Preparation method and application of N / S co-doped hierarchical pore carbon material

Abstract

The invention discloses a preparation method and application of an N / S co-doped hierarchical porous carbon material. The preparation method comprises the following steps: 1, purifying beta-cyclodextrin; 2, dissolving the purified beta-cyclodextrin, adding a cross-linking agent and ethanol to initiate cross-linking, carrying out phase separation, replacing the solvent, and freeze-drying to obtain a poly (beta-CD-co-HDI) integral material; 3, the poly (beta-CD-co-HDI) integral material is subjected to solvent replacement in a thiourea solution, freeze drying is performed after filtration, and a composite hierarchical porous material is obtained; 4, directly mixing the composite hierarchical porous material with an activating agent, or pre-carbonizing in a nitrogen atmosphere, cooling, mixing with the activating agent, and activating in the nitrogen atmosphere; and 5, carrying out acid pickling and drying on the activated product to obtain the N / S co-doped hierarchical porous carbon material. The prepared N / S co-doped hierarchical porous carbon material can be used as a supercapacitor electrode material, has excellent electrochemical performance and has great application potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of new energy materials, and specifically relates to a preparation method and application of a N / S co-doped multi-level porous carbon material. Background Art

[0002] Supercapacitors are a new type of energy storage device between batteries and traditional capacitors, with long service life and fast charging and discharging capabilities. Although supercapacitors exhibit higher power density than the current mainstream lithium-ion batteries (Advanced Functional Materials, 2023, 33 (14): 2213095.), their limited charge storage capacity greatly limits the energy density. Therefore, it is urgent to develop new supercapacitor electrode materials with excellent performance and green environmental protection (Chemical Engineering Journal, 2024, 499: 156693.). Supercapacitor electrode materials mainly include carbon-based materials, metal oxides, conductive polymers, etc. Among them, carbon-based electrode materials prepared using biomass as precursors have the advantages of rich pores, high conductivity, green preparation methods and low cost, and have been widely studied. However, traditional biomass-based carbon materials often cannot meet the needs of high energy density energy storage. Current research shows that the performance of carbon materials can be significantly improved by doping with heteroatoms such as N, S, P, and B, and redox active substances can be modified on the surface of carbon materials. The polarized chemical bonds formed between the surface defect sites of carbon materials and the redox species can produce a synergistic effect, which can not only effectively reduce the electrode / electrolyte interface energy and improve the wetting characteristics of electrolyte ions on the carbon electrode surface, but also enhance the overall electrochemical performance of the material by providing additional pseudocapacitive contribution (The Chemical Record, 2024, 24(1): e202300153.). Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a preparation method and application of N / S co-doped multi-level porous carbon material in view of the deficiencies of the above-mentioned prior art. The N / S co-doped multi-level porous carbon material prepared by the present invention can be used as a supercapacitor electrode material, and has excellent electrochemical properties. In a 1mol / L H2SO4 electrolyte, when the current density is 0.5A / g, the maximum specific capacitance can reach 521F / g, and the coulomb efficiency is 96% at this time. After 10,000 charge and discharge cycles at a current density of 10A / g, the capacity retention rate is 91%. The N / S co-doped multi-level porous carbon material has great application potential as a supercapacitor electrode material.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing N / S co-doped hierarchical porous carbon material, characterized in that it comprises the following steps:

[0005] Step 1, purifying β-cyclodextrin to remove insoluble impurities to obtain purified β-cyclodextrin;

[0006] Step 2: dissolving the purified β-cyclodextrin in step 1 in N,N-dimethylformamide, adding hexamethylene diisocyanate as a cross-linking agent, adding ethanol as a poor solvent to initiate cross-linking, performing solvent replacement with deionized water after phase separation, and freeze-drying to obtain a poly(β-CD-co-HDI) monolithic material;

[0007] Step 3, the poly (β-CD-co-HDI) monolithic material obtained in step 2 is subjected to solvent replacement in a thiourea solution, filtered and freeze-dried to obtain a poly (β-CD-co-HDI) / thiourea composite hierarchical porous material;

[0008] Step 4: pre-carbonize the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step 3 under a nitrogen atmosphere, take out the pre-carbonized product after cooling to room temperature, mix it with an activator, add water and perform rotary evaporation to dry it, and then activate it under a nitrogen atmosphere; or mix the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step 3 with an activator, add water and perform rotary evaporation to dry it, and then activate it under a nitrogen atmosphere;

[0009] Step 5: acid-wash and dry the product activated in step 4 to obtain a N / S co-doped hierarchical porous carbon material.

[0010] The above-mentioned method for preparing a N / S co-doped hierarchical porous carbon material is characterized in that the specific method of the purification treatment in step 1 includes:

[0011] Step 101, dissolving β-cyclodextrin in 85°C to 95°C distilled water to saturation, filtering to remove insoluble impurities while hot, cooling the filtrate to room temperature, refrigerating at 2°C to 6°C for 5h to 15h, and vacuum drying;

[0012] Step 102, repeating the method of step 101 2 to 4 times on the β-cyclodextrin dried in step 101 to obtain purified β-cyclodextrin.

[0013] The above-mentioned method for preparing a N / S co-doped multi-level porous carbon material is characterized in that the ratio of the mass of purified β-cyclodextrin to the volume of hexamethylene diisocyanate in step 2 is 1:3 to 3:1, wherein the unit of mass is g, the unit of volume is mL, and the volume of ethanol is 0.5% to 2% of the total volume of the cross-linking system; the temperature of the phase separation in step 2 is 70°C to 85°C, the time is 6h to 15h, and the solvent replacement process includes soaking in deionized water for no more than 48h.

[0014] The above-mentioned method for preparing a N / S co-doped hierarchical porous carbon material is characterized in that the concentration of the thiourea solution in step three is not greater than 3 mol / L, and the solvent replacement time does not exceed 24 hours.

[0015] The above-mentioned method for preparing a N / S co-doped hierarchical porous carbon material is characterized in that the pre-carbonization temperature in step 4 is 200°C to 500°C, the heating rate is 5°C / min to 20°C / min, and the pre-carbonization time does not exceed 2h.

[0016] The above-mentioned method for preparing a N / S co-doped hierarchical porous carbon material is characterized in that the mass ratio of the pre-carbonized product to the activator in step four is 1:(0.5~5), the amount of water added is 10mL / g~50mL / g, the activation temperature is 600℃~800℃, the heating rate is 5℃ / min~20℃ / min, and the time is 1h~3h.

[0017] The above-mentioned method for preparing a N / S co-doped hierarchical porous carbon material is characterized in that the activator described in step 4 is one or more of potassium hydroxide, sodium hydroxide, phosphoric acid and zinc chloride.

[0018] The above-mentioned method for preparing a N / S co-doped hierarchical porous carbon material is characterized in that the nitrogen flow rate in the pre-carbonization and activation stages in step 4 is 10 mL / min to 120 mL / min.

[0019] Furthermore, the present invention provides an application of the N / S co-doped multi-level porous carbon material prepared by the above method in a supercapacitor electrode.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. The present invention adopts β-cyclodextrin (β-CD) with a hydrophobic inner cavity structure, and uses a hexamethyldisilazane diisocyanate (HDI) crosslinking agent to perform a chemical crosslinking reaction. The isocyanate group (-NCO) of HDI will react with the hydroxyl group (-OH) of β-CD to crosslink the β-CD molecules together to obtain a poly (β-CD-co-HDI) overall material, thereby improving the molecular weight and stability of the β-CD monomer; then, a thiourea solution is used to perform solvent replacement on the poly (β-CD-co-HDI) overall material, and the thiourea molecules can enter the interior of the material through the rich macroporous structure of the poly (β-CD-co-HDI) overall material. The hydrophobic interaction, hydrogen bonding and van der Waals force between β-CD and thiourea molecules can make the thiourea molecules uniformly adhere to the interior of the material, and then freeze-drying is performed to obtain a poly (β-CD-co-HDI) / thiourea composite multi-level porous material; finally, a pre-carbonization and activation process is performed at high temperature to obtain an N / S co-doped multi-level porous carbon material.

[0022] 2. The β-CD used in the present invention is a biomass material with a wide source and low price. It has a unique hydrophobic cavity structure. When solvent replacement is carried out with a thiourea solution, the non-polar part of the thiourea molecule enters its cavity through the hydrophobic force, which can improve the uniformity of the thiourea molecules in the poly (β-CD-co-HDI) overall material, thereby largely solving the problems of difficult control and unevenness of heteroatom doping using traditional methods (such as mixing methods).

[0023] 3. The N / S co-doped multilevel porous carbon material prepared by the present invention can be used as a supercapacitor electrode material and has excellent electrochemical properties. In a 1 mol / L H2SO4 electrolyte, when the current density is 0.5 A / g, the maximum specific capacitance can reach 521 F / g, and the coulombic efficiency is 96%. After 10,000 charge and discharge cycles at a current density of 10 A / g, the capacity retention rate is 91%. The N / S co-doped multilevel porous carbon material has great application potential as a supercapacitor electrode material.

[0024] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a scanning electron microscope image of the poly(β-CD-co-HDI) monolithic material prepared in Example 1 (a is magnified 50,000 times, b is magnified 25,000 times, and c is magnified 10,000 times).

[0026] Figure 2 This is a scanning electron microscope image of the poly(β-CD-co-HDI) / thiourea-1-700-3N / S co-doped hierarchical porous carbon material prepared in Example 1.

[0027] Figure 3 Transmission electron microscope image and energy spectrum image of the poly (β-CD-co-HDI) / thiourea-1-700-3N / S co-doped hierarchical porous carbon material prepared in Example 1.

[0028] Figure 4 These are nitrogen adsorption / desorption isotherms of the N / S co-doped hierarchical porous carbon materials prepared in Examples 1 to 5.

[0029] Figure 5 This is a pore size distribution diagram of the N / S co-doped hierarchical porous carbon material prepared in Examples 1 to 5.

[0030] Figure 6 Constant current charge and discharge curves of N / S co-doped multi-level porous carbon materials prepared in Examples 1 to 3 at different activation temperatures (700° C., 650° C., and 750° C., respectively).

[0031] Figure 7Constant current charge-discharge curves of N / S co-doped multi-level porous carbon materials with thiourea solutions of different concentrations (1 mol / L, 0.5 mol / L, and 1.5 mol / L, respectively) prepared in Example 1, Example 4, and Example 5.

[0032] Figure 8 This is a cyclic stability test curve of the poly(β-CD-co-HDI) / thiourea-1-700-3N / S co-doped hierarchical porous carbon material prepared in Example 1. DETAILED DESCRIPTION

[0033] The present invention is described in detail below by way of examples, which are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Experimental methods without specific conditions in the examples are usually carried out according to conventional conditions and conditions described in the manual, or according to conditions recommended by the manufacturer; the equipment, materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial sources.

[0034] Example 1

[0035] Preparation of N / S co-doped hierarchical porous carbon material poly(β-CD-co-HDI) / thiourea-1-700-3:

[0036] Step 1: purifying β-cyclodextrin (hereinafter referred to as β-CD) to remove insoluble impurities. The specific method includes:

[0037] Step 101, dissolving β-CD in 90° C. distilled water to saturation, filtering while hot to remove insoluble impurities, cooling the filtrate to room temperature, refrigerating at 4° C. for 10 h, and vacuum drying;

[0038] Step 102, repeating the method of step 1 for 3 times on the β-CD dried in step 101 to obtain purified β-cyclodextrin;

[0039] Step 2: Add 1 g of the purified β-CD obtained in step 2 to 10 mL of N,N-dimethylformamide (DMF), dissolve it by ultrasound, and slowly add 1 mL of hexamethyldisilazane diisocyanate (HDI) to the dissolved solution under stirring at room temperature to fully dissolve and mix the HDI to form a uniform solution; then add 100 μL of ethanol to the above solution and mix it thoroughly, pour the mixed solution into a centrifuge tube, phase separate at 75°C for 10 hours, the solution gradually turns into a gel state, and cools to room temperature; the cooled gel state material is solvent replaced with deionized water for 1 day, and the deionized water is replaced every hour for the first three times; then, collect the sample, put it in a refrigerator, and freeze it at -20°C overnight; then freeze-dry it for 48 hours to obtain a poly (β-CD-co-HDI) monolithic material;

[0040] Step 3: Cut the poly(β-CD-co-HDI) monolithic material prepared in step 2 into small segments of about 1 cm, weigh 1 g, put it into a 1 mol / L thiourea solution for solvent replacement for 4 hours, then filter out the thiourea solution, and freeze-dry the monolithic material after solvent replacement for 48 hours to obtain a poly(β-CD-co-HDI) / thiourea composite hierarchical porous material;

[0041] Step 4: Place the poly (β-CD-co-HDI) / thiourea composite multi-level porous material obtained in step 3 into a tubular furnace, and heat it to 400 ° C at a heating rate of 5 ° C / min and a gas flow rate of 100 mL / min under a N2 atmosphere, and then pre-carbonize it for 1 hour; after cooling to room temperature, mix the pre-carbonized carbon material with KOH (NaOH can also be used instead) in a mass ratio of 1:3. In order to make the activation process more complete, add 50 mL of deionized water to 1 g of the mixture, and perform rotary evaporation to completely evaporate the deionized water; then place the evaporated mixture in a tubular furnace, and heat it to 700 ° C at a heating rate of 5 ° C / min and a gas flow rate of 100 mL / min under a N2 atmosphere, and keep it warm for 2 hours;

[0042] Step 5. Use dilute hydrochloric acid solution and deionized water to thoroughly wash the product obtained in step 4 until the product is neutral, collect the product, and dry it overnight at 105°C to obtain a N / S co-doped multi-level porous carbon material, recorded as poly(β-CD-co-HDI) / thiourea-1-700-3, where "1" refers to the thiourea concentration (mol / L), "700" refers to the activation temperature (°C), and "3" refers to the KOH ratio.

[0043] The SEM test results of the poly(β-CD-co-HDI) monolithic material prepared in this example are shown in Figure 1 ,As can be seen from the figure, the prepared poly(β-CD-co-HDI) monolithic material has a rich and interconnected three-dimensional network structure.

[0044] Figure 2 This is a scanning electron microscope image of the N / S co-doped multi-level porous carbon material prepared in this embodiment. The test results show that the prepared N / S co-doped multi-level porous carbon material has a honeycomb multi-level porous structure. Figure 3 Transmission electron microscope image and energy spectrum of the prepared N / S co-doped multi-level porous carbon material. The test results show that N and S atoms are uniformly doped in the carbon matrix. The specific surface area of ​​the N / S co-doped multi-level porous carbon material measured by nitrogen adsorption is 2451m 2 / g(see Figure 4 ), pore volume is 1.35cm 3 / g, average pore size 2.20nm (see Figure 5 ).

[0045] The N / S co-doped multi-level porous carbon material prepared in this embodiment was mixed with acetylene black and polytetrafluoroethylene in a mass ratio of 80:10:10, and then ethanol was added to grind to obtain a paste. The paste was evenly applied to the surface of 1cm×1cm nickel foam. The mass of N / S co-doped multi-level porous carbon material applied to each nickel foam was 2.5mg. The nickel foam after application was placed in a vacuum drying oven at 105°C for 12h, and the electrochemical performance was tested in a three-electrode system after tableting at a pressure of 10MPa. In 1mol / LH2SO4 electrolyte, when the current density is 0.5A / g, the specific capacitance can reach 521F / g (see Figure 6 and Figure 7 ), the coulombic efficiency is 96%. After 10,000 cycles of constant current charge and discharge at a current density of 10A / g, the specific capacitance can still be maintained above 91% (see Figure 8 ).

[0046] Example 2

[0047] Preparation of N / S co-doped hierarchical porous carbon material poly(β-CD-co-HDI) / thiourea-1-650-3:

[0048] This embodiment is the same as embodiment 1, except that in step 4, the evaporated mixture is placed in a tube furnace, heated to 650°C under a N2 atmosphere at a heating rate of 5°C / min and a gas flow rate of 100 mL / min, and kept warm for 2 h.

[0049] The specific surface area of ​​the N / S co-doped hierarchical porous carbon material of this embodiment was measured by gas adsorption method to be 1247 m 2 / g(see Figure 4 ), pore volume is 0.85cm 3 / g, average pore size 2.24nm (see Figure 5 ). After testing (electrode preparation and electrochemical performance test are the same as in Example 1), in 1 mol / L H2SO4 electrolyte, when the current density is 0.5A / g, the specific capacitance can reach 466F / g (see Figure 6 ).

[0050] Example 3

[0051] Preparation of N / S co-doped hierarchical porous carbon material poly(β-CD-co-HDI) / thiourea-1-750-3:

[0052] This embodiment is the same as embodiment 1, except that in step 4, the evaporated mixture is placed in a tube furnace, heated to 750°C under a N2 atmosphere at a heating rate of 5°C / min and a gas flow rate of 100 mL / min, and kept warm for 2 hours.

[0053] The specific surface area of ​​the N / S co-doped hierarchical porous carbon material of this embodiment was measured by gas adsorption method to be 2839 m 2 / g(see Figure 4 ), pore volume is 1.61cm 3 / g, average pore size 2.37nm (see Figure 5 ). After testing (electrode preparation and electrochemical performance test are the same as in Example 1), in 1 mol / L H2SO4 electrolyte, when the current density is 0.5A / g, the specific capacitance can reach 503F / g (see Figure 6 ).

[0054] Example 4

[0055] Preparation of N / S co-doped hierarchical porous carbon material poly(β-CD-co-HDI) / thiourea-0.5-700-3:

[0056] This embodiment is the same as embodiment 1, except that in step 3, the poly(β-CD-co-HDI) monolithic material is cut into small segments of about 1 cm, 1 g is weighed, and placed in a 0.5 mol / L thiourea solution for solvent replacement for 4 hours, then the thiourea solution is filtered out, and the monolithic material after solvent replacement is freeze-dried for 48 hours.

[0057] The specific surface area of ​​the N / S co-doped hierarchical porous carbon material of this embodiment was measured by gas adsorption method to be 2353 m 2 / g(see Figure 4 ), pore volume is 1.38cm 3 / g, average pore size 2.31nm (see Figure 5 ). After testing (electrode preparation and electrochemical performance test are the same as in Example 1), in 1 mol / L H2SO4 electrolyte, when the current density is 0.5A / g, the specific capacitance can reach 414F / g (see Figure 7 ).

[0058] Example 5

[0059] Preparation of N / S co-doped hierarchical porous carbon material poly(β-CD-co-HDI) / thiourea-1.5-700-3:

[0060] This embodiment is the same as embodiment 1, except that in step 3, the poly(β-CD-co-HDI) monolithic material is cut into small segments of about 1 cm, 1 g is weighed, and placed in a 1.5 mol / L thiourea solution for solvent replacement for 4 hours, then the thiourea solution is filtered out, and the monolithic material after solvent replacement is freeze-dried for 48 hours.

[0061] The specific surface area of ​​the N / S co-doped hierarchical porous carbon material of this embodiment was measured by gas adsorption method to be 2493 m 2 / g(see Figure 4), pore volume is 1.36cm 3 / g, average pore size 2.32nm (see Figure 5 ). After testing (electrode preparation and electrochemical performance test are the same as in Example 1), in 1 mol / L H2SO4 electrolyte, when the current density is 0.5A / g, the specific capacitance can reach 483F / g (see Figure 7 ).

[0062] Example 6

[0063] Preparation of N / S co-doped hierarchical porous carbon material poly(β-CD-co-HDI) / thiourea-3-800-5:

[0064] Step 1: purifying β-cyclodextrin (hereinafter referred to as β-CD) to remove insoluble impurities. The specific method includes:

[0065] Step 101, dissolving β-CD in 85°C distilled water to saturation, filtering to remove insoluble impurities while hot, cooling the filtrate to room temperature, refrigerating at 2°C for 5h, and vacuum drying;

[0066] Step 102, repeating the method of step 1 twice on the β-CD dried in step 101 to obtain purified β-cyclodextrin;

[0067] Step 2: Add 1 g of the purified β-CD obtained in step 2 to 10 mL of N,N-dimethylformamide (DMF), dissolve it by ultrasound, and slowly add 3 mL of hexamethyldisilazane diisocyanate (HDI) to the dissolved solution under stirring at room temperature to fully dissolve and mix the HDI to form a uniform solution; then add 260 μL of ethanol to the above solution and mix it thoroughly, pour the mixed solution into a centrifuge tube, phase separate at 70°C for 15 hours, the solution gradually turns into a gel state, and cools to room temperature; the cooled gel state material is subjected to solvent replacement with deionized water for 48 hours, and the deionized water is replaced every hour for the first three times; thereafter, the sample is collected, placed in a refrigerator, and frozen overnight at -20°C; and then freeze-dried for 48 hours to obtain a poly (β-CD-co-HDI) monolithic material;

[0068] Step 3: Cut the poly(β-CD-co-HDI) monolithic material prepared in step 2 into small segments of about 1 cm, weigh 1 g, put it into a 3 mol / L thiourea solution for solvent replacement for 24 hours, then filter out the thiourea solution, and freeze-dry the monolithic material after solvent replacement for 48 hours to obtain a poly(β-CD-co-HDI) / thiourea composite hierarchical porous material;

[0069] Step 4: Place the poly (β-CD-co-HDI) / thiourea composite multi-level porous material obtained in step 3 into a tubular furnace, heat it to 500 ° C at a heating rate of 20 ° C / min and a gas flow rate of 120 mL / min under a N2 atmosphere, and then pre-carbonize it for 2 hours; after cooling to room temperature, mix the pre-carbonized carbon material with zinc chloride in a mass ratio of 1:5. In order to make the activation process more complete, add 10 mL of deionized water to 1 g of the mixture, perform rotary evaporation, and completely evaporate the deionized water; then place the evaporated mixture in a tubular furnace, heat it to 800 ° C at a heating rate of 20 ° C / min and a gas flow rate of 120 mL / min under a N2 atmosphere, and keep it warm for 1 hour;

[0070] Step 5. Use dilute hydrochloric acid solution and deionized water to thoroughly wash the product obtained in step 4 until the product is neutral, collect the product, and dry it overnight at 105°C to obtain a N / S co-doped multi-level porous carbon material, recorded as poly(β-CD-co-HDI) / thiourea-3-800-5, where "3" refers to the thiourea concentration (mol / L), "800" refers to the activation temperature (°C), and "5" refers to the zinc chloride ratio.

[0071] The various properties of the N / S co-doped multi-level porous carbon material prepared in this example are basically consistent with those in Example 5, and it has great application potential as a supercapacitor electrode material.

[0072] Example 7

[0073] Preparation of N / S co-doped hierarchical porous carbon material poly(β-CD-co-HDI) / thiourea-1-600-0.5:

[0074] Step 1: purifying β-cyclodextrin (hereinafter referred to as β-CD) to remove insoluble impurities. The specific method includes:

[0075] Step 101, dissolving β-CD in 95°C distilled water to saturation, filtering while hot to remove insoluble impurities, cooling the filtrate to room temperature, refrigerating at 6°C for 15h, and vacuum drying;

[0076] Step 102, repeating the method of step 1 for 4 times on the β-CD dried in step 101 to obtain purified β-cyclodextrin;

[0077] Step 2: Add 3 g of the purified β-CD obtained in step 2 to 30 mL of N,N-dimethylformamide (DMF), dissolve it by ultrasound, and slowly add 1 mL of hexamethyldisilazane diisocyanate (HDI) to the dissolved solution under stirring at room temperature to fully dissolve and mix the HDI to form a uniform solution; then add 150 μL of ethanol to the above solution and mix it thoroughly, pour the mixed solution into a centrifuge tube, phase separate at 85°C for 6 hours, the solution gradually turns into a gel state, and cools to room temperature; the cooled gel state material is solvent replaced with deionized water for 12 hours, and the deionized water is replaced every hour for the first three times; then, collect the sample, put it in a refrigerator, and freeze it at -20°C overnight; then freeze-dry it for 48 hours to obtain a poly (β-CD-co-HDI) monolithic material;

[0078] Step 3: Cut the poly(β-CD-co-HDI) monolithic material prepared in step 2 into small segments of about 1 cm, weigh 1 g, put it into a 1 mol / L thiourea solution for solvent replacement for 4 hours, then filter out the thiourea solution, and freeze-dry the monolithic material after solvent replacement for 48 hours to obtain a poly(β-CD-co-HDI) / thiourea composite hierarchical porous material;

[0079] Step 4: Place the poly (β-CD-co-HDI) / thiourea composite multi-level porous material obtained in step 3 into a tubular furnace, and heat it to 200 ° C at a heating rate of 10 ° C / min and a gas flow rate of 10 mL / min under a N2 atmosphere, and then pre-carbonize for 2.5 hours; after cooling to room temperature, mix the pre-carbonized carbon material with phosphoric acid in a mass ratio of 1: 0.5. In order to make the activation process more complete, add 30 mL of deionized water to 1 g of the mixture, and perform rotary evaporation to completely evaporate the deionized water; then place the evaporated mixture in a tubular furnace, and heat it to 600 ° C at a heating rate of 10 ° C / min and a gas flow rate of 10 mL / min under a N2 atmosphere, and keep it warm for 3 hours;

[0080] Step 5. Use dilute hydrochloric acid solution and deionized water to thoroughly wash the product obtained in step 4 until the product is neutral, collect the product, and dry it overnight at 105°C to obtain a N / S co-doped multi-level porous carbon material, recorded as poly(β-CD-co-HDI) / thiourea-1-600-0.5, where "1" refers to the thiourea concentration (mol / L), "600" refers to the activation temperature (°C), and "0.5" refers to the phosphoric acid ratio.

[0081] The various properties of the N / S co-doped multi-level porous carbon material prepared in this example are basically consistent with those in Example 4, and it has great application potential as a supercapacitor electrode material.

[0082] Example 8

[0083] This embodiment is the same as Example 7, except that: in step 4, no pre-carbonization is performed, and the poly (β-CD-co-HDI) / thiourea composite multi-level porous material obtained in step 3 is directly mixed with phosphoric acid in a mass ratio of 1:0.5. In order to make the activation process more complete, 30 mL of deionized water is added to 1 g of the mixture, and rotary evaporation is performed to completely evaporate the deionized water; the evaporated mixture is then placed in a tubular furnace, and the temperature is increased to 600 ° C. under a N2 atmosphere at a heating rate of 10 ° C. / min and a gas flow rate of 10 mL / min, and kept warm for 3 hours.

[0084] The various properties of the N / S co-doped multi-level porous carbon material prepared in this example are basically consistent with those in Example 4, and it has great application potential as a supercapacitor electrode material.

[0085] The N / S co-doped multilevel porous carbon material prepared by the present invention using poly (β-CD-co-HDI) / thiourea composite multilevel porous material as a precursor realizes uniform co-doping distribution of N and S atoms in the matrix, and at the same time exhibits high specific surface area, excellent electrochemical performance and good cycle stability, demonstrating its broad application prospects and commercial value as an electrode material in the field of energy storage devices.

[0086] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a N / S co-doped hierarchical porous carbon material, characterized in that: The following steps are involved: Step 1, purifying β-cyclodextrin to remove insoluble impurities to obtain purified β-cyclodextrin; Step 2: dissolving the purified β-cyclodextrin in step 1 in N,N-dimethylformamide, adding hexamethylene diisocyanate as a cross-linking agent, adding ethanol as a poor solvent to initiate cross-linking, performing solvent replacement with deionized water after phase separation, and freeze-drying to obtain a poly(β-CD-co-HDI) monolithic material; Step 3, the poly (β-CD-co-HDI) monolithic material obtained in step 2 is subjected to solvent replacement in a thiourea solution, filtered and freeze-dried to obtain a poly (β-CD-co-HDI) / thiourea composite hierarchical porous material; Step 4: pre-carbonize the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step 3 under a nitrogen atmosphere, take out the pre-carbonized product after cooling to room temperature, mix it with an activator, add water and perform rotary evaporation to dry it, and then activate it under a nitrogen atmosphere; or mix the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step 3 with an activator, add water and perform rotary evaporation to dry it, and then activate it under a nitrogen atmosphere; Step 5: acid-wash and dry the product activated in step 4 to obtain a N / S co-doped hierarchical porous carbon material.

2. The method for preparing a N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that: The specific method of the purification process described in step 1 includes: Step 101, dissolving β-cyclodextrin in 85°C to 95°C distilled water to saturation, filtering to remove insoluble impurities while hot, cooling the filtrate to room temperature, refrigerating at 2°C to 6°C for 5h to 15h, and vacuum drying; Step 102, repeating the method of step 101 2 to 4 times on the β-cyclodextrin dried in step 101 to obtain purified β-cyclodextrin.

3. The method for preparing a N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that: The ratio of the mass of the purified β-cyclodextrin to the volume of hexamethylene diisocyanate in step 2 is 1:3 to 3:1, wherein the unit of mass is g, the unit of volume is mL, and the volume of ethanol is 0.5% to 2% of the total volume of the cross-linking system; the temperature of the phase separation in step 2 is 70° C. to 85° C., the time is 6 h to 15 h, and the solvent replacement process includes soaking in deionized water for no more than 48 h.

4. The method for preparing a N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that: The concentration of the thiourea solution in step 3 is not greater than 3 mol / L, and the solvent replacement time is not more than 24 h.

5. The method for preparing a N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that: The pre-carbonization temperature in step 4 is 200°C to 500°C, the heating rate is 5°C / min to 20°C / min, and the pre-carbonization time does not exceed 2h.

6. The method for preparing a N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that: In step 4, the mass ratio of the pre-carbonized product to the activator is 1:(0.5-5), the amount of water added is 10 mL / g-50 mL / g, the activation temperature is 600°C-800°C, the heating rate is 5°C / min-20°C / min, and the time is 1h-3h.

7. The method for preparing a N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that: The activator described in step 4 is one or more of potassium hydroxide, sodium hydroxide, phosphoric acid and zinc chloride.

8. The method for preparing a N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that: The nitrogen flow rates in the pre-carbonization and activation stages in step 4 are both 10 mL / min to 120 mL / min.

9. Use of the N / S co-doped multi-level porous carbon material prepared by the method as claimed in claim 1 in a supercapacitor electrode.

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