagasse, tea leaves, and camellia shells.

[0016] As one embodiment of the preparation method described in this invention, the pretreatment of the biomass raw material is as follows: the biomass raw material is crushed and sieved.

[0017] In one embodiment of the preparation method described in this invention, the sieving is performed through a 100-mesh sieve.

[0018] As one embodiment of the preparation method described in this invention, the activator includes at least one of potassium hydroxide and sodium hydroxide.

[0019] As one embodiment of the preparation method described in this invention, the activator includes a mixture of potassium hydroxide, potassium hydroxide and sodium hydroxide.

[0020] In the preparation method of the present invention, potassium hydroxide is a necessary component in the activator and cannot be completely replaced by other activators.

[0021] In one embodiment of the preparation method described in this invention, the mass ratio of potassium hydroxide to sodium hydroxide is (2~3):1.

[0022] In one embodiment of the preparation method described in this invention, the mass ratio of the hydrothermal carbon to the activator is 1:(3~5).

[0023] As one embodiment of the preparation method described in this invention, the pyrolysis conditions are: heating to 700~900℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, and maintaining this temperature for 1~3h.

[0024] As one embodiment of the preparation method described in this invention, the cleaning is performed by washing with dilute hydrochloric acid and water until neutral.

[0025] As one embodiment of the preparation method described in this invention, the drying temperature is 60~80℃ and the time is 10~24h.

[0026] This invention also claims protection for a nitrogen-sulfur co-doped functional porous carbon material prepared by the aforementioned preparation method.

[0027] As one embodiment of the nitrogen-sulfur co-doped functional porous carbon material of the present invention, the micropore diameter of the nitrogen-sulfur co-doped functional porous carbon material is <2 nm, and the surface area is 2900 m². 2 / g or more.

[0028] This invention also claims protection for a preparation method described above, or for the application of the nitrogen-sulfur co-doped functional porous carbon material in supercapacitor materials.

[0029] Compared with the prior art, the present invention has the following beneficial effects: (1) The preparation method of the present invention controls the added components and the synergistic effect between each operation step, and the nitrogen-sulfur co-doped functional porous carbon material obtained can have a rich void structure. When applied to supercapacitors, it can achieve high specific capacitance and good stability, effectively overcoming the problems of poor specific capacitance performance and stability of porous carbon materials in the prior art.

[0030] (2) The preparation method of the present invention is simple and fast, and can efficiently realize the resource utilization of waste lignocellulose and produce high-performance products, which has great potential in the sustainable utilization of biomass resources. Attached Figure Description

[0031] Figure 1 This is a characterization diagram of the nitrogen-sulfur co-doped functional porous carbon material prepared in Example 1 of the present invention.

[0032] Figure 2 The results of component analysis for each group in Experimental Example 1 of this invention are shown. Wherein, a represents the three-component ratio of the lignocellulose pretreatment, and b represents the solid residue rate and the removal rates of cellulose and hemicellulose.

[0033] Figure 3 The results show the elemental content analysis of each group in Experimental Example 1 of this invention. Wherein, a represents the elemental content analysis of hydrothermal carbon, and b represents the FTIR spectrum.

[0034] Figure 4 The XPS analysis results for each group in Experimental Example 1 of this invention are shown. Among them, a is the overall XPS analysis chromatogram of hydrothermal carbon, b is the N 1s spectrum, and c is the S 2p spectrum.

[0035] Figure 5 The diagram shows the N2 adsorption-desorption isotherms, specific surface area (a), and DFT pore size distribution of each group in Experimental Example 2 of this invention (b).

[0036] Figure 6 These are the XPS analysis spectra of each group in Experimental Example 2 of this invention. Among them, a is the overall XPS analysis spectrum of the nitrogen-sulfur co-doped functional porous carbon material, b is the N 1s spectrum, and c is the S 2p spectrum.

[0037] Figure 7 This represents the percentage of different functional groups in nitrogen (a) and sulfur (b) in each group during XPS analysis in Experimental Example 2 of this invention.

[0038] Figure 8 The graphs show the electrochemical performance test data of the porous carbons prepared in Example 1 and Comparative Examples 3-4 of this invention. In the graphs, Gly represents glycine, MSA represents methanesulfonic acid, and SA represents aminosulfonic acid. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0041] Example 1: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 5g of pretreated biomass raw material, 10g of aminosulfonic acid and 100ml of water, and carry out hydrothermal reaction. After the reaction is completed, separate the solid and liquid, and vacuum dry the obtained solid part to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0042] The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:2. The hydrothermal reaction conditions are: continuous reaction for 3 hours in a vacuum drying oven at 200°C; The vacuum drying temperature is 105°C; The biomass raw material is poplar wood; The pretreatment of the biomass raw materials is as follows: poplar wood is crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:4; The pyrolysis conditions are as follows: heating to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 2 hours; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 65°C and the time is 12 hours.

[0043] The prepared nitrogen-sulfur co-doped functional porous carbon materials were characterized, and the experimental results are as follows: Figure 1 As shown. Through SEM images ( Figure 1 a) It can be seen that the carbon shape of the nitrogen-sulfur co-doped functional porous carbon material becomes smaller and has a very rich void structure. Further TEM scanning shows that AC-21 has many tiny micropore structures (pore size <2nm), which can better store capacitance. Figure 1 b), while the EDS spectrum showed effective doping of N and S elements ( Figure 1 cd).

[0044] Example 2: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 5g of pretreated biomass raw material, 10g of aminosulfonic acid and 90ml of water, and carry out hydrothermal reaction. After the reaction is completed, separate the solid and liquid, and vacuum dry the obtained solid part to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0045] in, The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:2; The hydrothermal reaction conditions are: continuous reaction for 1 hour in a vacuum drying oven at 200°C; The vacuum drying temperature is 100℃; The biomass raw material is poplar wood; The pretreatment of the biomass raw materials is as follows: poplar wood is crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide and sodium hydroxide (mass ratio 2:1); The mass ratio of the hydrothermal carbon to the activator is 1:3; The pyrolysis conditions are as follows: heating to 700°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 1 hour; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 60°C and the time is 24 hours.

[0046] Example 3: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 5g of pretreated biomass raw material, 10g of aminosulfonic acid and 150ml of water, and carry out hydrothermal reaction. After the reaction is completed, separate the solid and liquid, and vacuum dry the obtained solid part to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0047] in, The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:2; The hydrothermal reaction conditions are: continuous reaction for 5 hours in a vacuum drying oven at 200°C; The vacuum drying temperature is 110℃; The biomass raw material is poplar wood; The pretreatment of the biomass raw materials is as follows: poplar wood is crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:5; The pyrolysis conditions are as follows: heating to 900°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 3 hours; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 80℃ and the time is 10 hours.

[0048] Example 4: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 7.5g of pretreated biomass raw material, 7.5g of aminosulfonic acid and 100ml of water, and carry out a hydrothermal reaction. After the reaction is completed, the solid and liquid are separated, and the obtained solid part is vacuum dried to obtain hydrothermal char. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0049] in, The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:1; The hydrothermal reaction conditions are: continuous reaction for 3 hours in a vacuum drying oven at 200°C; The vacuum drying temperature is 105°C; The biomass raw material is poplar wood; The pretreatment of the biomass raw materials is as follows: poplar wood is crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:4; The pyrolysis conditions are as follows: heating to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 2 hours; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 65°C and the time is 12 hours.

[0050] Compared with Example 1, the only difference in this example is that the mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:1.

[0051] Example 5: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 3.75g of pretreated biomass raw material, 11.25g of aminosulfonic acid and 100ml of water, and carry out hydrothermal reaction. After the reaction is completed, the solid and liquid are separated, and the obtained solid part is vacuum dried to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0052] in, The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:3; The hydrothermal reaction conditions are: continuous reaction for 3 hours in a vacuum drying oven at 200°C; The vacuum drying temperature is 105°C; The biomass raw material is poplar wood; The pretreatment of the biomass raw materials is as follows: poplar wood is crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:4; The pyrolysis conditions are as follows: heating to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 2 hours; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 65°C and the time is 12 hours.

[0053] Compared with Example 1, the only difference in this example is that the mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:3.

[0054] Example 6: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 10g of pretreated biomass raw material, 5g of aminosulfonic acid and 100ml of water, and carry out a hydrothermal reaction. After the reaction is completed, separate the solid and liquid, and vacuum dry the obtained solid part to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0055] in, The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 2:1; The hydrothermal reaction conditions are: continuous reaction for 3 hours in a vacuum drying oven at 200°C; The vacuum drying temperature is 105°C; The biomass raw material is poplar wood; The pretreatment of the biomass raw materials is as follows: poplar wood is crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:4; The pyrolysis conditions are as follows: heating to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 2 hours; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 65°C and the time is 12 hours.

[0056] Compared with Example 1, the only difference in this example is that the mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 2:1.

[0057] Example 7: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 5g of pretreated biomass raw material, 10g of aminosulfonic acid and 100ml of water, and carry out hydrothermal reaction. After the reaction is completed, separate the solid and liquid, and vacuum dry the obtained solid part to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0058] The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:2. The hydrothermal reaction conditions are: continuous reaction for 3 hours in a vacuum drying oven at 200°C; The vacuum drying temperature is 105°C; The biomass raw material is sugarcane bagasse; The pretreatment of the biomass raw materials is as follows: sugarcane bagasse is crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:4; The pyrolysis conditions are as follows: heating to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 2 hours; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 65°C and the time is 12 hours.

[0059] Compared with Example 1, the only difference in this example is that sugarcane bagasse is used as the biomass raw material.

[0060] Example 8: A method for preparing a nitrogen-sulfur co-doped functional porous carbon material S1. Biomass raw material pretreatment; S2. Mix 5g of pretreated biomass raw material, 10g of aminosulfonic acid and 100ml of water, and carry out hydrothermal reaction. After the reaction is completed, separate the solid and liquid, and vacuum dry the obtained solid part to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

[0061] The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:2. The hydrothermal reaction conditions are: continuous reaction for 3 hours in a vacuum drying oven at 200°C; The vacuum drying temperature is 105°C; The biomass raw material is camellia oleifera shell; The pretreatment of the biomass raw materials is as follows: the camellia oleifera shells are crushed and sieved (through a 100-mesh sieve). The activator is potassium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:4; The pyrolysis conditions are as follows: heating to 800°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintaining this temperature for 2 hours; The cleaning process involves repeatedly washing with 10wt% dilute hydrochloric acid and distilled water until neutral. The drying temperature is 65°C and the time is 12 hours.

[0062] Compared with Example 1, the only difference in this example is that the biomass raw material used is camellia shell.

[0063] Comparative Example 1 Compared with Example 1, the only difference in this comparative example is that sulfamic acid is not added.

[0064] The preparation method is the same as in Example 1.

[0065] Comparative Example 2 Compared with Example 1, the only difference in this comparative example is that an equal amount of thiourea is used instead of aminosulfonic acid.

[0066] The preparation method is the same as in Example 1.

[0067] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is that glycine is used instead of aminosulfonic acid in equal amounts.

[0068] The preparation method is the same as in Example 1.

[0069] Comparative Example 4 Compared with Example 1, the only difference in this comparative example is that an equal amount of methanesulfonic acid was used instead of aminosulfonic acid.

[0070] The preparation method is the same as in Example 1.

[0071] Experimental Example 1 The hydrothermal carbon prepared by hydrothermal reaction in Examples 1 (HTC-21), 4 (HTC-11), 5 (HTC-31), and Comparative Example 1 (HTC-0) was subjected to component analysis, elemental content analysis, and XPS analysis.

[0072] Component analysis methods: The hemicellulose, cellulose, and lignin content of the solid residue was analyzed by a two-step sulfuric acid hydrolysis experiment, with two parallel samples. 0.1500 ± 0.005 g of dried solid sample was weighed and placed in a 10 mL centrifuge tube. 1.5 mL of 72% sulfuric acid was added, and the mixture was shaken thoroughly to ensure complete sulfuric acid immersion. After thorough mixing, the sample was placed in a shaker at 30 °C for 1 hour to allow for complete hydrolysis. After hydrolysis, all portions were rinsed with a total of 42 mL of deionized water into 50 mL pressure-resistant bottles, which were then tightly capped. All pressure-resistant bottles were labeled and placed in a high-pressure steam sterilizer at 121 °C for 60 min for a second hydrolysis. After the second hydrolysis, the mixture was cooled and allowed to stand. A suitable amount of the supernatant from the pressure-resistant bottles was then transferred to a 5 mL centrifuge tube, and calcium carbonate powder was added to neutralize the remaining sulfuric acid. After neutralization, the remaining solid was aspirated using a syringe and filtered through a filter membrane. The glucose and xylose content in the filtered liquid was determined by HPLC, and the cellulose and hemicellulose content was calculated. The remaining liquid and solid portions were shaken well and placed in a pre-weighed sand core funnel (M1) for filtration. The filtered sand core funnel was then dried overnight in an oven at 105°C, and weighed to obtain a second mass, M2. The dried sand core funnel was then placed in a muffle furnace and calcined at 575°C for 6 hours. After cooling, the remaining sand core funnel mass, M3, was weighed. The calculation formulas for each component are as follows: (1.1) (1.2) (1.3) (1.4) Where M is mass (g), C is concentration (g / L), 0.9 is the correction parameter for the ratio of the relative molecular mass of glucose residues to glucose molecules (162 / 180), 0.88 is the correction parameter for the ratio of the relative molecular mass of xylose residues to xylose molecules (132 / 150), and V is 42 + 1.5 = 43.5 mL of filtrate.

[0073] Elemental analysis method: (Analysis of nitrogen and sulfur content using ICP) Inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7700X) was used to determine the metal or non-metal content in solid or liquid samples. Samples were first digested with microwave solutions (H₂SO₄, HNO₃) before testing. 3、 (A mixed solution of HF), which was then diluted and brought to a fixed volume before testing.

[0074] XPS analysis method: The image was obtained using a monochromatic Al K-α X-ray spectrometer (1486.8 eV) at 2 × 10⁻⁶ Å on a Thermo Scientific K-Alpha spectrometer in the United States. -9 Recording was performed at Mbar, and the final binding energy (BE) was calibrated according to the standard C 1s BE (284.8 eV) to characterize the chemical state and chemical environment of the elements on the surface of the solid sample.

[0075] Experimental results are as follows Figure 2-4 As shown.

[0076] from Figure 2 The experimental results show that Comparative Example 1, which did not contain added sulfamic acid, still contained 54.23% cellulose, and the hemicellulose was almost completely hydrolyzed. Figure 2 (b) In Examples 1 and 4-5, where sulfamic acid was added, cellulose and hemicellulose were almost completely removed. The removal rate in Example 1 was as high as 98.32%, leaving only lignin and ash in the solid fraction, with a solid yield of 42.4%. Different proportions of sulfamic acid added did not show significant differences in the removal rates of cellulose and hemicellulose. This indicates that the introduction of sulfamic acid effectively disrupted hydrogen and covalent bonds, thereby removing cellulose and hemicellulose and achieving lignin enrichment in the poplar wood component.

[0077] from Figure 3 The experimental results show that aminosulfonic acid-assisted hydrothermal pretreatment significantly increased the nitrogen and sulfur content of HTC. Figure 3 (a) demonstrates the effective doping of aminosulfonic acid into the lignin structure.

[0078] Among them, the hydrothermal carbon (HTC-21) prepared in Example 1 showed the best doping efficiency, with a nitrogen content of 1.87% and a sulfur content of 1.36%. However, the introduction of excess aminosulfonic acid led to a decrease in NS doping efficiency, which is attributed to the possible hydrolysis reaction of sulfonate groups under excess acid concentration, resulting in instability of sulfur doping. Nitrogen-containing groups have better retention than sulfur-containing sulfonic acid groups, which may be due to their enhanced nucleophilic reactivity with hydroxyl groups and higher chemical stability after grafting. In order to better understand the effect of aminosulfonic acid-assisted hydrothermal pretreatment on lignin structure, FTIR and XPS were used to characterize and analyze the pretreatment residue. FTIR spectra show ( Figure 3 b) at 1596 cm -1 (Aromatic skeletal vibration), 1511 cm -1 (C=C stretching) and 1426 cm -1 Typical lignin signals are present at the (CH deformation) site. And at 1116 cm... -1 and 1026 cm -1The vibrations at 914 cm⁻¹ represent both symmetric and asymmetric vibrations of the S=O bond in aminosulfonic acid. It can be observed that the peak intensity of HTC-11, with the addition of aminosulfonic acid, is significantly enhanced, while HTC-0 shows almost no vibration. Simultaneously, peak intensities at 914 cm⁻¹ for HTC-11, HTC-21, and HTC-31 are also observed. -1 The characteristic peak of SC shows obvious vibrations, indicating that the sulfonic acid group was effectively grafted onto the hydroxyl group of lignin through esterification, forming a new bond.

[0079] In addition, XPS analysis ( Figure 4 a) shows that the nitrogen (N) and sulfur (S) peak intensities of the hydrothermal carbon were significantly enhanced after hydrothermal treatment assisted by aminosulfonic acid. In the original sample without added sulfanilamide, nitrogen mainly existed in the C=N bond configuration, accounting for 81.06% of the total nitrogen content. Figure 4 b). In the samples modified with aminosulfonic acid, the C=N bonds underwent a significant transformation into CN bonds, with HTC-21 exhibiting the highest CN bond ratio at 59.62%. Simultaneously, the ammonium functional group NH... 4+ The content also increased. This transformation indicates that sulfamic acid, through grafting onto lignin, altered the original N configuration of the hydrothermal carbon, promoting CN bond formation. Comparative analysis of HTC-21 and HTC-31 showed that the breaking of natural C=N bonds was dose-dependent; the higher the concentration of sulfamic acid, the more CN bonds were formed. However, excessive acid loading led to group dissociation and shedding; the CN bond content of HTC-11 decreased by 2.26% compared to HTC-21. Sulfur species analysis showed that the C-SOx-C configuration (83.2-91.4% of total sulfur) was dominant, while the CS bond (<5.8%) accounted for a very low proportion. Figure 4 (c) Simultaneously, the peak position of C-SOx-C shifts; the higher the concentration of aminosulfonic acid, the further the peak shifts towards a lower binding energy position. This is because at lower aminosulfonic acid concentrations, both the CSC and C-SOx-C configurations coexist. As the concentration increases, C-SOx-C is reduced, lowering the oxidation state. At excessively high concentrations, C-SOx-C is reduced to CSC bonds. Notably, the spectrum of HC-21 completely lacks the characteristic CSC peak, providing further clues for subsequent activation.

[0080] The experimental results above show that during the sulfamic acid-assisted hydrothermal pretreatment, sulfamic acid provides acidic H protons to preferentially hydrolyze hemicellulose, disrupting the bonds between these three major components. With increasing pretreatment time, active hydrogen protons hydrolyze cellulose under temperature-driven conditions. Simultaneously, its sulfonic acid groups can bind to glucose or xylose monosaccharides from cellulose or hemicellulose hydrolysis, as well as hydroxyl groups on lignin residues, achieving nitrogen-sulfur co-doping of both liquid and solid components.

[0081] Experimental Example 2 XPS was used to characterize the nitrogen-sulfur co-doped functional porous carbon materials prepared in Examples 1, 4-5 and Comparative Example 1 to evaluate the influence of nitrogen and sulfur element morphology on their performance.

[0082] Experimental methods: BET analysis: Weigh 150-200 mg of solid powder sample (80-100 mesh) and perform BET specific surface area analysis and DFT pore size analysis on a Micromeritics ASAP2460 analyzer in the United States.

[0083] XRD analysis: Powder samples with a particle size of 80-100 mesh were prepared and scanned using a Rigaku Ultima IV X-ray diffractometer. The experimental conditions were: copper target radiation λ = 0.154 nm, radiation tube voltage = 50 kV, radiation tube current = 200 mA, scanning range θ = 5° to 80°, step width = 0.02°, and scanning speed = 8° / min.

[0084] Raman analysis: Raman spectroscopy was performed using a Via-reflex Renishaw spectrometer with a 532 nm laser wavelength to measure and analyze solid samples.

[0085] Infrared analysis: Weigh 1.5-2 mg of lignocellulose raw material or pretreated sample and mix it uniformly with potassium bromide crystals at a mass ratio of 1:50, then grind it into powder and press it into thin sheets. Analyze the sample using a Bruker Vertex 70 Fourier transform infrared spectrometer at 4000–400 cm⁻¹. -1 Spectral scanning was performed within the range to analyze the differences in functional group structures of the prepared samples.

[0086] Experimental results are as follows Figure 5-7 As shown.

[0087] The BET nitrogen adsorption-desorption isotherm of the nitrogen-sulfur co-doped functional porous carbon material shows that it is type IV. Figure 5 a), and revealed different texture characteristics: Comparative Example 1 (AC-0) exhibited the highest specific surface area of ​​3171.50 m². 2 / g, mainly composed of mesopores of 2-50 nm, while the specific surface area of ​​the porous carbon prepared using the method of this invention decreased to some extent. Although Example 1 (AC-21) had a lower surface area (2987.81 nm), 2 / g), but its micropore (pore size <2 nm) density is higher, which was verified by DFT pore size distribution analysis. Figure 5 b).

[0088] Figure 6b shows the N1s spectra of the nitrogen-sulfur co-doped functional porous carbon materials prepared in Example 1 (AC-11), Example 4 (AC-21), and Example 5 (AC-31), respectively, exhibiting three characteristic peaks: graphitic nitrogen (402.1 eV), pyrrole nitrogen (400.3 eV), and pyridine nitrogen (398.5 eV), as well as the S2p spectrum (…). Figure 6 The two significant characteristic peaks in c) correspond to C-SOx-C sulfoxide (168.8 eV) and CSC thiophene (164.6 eV).

[0089] To further analyze the distribution of nitrogen and sulfur elements, the relative proportion of each configuration was quantified. Figure 7 (a, b) As the doping ratio increased, the graphitic nitrogen content decreased from 65.3% in Example 5 (AC-31) to 57.87% in Example 4 (AC-11), indicating that unstable pyrrole nitrogen and pyridine nitrogen were converted into thermodynamically more stable graphitic nitrogen during pyrolysis. Example 1 (AC-21) exhibited the highest pyridine nitrogen content (28.38%) and the lowest pyrrole nitrogen content (9.61%), fully demonstrating the excellent thermal stability of this material under high-temperature pyrolysis conditions.

[0090] Experimental Example 3: Electrochemical Performance Testing The nitrogen-sulfur co-doped functional porous carbon materials (80 wt%), conductive acetylene black (10 wt%), and polytetrafluoroethylene (PTFE, 10 wt%) prepared in Examples 1, 4-8, and Comparative Examples 1-4 were mixed in ethanol to form a slurry, ground into a carbon film, and then dried in a 65°C oven for 6 h. The resulting carbon film was coated onto the surface of nickel foam (1×1 cm), and then compressed under 20 MPa pressure to prepare a supercapacitor electrode. The specific capacitance, coulombic efficiency, and capacitance retention were then tested. The corresponding test methods are as follows: Specific capacity: Measured by galvanostatic charge-discharge (GCD) over the same potential range of 0.2–10 A g. -1 Different current densities were used to measure the specific capacitance C (F g). -1 Calculate according to the following formula: (2.1) Where I(A) represents the discharge current, Δt(s) represents the discharge time, m(g) represents the active mass of the working electrode material, and ΔV(V) represents the potential range.

[0091] Coulomb efficiency: ; Where td represents the charging time and tc represents the discharging time, which can be found in the GCD curve. Capacitance retention rate: ; The experimental results are shown in Table 1.

[0092] Table 1. Experimental results of cyclic performance and specific capacity for each group

[0093] The experimental data in Table 1 show that the nitrogen-sulfur co-doped functional porous carbon material prepared in the embodiments of the present invention can achieve a high specific capacitance when applied to supercapacitors. Moreover, after 5000 cycles, its capacitance retention rate can still be maintained at a high level of over 90%, indicating that the nitrogen-sulfur co-doped functional porous carbon material prepared in the embodiments of the present invention can achieve excellent stability when applied to supercapacitors.

[0094] In Example 6, the proportion of aminosulfonic acid added during the preparation of the nitrogen-sulfur co-doped functional porous carbon material was inappropriate, resulting in a decrease in the specific capacity and stability of the final nitrogen-sulfur co-doped functional porous carbon material. In Examples 7 and 8, sugarcane bagasse and camellia shells were used as biomass raw materials for the preparation of porous carbon materials, and the resulting porous carbon materials exhibited inferior electrochemical performance compared to Example 1.

[0095] In Comparative Example 1, no aminosulfonic acid component was added during the preparation of porous carbon, and the specific capacity and capacitance retention rate of the resulting porous carbon material were significantly worse than those of the Example. In Comparative Example 2, an equal amount of thiourea was used to replace the aminosulfonic acid component during the preparation of porous carbon material, and the electrochemical performance of the resulting porous carbon material was significantly worse.

[0096] In Comparative Example 3, glycine was used to maintain the amino group and change the sulfonic acid group to achieve nitrogen-only doping. In Comparative Example 4, methanesulfonic acid was used to maintain the sulfonic acid group and change the amino group to achieve sulfur-only doping. Both the resulting single nitrogen doping and single sulfur doping showed worse performance than nitrogen-sulfur co-doping, proving that the reaction between the added aminosulfonic acid component and biomass and other components in this invention can achieve the synergistic effect of nitrogen-sulfur co-doping.

[0097] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a nitrogen-sulfur co-doped functional porous carbon material, characterized in that, Includes the following steps: S1. Biomass raw material pretreatment; S2. The pretreated biomass raw material, aminosulfonic acid and water are mixed and subjected to hydrothermal reaction. After the reaction is completed, the solid and liquid are separated and the obtained solid part is vacuum dried to obtain hydrothermal carbon. S3. Pyrolysis activation: Hydrothermal carbon and activator are mixed, ground, and pyrolyzed to obtain carbon powder. The carbon powder is then washed and dried to obtain the nitrogen-sulfur co-doped functional porous carbon material.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the pretreated biomass raw material to the aminosulfonic acid is 1:(1~3).

3. The preparation method according to claim 1, characterized in that, The amount of water added is 10 to 30 times the mass of the pretreated biomass raw material; The hydrothermal reaction conditions are: continuous reaction in a vacuum drying oven at 200℃ for 1-5 hours; The vacuum drying temperature is 100~110℃.

4. The preparation method according to claim 1, characterized in that, The biomass raw materials include at least one of poplar wood, sugarcane bagasse, tea leaves, and camellia shells; The pretreatment of the biomass raw materials is as follows: the biomass raw materials are crushed and sieved.

5. The preparation method according to claim 1, characterized in that, The activator includes at least one of potassium hydroxide and sodium hydroxide; The mass ratio of the hydrothermal carbon to the activator is 1:(3~5).

6. The preparation method according to claim 1, characterized in that, The pyrolysis conditions are as follows: heating to 700~900℃ at a heating rate of 5℃ / min under a nitrogen atmosphere, and maintaining this temperature for 1~3h.

7. The preparation method according to claim 1, characterized in that, The cleaning process involves washing with dilute hydrochloric acid and water until the solution is neutral. The drying temperature is 60~80℃, and the time is 10~24h.

8. A nitrogen-sulfur co-doped functional porous carbon material prepared by any one of the preparation methods described in claims 1 to 7.

9. The nitrogen-sulfur co-doped functional porous carbon material as described in claim 8, characterized in that, The nitrogen-sulfur co-doped functional porous carbon material has a micropore size of <2 nm and a surface area of ​​2900 m². 2 / g or more.

10. A preparation method as described in any one of claims 1-7, or the application of nitrogen-sulfur co-doped functional porous carbon material as described in any one of claims 8-9 in supercapacitor materials.

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