Preparation method and application of n / s co-doped hierarchical porous carbon material

Abstract

The application discloses a preparation method and application of N / S co-doped multi-level pore carbon material, and comprises the following steps: firstly, purifying beta-cyclodextrin; secondly, dissolving the purified beta-cyclodextrin, adding a crosslinking agent and ethanol to initiate crosslinking, replacing the solvent after phase separation, and freeze-drying to obtain a poly(beta-CD-co-HDI) integrated material; thirdly, replacing the solvent of the poly(beta-CD-co-HDI) integrated material in a thiourea solution, filtering, and freeze-drying to obtain a composite multi-level pore material; fourthly, directly mixing the composite multi-level pore material with an activating agent, or pre-carbonizing under a nitrogen atmosphere, mixing with the activating agent after cooling, and activating under the nitrogen atmosphere; and fifthly, acid-washing the activated product, drying, and obtaining the N / S co-doped multi-level pore carbon material. The prepared N / S co-doped multi-level pore carbon material can be used as an electrode material of a super capacitor, has excellent electrochemical performance, and has great application potential.

Description

TECHNICAL FIELD

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

[0002] Super capacitors are a new type of energy storage device between batteries and traditional capacitors, which have long service life and fast charging and discharging capacity. Although super capacitors show higher power density compared with the current mainstream lithium ion batteries (Advanced Functional Materials, 2023, 33(14): 2213095.), the limited charge storage capacity greatly limits the energy density. Therefore, it is urgent to develop new super capacitor electrode materials with excellent performance and green environmental protection (Chemical Engineering Journal, 2024, 499: 156693.). Super capacitor electrode materials mainly include carbon-based materials, metal oxides, conductive polymers, etc.; among them, the carbon-based electrode materials prepared by taking biomass as a precursor have the advantages of rich pores, high conductivity, green and low-cost preparation method, etc., and thus are widely studied. However, the traditional biomass-based carbon materials are often difficult to meet the energy storage needs of high energy density. Current studies show that doping N, S, P, B and other heteroatoms can significantly improve the performance of carbon materials, and realize the modification of redox active substances on the surface of carbon materials. The polarization chemical bonds formed between the defect sites on the surface of carbon materials and the redox substances can produce a synergistic effect, which not only can effectively reduce the electrode / electrolyte interface energy, improve the wetting characteristics of electrolyte ions on the surface of carbon electrodes, but also can contribute to the overall electrochemical performance of the material by providing additional pseudo-capacitance (The Chemical Record, 2024, 24(1): e202300153.). SUMMARY

[0003] The technical problem to be solved by the present application is to provide a preparation method and application of N / S co-doped multi-level porous carbon material to solve the problems of the prior art. The N / S co-doped multi-level porous carbon material prepared by the present application can be used as a super capacitor electrode material, which has excellent electrochemical performance. In a 1 mol / L H2SO4 electrolyte, the highest specific capacitance can reach 521 F / g at a current density of 0.5 A / g, the coulombic efficiency is 96% at this time, and the capacity retention rate is 91% after 10,000 cycles of charging and discharging at a current density of 10 A / g. The N / S co-doped multi-level porous carbon material has great application potential as a super capacitor electrode material.

[0004] To solve the above technical problems, the technical scheme adopted by the present application is: a preparation method of N / S co-doped multi-level porous carbon material, characterized in that it comprises the following steps:

[0005] Step one, purifying β-cyclodextrin to remove insoluble impurities, obtaining purified β-cyclodextrin;

[0006] Step two, dissolving the purified β-cyclodextrin in step one in N,N-dimethylformamide, adding hexamethylene diisocyanate as a crosslinking agent, adding ethanol as a poor solvent to initiate crosslinking, after phase separation, using deionized water for solvent replacement, freeze-drying to obtain poly(β-CD-co-HDI) monolithic material;

[0007] Step three, carrying out solvent replacement of the poly(β-CD-co-HDI) monolithic material obtained in step two in a thiourea solution, filtering and freeze-drying to obtain a poly(β-CD-co-HDI) / thiourea composite hierarchical porous material;

[0008] Step four, pre-carbonizing the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three under a nitrogen atmosphere, cooling to room temperature, taking out the pre-carbonized product, mixing with an activating agent, adding water and performing rotary evaporation drying, and then activating under a nitrogen atmosphere; or mixing the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three with an activating agent, adding water and performing rotary evaporation drying, and then activating under a nitrogen atmosphere;

[0009] Step five, acid washing the activated product in step four and drying to obtain an N / S co-doped hierarchical porous carbon material.

[0010] The preparation method of the N / S co-doped hierarchical porous carbon material described above, characterized in that the specific method of the purification treatment in step one comprises:

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

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

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

[0014] The preparation method of the N / S co-doped multi-level porous carbon material has the advantages that: the concentration of the thiourea solution in the third step is not more than 3 mol / L, and the solvent replacement time is not more than 24 h.

[0015] The preparation method of the N / S co-doped multi-level porous carbon material has the advantages that: the temperature of the pre-carbonization in the fourth step is 200-500 DEG C, the heating rate is 5-20 DEG C / min, and the pre-carbonization time is not more than 2 h.

[0016] The preparation method of the N / S co-doped multi-level porous carbon material has the advantages that: the mass ratio of the pre-carbonized product to the activating agent in the fourth step is 1:(0.5-5), the water addition amount is 10-50 mL / g, the activation temperature is 600-800 DEG C, the heating rate is 5-20 DEG C / min, and the time is 1-3 h.

[0017] The preparation method of the N / S co-doped multi-level porous carbon material has the advantages that: the activating agent in the fourth step is one or more of potassium hydroxide, sodium hydroxide, phosphoric acid and zinc chloride.

[0018] The preparation method of the N / S co-doped multi-level porous carbon material has the advantages that: the nitrogen flow rate in the pre-carbonization and activation stages in the fourth step is 10-120 mL / min.

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

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

[0021] 1. The application adopts β-cyclodextrin (β-CD) with a hydrophobic inner cavity structure, and performs chemical cross-linking reaction by using hexamethylene diisocyanate (HDI) cross-linking agent; the isocyanate groups (-NCO) of the HDI can react with the hydroxyl groups (-OH) of the β-CD to cross-link the β-CD molecules together, so that the molecular weight and stability of the β-CD monomers are improved; then, the poly(β-CD-co-HDI) monolithic material is subjected to solvent replacement by using a thiourea solution; the thiourea molecules can enter the material interior through the abundant macroporous structure of the poly(β-CD-co-HDI) monolithic material; the hydrophobic interaction, hydrogen bond interaction and van der Waals force between the β-CD and the thiourea molecules can make the thiourea molecules uniformly adhere to the material interior; after freeze-drying, the poly(β-CD-co-HDI) / thiourea composite multi-level porous material is obtained; finally, the N / S co-doped multi-level porous carbon material is obtained through the pre-carbonization and activation processes at high temperature.

[0022] 2. The β-CD used in the application is a biomass material, which is widely available and low in price. It has a unique hydrophobic cavity structure. When solvent replacement is performed with a thiourea solution, the nonpolar part of the thiourea molecule enters the cavity inside the material by hydrophobic force, which can improve the uniformity of the thiourea molecule in the poly(β-CD-co-HDI) monolithic material, thereby greatly solving the problems of difficult control and non-uniformity of doping heteroatoms by using traditional methods (such as mixing method).

[0023] 3. The N / S co-doped hierarchical porous carbon material prepared in the application can be used as an electrode material for supercapacitors, which has excellent electrochemical performance. In a 1 mol / L H2SO4 electrolyte, the highest specific capacitance can reach 521 F / g at a current density of 0.5 A / g, and the coulombic efficiency is 96% at this time. The capacity retention rate is 91% after 10,000 cycles of charge and discharge at a current density of 10 A / g. The N / S co-doped hierarchical porous carbon material has great application potential as an electrode material for supercapacitors.

[0024] The technical solutions of the application will be further described in detail below in combination with the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

[0028] Figure 4 Nitrogen adsorption / desorption isotherm curves of the N / S co-doped hierarchical porous carbon materials prepared in Examples 1-5.

[0029] Figure 5 Pore size distribution graphs of the N / S co-doped hierarchical porous carbon materials prepared in Examples 1-5.

[0030] Figure 6 Galvanostatic charge / discharge curves of the N / S co-doped hierarchical porous carbon materials prepared in Examples 1-3 at different activation temperatures (700℃, 650℃, and 750℃, respectively).

[0031] Figure 7Galvanostatic charge-discharge curves of N / S co-doped hierarchical porous carbon materials prepared by different concentrations of thiourea solution (1 mol / L, 0.5 mol / L, 1.5 mol / L) for Example 1, Example 4, Example 5.

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

[0033] The application will be described in detail below by way of examples, which are only used to further illustrate the application and cannot be understood as limiting the scope of protection of the application. The experimental methods not specified in the examples are usually carried out according to the conventional conditions and the conditions described in the manual, or according to the conditions suggested by the manufacturer; the equipment, materials, reagents, etc. used, if not specially specified, can be obtained from commercial channels.

[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 one, purify β-cyclodextrin (hereinafter referred to as β-CD) to remove insoluble impurities, the specific method includes:

[0037] Step 101, dissolve β-CD in 90℃ distilled water to saturation, filter out insoluble impurities while hot, cool the filtrate to room temperature, then store at 4℃ for 10h, and vacuum dry;

[0038] Step 102, repeat the drying β-CD after step 101 according to the method of step one for 3 times to obtain purified β-cyclodextrin;

[0039] Step two, add 1g of purified β-CD of step two into 10mL of N,N-dimethylformamide (DMF), and ultrasonically dissolve it, slowly add 1mL of hexamethylene diisocyanate (HDI) into the dissolved solution under stirring at room temperature, so that the HDI is fully dissolved and mixed to form a uniform solution; then add 100μL of ethanol into the above solution and mix well, pour the mixed solution into a centrifuge tube, and separate the phases at 75℃ for 10h, the solution gradually changes to a gel state, and cool to room temperature; replace the solvent of the cooled gel state material with deionized water for 1 day, and change the deionized water every hour for the first three times; then collect the sample, put it in the refrigerator, and freeze at-20℃ overnight; then freeze-dry for 48h to obtain poly(β-CD-co-HDI) monolithic material;

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

[0041] Step four, put the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three into a tube furnace, heat to 400℃ at a heating rate of 5℃ / min under N2 atmosphere, and then pre-carbonize for 1 h; after cooling to room temperature, mix the pre-carbonized carbon material with KOH (NaOH can also be used instead) according to a mass ratio of 1:3, add 50 mL of deionized water to 1 g of the mixture in order to make the activation process more sufficient, and perform rotary evaporation to completely evaporate the deionized water; then put the evaporated mixture into a tube furnace, heat to 700℃ at a heating rate of 5℃ / min under N2 atmosphere, and keep the temperature for 2 h at a gas flow rate of 100 mL / min;

[0042] Step five, wash the product obtained in step four with dilute hydrochloric acid solution and deionized water until the product is neutral, collect the product, and dry it at 105℃ overnight to obtain an N / S co-doped hierarchical porous carbon material, which is denoted as poly(β-CD-co-HDI) / thiourea-1-700-3, wherein "1" refers to the thiourea concentration (mol / L), "700" refers to the activation temperature (℃), and "3" refers to the KOH ratio.

[0043] The scanning electron microscopy 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 three-dimensional network structure.

[0044] Figure 2 The scanning electron microscopy test results of the N / S co-doped hierarchical porous carbon material prepared in this example show that the prepared N / S co-doped hierarchical porous carbon material has a honeycomb-like hierarchical porous structure. Figure 3 The transmission electron microscopy and energy spectrum of the prepared N / S co-doped hierarchical porous carbon material show that N and S atoms are uniformly doped in the carbon matrix. The nitrogen adsorption method shows that the specific surface area of the N / S co-doped hierarchical porous carbon material is 2451 m 2 / g (see Figure 4 ), the pore volume is 1.35 cm 3 / g, and the average pore size is 2.20 nm (see Figure 5 ).

[0045] The N / S co-doped hierarchical porous carbon material prepared in this example was mixed with acetylene black and polytetrafluoroethylene in a mass ratio of 80:10:10, and then ground with ethanol to obtain a paste. The paste was evenly applied to the surface of a 1 cm x 1 cm nickel foam, and the mass of the N / S co-doped hierarchical porous carbon material on each nickel foam was 2.5 mg. The nickel foam coated with the paste was dried in a vacuum drying oven at 105°C for 12 h, and then pressed into a tablet under a pressure of 10 MPa. The electrochemical performance was tested in a three-electrode system. In a 1 mol / L H2SO4 electrolyte, the specific capacitance was 521 F / g at a current density of 0.5 A / g (see Figure 6 and Figure 7 ), and the coulombic efficiency was 96% at this time. After 10,000 cycles of galvanostatic charge and discharge at a current density of 10 A / g, the specific capacitance could still be maintained at more than 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 example is the same as Example 1, except that in step four, the mixture after evaporation was placed in a tube furnace, heated to 650°C at a rate of 5°C / min under a N2 atmosphere, and the gas flow rate was 100 mL / min, and the temperature was maintained for 2 h.

[0049] The specific surface area of the N / S co-doped hierarchical porous carbon material in this example was 1247 m 2 / g (see Figure 4 ), the pore volume was 0.85 cm 3 / g, and the average pore size was 2.24 nm (see Figure 5 ). After testing (the electrode preparation and electrochemical performance testing were the same as in Example 1), in a 1 mol / L H2SO4 electrolyte, the specific capacitance was 466 F / g at a current density of 0.5 A / 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 example is the same as Example 1, except that in step four, the mixture after evaporation was placed in a tube furnace, heated to 750°C at a rate of 5°C / min under a N2 atmosphere, and the gas flow rate was 100 mL / min, and the temperature was maintained for 2 h.

[0053] The specific surface area of ​​the N / S co-doped hierarchical porous carbon material in this embodiment, as measured by gas adsorption, is 2839 m². 2 / g (see Figure 4 The pore volume is 1.61 cm. 3 / g, with an average pore size of 2.37nm (see Figure 5 According to tests (electrode preparation and electrochemical performance testing were the same as in Example 1), in a 1 mol / L H2SO4 electrolyte, at a current density of 0.5 A / g, the specific capacitance can reach 503 F / 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 three, 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 h, then the thiourea solution is filtered off, and the monolithic material after solvent replacement is freeze-dried for 48 h.

[0057] The specific surface area of ​​the N / S co-doped hierarchical porous carbon material in this embodiment, as measured by gas adsorption, is 2353 m². 2 / g (see Figure 4 The pore volume is 1.38 cm. 3 / g, with an average pore size of 2.31nm (see Figure 5 According to the test (electrode preparation and electrochemical performance testing were the same as in Example 1), in a 1 mol / L H2SO4 electrolyte, at a current density of 0.5 A / g, the specific capacitance can reach 414 F / g (see Example 1). 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 three, 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 h, then the thiourea solution is filtered off, and the monolithic material after solvent replacement is freeze-dried for 48 h.

[0061] The specific surface area of ​​the N / S co-doped hierarchical porous carbon material in this embodiment, as measured by gas adsorption, is 2493 m². 2 / g (see Figure 4), pore volume is 1.36 cm 3 / g, average pore size is 2.32 nm (see Figure 5 ). After testing (electrode preparation and electrochemical performance test are the same as example 1), in 1 mol / L H2SO4 electrolyte, the specific capacitance can reach 483 F / g at a current density of 0.5 A / 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 one, purify β-cyclodextrin (hereinafter referred to as β-CD) to remove insoluble impurities, the specific method includes:

[0065] Step 101, dissolve β-CD in 85℃ distilled water to saturation, filter out insoluble impurities while hot, cool the filtrate to room temperature, then store at 2℃ for 5h, and vacuum dry;

[0066] Step 102, repeat the method of step one for 2 times for the dried β-CD of step 101 to obtain purified β-cyclodextrin;

[0067] Step two, add 1g of purified β-CD of step two into 10mL of N,N-dimethylformamide (DMF), and ultrasonically dissolve it, then slowly add 3mL of hexamethylene diisocyanate (HDI) into the dissolved solution under stirring at room temperature, so that the HDI is fully dissolved and mixed to form a uniform solution; then add 260μL of ethanol into the above solution and mix well, pour the mixed solution into a centrifuge tube, and separate the phases at 70℃ for 15h, the solution gradually changes into a gel state, and cool to room temperature; use deionized water to replace the solvent for 48h for the cooled gel state material, and change the deionized water every hour for the first three times; then collect the sample, and freeze it at-20℃ overnight; then freeze dry for 48h to obtain poly(β-CD-co-HDI) monolithic material;

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

[0069] Step four, the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three was placed in a tube furnace, and heated to 500℃ at a heating rate of 20℃ / min under N2atmosphere, with a gas flow rate of 120mL / min, and then pre-carbonized for 2h; after cooling to room temperature, the pre-carbonized carbon material was mixed with zinc chloride at a mass ratio of 1:5, and 10mL of deionized water was added to 1g of the mixture in order to make the activation process more complete, and the deionized water was completely evaporated by rotary evaporation; the mixture after evaporation was placed in a tube furnace, and heated to 800℃ at a heating rate of 20℃ / min under N2atmosphere, with a gas flow rate of 120mL / min, and then kept for 1h;

[0070] Step five, the product obtained in step four was washed with dilute hydrochloric acid solution and deionized water until the product was neutral, and the product was collected and dried at 105℃ overnight to obtain an N / S co-doped hierarchical porous carbon material, denoted as poly(β-CD-co-HDI) / thiourea-3-800-5, wherein "3" refers to the concentration of thiourea (mol / L), "800" refers to the activation temperature (℃), and "5" refers to the ratio of zinc chloride.

[0071] The N / S co-doped hierarchical porous carbon material prepared in this example has basically the same performance as that of Example 5, and has great application potential as an electrode material for supercapacitors.

[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 one, the β-cyclodextrin (hereinafter referred to as β-CD) was purified to remove insoluble impurities, and the specific method included:

[0075] Step 101, β-CD was dissolved in distilled water at 95℃ to saturation, and the insoluble impurities were removed by hot filtration. The filtrate was cooled to room temperature and then refrigerated at 6℃ for 15h, and then vacuum dried;

[0076] Step 102, the dried β-CD obtained in step 101 was repeated 4 times according to the method of step one to obtain purified β-cyclodextrin;

[0077] Step two, 3 g of purified β-CD of step two was added into 30 mL of N,N- dimethylformamide (DMF) and dissolved by ultrasonic, 1 mL of hexamethylene diisocyanate (HDI) was slowly added into the dissolved solution under stirring at room temperature, and the HDI was fully dissolved and mixed to form a uniform solution; then 150 μL of ethanol was added into the above solution and fully mixed, and the mixture was poured into a centrifuge tube, phase separation was carried out at 85℃ for 6 h, and the solution gradually changed into a gel state, and cooled to room temperature; the cooled gel state material was solvent exchanged with deionized water for 12 h, and the deionized water was replaced every hour for the first three times; then, the sample was collected and placed in a refrigerator and frozen at -20℃ overnight; and then freeze-dried for 48 h to obtain a poly(β-CD-co-HDI) monolithic material;

[0078] Step three, the poly(β-CD-co-HDI) monolithic material prepared in step two was cut into small pieces of about 1 cm, 1 g was weighed and placed in a 1 mol / L thiourea solution for solvent exchange for 4 h, and then the thiourea solution was filtered off, and the solvent-exchanged monolithic material was freeze-dried for 48 h to obtain a poly(β-CD-co-HDI) / thiourea composite hierarchical porous material;

[0079] Step four, the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three was placed in a tube furnace, and heated to 200℃ at a heating rate of 10℃ / min under N2 atmosphere at a gas flow rate of 10 mL / min, and then pre-carbonized for 2.5 h; after cooling to room temperature, the pre-carbonized carbon material was mixed with phosphoric acid at a mass ratio of 1:0.5, and 30 mL of deionized water was added to 1 g of the mixture for rotary evaporation to completely evaporate the deionized water; then the evaporated mixture was placed in a tube furnace, and heated to 600℃ at a heating rate of 10℃ / min under N2 atmosphere at a gas flow rate of 10 mL / min, and kept for 3 h;

[0080] Step five, the product obtained in step four was washed with dilute hydrochloric acid solution and deionized water until the product was neutral, and the product was collected and dried at 105℃ overnight to obtain an N / S co-doped hierarchical porous carbon material, which was recorded as poly(β-CD-co-HDI) / thiourea-1-600-0.5, wherein "1" refers to the concentration of thiourea (mol / L), "600" refers to the activation temperature (℃), and "0.5" refers to the proportion of phosphoric acid.

[0081] The N / S co-doped hierarchical porous carbon material prepared in this example has basically the same performance as that of Example 4, and has great application potential as an electrode material for supercapacitors.

[0082] Example 8

[0083] The present example is the same as example 7, except that in step four, no pre-carbonization is performed, and the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three is directly mixed with phosphoric acid at a mass ratio of 1:0.5. In order to enable the activation process to be 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 mixture after evaporation is placed in a tube furnace, and heated to 600°C at a temperature increase rate of 10°C / min under a N2 atmosphere, with a gas flow rate of 10 mL / min, and held for 3 h.

[0084] The N / S co-doped hierarchical porous carbon material prepared in the present example has substantially the same performance as that of example 4, and has great application potential as an electrode material for supercapacitors.

[0085] The N / S co-doped hierarchical porous carbon material prepared by using the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material as a precursor realizes uniform co-doping of N and S atoms in the matrix, and simultaneously exhibits a high specific surface area, excellent electrochemical performance and good cycle stability, and shows a wide application prospect and commercial value as an electrode material in the field of energy storage devices.

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

Claims

1. A method for preparing N / S co-doped hierarchical porous carbon material, characterized in that, The method comprises the following steps: Step one, purifying β-cyclodextrin to remove insoluble impurities and obtaining purified β-cyclodextrin; Step two, dissolving the purified β-cyclodextrin in step one in N,N-dimethylformamide, adding hexamethylene diisocyanate as a crosslinking agent, adding ethanol as a poor solvent to initiate crosslinking, performing solvent replacement with deionized water after phase separation, and freeze-drying to obtain poly(β-CD-co-HDI) monolithic material; Step three, performing solvent replacement of the poly(β-CD-co-HDI) monolithic material obtained in step two in a thiourea solution, filtering and freeze-drying to obtain poly(β-CD-co-HDI) / thiourea composite hierarchical porous material; Step four, pre-carbonizing the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three under a nitrogen atmosphere, removing the pre-carbonized product after cooling to room temperature, mixing the product with an activating agent, adding water and performing rotary evaporation drying, and then performing activation under a nitrogen atmosphere; or mixing the poly(β-CD-co-HDI) / thiourea composite hierarchical porous material obtained in step three with an activating agent, adding water and performing rotary evaporation drying, and then performing activation under a nitrogen atmosphere; Step five, acid washing the activated product in step four and drying to obtain N / S co-doped hierarchical porous carbon material.

2. The method according to claim 1, wherein, The specific method of the purification treatment in step one comprises: Step 101, dissolving β-cyclodextrin in 85-95°C distilled water until saturation, filtering out insoluble impurities while hot, and cooling the filtrate to room temperature and then refrigerating at 2-6°C for 5-15 hours and vacuum drying; Step 102, repeating the drying of the β-cyclodextrin in step 101 according to the method of step 101 for 2-4 times to obtain purified β-cyclodextrin.

3. The method according to claim 1, wherein, In step two, the mass of the purified β-cyclodextrin to the volume of hexamethylene diisocyanate is 1:3-3:1, wherein the unit of mass is g and the unit of volume is mL, and the volume of ethanol is 0.5%-2% of the total volume of the crosslinking system; the phase separation temperature in step two is 70-85°C, and the time is 6-15 hours, and the solvent replacement process includes deionized water soaking for no more than 48 hours.

4. The method according to claim 1, wherein, In step three, the concentration of the thiourea solution is no more than 3 mol / L, and the solvent replacement time is no more than 24 hours.

5. The method for preparing an N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that, In step four, the pre-carbonization temperature is 200-500°C, the heating rate is 5-20°C / min, and the pre-carbonization time is no more than 2 hours.

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

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

8. The method for preparing an N / S co-doped hierarchical porous carbon material according to claim 1, characterized in that, In step four, the nitrogen flow rate of the pre-carbonization and activation stages is 10-120 mL / min.

9. Use of the N / S co-doped hierarchical porous carbon material prepared by the method of claim 1 as an electrode for supercapacitors.

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