Crab shell-based porous carbon and preparation method and application thereof

Abstract

The application provides crab shell based porous carbon and a preparation method and application thereof, and belongs to the field of porous carbon materials. The preparation method of the crab shell based porous carbon provided by the application comprises the following steps: pre-carbonizing crab shell powder to obtain an intermediate carbon product; mixing the intermediate carbon product, hexadecyl trimethyl ammonium bromide, tetraethyl orthosilicate, ammonia water and a solvent to perform hydrolysis polycondensation reaction, to obtain a composite product; sequentially performing first acid pickling, calcination and second acid pickling on the composite product, to obtain the crab shell based porous carbon. The surface area of the crab shell based porous carbon prepared by the preparation method provided by the application can reach 319.3 m 2 g ‑1 , the pore volume can reach 0.314 cm 3 g ‑1 , the prepared capacitor has high surface area and pore volume, and has good electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of porous carbon materials, and more particularly to a crab shell-based porous carbon, its preparation method, and its applications. Background Technology

[0002] With the overexploitation and use of fossil fuels, problems such as fossil fuel depletion and environmental pollution are becoming increasingly serious. Therefore, developing renewable and clean energy to solve energy and environmental problems is an urgent need for human society today. Currently, clean and renewable energy sources such as solar, wind, tidal, and biomass energy are gradually coming into focus.

[0003] The development and utilization of clean and renewable energy sources such as solar and wind power often rely on efficient and stable energy storage systems. Supercapacitors, due to their high power density, extended cycle stability, and fast charging / discharging capabilities, have become one of the most important energy storage devices. Based on their energy storage mechanisms, supercapacitors can be mainly classified into three types: electric double-layer capacitors (EDLCs), pseudocapacitors, and hybrid capacitors. Based on the energy storage mechanism of EDLCs, their electrode materials are mostly carbon-based materials, such as activated carbon and carbon nanotubes. Their specific capacitance is closely related to the specific surface area and specific surface properties of the electrode material. Biomass-based carbon materials are widely recognized as the most commercially promising supercapacitor electrode materials due to their high specific surface area, good conductivity, ease of processing, non-toxicity, and low cost.

[0004] Coastal cities are rich in seafood, resulting in a massive volume of seafood processing byproducts annually. As waste from crustaceans, crab shells are among the most abundant biomass in nature. According to incomplete statistics, approximately 6 to 8 million tons of crab shells are produced globally each year. Crab shells contain abundant protein, shell meal, calcium, and minerals, making them an excellent precursor for biochar. However, currently, crab shells are typically treated as solid waste and disposed of in landfills. Over time, the remaining shells decompose into various chemical substances or microorganisms, causing environmental pollution and wasting biological resources.

[0005] Therefore, how to prepare crab shells into high-performance capacitor carbon has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a crab shell-based porous carbon, its preparation method, and its applications. The crab shell-based porous carbon prepared by the method provided by this invention has high surface area and pore volume, and enables capacitors made using crab shell-based porous carbon to have good electrochemical performance.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing crab shell-based porous carbon, comprising the following steps: (1) Pre-carbonize the crab shell powder to obtain intermediate carbon products; (2) The intermediate carbon product obtained in step (1), hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia and solvent are mixed and subjected to hydrolysis and polycondensation reaction to obtain a composite product; (3) The composite product obtained in step (2) is subjected to first acid washing, calcination and second acid washing in sequence to obtain crab shell-based porous carbon.

[0008] Preferably, the particle size of the crab shell powder in step (1) is ≤0.18mm.

[0009] Preferably, in step (1), the pre-carbonization temperature is 280~320℃, the pre-carbonization time is 1.5~2.5h, and the heating rate to the pre-carbonization temperature is 4~6℃ / min.

[0010] Preferably, the ratio of the mass of the intermediate carbon product, the mass of hexadecyltrimethylammonium bromide, the volume of tetraethyl orthosilicate, the volume of ammonia, and the volume of solvent in step (2) is (0.15~0.25) g : (0.45~0.55) g : (0.3~0.5) mL : 1 mL : (100~110) mL.

[0011] Preferably, the temperature of the hydrolysis-condensation reaction in step (2) is 25~35℃, and the time of the hydrolysis-condensation reaction is 14~18h.

[0012] Preferably, the temperature of the first pickling in step (3) is 65~75℃, and the time of the first pickling is 10~14h.

[0013] Preferably, the calcination temperature in step (3) is 650~750℃, the calcination time is 1.5~2.5h, and the heating rate to the calcination temperature is 4~6℃ / min.

[0014] Preferably, the temperature of the second pickling in step (3) is 20~30℃, and the time of the second pickling is 10~14h.

[0015] The present invention also provides a crab shell-based porous carbon prepared by the preparation method described above, wherein the pore structure of the crab shell-based porous carbon includes macropores, mesopores and micropores.

[0016] The present invention also provides the application of the crab shell-based porous carbon described in the above technical solution in capacitors.

[0017] This invention provides a method for preparing crab shell-based porous carbon, comprising the following steps: (1) pre-carbonizing crab shell powder to obtain an intermediate carbon product; (2) mixing the intermediate carbon product obtained in step (1), hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia, and solvent to carry out a hydrolysis-condensation reaction to obtain a composite product; (3) subjecting the composite product obtained in step (2) to a first acid wash, calcination, and a second acid wash in sequence to obtain crab shell-based porous carbon. This invention reacts the intermediate carbon product formed from crab shell powder with hexadecyltrimethylammonium bromide and tetraethyl orthosilicate to coat the surface of the intermediate carbon product with a layer of silica. Furthermore, the subsequent first acid wash, calcination, and second acid wash remove hexadecyltrimethylammonium bromide and silica from the material, forming numerous pores on the carbon material, increasing the surface area and pore volume of the porous carbon, and thus improving the electrochemical performance of capacitors made from this porous carbon. Example results show that the surface area of ​​the crab shell-based porous carbon prepared by the method provided by this invention can reach 319.3 m². 2 g -1 The pore volume can reach 0.314 cm. 3 g -1 It possesses high surface area and pore volume; in a three-electrode system, the specific capacitance of the crab shell-based porous carbon in 6M KOH electrolyte at 0.5A / g is 134.3F / g. The supercapacitor assembled with crab shell-based porous carbon as the electrode material retains 98.81% of its initial capacitance after 5000 cycles at a current density of 1A / g; at a power density of 307.06W / kg, the energy density can reach 3.48Wh / kg, and at a power density of 18000W / kg, the energy density can still be maintained at 0.5Wh / kg, demonstrating excellent electrochemical performance. Attached Figure Description

[0018] Figure 1 The images shown are SEM images of the intermediate carbon product (HCB) in Example 1 of this invention, with the left image magnified by 10,000 times and the right image magnified by 30,000 times. Figure 2 The image shows a SEM image of the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1 of this invention, with the left image magnified by 10,000 times and the right image magnified by 30,000 times. Figure 3 The images shown are SEM images of crab shell-based porous carbon (HCB@SiO2-M) in Example 1 of this invention, with the left image magnified by 10,000 times and the right image magnified by 30,000 times. Figure 4 This is a TEM image of the intermediate carbon product (HCB) in Example 1 of the present invention; Figure 5This is a TEM image of the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1 of the present invention. Figure 6 The images shown are TEM images of crab shell-based porous carbon (HCB@SiO2-M) in Example 1 of this invention, with the left image magnified by 300,000 times and the right image magnified by 3,000,000 times. Figure 7 The N2 adsorption-desorption curves of the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown. Figure 8 The pore size distribution diagrams are shown for the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1. Figure 9 The images show the XRD patterns of the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1. Figure 10 Fourier transform infrared spectra of the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1. Figure 11 The elemental distribution and individual elemental mapping diagram of the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 of the present invention are shown. Figure 12 The total XPS spectra of the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown. Figure 13 The N 1s spectrum peak diagram of crab shell-based porous carbon (HCB@SiO2-M) in Example 1 of the present invention; Figure 14 The O 1s spectrum peak diagram of crab shell-based porous carbon (HCB@SiO2-M) in Example 1 of the present invention; Figure 15 The CV curves of the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown at a scan rate of 5 mV / s. Figure 16The CV curves of the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown at a scan rate of 200 mV / s. Figure 17 The graph shows the specific capacity of the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 as a function of current density. Figure 18 The GCD diagrams of three electrodes prepared by the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown at a current density of 0.5 A / g. Figure 19 GCD diagrams of three electrodes prepared from the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1, at a current density of 20 A / g. Figure 20 Nyquist plots of electrodes prepared from the intermediate carbon product (HCB) in Example 1 of the present invention, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1. Figure 21 CV curves of the electrode prepared by the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 of the present invention at different scan rates; Figure 22 GCD curves of the electrode prepared by the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 of the present invention at different current densities; Figure 23 This is a CV curve of the test example HCB@SiO2-M / / HCB@SiO2-M under different voltage scan rates. Figure 24 The GCD curves of HCB@SiO2-M / / HCB@SiO2-M under different current densities are shown in the test examples of this invention. Figure 25 The Nyquist plot of the test example HCB@SiO2-M / / HCB@SiO2-M of this invention; Figure 26 This is a graph showing the specific capacitance of HCB@SiO2-M / / HCB@SiO2-M under different current densities in the test example of this invention. Figure 27Ragone plot of HCB@SiO2-M / / HCB@SiO2-M, a test example of the present invention; Figure 28 The graph shows the cycling performance of the test example HCB@SiO2-M / / HCB@SiO2-M at a current density of 1A / g. Detailed Implementation

[0019] This invention provides a method for preparing crab shell-based porous carbon, comprising the following steps: (1) Pre-carbonize the crab shell powder to obtain intermediate carbon products; (2) The intermediate carbon product obtained in step (1), hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia and solvent are mixed and subjected to hydrolysis and polycondensation reaction to obtain a composite product; (3) The composite product obtained in step (2) is subjected to first acid washing, calcination and second acid washing in sequence to obtain crab shell-based porous carbon.

[0020] This invention pre-carbonizes crab shell powder to obtain intermediate carbon products.

[0021] In one embodiment of the present invention, the particle size of the crab shell powder can be ≤0.18mm. Limiting the particle size of the crab shell powder to the above range allows for better pre-carbonization of the crab shell.

[0022] In one embodiment of the present invention, the crab shell powder can be prepared by washing, drying, crushing and sieving crab shells in sequence to obtain crab shell powder.

[0023] In one embodiment of the present invention, the cleaning agent used for cleaning can be deionized water. The present invention does not specifically limit the number of cleaning cycles or the cleaning time; the number of cleaning cycles and the cleaning time commonly used by those skilled in the art can be used to clean the crab shell.

[0024] In one embodiment of the present invention, the drying can be carried out in an oven; the drying temperature can be 100~110℃, or even 105℃; the drying time can be 22~26h, or even 24h. The present invention limits the drying temperature and time to the above ranges to ensure sufficient drying of the crab shells.

[0025] The present invention does not have any special limitations on the crushing operation, and crushing operations commonly used by those skilled in the art can be used.

[0026] In one embodiment of the present invention, the sieving is performed through an 80-mesh sieve. By passing the crab shell powder through an 80-mesh sieve, the particle size of the crab shell powder can be ≤0.18mm.

[0027] In one embodiment of the present invention, the pre-carbonization can be carried out in a tube furnace; the pre-carbonization can be carried out in a nitrogen atmosphere; the flow rate of nitrogen in the nitrogen atmosphere can be 200 mL / min; the pre-carbonization temperature can be 280~320℃, and can specifically be 280℃, 290℃, 300℃, 310℃ or 320℃; the pre-carbonization time can be 1.5~2.5h, and can specifically be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h; the heating rate to the pre-carbonization temperature can be 4~6℃ / min, and can specifically be 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min or 6℃ / min. The present invention limits the atmosphere, temperature, time and heating rate of pre-carbonization to the above ranges to achieve pre-carbonization of crab shells, which is beneficial to the subsequent reaction.

[0028] The present invention does not have any special limitation on the cooling method after the pre-carbonization and heat preservation is completed. The pre-carbonized product can be cooled to room temperature by a cooling method commonly used by those skilled in the art.

[0029] In one embodiment of the present invention, after the pre-carbonization is completed, the cooled pre-carbonized product can be sequentially acid-washed, cleaned and dried to obtain an intermediate carbon product.

[0030] In one embodiment of the present invention, the pickling solution used for pickling can be hydrochloric acid; the concentration of the hydrochloric acid can be 2M; the pickling temperature can be 20~30℃, or even 25℃; the pickling time can be 5.5~6.5h, or even 6h. The present invention can remove inorganic substances such as calcium salts from pre-carbonized products through pickling.

[0031] In one embodiment of the present invention, after acid washing, the product can be further filtered to obtain a solid product, which is then washed. The present invention does not impose any particular limitation on the filtration operation; any filtration operation commonly used by those skilled in the art can be employed.

[0032] In one embodiment of the present invention, the cleaning solution used for cleaning can be deionized water. The present invention does not impose any special limitations on the cleaning operation; the solid product obtained after acid washing can be cleaned to neutrality using the cleaning cycles and times commonly used by those skilled in the art.

[0033] As one embodiment of the present invention, the selection of drying parameters is the same as the selection of drying parameters after washing the crab shells, and will not be repeated here.

[0034] After obtaining the intermediate carbon product, the present invention mixes the intermediate carbon product, hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia and solvent to carry out a hydrolysis-condensation reaction to obtain a composite product.

[0035] In one embodiment of the present invention, the mass concentration of the ammonia water can be 25-28%.

[0036] In one embodiment of the present invention, the solvent is a mixture of anhydrous ethanol and deionized water. In an embodiment of the present invention, the volume ratio of anhydrous ethanol to deionized water is 30:75.

[0037] In one embodiment of the present invention, the ratio of the mass of the intermediate carbon product, the mass of hexadecyltrimethylammonium bromide, the volume of tetraethyl orthosilicate, the volume of ammonia, and the volume of solvent can be (0.15~0.25) g : (0.45~0.55) g : (0.3~0.5) mL : 1 mL : (100~110) mL, or (0.18~0.22) g : (0.48~0.52) g : (0.35~0.45) mL : 1 mL : (102~108) mL, or 0.2 g : 0.4 g : 0.4 mL : 1 mL : 105 mL. By limiting the ratio of the mass of the intermediate carbon product, the mass of hexadecyltrimethylammonium bromide, the volume of tetraethyl orthosilicate, the volume of ammonia, and the volume of solvent to the above ranges, a layer of silica can be coated on the surface of the intermediate carbon product, laying the foundation for the subsequent formation of a mesoporous structure on the surface of the carbon material.

[0038] As one embodiment of the present invention, the mixing process can be as follows: first, the intermediate carbon product is mixed with water for dispersion, then anhydrous ethanol and ammonia are added, then hexadecyltrimethylammonium bromide is added and stirred, and then tetraethyl orthosilicate is added.

[0039] In one embodiment of the present invention, the dispersion can be ultrasonic dispersion; the ultrasonic dispersion time can be 30-35 minutes. The present invention does not specifically limit the frequency of the ultrasonic dispersion; any ultrasonic frequency commonly used by those skilled in the art can be used.

[0040] In one embodiment of the present invention, the stirring time for adding hexadecyltrimethylammonium bromide can be 30 minutes. The present invention does not impose a particular limitation on the stirring speed; stirring speeds commonly used by those skilled in the art can be employed.

[0041] In one embodiment of the present invention, the addition rate of tetraethyl orthosilicate can be 0.6~1.0 mL / min, 0.7~0.9 mL / min, or 0.8 mL / min. Limiting the addition rate of tetraethyl orthosilicate to the above range allows for better reaction.

[0042] In one embodiment of the present invention, the temperature of the hydrolysis-condensation reaction can be 25~35℃, specifically 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, or 35℃; the time of the hydrolysis-condensation reaction can be 14~18h, specifically 14h, 15h, 16h, 17h, or 18h. By limiting the temperature and time of the hydrolysis-condensation reaction to the above ranges, the present invention allows for a more complete reaction.

[0043] As one embodiment of the present invention, after the hydrolysis-condensation reaction is completed, the hydrolysis-condensation reaction products can be washed and dried sequentially to obtain a composite product.

[0044] In one embodiment of the present invention, the solvent used for washing can be water or anhydrous ethanol. In an embodiment of the present invention, the washing is performed by alternating between water and anhydrous ethanol. The present invention does not have a particular limitation on the number of washings, as long as the hydrolysis and condensation reaction product is washed until neutral. In one embodiment of the present invention, centrifugation is performed after each washing. The present invention does not have a particular limitation on the speed and time of centrifugation, and centrifugation operations commonly used by those skilled in the art can be used to achieve solid-liquid separation.

[0045] The drying parameter range after washing in this invention is the same as the drying parameter range selected above, and will not be repeated here.

[0046] After obtaining the composite product, the present invention sequentially performs a first acid wash, calcination, and a second acid wash on the composite product to obtain crab shell-based porous carbon.

[0047] In one embodiment of the present invention, the pickling solution used for the first pickling can be an ethanol solution of hydrochloric acid; the mass ratio of hydrochloric acid to ethanol can be (1~2) g: 200 mL, or 1.5 g: 200 mL; the mass concentration of hydrochloric acid can be 36~38%. By limiting the pickling solution used for the first pickling to the above range, the present invention can better remove hexadecyltrimethylammonium bromide from the composite product.

[0048] In one embodiment of the present invention, the temperature of the first pickling can be 65~75℃, and can specifically be 65℃, 66℃, 67℃, 68℃, 69℃, 70℃, 71℃, 72℃, 73℃, 74℃ or 75℃; the time of the first pickling can be 10~14h, and can specifically be 10h, 11h, 12h, 13h or 14h. Limiting the temperature and time of the first pickling to the above ranges in the present invention can better remove hexadecyltrimethylammonium bromide from the composite product.

[0049] As one embodiment of the present invention, the first pickling can be followed by washing and drying.

[0050] The washing and drying after the first pickling in this invention are the same as the washing and drying described above, and will not be repeated here.

[0051] In one embodiment of the present invention, the calcination can be carried out in a tube furnace; the calcination can be carried out in a nitrogen atmosphere; the flow rate of nitrogen in the nitrogen atmosphere can be 200 mL / min; the calcination temperature can be 650~750℃, and can specifically be 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃ or 750℃; the calcination time can be 1.5~2.5h, and can specifically be 1.5h, 1.6h, 1.7h, 1.8h, 1.9h, 2.0h, 2.1h, 2.2h, 2.3h, 2.4h or 2.5h; the heating rate to the calcination temperature can be 4~6℃ / min, and can specifically be 4℃ / min, 4.5℃ / min, 5℃ / min, 5.5℃ / min or 6℃ / min. The present invention limits the calcination atmosphere, temperature, time, and heating rate to the above ranges to achieve sufficient carbonization of the crab shell.

[0052] In one embodiment of the present invention, the pickling solution used for the second pickling can be an aqueous solution of HF; the volume ratio of HF to water in the aqueous solution of HF can be (4~6):15, or specifically 4:15, 4.5:15, 5:15, 5.5:15, or 6:15; the HF is a high-purity reagent with a purity ≥40.0%. By limiting the pickling solution used for the second pickling to the above-mentioned range, the present invention can better remove silica from the calcined product and form a mesoporous structure.

[0053] In one embodiment of the present invention, the temperature of the second pickling can be 20~30℃, and can specifically be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃; the time of the second pickling can be 10~14h, and can specifically be 10h, 11h, 12h, 13h or 14h. Limiting the temperature and time of the second pickling within the above ranges allows for better removal of silica from the calcined product.

[0054] This invention involves reacting an intermediate carbon product formed from crab shell powder with hexadecyltrimethylammonium bromide and tetraethyl orthosilicate to coat the surface of the intermediate carbon product with a layer of silica. Subsequent first acid washing, calcination, and second acid washing remove hexadecyltrimethylammonium bromide and silica from the material, forming a large number of pores on the carbon material, increasing the surface area and pore volume of the porous carbon, and thus improving the electrochemical performance of capacitors made from this porous carbon.

[0055] The present invention also provides a crab shell-based porous carbon prepared by the preparation method described above, wherein the pore structure of the crab shell-based porous carbon includes macropores, mesopores and micropores.

[0056] The present invention also provides the application of the crab shell-based porous carbon described in the above technical solution in capacitors.

[0057] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0058] The raw materials and their sources used in the embodiments and test examples of this invention are shown in Table 1.

[0059] Table 1. Raw materials and their sources used in the examples and test cases.

[0060] The equipment and models used in the embodiments and test examples of this invention are shown in Table 2.

[0061] Table 2. Equipment and models used in the embodiments and test examples.

[0062] Example 1 A method for preparing crab shell-based porous carbon comprises the following steps: (1) After cleaning the crab shells with deionized water, put them into an oven (electric constant temperature drying oven) and dry them at 105℃ for 24h. Crush the dried crab shells with a pulverizer and pass them through an 80-mesh sieve to obtain crab shell powder. Then put the crab shell powder into a corundum boat and transfer it to a tube furnace. Under a nitrogen atmosphere (nitrogen flow rate of 200mL / min), raise the temperature to 300℃ at a heating rate of 5℃ / min. After pre-carbonizing for 2h, cool it. Wash the cooled pre-carbonized product with 2M hydrochloric acid (washing temperature of 25℃, washing time of 6h). Then filter to obtain a solid product. Wash the solid product with deionized water until neutral and put it into an oven to dry at 105℃ for 24h to obtain an intermediate carbon product (denoted as HCB). (2) First, the intermediate carbon product obtained in step (1) is mixed with water and ultrasonically dispersed for 30 min. Then, anhydrous ethanol and ammonia (the mass concentration of ammonia is 25%, and the volume ratio of anhydrous ethanol to deionized water is 30:75) are added. Then, hexadecyltrimethylammonium bromide is added and stirred for 30 min. Then, tetraethyl orthosilicate is added (the addition rate is 0.8 mL / min). The hydrolysis and polycondensation reaction is carried out at 30 °C for 16 h. Then, the hydrolysis and polycondensation reaction product is washed alternately with water and anhydrous ethanol (centrifugation is performed after each washing) until the hydrolysis and polycondensation reaction product is neutral. The final centrifuged product is dried at 105 °C for 24 h to obtain the composite product. The mass ratio of the intermediate carbon product, the mass of hexadecyltrimethylammonium bromide, the volume of tetraethyl orthosilicate, the volume of ammonia, and the volume of the solvent (a mixed solvent of anhydrous ethanol and deionized water) is 0.2 g: 0.4 g: 0.4 mL: 1 mL: 105 mL. (3) The composite product obtained in step (2) is subjected to a first acid wash (the acid wash solution is an ethanol solution of hydrochloric acid, the mass ratio of hydrochloric acid to ethanol is 1.5g:200mL, the mass concentration of hydrochloric acid is 38%, the temperature of the first acid wash is 70℃, and the time of the first acid wash is 12h), the product of the first acid wash is washed (using water and anhydrous ethanol alternately, and centrifuged after each wash) and dried (dried at 105℃ for 24h), and the dried product is calcined (calcination is carried out in a nitrogen atmosphere, and the flow rate of nitrogen in the nitrogen atmosphere is 200mL / min). The calcination temperature was 700°C, the calcination time was 2 hours, and the heating rate to the calcination temperature was 5°C / min. The calcined product was subjected to a second acid wash (the acid wash solution was an aqueous solution of HF, the volume ratio of HF to water in the aqueous solution was 5:15, the second acid wash temperature was 25°C, and the second acid wash time was 12 hours). The product after the second acid wash was washed (alternating between water and anhydrous ethanol, and centrifuged after each wash) and dried (dried at 105°C for 24 hours) to obtain crab shell-based porous carbon (denoted as HCB@SiO2-M).

[0063] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that the first acid wash was not performed in step (3). The rest is the same as in Example 1. The resulting crab shell-based porous carbon is denoted as HCB@SiO2.

[0064] Test case (a) The morphology, structure and elemental distribution of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1 and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 were observed and analyzed using X-ray spectroscopy scanning electron microscopy (Gemini300 thermal field emission scanning electron microscope) and energy dispersive spectroscopy (EDS) (Oxford X-MAX).

[0065] The SEM image of the intermediate carbon product (HCB) in Example 1 is shown below. Figure 1 As shown, the left image is magnified 10,000 times, and the right image is magnified 30,000 times; the SEM image of the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1 is shown below. Figure 2 As shown, the left image is magnified 10,000 times, and the right image is magnified 30,000 times; the SEM image of the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 is shown below. Figure 3 As shown, the left image is magnified by 10,000 times, and the right image is magnified by 30,000 times.

[0066] from Figures 1-3As can be seen, the surface of HCB is uneven, exhibiting a peeling, lamellar structure with pores primarily of macropore or mesopore size and relatively smooth carbon walls. This phenomenon is largely due to the inward contraction of the crab shell after a period of heating. HCB@SiO2, compared to HCB, possesses a richer pore structure and no longer exhibits a lamellar structure. This is likely because the presence of hard silica prevents drastic deformation within the crab shell structure and provides a "confined space" for the conversion between organic and carbonaceous materials. However, the overall pore structure is still relatively sparse. This may be because the presence of the silicon layer prevents volatiles from escaping the "confined space" during pyrolysis, causing some volatile carbonaceous substances to deposit on the material surface, negatively impacting pore formation. The SEM image of HCB@SiO2-M shows that the material pyrolyzed after removing CTAB also exhibits some degree of pore development. The results indicate the presence of numerous interconnected small pores on the macropore walls, all of which are mesopore size. This suggests that removing CTAB is more conducive to pore formation. This may be because the removal of CTAB creates numerous mesoporous channels in the "confined space" covered by the silicon layer, forming a semi-open closed condition. This allows the volatiles in the crab shell to escape from the "confined space" at a relatively suitable rate during pyrolysis. HCB@SiO2-M exhibits a hierarchical porous structure, which is beneficial for accelerating the homogeneous diffusion of ions and improving the rate performance of the material.

[0067] (ii) The internal structural state of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 were observed using a high-resolution transmission electron microscope (HRTEM).

[0068] TEM image of the intermediate carbon product (HCB) in Example 1 is shown below. Figure 4 As shown; the TEM image of crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1 is shown below. Figure 5 As shown; the TEM image of crab shell-based porous carbon (HCB@SiO2-M) in Example 1 is shown below. Figure 6 As shown, the left image is magnified by 300,000 times, and the right image is magnified by 3,000,000 times.

[0069] from Figures 4-6 It can be seen that HCB exhibits a relatively compact structure, while the HCB@SiO2 and HCB@SiO2-M structures are more loose and dispersed. This verifies that the silica layer effectively inhibits the severe inward deformation of the crab shell structure. Figure 6 The left image shows the distribution of micropores on HCB@SiO2-M. Furthermore, many ordered mesoporous structures with large specific surface areas were also observed, thus reducing the resistance to ion transport. Additionally, high-magnification TEM images of HCB@SiO2-M (…) Figure 6 (See right image) Some short-range ordered graphitized regions can be observed. Furthermore, the lattice spacing of the carbon material is 0.338 nm, indicating that it possesses a graphitic carbon structure. This ensures the material's good electrical conductivity.

[0070] (III) The pore structures of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 were determined using a surface area and pore size analyzer (ASAP 2460, Micromeritics, Norcross, GA, USA). Before testing, the samples were evacuated at 200°C, and the testing temperature was 77K. Nitrogen gas was used as the adsorbed gas. The surface and pore structures of the nanomaterials were obtained using numerical simulations such as BET (Brunauer-Emmett-Teler) and NLDFT (nonlocal density functional theory).

[0071] The N2 adsorption-desorption curves of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown below. Figure 7 As shown; the pore size distribution diagrams of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are as follows. Figure 8 As shown.

[0072] Detailed parameters of N2 adsorption and desorption of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown in Table 3.

[0073] Table 3. Detailed parameters of N2 adsorption and desorption for the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1.

[0074] from Figures 7-8As shown in Table 3, the material exhibits strong mesoporosity. When the pressure exceeds 0.9, the hysteresis phenomenon increases significantly, which is related to its large porosity and consistent with SEM observations. Appropriate pore size can improve the charge accumulation properties of carbon materials. Figure 8 It can be seen that the pores of all three materials are relatively dense. The surface area and pore volume of each material were analyzed using the BET method, and the results are shown in Table 3. Table 3 shows that, compared to HCB and HCB@SiO2, the carbon material HCB@SiO2-M prepared by removing the hexadecyltrimethylammonium bromide (CTAB) template has the highest specific surface area (319.3 m²). 2 The specific surface area and pore volume of HCB@SiO2 are close to those of HCB. This is consistent with the results in SEM. The difference in pore volume among the three carbon materials indicates that the pore structure concentrated around 4.0 nm in HCB@SiO2 and HCB@SiO2-M mainly comes from the vacancies left by the removed silica.

[0075] (iv) The crystal structures of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 were determined using an X-ray diffractometer (Bruker D8 ADVANCE X-ray diffractometer, Germany). The test conditions were: Cu Kα radiation (λ=0.15406nm), tube voltage of 40kV, scan rate of 10° / min, and scan range of 5°~80°.

[0076] The XRD patterns of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown below. Figure 9 As shown.

[0077] from Figure 9 It can be seen that the X-ray diffraction patterns all exhibit broad spectral diffraction peaks at 24° and 43°, consistent with the (002) and (100) crystal planes, respectively, which are attributed to amorphous carbon, demonstrating the amorphous characteristics of the material. This is consistent with... Figure 6 The TEM results were very consistent. Furthermore, no other peaks were detected in the sample, confirming that the silica "skeleton" and CTAB in the material had been completely removed (CTAB in HCB@SiO2 was removed during calcination).

[0078] (v) The intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 were functionalized using an infrared spectrometer (Nicolex iS10 FT-IR spectrometer).

[0079] The Fourier transform infrared spectra of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown below. Figure 10 As shown; the elemental distribution and individual elemental mapping of the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown below. Figure 11 As shown.

[0080] from Figure 10 It can be seen that 3446cm -1 The absorption peak at 2929 cm⁻¹ corresponds to the intermolecular hydrogen bond (OH bond). -1 The absorption peaks that appear correspond to CH bonds, and the three materials show absorption peaks at 1560 cm⁻¹. -1 A CN absorption peak appears at 1185 cm⁻¹. -1 The absorption peaks at that point correspond to -OH and COC bonds.

[0081] from Figure 11 It can be seen that the heteroatoms in the carbon precursor can be easily utilized through confined pyrolysis, enabling the material to achieve in-situ uniform doping of N and O elements.

[0082] (vi) The intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 were analyzed by X-ray photoelectron spectroscopy (Thermo Fisher Scientific 250Xi). The C1s peak (284.0 eV) was used to calibrate them.

[0083] The XPS total spectra of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are as follows: Figure 12 As shown; the N 1s spectrum peak diagram of crab shell-based porous carbon (HCB@SiO2-M) in Example 1 is shown below. Figure 13 As shown; the O1s spectrum peak diagram of crab shell-based porous carbon (HCB@SiO2-M) in Example 1 is as follows. Figure 14As shown in Table 4, the XPS elemental analysis data of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown in Table 4.

[0084] Table 4. XPS elemental analysis data of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1.

[0085] from Figures 12-14 As shown in Table 4, all samples contained C, N, and O elements, but no peaks related to Si were found, indicating that the silicon was completely removed after etching (second acid washing). Quantitative results are presented in the table. The nitrogen content of each material varied from 6.79% to 7.32%, and the oxygen content ranged from 3.69% to 5.67%. HCB@SiO2-M exhibited relatively abundant surface heteroatoms N (7.32%) and O (3.69%). From... Figure 13 It can be seen that the N 1s spectrum of HCB@SiO2-M has four peaks: Pyridinic N (398.2 eV), Pyrrolic N (400.8 eV), Graphitic N (403.1 eV), and Oxidized N (404.4 eV). This indicates that the N element contained in crab shells was successfully introduced into the carbon framework during the synthesis process. At high temperatures, graphitized nitrogen is both the most stable form of nitrogen and can significantly affect its electrical conductivity. Combining it with pyridine nitrides enhances its pseudocapacitive effect. Figure 14 The O 1s spectrum of HCB@SiO2-M shows peaks at 531.1 eV, 532.5 eV, and 533.8 eV, corresponding to C=O groups, C-OH and / or COC groups, and HOH. The C=O bond enhances the wettability of the carbon material and introduces additional pseudocapacitance, thereby increasing its specific capacitance. These results indicate that co-doping with N and O elements can improve its wettability and conductivity, resulting in high stability.

[0086] (vii) Electrochemical performance testing (1) Preparation method of electrode sheet: Cut the foamed nickel into nickel sheets of 1cm×2cm, then soak them in anhydrous ethanol and sonicate them for 30min to remove surface grease. After cleaning, place them in a vacuum drying oven at 55℃ to dry for later use. Mix the prepared carbon material with acetylene black and polytetrafluoroethylene in a weight ratio of 8:1:1. Add an appropriate amount of 50% ethanol solution and grind it repeatedly in a mortar to form a uniformly dispersed viscous slurry. Use a spatula to evenly coat the viscous slurry onto the surface of the treated foamed nickel block. After the ethanol has completely evaporated, press the foamed nickel block under a pressure of 15MPa for 60 seconds to obtain a thin sheet. Place the thin sheet in an oven at 105℃ and dry for 12h to obtain the final working electrode. Tests were conducted in a three-electrode system. The electrolyte was 6M KOH, the working electrode was the prepared carbon material electrode, the auxiliary electrode was a platinum electrode, and the reference electrode was a Hg / HgO electrode.

[0087] 1) Cyclic voltammetry test: Cyclic voltammetry tests were performed in a potential window from -1.0V to 0V, and the specific capacitance of the electrode material was calculated using formula (1-1).

[0088] (1-1) In the formula, C represents the specific capacitance of the electrode material (F / g), i represents the current density (A / g), and v represents the voltage sweep rate (V / s).

[0089] 2) Constant Current Charge-Discharge Test: Constant current charging and discharging tests are conducted under a voltage window of -1.0V to 0V. The true capacity of the battery can be obtained through a constant charge / discharge curve. Based on this, the charge-discharge characteristics are studied by measuring the specific capacity during the charge-discharge process, and the calculation formula is shown in equation (1-2): (1-2) In the formula, C represents the specific capacitance of the electrode material (F / g), and I represents the discharge current (A). The value represents the discharge time (s), and m represents the total mass of active material (g). This represents the voltage difference after deducting the voltage drop IR.

[0090] 3) AC impedance test: The AC impedance test is performed under open circuit voltage, frequency range of 0.01Hz to 100kHz, and amplitude of 5mV.

[0091] The CV curves of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 at a scan rate of 5 mV / s are shown below. Figure 15 As shown; the CV plot at a scan rate of 200 mV / s is as follows. Figure 16 As shown. From Figure 15 and 16 As can be seen, the CV curves of the three samples all exhibit a rectangular shape, indicating that all three materials mainly exhibit double-layer capacitance characteristics. However, redox peaks appear at -0.3V and -0.7V, indicating that the materials also possess certain pseudocapacitive characteristics. At scan rates of 5mV / s and 200mV / s, the CV curve of HCB@SiO2-M has the largest enclosing area compared to the other two materials, indicating that HCB@SiO2-M has excellent capacitance characteristics.

[0092] The specific capacity of the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 as a function of current density are shown in the graph below. Figure 17 As shown. From Figure 17 It can be seen that HCB@Si O2 The -M electrode exhibits higher specific capacitance values ​​than other electrodes, demonstrating superior charge-discharge performance. During cycling, it exhibits excellent rate performance due to its low ion conduction resistance and small diffusion path.

[0093] The GCD diagrams of three electrodes prepared from the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 at a current density of 0.5 A / g are shown below. Figure 18 As shown, the GCD diagram at a current density of 20 A / g is as follows. Figure 19 As shown in the figure, calculations show that HCB@SiO2-M achieves a specific capacitance of 134.3 F / g at a current density of 0.5 A / g, which is greater than that of HCB@SiO2 (88.1 F / g) and HCB (107.0 F / g). HCB and HCB@SiO2 exhibit poorer performance due to their smaller specific surface area and lower pore volume. At a current density of 20 A / g, HCB@SiO2-M also achieves a specific capacitance of 72.8 F / g, which is greater than the other two samples.

[0094] The Nyquist plots of the electrodes prepared from the intermediate carbon product (HCB) in Example 1, the crab shell-based porous carbon (HCB@SiO2) in Comparative Example 1, and the crab shell-based porous carbon (HCB@SiO2-M) in Example 1 are shown below. Figure 20 As shown. From Figure 20As can be seen, the HCB@SiO2-M electrode exhibits the steepest linear curve, indicating better capacity and facilitating ion transport within the battery at a lower series impedance. In the higher frequency range, the radius of the semicircle coincides with the charge transport resistance Rct. This curve shows that the Rct of the HCB@SiO2-M electrode is lower than that of HCB and HCB@SiO2. This is because the porosity of the HCB@SiO2-M carbon mass serves as a convenient pathway for electrolyte transport, reducing carrier transport resistance and resulting in a lower Rct.

[0095] The CV curves of the electrode prepared by crab shell-based porous carbon (HCB@SiO2-M) in Example 1 at different scan rates are shown in the figure below. Figure 21 As shown, the GCD curves under different current densities are as follows: Figure 22 As shown. From Figure 21 and 22 It can be seen that the closed area of ​​the HCB@SiO2-M electrode continuously increases with the increase of scan rate, and a pseudocapacitive peak appears in its current-voltage characteristic between -0.7V and -0.3V, indicating that the nitrogen doping and oxygen atoms underwent a redox reaction. HCB@SiO2-M exhibits an extremely symmetrical triangular structure at different current densities, demonstrating excellent double-layer capacitance characteristics and enabling high-rate charge transport.

[0096] (2) Assembly of the supercapacitor device: Two electrode plates (HCB@SiO2-M) with similar active material mass were selected as the positive and negative electrodes of the aqueous symmetrical supercapacitor. They were assembled in the order of "positive electrode shell - positive electrode plate - separator - negative electrode plate - gasket - spring plate - negative electrode shell" and installed into a CR2032 button cell case. Sufficient electrolyte was added inside. The button cell was sealed into a button shape using a button cell sealing machine to form an aqueous symmetrical supercapacitor (HCB@SiO2-M / / HCB@SiO2-M). The test was conducted in a two-electrode system, where the electrolyte was 3M KOH and the separator was an aqueous separator (NKK-MPF30AC-100). The assembled supercapacitor needed to stand for 24 hours before the test to ensure that the electrolyte was fully impregnated.

[0097] The supercapacitor was subjected to cyclic voltammetry and constant current charge-discharge tests within a potential window of 0V to 1.2V. The formulas for determining the specific capacitance in the cyclic voltammetry and constant current charge-discharge tests are the same as those in formulas (1-1) and (1-2).

[0098] Furthermore, in the performance evaluation of assembled supercapacitor devices, energy density and power density are calculated using formulas (1-3) and (1-4).

[0099] (1-3) In the formula, E represents the energy density (Wh / kg), C represents the specific capacitance of the electrode material (F / g), and V represents the potential difference during the discharge time (V).

[0100] (1-4) In the formula, P represents power density (W / kg) and E represents energy density (Wh / kg). This indicates the discharge time (s).

[0101] The CV curves of HCB@SiO2-M / / HCB@SiO2-M at different voltage sweep rates are shown in the figure. Figure 23 As shown, from Figure 23 As can be seen, HCB@SiO2-M / / HCB@SiO2-M exhibits good rectangular characteristics. At different scanning speeds, the shape of HCB@SiO2-M / / HCB@SiO2-M does not undergo significant deformation, demonstrating good capacitance performance and low internal resistance.

[0102] The GCD curves of HCB@SiO2-M / / HCB@SiO2-M at different current densities are shown in the figure. Figure 24 As shown. From Figure 24 It can be seen that, over a wide range, HCB@SiO2-M / / HCB@SiO2-M exhibits a symmetrical triangular structure with negligible IR drop, indicating that it has good double-layer capacitance characteristics.

[0103] The Nyquist plot of HCB@SiO2-M / / HCB@SiO2-M is shown below. Figure 25 As shown. From Figure 25 As can be seen, the HCB@SiO2-M / / HCB@SiO2-M device exhibits ideal capacitive behavior in the low-frequency region. The high-frequency region shows a transition from the vertical curve to the 45° Warburg region, as well as a semi-circular graph representing the charge transfer resistance Rct, indicating that HCB@SiO2-M / / HCB@SiO2-M can undergo rapid charge transfer.

[0104] The specific capacitance curves of HCB@SiO2-M / / HCB@SiO2-M at different current densities are shown in the figure below. Figure 26 As shown. From Figure 26 It can be seen that the specific capacitance of the device is 69.6 F / g when the current density is 0.5 A / g, and 10 F / g when the current density increases to 20 A / g. This indicates that the HCB@SiO2-M / / HCB@SiO2-M device has excellent rate performance.

[0105] The energy density and power density of HCB@SiO2-M / / HCB@SiO2-M can be calculated using formulas (1-3) and (1-4). The Ragone plot of HCB@SiO2-M / / HCB@SiO2-M is shown below. Figure 27 As shown. From Figure 27 It can be seen that HCB@SiO2-M / / HCB@SiO2-M achieves an energy density of 3.48 Wh / kg at a power density of 307.06 W / kg, and maintains an energy density of 0.5 Wh / kg even at a power density of 18000 W / kg. The performance of HCB@SiO2-M / / HCB@SiO2-M devices is similar to that of materials prepared by similar methods.

[0106] The cycling performance of HCB@SiO2-M / / HCB@SiO2-M at a current density of 1A / g is shown in the figure below. Figure 28 As shown. From Figure 28 It can be seen that, at a current density of 1 A / g, after 5000 cycles, the capacitance of the device can be maintained at 98.8% of the initial capacitance, indicating that it has excellent cycle stability, which is crucial for energy storage devices.

[0107] The surface area of ​​the crab shell-based porous carbon prepared by the method provided in this invention can reach 319.3 m². 2 g -1 The pore volume can reach 0.314 cm. 3 g -1 It possesses high surface area and pore volume; in a three-electrode system, the specific capacitance of the crab shell-based porous carbon in 6M KOH electrolyte at 0.5A / g is 134.3F / g. The supercapacitor assembled with crab shell-based porous carbon as the electrode material retains 98.81% of its initial capacitance after 5000 cycles at a current density of 1A / g; at a power density of 307.06W / kg, the energy density can reach 3.48Wh / kg, and at a power density of 18000W / kg, the energy density can still be maintained at 0.5Wh / kg, demonstrating excellent electrochemical performance.

[0108] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing crab shell-based porous carbon, comprising the following steps: (1) Pre-carbonize the crab shell powder to obtain intermediate carbon products; (2) The intermediate carbon product obtained in step (1), hexadecyltrimethylammonium bromide, tetraethyl orthosilicate, ammonia and solvent are mixed and subjected to hydrolysis and polycondensation reaction to obtain a composite product; (3) The composite product obtained in step (2) is subjected to first acid washing, calcination and second acid washing in sequence to obtain crab shell-based porous carbon.

2. The preparation method according to claim 1, characterized in that, The particle size of the crab shell powder in step (1) is ≤0.18mm.

3. The preparation method according to claim 1, characterized in that, In step (1), the pre-carbonization temperature is 280~320℃, the pre-carbonization time is 1.5~2.5h, and the heating rate to the pre-carbonization temperature is 4~6℃ / min.

4. The preparation method according to claim 1, characterized in that, The ratio of the mass of the intermediate carbon product, the mass of hexadecyltrimethylammonium bromide, the volume of tetraethyl orthosilicate, the volume of ammonia, and the volume of solvent in step (2) is (0.15~0.25) g : (0.45~0.55) g : (0.3~0.5) mL : 1 mL : (100~110) mL.

5. The preparation method according to claim 1, characterized in that, The temperature of the hydrolysis-condensation reaction in step (2) is 25~35℃, and the time of the hydrolysis-condensation reaction is 14~18h.

6. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the first pickling is 65~75℃ and the time of the first pickling is 10~14h.

7. The preparation method according to claim 1, characterized in that, In step (3), the calcination temperature is 650~750℃, the calcination time is 1.5~2.5h, and the heating rate to the calcination temperature is 4~6℃ / min.

8. The preparation method according to claim 1, characterized in that, The temperature of the second pickling in step (3) is 20~30℃, and the time of the second pickling is 10~14h.

9. The crab shell-based porous carbon prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The pore structure in the crab shell-based porous carbon includes macropores, mesopores, and micropores.

10. The application of the crab shell-based porous carbon of claim 9 in a capacitor.

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