A nitrogen-doped carbon material and a method for preparing the same

Abstract

The application discloses a kind of nitrogen-doped carbon materials.The pore structure of the carbon material is composed of micropore and mesopore;Its specific surface area is 950-1080m 2 / g, the content of doped nitrogen is 2.9-5.0wt%;The form of nitrogen includes: pyridine-N, pyrrole-N and graphite-N.The nitrogen-doped carbon material is generated by taking CaC2 as carbon source, N2 as nitrogen source, and reacting at 800-900℃.The application uses colorless and odorless, higher safety N2, not irritating NH3 or other nitrogen-containing solid substances as nitrogen source, effectively realizes the nitrogen doping of carbon material.The method can effectively control the content and form of doped nitrogen by reaction temperature, avoids the adverse effects on environment and human body when using irritating gas such as NH3 as nitrogen source;The nitrogen-doped carbon material has high specific capacitance and rate performance.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon materials, and particularly relates to a nitrogen-doped carbon material and its preparation method. Background Technology

[0002] Supercapacitors, as one of the leading electrochemical energy storage technologies, are widely used in energy, telecommunications, military equipment, and industrial production due to their high power density and long cycle life. Carbon electrode materials, as a core component of supercapacitors, play a crucial role in their energy storage performance. Currently, porous carbon materials are the mainstream electrode materials for supercapacitors. Introducing nitrogen atoms into porous carbon materials can improve their capacitance performance; nitrogen doping can alter the local electronic structure of carbon materials, enhancing their wettability with the electrolyte and increasing their specific capacitance. Nitrogen-doped porous carbon materials, with their high specific surface area, abundant pore structure, and numerous nitrogen-containing functional groups, possess unique physicochemical properties, demonstrating enormous application potential in electrode materials, adsorbents, hydrogen storage, and catalysis.

[0003] Currently, the synthesis methods for nitrogen-containing porous carbon materials can be divided into two categories: one is the in-situ synthesis of nitrogen-containing materials, and the other is the modification of porous carbon materials. The synthesis of in-situ nitrogen-doped carbon materials often involves the synthesis of nitrogen-containing compounds through methods such as template methods and sol-gel methods, which have disadvantages such as complex operation and high cost. The latter mainly introduces the target functional group into the porous carbon material through appropriate chemical methods, such as reacting carbon precursors with nitrogen-containing strong reducing gases (such as NH3) or solids (such as urea, melamine, etc.) and incorporating nitrogen into the carbon material under high temperature and / or high pressure conditions; however, this method often suffers from disadvantages such as low doping efficiency and emission of large amounts of toxic gases.

[0004] Therefore, developing a clean, environmentally friendly, low-cost, and easily scalable process for preparing nitrogen-doped carbon materials has significant practical value. Summary of the Invention

[0005] Based on the above-mentioned technical problems, the present invention provides a nitrogen-doped carbon material and its preparation method; the method uses CaC2 as a carbon source and N2 as a nitrogen source, and reacts at a certain temperature to obtain the material; the whole process is low-cost, clean and environmentally friendly, and the form and content of nitrogen doping can be efficiently adjusted by adjusting the reaction temperature; the nitrogen-doped carbon material obtained thereby has excellent capacitance performance.

[0006] The specific solution of this invention is as follows:

[0007] This invention provides a nitrogen-doped carbon material, wherein the carbon material has a porous structure composed of micropores and mesopores, and a specific surface area of ​​950-1080 m². 2 / g; the content of doped nitrogen is 2.9-5.0wt%, and the nitrogen exists in the forms of pyridine-N, pyrrole-N and graphite-N.

[0008] Preferably, the mesopore size is 3.5-7.0 nm.

[0009] Preferably, the mass ratio of pyridine-N, pyrrole-N, and graphite-N is 1-3:4-6:3-4.

[0010] Preferably, the nitrogen-doped carbon material is prepared by chemical reaction using CaC2 as the carbon source and N2 as the nitrogen source at 800-900℃.

[0011] The present invention also provides a method for preparing the nitrogen-doped carbon material, comprising: S1, mixing CaC2 with ball milling beads and performing ball milling treatment; S2, reacting the ball-milled CaC2 with N2 at 800-900℃ for 2-5 hours.

[0012] Preferably, in S1, the mass ratio of CaC2 to the milling beads is 1:15-20; the milling speed is 500-900 r / min; and the milling time is 15-24 h.

[0013] Preferably, the process further includes cooling the material after the S2 reaction to room temperature, washing it first with hydrochloric acid, then repeatedly washing it with deionized water and anhydrous ethanol, and drying it to obtain the final product.

[0014] Beneficial effects of this invention:

[0015] Compared to existing methods that use irritating and flammable nitrogen-containing gases (such as NH3) or solid nitrogen sources (such as urea and melamine), this invention uses CaC2 as the carbon source and inert gas N2 as the nitrogen source, reacting at 800-900℃. The originally inert N2 is incorporated into the CaC2-derived carbon material during the reaction, effectively achieving nitrogen doping. Furthermore, the entire process is controllable; the form and content of the doped N can be effectively regulated by controlling the reaction temperature. It also avoids the adverse effects on the environment and human health caused by irritating gases such as NH3.

[0016] The nitrogen-doped carbon material obtained by the above method consists of micropores and mesopores, with nitrogen existing in the form of pyridine-N, pyrrole-N, and graphite-N, and exhibits excellent capacitance performance. Attached Figure Description

[0017] Figure 1 The images show X-ray photoelectron spectroscopy (XPS) spectra of nitrogen-doped carbon materials, where A and B correspond to Examples 1 and 2, respectively.

[0018] Figure 2The image shows the fine N1s spectrum in the XPS spectrum of nitrogen-doped derived carbon materials, where A and B correspond to Example 1 and Example 2, respectively.

[0019] Figure 3 The figures show the cyclic voltammetry curves of nitrogen-doped derived carbon materials in 6.0 mol / L KOH electrolyte, where A and B correspond to Example 1 and Example 2, respectively. Detailed Implementation

[0020] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0021] Example 1

[0022] A nitrogen-doped carbon material, wherein the carbon material has a porous structure composed of micropores and mesopores, and has a specific surface area of ​​1080 m². 2 / g; the nitrogen content is 5.0wt%, and the nitrogen exists in the forms of pyridine-N, pyrrole-N and graphite-N, with a mass ratio of 1:6:3; the mesopore size is 3.5-6.0nm.

[0023] Its preparation methods include:

[0024] S1. Weigh CaC2 and milling beads at a mass ratio of 1:20 and place them in a vacuum-dried milling jar. Mix them directly in air and seal the milling jar. Use a planetary ball mill to mill the mixture at a rate of 700 r / min for 24 h to obtain a black powder.

[0025] S2. After passing the black powder through a 200-mesh sieve, take an appropriate amount of the black powder and place it in a porcelain boat in a tube furnace; use N2 as the nitrogen source, raise the temperature to 800℃ at a rate of 5℃ / min, and keep it at that temperature for 3 hours, then let it cool naturally to room temperature.

[0026] S3. Wash the product with 3 mol / L hydrochloric acid solution after the reaction, and then wash the material with deionized water and ethanol in small amounts several times until the washing solution is neutral. Then filter, dry and cool naturally to room temperature to obtain nitrogen-doped carbon material.

[0027] Example 2

[0028] A nitrogen-doped carbon material, wherein the carbon material has a porous structure composed of micropores and mesopores, and has a specific surface area of ​​950 m². 2 / g; the nitrogen content is 2.9wt%, and the nitrogen exists in the forms of pyridine-N, pyrrole-N and graphite-N, with a mass ratio of 3:4:4; the mesopore size is 4.5-7.0nm.

[0029] Its preparation methods include:

[0030] S1. Weigh CaC2 and milling beads at a mass ratio of 1:20 and place them in a vacuum-dried milling jar. Mix them directly in air and seal the milling jar. Use a planetary ball mill to mill the mixture at a rate of 700 r / min for 24 h to obtain a black powder.

[0031] S2. After passing the black powder through a 200-mesh sieve, take an appropriate amount of black powder and place it in a porcelain boat in a tube furnace; then use N2 as a nitrogen source, raise the temperature to 900℃ at a rate of 5℃ / min, and hold for 3 hours, and then let it cool naturally to room temperature.

[0032] S3. Wash the product with 3 mol / L hydrochloric acid solution after the reaction, and then wash the material with deionized water and ethanol in small amounts several times until the washing solution is neutral. Then filter, dry and cool naturally to room temperature to obtain nitrogen-doped carbon material.

[0033] The performance of the nitrogen-doped carbon materials obtained in Examples 1-2 was tested, as follows:

[0034] Figure 1 The images show the X-ray photoelectron spectroscopy (XPS) spectra of the nitrogen-doped carbon materials obtained in Examples 1 and 2, where A and B correspond to Examples 1 and 2, respectively.

[0035] Comparative fitting revealed that the carbon materials obtained in Examples 1 and 2 both contained a certain amount of nitrogen, and the nitrogen content actually decreased as the temperature increased from 800℃ to 900℃.

[0036] Figure 2 The images show the fine N1s spectra of the nitrogen-doped carbon materials obtained in Examples 1 and 2, where A and B correspond to Examples 1 and 2, respectively.

[0037] It can be seen that with increasing temperature, the pyridine-N peak gradually weakens, while the pyrrole-N and graphite-N peaks significantly strengthen. This may be due to the increased graphitization of the derived carbon materials with increasing temperature. The presence of the pyridine-N, pyrrole-N, and graphite-N peaks confirms the presence of nitrogen-containing groups.

[0038] Using the nitrogen-doped carbon materials obtained in Examples 1-2 as the capacitor carbon material, 6 mol / L KOH solution as the electrolyte, and PP / PE membrane as the separator, 2032-type button-type supercapacitors were fabricated, and their electrochemical performance was tested. The cyclic voltammetry curves were obtained as follows: Figure 3 As shown, A and B correspond to Example 1 and Example 2, respectively.

[0039] It can be seen that the nitrogen-doped derived carbon material obtained by this invention has high specific capacitance and rate performance. When used as an electrode material for supercapacitors, it can significantly improve the energy storage performance of supercapacitors, enabling its application in fields with high energy density requirements, such as large-scale engineering machinery, wind turbines, and new energy vehicles.

[0040] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A nitrogen-doped carbon material, characterized in that, The carbon material has a porous structure, consisting of micropores and mesopores, with a specific surface area of ​​950-1080 m². 2 / g; the content of doped nitrogen is 2.9-5.0 wt%, and the nitrogen exists in the form of pyridine-N, pyrrole-N and graphite-N; the nitrogen-doped carbon material is prepared by chemical reaction at 800-900 °C using CaC2 as carbon source and N2 as nitrogen source.

2. The nitrogen-doped carbon material according to claim 1, characterized in that, The mesopore size is 3.5-7.0 nm.

3. The nitrogen-doped carbon material according to claim 1 or 2, characterized in that, The mass ratio of pyridine-N, pyrrole-N, and graphite-N is 1-3 : 4-6 : 3-4.

4. The method for preparing the nitrogen-doped carbon material according to any one of claims 1-3, characterized in that, include: S1. Mix CaC2 with milling beads and mill them; S2. React the milled CaC2 with N2 at 800-900 ℃ for 2-5 h.

5. The method for preparing nitrogen-doped carbon material according to claim 4, characterized in that, In S1, the mass ratio of CaC2 to the milling beads is 1:15-20; the milling speed is 500-900 r / min; and the milling time is 15-24 h.

6. The method for preparing nitrogen-doped carbon material according to claim 4 or 5, characterized in that, It also includes cooling the material after the S2 reaction to room temperature, washing it first with hydrochloric acid, then repeatedly washing it with deionized water and anhydrous ethanol, and drying it to obtain the final product.

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