Preparation method of nitrogen, oxygen and sulfur co-doped porous carbon material and porous carbon material and application

Abstract

The invention discloses a preparation method of a nitrogen, oxygen and sulfur co-doped porous carbon material, a porous carbon material and an application thereof. Sodium carboxymethyl cellulose and sodium lignin sulfonate are used as carbon, oxygen and sulfur sources respectively, and a three-dimensional gel network of carboxymethyl cellulose-urea-sodium lignin sulfonate is constructed through hydrogen bond interaction between urea and precursors and electrostatic attraction between divalent zinc ions and carboxylmethyl and sulfonic acid groups, and finally a nitrogen, oxygen and sulfur co-doped porous carbon powder is obtained. The prepared porous carbon material is applied to the field of supercapacitor electrodes. The present invention successfully introduces high content of nitrogen, oxygen and sulfur elements into the carbon skeleton; at the same time, combined with the zinc oxide-potassium hydroxide dual activation strategy, zinc oxide in the pre-carbonization stage provides a mesoporous template, and a porous carbon pore structure is initially formed, and a hierarchical porous carbon material with rich heteroatom content, high specific surface area and high mesoporosity is successfully prepared.

Description

Technical Field

[0001] The present invention relates to a method for preparing a porous carbon material, and in particular to a method for preparing a nitrogen, oxygen and sulfur co-doped porous carbon material, the porous carbon material and applications, and belongs to the technical field of electrode materials for supercapacitors. Background Art

[0002] The continuous changes and progress in the energy field have brought new challenges and opportunities to energy storage and conversion equipment. As an emerging electrochemical energy storage device, supercapacitors have attracted widespread attention due to their excellent stability, high power density and fast charging and discharging characteristics. At present, the market share of supercapacitors at home and abroad is also increasing year by year.

[0003] Supercapacitors store energy by electrostatically adsorbing electrolyte ions on the electrode-electrolyte surface. Therefore, porous carbon electrodes have become the most common electrode materials due to their excellent conductivity, large specific surface area, developed pore structure and abundant precursor sources. The specific surface area and pore structure of porous carbon are crucial to the electrochemical performance of the electrode. Micropores (<2nm) provide the main site for ion adsorption, and mesopores (2-50nm) provide channels for ion diffusion. A major factor restricting pure porous carbon electrode materials is that when relying solely on double-layer energy storage, when the specific surface area exceeds 3000m 2 / g, the resulting specific capacitance is limited (<250F / g).

[0004] Heteroatom doping is one of the main means to improve the wettability, conductivity and pseudocapacitive properties of electrode materials by introducing more defects and active sites on the porous carbon surface. In recent years, in order to improve the electrochemical performance of porous carbon electrodes, more and more researchers have combined pore-forming engineering and doping technology to prepare high-performance porous carbon electrodes. Lin et al. (Science. 2015, 350, 1508-1513) prepared nitrogen-doped ordered porous carbon, and obtained an excellent specific capacitance of 855F / g and a high specific energy density of 41Wh / kg in an aqueous electrolyte system; Wang et al. (ACS Applied Materials & Interfaces. 2022, 14, 9013-9023) used commercial candles, melamine, and sodium dihydrogen phosphate monohydrate as carbon sources, nitrogen sources, and phosphorus sources, respectively, to prepare nitrogen- and phosphorus-co-doped onion-shaped porous carbon, which was applied in zinc ion capacitors. The device obtained a specific capacitance value of 855F / g at a current density of 0.5A / g. When the current density increased to 20A / g, the capacitance retention rate was 63%, and a high energy density of 149.5Wh / kg was obtained. Summary of the invention

[0005] In order to solve the shortcomings of the above-mentioned technology, the present invention provides a preparation method of nitrogen, oxygen and sulfur co-doped porous carbon material and porous carbon material, and application thereof, and prepares high-performance porous carbon material by perfectly combining pore-making engineering and doping design.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a nitrogen, oxygen and sulfur co-doped porous carbon material, comprising the following steps:

[0007] Step 1, dissolving carboxymethyl cellulose, urea and sodium lignin sulfonate in an aqueous solution, and stirring thoroughly to obtain a uniform hydrogel solution;

[0008] Step 2, adjusting the zinc chloride solution to neutral, and adding the adjusted zinc chloride solution to the hydrogel solution in step 1;

[0009] Step 3, adding a crosslinking agent to the hydrogel solution of step 2, and stirring thoroughly to obtain a uniform hydrogel;

[0010] Step 4: freeze-drying the hydrogel in step 3 to obtain carboxymethyl cellulose-urea-sodium lignin sulfonate composite aerogel;

[0011] Step 5: pre-carbonizing the aerogel in step 4 to obtain a pre-carbonized porous material;

[0012] Step 6: activating the pre-carbonized porous carbon material obtained in step 5: dissolving the pre-carbonized porous carbon and potassium hydroxide in deionized water in a certain proportion, stirring thoroughly to obtain a uniform mixed solution, and drying at high temperature to obtain a pre-carbonized porous carbon / potassium hydroxide mixed powder;

[0013] Step 7: subjecting the pre-carbonized porous carbon / potassium hydroxide mixed powder in step 6 to high temperature activation treatment to obtain nitrogen, oxygen, and sulfur co-doped porous carbon / metal oxide composite powder;

[0014] Step 8: Immerse the nitrogen, oxygen, and sulfur co-doped porous carbon / metal oxide composite powder in step 7 in an acid solution, filter, and dry to obtain nitrogen, oxygen, and sulfur co-doped porous carbon powder.

[0015] Preferably, in step 1, the mass ratio of carboxymethyl cellulose, urea and sodium lignin sulfonate is 3:2:3; in step 2, the mass ratio of zinc chloride to carboxymethyl cellulose is (0-2):3, and the pH is adjusted to neutral with aqueous ammonia.

[0016] Preferably, in step three, the cross-linking agent is D-(+) glucono σ-lactone, and the mass ratio of the cross-linking agent to the carboxymethyl cellulose is 1.5:3.

[0017] Preferably, in step 4, the freezing time is 24 hours and the vacuum drying time is 48 hours.

[0018] Preferably, in step five, the pre-carbonization temperature is 600° C., the holding time is 2 hours, the heating rate is 5° C. / min, and the mixture is naturally cooled to room temperature.

[0019] Preferably, in step six, the mass ratio of potassium hydroxide to pre-carbonized porous carbon is 3:1; the pre-carbonized porous carbon / potassium hydroxide mixed solution is placed in an oven at 80° C. for 12 hours, and its water is evaporated to obtain a mixed powder.

[0020] Preferably, in step seven, the activation temperature is 600° C., the holding time is 2 hours, the heating rate is 5° C. / min, and the mixture is naturally cooled to room temperature.

[0021] Preferably, in step eight, the acid solution is hydrochloric acid with a concentration of 3M, and after filtration, it is dried in an oven at 80°C for 12 hours. Hydrochloric acid can wash away residual metal oxides, and excess hydrochloric acid can be evaporated and removed in the high-temperature drying stage, and the influence of impurity elements introduced by hydrochloric acid is smaller.

[0022] A nitrogen, oxygen and sulfur co-doped porous carbon material prepared by the preparation method, wherein the porous carbon material has a micro-mesoporous structure.

[0023] An application of nitrogen, oxygen and sulfur co-doped porous carbon material prepared by the above preparation method, wherein the prepared porous carbon material is applied to the field of supercapacitor electrodes.

[0024] The reaction mechanism of the present invention is:

[0025] Regarding step one: utilize hydrogen bonds between urea molecules to open the aggregation structure of sodium lignin sulfonate and carboxymethyl cellulose, and construct a three-dimensional gel network through hydrogen bonds between urea, carboxymethyl cellulose and sodium lignin sulfonate molecules. At the same time, carboxymethyl cellulose as a carbon / oxygen source, sodium lignin sulfonate as a carbon / sulfur source, and urea as a nitrogen source are conducive to obtaining a porous carbon electrode material with a high heteroatom content.

[0026] Regarding step 2: Use ammonia water to adjust the zinc chloride solution to neutrality. The divalent zinc metal will react with hydroxide ions to form a white precipitate of zinc hydroxide, which can provide a template for zinc hydroxide. At the same time, the excess zinc ions in the solution will complex with the carboxyl and sulfonic acid groups to establish an ordered three-dimensional molecular chain structure.

[0027] Regarding step three: D-(+) glucono σ-lactone increases the cross-linking degree of the gel precursor network through hydrogen bonding with carboxymethyl cellulose and sodium lignin sulfonate.

[0028] Regarding step four: low-temperature freezing combined with vacuum drying removes moisture from the hydrogel. The vacuum-extracted ice crystals leave holes in the original gel network, which is conducive to the subsequent carbonization activation operation.

[0029] Regarding step five: carboxymethyl cellulose and sodium lignin sulfonate can be decomposed to produce inorganic salt templates of sodium carbonate and sodium sulfate under pre-carbonization treatment at 600°C, and zinc hydroxide can undergo a decomposition reaction to produce zinc oxide, both of which can be used as mesoporous templates; at the same time, carboxymethyl cellulose and sodium lignin sulfonate will undergo dehydrogenation and deoxygenation reactions, releasing gases such as carbon dioxide, water vapor, and carbon monoxide, further stripping the gel precursor, thereby leaving microporous channels.

[0030] Regarding step six: Use the inorganic sodium salts, zinc oxide and other metal oxides remaining in the pre-carbonized porous carbon to provide a mesoporous template, and assist the additionally added potassium hydroxide activator to further etch the porous carbon channels.

[0031] Regarding step seven: utilizing the redox reaction between potassium hydroxide and carbon, further etching the carbon material to generate a microporous structure based on the obtained pre-carbonized mesoporous carbon structure, thereby obtaining the target micro-mesoporous hierarchical porous carbon.

[0032] Regarding step eight: The pickling process dissolves and removes impurities such as metal oxides generated after the carbonization-activation process, unclogs the pore structure, and improves the pore utilization rate of porous carbon.

[0033] The present invention selects a self-doped natural polymer derivative that is inexpensive, widely available, and rich in carbon content as a carbon source precursor, and successfully introduces high-content nitrogen, oxygen, and sulfur elements into the carbon skeleton by utilizing the rich heteroatom content in the precursor; at the same time, a zinc oxide-potassium hydroxide dual activation strategy is combined to improve the activation efficiency. In the pre-carbonization stage, zinc oxide provides a mesoporous template to preliminarily form a porous carbon pore structure, which provides a pore structure basis for subsequent potassium hydroxide activation and improves the activation efficiency of the hydrogen oxidizing agent.

[0034] The present invention successfully prepared a hierarchical porous carbon material with rich heteroatom content, high specific surface area and high mesoporosity. The nitrogen, oxygen and sulfur contents were 1.95at% to 6.91at%, 10.28at% to 17.4at%, and 0.35at% to 0.78at%, respectively, and the specific surface area was 511.7m 2 / g~2898.2m 2 / g, and has a high mesopore content of 19.64% to 36.36%, and also provides the application of the self-doped high specific surface area porous carbon material in supercapacitor electrode materials. In a 6M KOH electrolyte three-electrode system, when the current density is 0.1A / g, the specific capacitance can reach up to 342.5F / g. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a nitrogen adsorption-desorption curve of the porous carbon material prepared in Example 1 of the present invention.

[0036] Figure 2This is a pore size distribution curve of the porous carbon material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0037] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0038] The present invention uses sodium carboxymethyl cellulose and sodium lignin sulfonate as carbon, oxygen and sulfur sources respectively, and constructs a three-dimensional gel network of carboxymethyl cellulose-urea-sodium lignin sulfonate through hydrogen bond interaction between urea and precursors and electrostatic attraction between divalent zinc ions and carboxymethyl and sulfonic acid groups. The introduction of metal zinc ions increases the crosslinking degree of the gel network. At the same time, zinc oxide decomposed and formed in the pre-carbonization stage can provide an in-situ mesoporous template, which is conducive to potassium hydroxide in the subsequent activation stage to more fully enter the pores of the carbon material, improve the activation efficiency, and thus prepare a porous carbon material with a higher specific surface area and a more developed pore structure.

[0039] The primary purpose of the present invention is to provide a method for preparing porous carbon with high specific surface area and rich heteroatom content.

[0040] Another object of the present invention is to provide an application of the nitrogen, oxygen and sulfur co-doped porous carbon material in the field of porous carbon electrode materials for supercapacitors.

[0041] The present invention is further described in detail below in conjunction with the examples, but the embodiments of the present invention are not limited thereto. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the reagents or instruments used do not indicate the manufacturer, they are all conventional reagent products that can be obtained commercially.

[0042] Example 1

[0043] Weigh 2g of carboxymethyl cellulose, 1.3g of urea and 2g of sodium lignin sulfonate, add them to 90ml of deionized water, stir them thoroughly for 12 hours to obtain a uniform hydrogel solution; weigh 1.5g of zinc chloride and dissolve it in 10ml of deionized water, adjust the zinc chloride solution to neutrality with ammonia water, add the zinc chloride solution adjusted to neutrality into the prepared carboxymethyl cellulose-urea-sodium lignin sulfonate gel, and continue to stir evenly; weigh 1.5g of D-(+) glucono σ-lactone as a crosslinking agent and add it to the above-prepared gel solution, stir it thoroughly for 12 hours to obtain a uniform carboxymethyl cellulose-urea-sodium lignin sulfonate-zinc hydrogel mixed solution;

[0044] The prepared hydrogel mixed solution was transferred into a mold, freeze-dried for 72 hours to obtain a carboxymethyl cellulose-urea-sodium lignin sulfonate-zinc composite aerogel, and the aerogel was transferred into a quartz tube furnace and heated to 600°C at a heating rate of 5°C / min, and kept warm for 2 hours to obtain a pre-carbonized porous carbon material;

[0045] Pre-carbonized porous carbon and potassium hydroxide activator were dissolved in 20 ml of deionized water in a mass ratio of 1:3, ultrasonicated and fully stirred, placed in an oven at 80°C overnight, and the water was evaporated to obtain a pre-carbonized porous carbon / potassium hydroxide mixed powder;

[0046] The pre-carbonized porous carbon / potassium hydroxide mixed powder obtained above was transferred to a quartz tube furnace, heated to 600°C at a heating rate of 5°C / min, and kept warm for 2 hours. The obtained black porous carbon powder was dissolved in 3M hydrochloric acid, acid-washed overnight, filtered and dried to obtain the final product, nitrogen, oxygen, and sulfur co-doped porous carbon material.

[0047] Example 2

[0048] Weigh 2g of carboxymethyl cellulose, 1.3g of urea and 2g of sodium lignin sulfonate, add them to 90ml of deionized water, stir them thoroughly for 12 hours to obtain a uniform hydrogel solution; weigh 1.0g of zinc chloride and dissolve it in 10ml of deionized water, adjust the zinc chloride solution to neutrality with ammonia water, add the zinc chloride solution adjusted to neutrality into the prepared carboxymethyl cellulose-urea-sodium lignin sulfonate gel, and continue to stir evenly; weigh 1.5g of D-(+) glucono σ-lactone as a crosslinking agent and add it to the above-prepared gel solution, stir it thoroughly for 12 hours to obtain a uniform carboxymethyl cellulose-urea-sodium lignin sulfonate-zinc hydrogel mixed solution;

[0049] The prepared hydrogel mixed solution was transferred into a mold, freeze-dried for 72 hours to obtain a carboxymethyl cellulose-urea-sodium lignin sulfonate-zinc composite aerogel, and the aerogel was transferred into a quartz tube furnace and heated to 600°C at a heating rate of 5°C / min, and kept warm for 2 hours to obtain a pre-carbonized porous carbon material;

[0050] Pre-carbonized porous carbon and potassium hydroxide activator were dissolved in 20 ml of deionized water in a mass ratio of 1:3, ultrasonicated and fully stirred, placed in an oven at 80°C overnight, and the water was evaporated to obtain a pre-carbonized porous carbon / potassium hydroxide mixed powder;

[0051] The pre-carbonized porous carbon / potassium hydroxide mixed powder obtained above was transferred to a quartz tube furnace, heated to 600°C at a heating rate of 5°C / min, and kept warm for 2 hours. The obtained black porous carbon powder was dissolved in 3M hydrochloric acid, acid-washed overnight, filtered and dried to obtain the final product, nitrogen, oxygen, and sulfur co-doped porous carbon material.

[0052] Example 3

[0053] Weigh 2g of carboxymethyl cellulose, 1.3g of urea and 2g of sodium lignin sulfonate, add them to 90ml of deionized water, stir them thoroughly for 12 hours to obtain a uniform hydrogel solution; weigh 2.0g of zinc chloride and dissolve it in 10ml of deionized water, adjust the zinc chloride solution to neutrality with ammonia water, add the zinc chloride solution adjusted to neutrality into the prepared carboxymethyl cellulose-urea-sodium lignin sulfonate gel, and continue to stir evenly; weigh 1.5g of D-(+) glucono σ-lactone as a crosslinking agent and add it to the above-prepared gel solution, stir it thoroughly for 12 hours to obtain a uniform carboxymethyl cellulose-urea-sodium lignin sulfonate-zinc hydrogel mixed solution;

[0054] The prepared hydrogel mixed solution was transferred into a mold, freeze-dried for 72 hours to obtain a carboxymethyl cellulose-urea-sodium lignin sulfonate-zinc composite aerogel, and the aerogel was transferred into a quartz tube furnace and heated to 600°C at a heating rate of 5°C / min, and kept warm for 2 hours to obtain a pre-carbonized porous carbon material;

[0055] Pre-carbonized porous carbon and potassium hydroxide activator were dissolved in 20 ml of deionized water in a mass ratio of 1:3, ultrasonicated and fully stirred, placed in an oven at 80°C overnight, and the water was evaporated to obtain a pre-carbonized porous carbon / potassium hydroxide mixed powder;

[0056] The pre-carbonized porous carbon / potassium hydroxide mixed powder obtained above was transferred to a quartz tube furnace, heated to 600°C at a heating rate of 5°C / min, and kept warm for 2 hours. The obtained black porous carbon powder was dissolved in 3M hydrochloric acid, acid-washed overnight, filtered and dried to obtain the final product, nitrogen, oxygen, and sulfur co-doped porous carbon material.

[0057] Comparative Example 1 (Compared with Example 1, zinc chloride was not added and only potassium hydroxide was used for activation)

[0058] The preparation method is basically the same as that in Example 1, except that: when preparing the mixed hydrogel precursor, zinc chloride is not added, and only potassium hydroxide added in the activation stage is used as a single activator, so as to compare the difference in structural properties between the porous carbon prepared by single potassium hydroxide activation and zinc oxide-potassium hydroxide activation.

[0059] Comparative Example 2 (Compared with Example 1, potassium hydroxide was not added, and only zinc chloride was used for activation)

[0060] The preparation method is basically the same as that in Example 1, except that potassium hydroxide is not added in the activation stage, and only zinc oxide is used as a single activator, so as to compare the difference in structural properties between porous carbon prepared by single zinc oxide activation and zinc oxide-potassium hydroxide activation.

[0061] Results and Analysis

[0062] The nitrogen, oxygen and sulfur co-doped high specific surface area porous carbon obtained in the examples and comparative examples was structurally characterized and its performance in supercapacitor electrode materials was tested. The results are shown in Tables 1 and Figure 1-2 .

[0063] The specific surface area and pore structure of the samples were tested using a fully automatic specific surface area and porosity adsorption analyzer (Autosorb-IQ3).

[0064] In the supercapacitor electrode performance test, the nitrogen, oxygen, and sulfur co-doped porous carbon, acetylene black, and polytetrafluoroethylene obtained by the present invention were used in a mass ratio of 8:1:1 to prepare a supercapacitor working electrode, and glassy carbon was used as a current collector, activated carbon was used as a counter electrode, and mercury / mercury was used as a reference electrode. Electrochemical tests were performed in a 6M potassium hydroxide electrolyte. The test window was -1V to 0V, and the charge and discharge current density was 0.1A / g and 10A / g.

[0065] Table 1 shows the pore structure characteristic parameters and specific capacitance of high specific surface area porous carbon materials co-doped with nitrogen, oxygen and sulfur.

[0066]

[0067]

[0068] Table 1 shows that the nitrogen, oxygen and sulfur co-doped porous carbon material with high specific surface area obtained in Example 1 exhibits a surface area of ​​2898.2 m 2 / g high specific surface area, V total 1.36cm 3 / g, which is much higher than the porous carbon values ​​obtained by other zinc chloride ratios (Example 2 and Example 3) and using a single activator (Comparative Example 1 and Comparative Example 2), indicating that the zinc chloride ratio in Example 1 is the most suitable among all the embodiments. At the same time, the dual activation efficiency of zinc oxide and potassium hydroxide is better than that of the sample using a single activator. The porous carbon obtained in Example 1 also exhibits excellent performance in the application of supercapacitor electrode materials. When the current density is 0.1A / g, the specific capacitance is 342.5F / g, and when the current density is increased to 10A / g, the specific capacitance remains at 197.3F / g. This is because an appropriate amount of zinc oxide provides a mesoporous template in the pre-carbonization stage, which provides a more developed and sufficient network channel for the subsequent activation of potassium hydroxide, which is beneficial to improve the activation efficiency of potassium hydroxide, thereby obtaining a porous carbon material with a more developed pore structure, a higher specific surface area, and better electrochemical performance.

[0069] The specific surface areas of Comparative Examples 1 and 2 are much lower than the specific surface areas of the porous carbons in Examples 1 to 3, which further confirms that the dual activation of zinc oxide and potassium hydroxide is conducive to obtaining a higher specific surface area and better activation efficiency, and also demonstrates the advantages of the dual activation strategy.

[0070] In summary, Examples 1-3 explore the effect of changes in zinc oxide content on the pore structure and electrochemical properties of the final porous carbon material by adjusting the content of zinc oxide added. Comparative Examples 1-2 are respectively activated using potassium hydroxide and zinc oxide alone, and compared with the sample in Example 1 in which zinc oxide and potassium hydroxide dual activators were added, it is proved that the zinc oxide-potassium hydroxide dual activation strategy of the present invention can successfully produce nitrogen, oxygen, and sulfur co-doped high specific surface area porous carbon, and exhibits excellent performance in the application of supercapacitor electrode materials.

[0071] Figure 1 This is the nitrogen adsorption-desorption curve of the nitrogen, oxygen and sulfur co-doped high specific surface area porous carbon material prepared in Example 1 of the present invention. As can be seen from the figure, in the nitrogen adsorption-desorption curve, the nitrogen adsorption amount increases significantly in the low pressure region, and an obvious hysteresis loop appears in the medium and high pressure region, indicating the presence of micro-mesoporous structure in the porous carbon, confirming the formation of a hierarchical porous structure of the carbon material.

[0072] Figure 2 This is the pore size distribution curve of the nitrogen, oxygen and sulfur co-doped high specific surface area porous carbon material obtained in Example 1. As can be seen from the figure, the micropores of the material are concentrated at 0.6nm and 1.4nm, and the mesopores are concentrated at 4nm. The micropores come from the redox reaction of potassium hydroxide at high temperature to produce carbon dioxide, water vapor and other gases, which volatilize and release from the carbon matrix to leave pores; the mesopores come from zinc oxide providing a mesoporous template during the pre-carbonization process. The dual activation strategy is combined to successfully prepare a heteroatom-rich porous carbon material with a high specific surface area and a developed pore structure.

[0073] The above implementation modes are not limitations of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the scope of the technical solution of the present invention also belong to the protection scope of the present invention.

Claims

1. A method for preparing a nitrogen, oxygen and sulfur co-doped porous carbon material, characterized in that: The following steps are involved: Step 1, dissolving carboxymethyl cellulose, urea and sodium lignin sulfonate in an aqueous solution, and stirring thoroughly to obtain a uniform hydrogel solution; Step 2, adjusting the zinc chloride solution to neutral, and adding the adjusted zinc chloride solution to the hydrogel solution in step 1; Step 3, adding a crosslinking agent to the hydrogel solution of step 2, and stirring thoroughly to obtain a uniform hydrogel; Step 4: freeze-drying the hydrogel in step 3 to obtain carboxymethyl cellulose-urea-sodium lignin sulfonate composite aerogel; Step 5: pre-carbonizing the aerogel in step 4 to obtain a pre-carbonized porous material; Step 6: activating the pre-carbonized porous carbon material obtained in step 5: dissolving the pre-carbonized porous carbon and potassium hydroxide in deionized water in a certain proportion, stirring thoroughly to obtain a uniform mixed solution, and drying to obtain a pre-carbonized porous carbon / potassium hydroxide mixed powder; Step 7: subjecting the pre-carbonized porous carbon / potassium hydroxide mixed powder in step 6 to high temperature activation treatment to obtain nitrogen, oxygen, and sulfur co-doped porous carbon / metal oxide composite powder; Step 8: Immerse the nitrogen, oxygen, and sulfur co-doped porous carbon / metal oxide composite powder in step 7 in an acid solution, filter, and dry to obtain nitrogen, oxygen, and sulfur co-doped porous carbon powder.

2. The method for preparing nitrogen, oxygen and sulfur co-doped porous carbon material according to claim 1, characterized in that: In the step 1, the mass ratio of carboxymethyl cellulose, urea and sodium lignin sulfonate is 3:2:3; in the step 2, the mass ratio of zinc chloride to carboxymethyl cellulose is (0-2):3, and the pH is adjusted to neutral with ammonia water.

3. The method for preparing nitrogen, oxygen and sulfur co-doped porous carbon material according to claim 1, characterized in that: In the step three, the cross-linking agent is D-(+) glucono σ-lactone, and the mass ratio of the cross-linking agent to the carboxymethyl cellulose is 1.5:

3.

4. The method for preparing nitrogen, oxygen and sulfur co-doped porous carbon material according to claim 1, characterized in that: In the step 4, the freezing time is 24 hours and the vacuum drying time is 48 hours.

5. The method for preparing nitrogen, oxygen and sulfur co-doped porous carbon material according to claim 1, characterized in that: In the step 5, the pre-carbonization temperature is 600° C., the holding time is 2 hours, the heating rate is 5° C. / min, and the mixture is naturally cooled to room temperature.

6. The method for preparing nitrogen, oxygen and sulfur co-doped porous carbon material according to claim 1, characterized in that: In the step six, the mass ratio of potassium hydroxide to pre-carbonized porous carbon is 3:1; the pre-carbonized porous carbon / potassium hydroxide mixed solution is placed in an oven at 80° C. for 12 hours, and its water is evaporated to obtain a mixed powder.

7. The method for preparing nitrogen, oxygen and sulfur co-doped porous carbon material according to claim 1, characterized in that: In the step 7, the activation temperature is 600°C, the holding time is 2 hours, the heating rate is 5°C / min, and the mixture is naturally cooled to room temperature.

8. The method for preparing nitrogen, oxygen and sulfur co-doped porous carbon material according to claim 1, characterized in that: In the step eight, the acid solution is hydrochloric acid with a concentration of 3M, and after filtering, it is dried in an oven at 80° C. for 12 hours.

9. A nitrogen, oxygen and sulfur co-doped porous carbon material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The porous carbon material has a micro-mesoporous structure.

10. An application of nitrogen, oxygen and sulfur co-doped porous carbon material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The prepared porous carbon material is applied in the field of supercapacitor electrodes.

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