Preparation method and application of iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material

Abstract

The invention belongs to the technical field of nano composite materials, and relates to a preparation method of an iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material, which comprises the following steps: putting cellulose, sodium bicarbonate and thiourea into a mortar, uniformly grinding, putting into a tubular furnace, calcining at high temperature under the protection of inert gas, naturally cooling, centrifugally separating and collecting the calcined powder, thereby obtaining the iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material. The nitrogen and sulfur co-doped carbon nanosheets are obtained; ultrasonically dispersing iron nitrate nonahydrate in ethanol, heating in an oil bath until the ethanol is evaporated to dryness, and carrying out heat treatment to obtain an iron-based precursor; the obtained iron-based precursor, selenium dioxide and nitrogen and sulfur co-doped carbon nanosheets are ultrasonically dispersed in benzyl alcohol, the mixture is transferred into a reaction kettle with a polytetrafluoroethylene lining, the composite material is obtained after solvothermal reaction, and the morphology of the composite material is that iron diselenide nanoparticles are evenly and densely attached to the surfaces of the nitrogen and sulfur co-doped carbon nanosheets. The method is simple and easy to implement, suitable for large-scale production, easy to implement industrially and expected to be applied to the negative electrode of the hybrid supercapacitor.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanocomposite materials, relates to composite electrode materials, and particularly relates to a preparation method and application of an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material. Technical Background

[0002] At present, green and efficient energy sources such as nuclear energy, solar energy, hydropower, wind energy, tidal energy, geothermal energy, and biomass energy are continuously being developed and utilized, which alleviates the energy shortage to a certain extent and is of great significance to the development of energy. A hybrid supercapacitor is a new type of electronic device that effectively stores and releases electrical energy using the principle of electrochemical conversion. It has advantages such as a long cycle life and fast charge and discharge, can generate a high current in a short time and quickly provide energy, and exhibits extremely high power supply. Reasonably designing advanced electrode materials with a unique structure is one of the most effective ways to optimize the electrochemical properties of hybrid supercapacitors. The most common negative electrode material for hybrid supercapacitors is activated carbon, which has advantages such as rich and low-cost raw materials, a long cycle life, good conductivity, and environmental friendliness. However, the charge transfer behavior in activated carbon conforms to the characteristics of the electric double layer, and the actual specific capacitance is not ideal during application. Therefore, it is imperative to explore negative electrode materials with high performance.

[0003] Advanced carbonaceous materials with a nanosheet structure have attracted much attention due to their unique two-dimensional structural advantages. Such materials can expose more ion adsorption sites and significantly shorten the ion transport path, thus showing great potential in electrochemical applications. In recent years, defect engineering, as an effective strategy, has been applied to improve the electrochemical performance of carbonaceous materials. For example, introducing heteroatoms (such as nitrogen, sulfur, phosphorus, and fluorine, etc.) into the carbon skeleton through external doping can not only rearrange the electronic structure of the carbonaceous materials but also introduce additional pseudocapacitance. In addition, this doping method can significantly improve the wettability of the materials, thereby greatly enhancing their overall electrochemical performance. On the other hand, iron-based materials (mainly oxides and sulfides, etc.) have received some attention in the research field of transition metal materials due to their relatively wide negative potential window and high theoretical capacity. Iron is the most abundant transition metal element in the earth's crust, has multiple valence states and rich valence transition processes, and can achieve efficient charge transfer, making it a promising type of negative electrode material for hybrid supercapacitors. However, iron-based materials have been facing many challenges, including poor stability and low actual specific capacitance. During the Faraday reaction process, the relatively low conductivity and structural collapse of iron-based materials significantly hinder the reaction kinetics, thus seriously affecting their electrochemical performance.

[0004] Constructing composite materials based on carbonaceous materials has become an effective strategy for regulating the electrochemical properties of iron-based materials. Such carbon materials, with their high specific surface area, dense pore size distribution, and adjustable structure, especially two-dimensional carbon materials, exhibit excellent surface modification ability and carrier performance after being combined with iron-based materials. They can create additional electron transport paths, significantly enhance the rapid charge transfer ability, and thus greatly improve the conductivity cycle stability of iron-based materials. Summary of the Invention

[0005] Aiming at the deficiencies in the above-mentioned existing technologies, the purpose of the present invention is to provide a preparation method of iron diselenide / nitrogen and sulfur co-doped carbon nanosheets.

[0006] Technical Solution

[0007] A preparation method of an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material includes the following steps:

[0008] (1) Put cellulose, sodium bicarbonate, and thiourea in a mortar, grind evenly, place the obtained product in a tubular furnace, calcine at high temperature under the protection of an inert gas, cool naturally, centrifuge to collect the calcined powder, wash with deionized water and ethanol, and then dry to obtain nitrogen and sulfur co-doped carbon nanosheets;

[0009] (2) Ultrasonically disperse ferric nitrate nonahydrate in ethanol, heat the solution in an oil bath until the ethanol evaporates completely, and perform heat treatment on the powder;

[0010] (3) Ultrasonically disperse the obtained iron-based precursor, selenium dioxide, and nitrogen and sulfur co-doped carbon nanosheets in benzyl alcohol, transfer the mixed solution into a reaction kettle with a polytetrafluoroethylene inner liner, perform a solvothermal reaction, centrifuge the precipitate, wash with deionized water and ethanol to obtain an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material.

[0011] In a preferred embodiment of the present invention, in step (1), the inert gas is nitrogen.

[0012] In a preferred embodiment of the present invention, in step (1), the mass ratio of cellulose, sodium bicarbonate, and thiourea is 1:1-4:4-6, preferably 1:3:5.

[0013] In a preferred embodiment of the present invention, in step (1), the calcination temperature is 600-800 °C, the calcination time is 1-3 h, and the heating rate is 4-6 °C / min, preferably calcine at 700 °C for 2 h, and the heating rate is 5 °C / min.

[0014] In a preferred embodiment of the present invention, in step (2), the material ratio of ferric nitrate nonahydrate to ethanol is 1 mmol:50-150 mL, preferably 1 mmol:100 mL, and the oil bath temperature is 80-90 °C, preferably 85 °C.

[0015] In a preferred disclosure example of the present invention, in step (2), the heat treatment temperature is 180 - 220 °C, the calcination time is 8 - 12 h, and preferably, the reaction is carried out at 200 °C for 10 h.

[0016] In a preferred disclosure example of the present invention, in step (3), the mass ratio of the iron-based precursor, selenium dioxide, and nitrogen-sulfur co-doped carbon nanosheets is 1.5:1 - 2:1 - 2, preferably 1:1:1, and the material ratio of the iron-based precursor to benzyl alcohol is 3 mg:7 mL.

[0017] In a preferred disclosure example of the present invention, in step (3), the solvothermal temperature is 170 - 190 °C, the reaction time is 8 - 12 h, and preferably, the reaction is carried out at 180 °C for 10 h.

[0018] The iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material prepared by the method disclosed in the present invention has a morphology in which iron diselenide nanoparticles are uniformly and densely attached to the surface of the nitrogen-sulfur co-doped carbon nanosheets.

[0019] Another object of the present invention is to apply the prepared composite material to the negative electrode of a hybrid supercapacitor.

[0020] Experimental procedure: The electrochemical performance of the iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material was tested using a three-electrode system. The electrolyte was 6 M KOH, Hg / HgO (1 M KOH) was used as the reference electrode, and a Pt sheet was used as the counter electrode.

[0021] Preparation process of the working electrode: According to the mass ratio, iron diselenide / nitrogen-sulfur co-doped carbon nanosheets (80%), acetylene black (10%), and polytetrafluoroethylene (10%) were mixed and ground in ethanol to form a uniform slurry. The slurry was coated on the surface of nickel foam and compacted under a pressure of 10 MPa and dried at 60 °C.

[0022] The iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material prepared by the present invention has the following advantages: (1) The ultra-small size of iron diselenide nanoparticles is beneficial to increasing the surface active sites and improving its pseudocapacitance; (2) The surface Faraday behavior of iron diselenide can increase the pseudocapacitance of nitrogen-sulfur co-doped carbon nanosheets, which is beneficial to improving the specific capacitance of the carbon nanosheets; (3) The composite of nitrogen-sulfur co-doped carbon nanosheets helps to prevent the aggregation of iron diselenide during charge and discharge, and at the same time improves the conductivity of iron diselenide. These advantages enable the composite material to exhibit excellent electrochemical performance, showing a high specific capacitance (the specific capacitance is 390.6 F / g at a current density of 1 A / g) and excellent cycle stability (after cycling 10,000 times at a current density of 15 A / g, the specific capacitance retention rate is 90.2%) when used as the negative electrode material of a hybrid supercapacitor.

[0023] Beneficial effects

[0024] The present invention first prepares nitrogen and sulfur co-doped carbon nanosheets, and then uses the in-situ synthesis method to uniformly and densely attach iron diselenide nanoparticles to its surface, with good attachment effect. The present invention is simple and feasible, suitable for large-scale production, and easy to implement industrially. There is a synergistic effect between iron diselenide and nitrogen and sulfur co-doped carbon nanosheets in the composite material, which can improve the electrochemical performance of single materials and is expected to be applied in the negative electrode of hybrid supercapacitors. Description of the Drawings

[0025] Figure 1 . X-ray diffraction (XRD) pattern of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite prepared in Example 1;

[0026] Figure 2 . X-ray photoelectron spectroscopy (XPS) of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite prepared in Example 1;

[0027] Figure 3 . Transmission electron microscopy (TEM) photograph of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite prepared in Example 1;

[0028] Figure 4 . Charge-discharge curve of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite prepared in Example 1 in 6 M KOH;

[0029] Figure 5 . Cycling performance of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite prepared in Example 1 at a current density of 15 A / g. Detailed Embodiments

[0030] The present invention will be described in detail below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0031] Example 1

[0032] A preparation method of an iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material includes: mixing 0.5 g of cellulose, 1.5 g of sodium bicarbonate, and 2.5 g of thiourea in a mortar and grinding them evenly. Place the obtained product in a tube furnace and calcine it at 700 °C for 2 h under nitrogen protection with a heating rate of 5 °C / min. Collect the calcined powder, perform centrifugal separation, wash it with deionized water and ethanol, and then dry the obtained sample to obtain nitrogen-sulfur co-doped carbon nanosheets. Ultrasonically disperse 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heat the solution in an 85 °C oil bath until the ethanol evaporates completely. Put the collected powder into an oven and heat it at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically disperse 15 mg of the iron-based precursor, 15 mg of selenium dioxide, and 15 mg of nitrogen-sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transfer the obtained mixed solution into a reaction kettle with a polytetrafluoroethylene inner lining, and perform a solvothermal reaction at 180 °C for 10 h. Centrifuge the obtained precipitate, wash it with deionized water and ethanol to obtain the iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material.

[0033] Figure 1 XRD pattern of the composite material prepared in this example. All diffraction peaks in the figure correspond to orthorhombic iron diselenide (standard card: 01-079-1892), indicating that iron diselenide is successfully obtained.

[0034] Figure 2 XPS pattern of the composite material prepared in this example. It can be clearly seen that the composite material is composed of nitrogen, sulfur, carbon, oxygen, iron, and selenium elements, indicating that the nitrogen-sulfur co-doped carbon nanosheets and iron diselenide are successfully compounded together.

[0035] Figure 3 TEM image of the composite material prepared in this example. It can be seen that iron diselenide nanoparticles are evenly and densely attached to the surface of the nitrogen-sulfur co-doped carbon nanosheets with good attachment effect.

[0036] Figure 4 Charge-discharge curve of the composite material prepared in this example in 6 M KOH. The specific capacitance of the composite material is 390.6 F / g at a current density of 1 A / g.

[0037] Figure 5 Cycling performance of the composite material prepared in this example. The composite material was subjected to a stability test. After 10,000 charge-discharge cycles at a current density of 15 A / g, it still maintained good cycling stability, and the specific capacitance retention rate was 90.2%.

[0038] Example 2

[0039] A preparation method of iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite, comprising: mixing 0.5 g of cellulose, 0.5 g of sodium bicarbonate and 2.5 g of thiourea in a mortar and grinding evenly. Placing the obtained product in a tubular furnace, calcining at 700 °C for 2 h under nitrogen protection, with a heating rate of 5 °C / min. Collecting the calcined powder, separating by centrifugation, washing with deionized water and ethanol, and drying the obtained sample to obtain nitrogen and sulfur co-doped carbon nanosheets. Ultrasonically dispersing 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heating the solution in an 85 °C oil bath until the ethanol evaporates completely. Placing the collected powder in an oven and heating at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically dispersing 15 mg of the iron-based precursor, 15 mg of selenium dioxide and 15 mg of nitrogen and sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transferring the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, carrying out a solvothermal reaction at 180 °C for 10 h, separating the obtained precipitate by centrifugation, washing with deionized water and ethanol, to obtain the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite.

[0040] At a current density of 1 A / g, its specific capacitance is 232.4 F / g.

[0041] Example 3

[0042] A preparation method of iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite, comprising: mixing 0.5 g of cellulose, 1.5 g of sodium bicarbonate and 2.0 g of thiourea in a mortar and grinding evenly. Placing the obtained product in a tubular furnace, calcining at 700 °C for 2 h under nitrogen protection, with a heating rate of 5 °C / min. Collecting the calcined powder, separating by centrifugation, washing with deionized water and ethanol, and drying the obtained sample to obtain nitrogen and sulfur co-doped carbon nanosheets. Ultrasonically dispersing 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heating the solution in an 85 °C oil bath until the ethanol evaporates completely. Placing the collected powder in an oven and heating at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically dispersing 15 mg of the iron-based precursor, 15 mg of selenium dioxide and 15 mg of nitrogen and sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transferring the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, carrying out a solvothermal reaction at 180 °C for 10 h, separating the obtained precipitate by centrifugation, washing with deionized water and ethanol, to obtain the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite.

[0043] At a current density of 1 A / g, its specific capacitance is 342.6 F / g.

[0044] Example 4

[0045] A preparation method of an iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material, comprising: mixing 0.5 g of cellulose, 1.5 g of sodium bicarbonate and 2.5 g of thiourea in a mortar and grinding evenly. Placing the obtained product in a tube furnace, calcining at 800 °C for 2 h under nitrogen protection, with a heating rate of 5 °C / min. Collecting the calcined powder, separating by centrifugation, washing with deionized water and ethanol, and drying the obtained sample to obtain nitrogen-sulfur co-doped carbon nanosheets. Ultrasonically dispersing 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heating the solution in an 85 °C oil bath until the ethanol evaporates completely. Putting the collected powder into an oven and heating at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically dispersing 15 mg of the iron-based precursor, 15 mg of selenium dioxide and 15 mg of nitrogen-sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transferring the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, carrying out a solvothermal reaction at 180 °C for 10 h, separating the obtained precipitate by centrifugation, washing with deionized water and ethanol, to obtain an iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material.

[0046] At a current density of 1 A / g, its specific capacitance is 351.8 F / g.

[0047] Example 5

[0048] A preparation method of an iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material, comprising: mixing 0.5 g of cellulose, 1.5 g of sodium bicarbonate and 2.5 g of thiourea in a mortar and grinding evenly. Placing the obtained product in a tube furnace, calcining at 700 °C for 1 h under nitrogen protection, with a heating rate of 5 °C / min. Collecting the calcined powder, separating by centrifugation, washing with deionized water and ethanol, and drying the obtained sample to obtain nitrogen-sulfur co-doped carbon nanosheets. Ultrasonically dispersing 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heating the solution in an 85 °C oil bath until the ethanol evaporates completely. Putting the collected powder into an oven and heating at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically dispersing 15 mg of the iron-based precursor, 15 mg of selenium dioxide and 15 mg of nitrogen-sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transferring the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, carrying out a solvothermal reaction at 180 °C for 10 h, separating the obtained precipitate by centrifugation, washing with deionized water and ethanol, to obtain an iron diselenide / nitrogen-sulfur co-doped carbon nanosheet composite material.

[0049] At a current density of 1 A / g, its specific capacitance is 367.3 F / g.

[0050] Example 6

[0051] A preparation method of iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite, comprising: mixing 0.5 g of cellulose, 1.5 g of sodium bicarbonate and 2.5 g of thiourea in a mortar and grinding evenly. Placing the obtained product in a tube furnace, calcining at 700 °C for 2 h under nitrogen protection, with a heating rate of 5 °C / min. Collecting the calcined powder, separating by centrifugation, washing with deionized water and ethanol, and drying the obtained sample to obtain nitrogen and sulfur co-doped carbon nanosheets. Ultrasonically dispersing 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heating the solution in an 85 °C oil bath until the ethanol is evaporated to dryness. Placing the collected powder in an oven and heating at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically dispersing 15 mg of the iron-based precursor, 10 mg of selenium dioxide and 15 mg of nitrogen and sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transferring the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, carrying out a solvothermal reaction at 180 °C for 10 h, separating the obtained precipitate by centrifugation, washing with deionized water and ethanol, to obtain an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite.

[0052] At a current density of 1 A / g, its specific capacitance is 292.7 F / g.

[0053] Example 7

[0054] A preparation method of iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite, comprising: mixing 0.5 g of cellulose, 1.5 g of sodium bicarbonate and 2.5 g of thiourea in a mortar and grinding evenly. Placing the obtained product in a tube furnace, calcining at 700 °C for 2 h under nitrogen protection, with a heating rate of 5 °C / min. Collecting the calcined powder, separating by centrifugation, washing with deionized water and ethanol, and drying the obtained sample to obtain nitrogen and sulfur co-doped carbon nanosheets. Ultrasonically dispersing 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heating the solution in an 85 °C oil bath until the ethanol is evaporated to dryness. Placing the collected powder in an oven and heating at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically dispersing 15 mg of the iron-based precursor, 15 mg of selenium dioxide and 10 mg of nitrogen and sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transferring the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, carrying out a solvothermal reaction at 180 °C for 10 h, separating the obtained precipitate by centrifugation, washing with deionized water and ethanol, to obtain an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite.

[0055] At a current density of 1 A / g, its specific capacitance is 312.4 F / g.

[0056] Example 8

[0057] A preparation method of an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material includes: mixing 0.5 g of cellulose, 1.5 g of sodium bicarbonate and 2.5 g of thiourea in a mortar and grinding them evenly. Placing the obtained product in a tube furnace, calcining at 700 °C for 2 h under nitrogen protection, with a heating rate of 5 °C / min. Collecting the calcined powder, separating it by centrifugation, washing it with deionized water and ethanol, and then drying the obtained sample to obtain nitrogen and sulfur co-doped carbon nanosheets. Ultrasonically dispersing 0.3 mmol of ferric nitrate nonahydrate in 30 mL of ethanol, and heating the solution in an 85 °C oil bath until the ethanol evaporates completely. Placing the collected powder in an oven and heating it at 200 °C for 10 h to obtain an iron-based precursor. Ultrasonically dispersing 15 mg of the iron-based precursor, 15 mg of selenium dioxide and 20 mg of nitrogen and sulfur co-doped carbon nanosheets in 35 mL of benzyl alcohol, transferring the obtained mixed solution into a reaction kettle lined with polytetrafluoroethylene, carrying out a solvothermal reaction at 180 °C for 10 h, separating the obtained precipitate by centrifugation, and washing it with deionized water and ethanol to obtain the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material.

[0058] At a current density of 1 A / g, its specific capacitance is 299.2 F / g.

[0059] The above are the embodiments of the present invention, and thus do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, shall similarly be included within the patent protection scope of the present invention.

Claims

1. A preparation method of an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite, characterized in that, It includes the following steps: (1) Put cellulose, sodium bicarbonate and thiourea in a mortar, grind them evenly, place the obtained product in a tube furnace, calcine at high temperature under the protection of an inert gas, cool naturally, centrifuge to separate and collect the calcined powder, wash it with deionized water and ethanol, and then dry it to obtain nitrogen and sulfur co-doped carbon nanosheets; (2) Ultrasonically disperse ferric nitrate nonahydrate in ethanol, heat the solution in an oil bath until the ethanol evaporates completely, and perform heat treatment on the powder; (3) Ultrasonically disperse the obtained iron-based precursor, selenium dioxide and nitrogen and sulfur co-doped carbon nanosheets in benzyl alcohol, transfer the mixed solution into a reaction kettle with a polytetrafluoroethylene liner, carry out a solvothermal reaction, centrifuge and separate the precipitate, wash it with deionized water and ethanol to obtain an iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material.

2. The preparation method of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material according to claim 1, wherein: In step (1), the inert gas is nitrogen.

3. The preparation method of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material according to claim 1, wherein: In step (1), the mass ratio of cellulose, sodium bicarbonate and thiourea is 1:1-4:4-6, preferably 1:3:

5.

4. The preparation method of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material according to claim 1, characterized in that: In step (1), the calcination temperature is 600-800 °C, the calcination time is 1-3 h, and the heating rate is 4-6 °C / min. Preferably, it is calcined at 700 °C for 2 h and the heating rate is 5 °C / min.

5. The preparation method of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material according to claim 1, wherein: In step (2), the material ratio of ferric nitrate nonahydrate to ethanol is 1 mmol:50-150 mL, preferably 1 mmol:100 mL, and the oil bath temperature is 80-90 °C, preferably 85 °C.

6. The preparation method of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material according to claim 1, characterized in that: In step (2), the heat treatment temperature is 180-220 °C, and the calcination time is 8-12 h. Preferably, the reaction is carried out at 200 °C for 10 h.

7. The preparation method of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material according to claim 1, wherein: In step (3), the mass ratio of the iron-based precursor, selenium dioxide and nitrogen and sulfur co-doped carbon nanosheets is 1.5:1-2:1-2, preferably 1:1:1, and the material ratio of the iron-based precursor to benzyl alcohol is 3 mg:7 mL.

8. The preparation method of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material according to claim 1, characterized in that: In step (3), the solvothermal temperature is 170-190 °C, and the reaction time is 8-12 h. Preferably, the reaction is carried out at 180 °C for 10 h.

9. The iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material prepared by the method according to any one of claims 1-8, characterized in that: Its morphology is that iron diselenide nanoparticles are uniformly and densely attached to the surface of nitrogen and sulfur co-doped carbon nanosheets.

10. Application of the iron diselenide / nitrogen and sulfur co-doped carbon nanosheet composite material as described in claim 9, characterized in that: It is applied to the negative electrode of a hybrid supercapacitor.

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