Method for preparing n-doped porous carbon material based on attapulgite and application thereof in supercapacitor
By using attapulgite clay, waste cooking oil, and egg white to prepare N-doped porous carbon materials, the problems of insufficient conductivity and energy density in supercapacitors have been solved. This has enabled a high specific capacitance and an environmentally friendly and economical preparation method, thereby improving the performance of supercapacitors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUAIYIN INSTITUTE OF TECHNOLOGY
- Filing Date
- 2024-11-19
- Publication Date
- 2026-07-10
AI Technical Summary
Existing supercapacitors have low energy density, and carbon materials have insufficient conductivity and specific capacitance. Most existing carbon materials are synthesized from petroleum coke and biomass, and their microporous structure limits performance improvement. Furthermore, the etching process generates a large amount of waste liquid that is difficult to treat.
Using attapulgite clay as a template, and combining waste cooking oil and recycled egg white as carbon and nitrogen sources, N-doped porous carbon materials were prepared by carbonization-alkali-acid combined etching to form a hollow porous structure and improve the electrode performance of the material.
This method enables the low-cost and environmentally friendly preparation of N-doped porous carbon materials, improving the specific capacitance of supercapacitors and solving the problems of poor material conductivity and low energy density in existing technologies. Furthermore, the etching process recovers valuable solutions and reduces the amount of waste liquid to be disposed of.
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Figure CN119601392B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrochemical energy storage technology, and in particular to a method for preparing N-doped porous carbon materials based on attapulgite and their application in supercapacitors. Specifically, it relates to a method for preparing N-doped porous carbon supercapacitor materials based on attapulgite clay, waste cooking oil, and recycled egg white, and their application. Background Technology
[0002] Supercapacitors have attracted widespread attention due to their advantages of high power density, short charging time, long lifespan, and environmental friendliness. However, their relatively low energy density limits their applications. To improve supercapacitor performance, porous carbon materials with high specific surface area, excellent specific capacitance, and high specific charge are increasingly being studied. Currently used carbon materials are mostly synthesized from petroleum coke and biomass (CN115642039A), containing numerous micropores. These disordered pore structures result in poor conductivity, limiting performance improvement. Introducing nitrogen can improve the conductivity of carbon materials and the corresponding overall capacity (CN115708179A).
[0003] Attapulgite clay is a one-dimensional natural porous inorganic crystal. By loading it with biomass sucrose or furfuryl alcohol and then carbonizing and etching to remove the template, porous carbon nanotubes with high specific surface area can be obtained, exhibiting good battery performance. Waste cooking oil and recycled egg white are waste products from the catering and food processing industries. Waste cooking oil can be carbonized to generate carbon materials. Egg white solid solution is 90% protein and has a nitrogen content of approximately 16%, which can be used as a dopant to dope carbon materials, while simultaneously being carbonized to form carbon materials. Summary of the Invention
[0004] Purpose of the invention: To address the problems existing in the prior art, this invention provides a method for preparing N-doped porous carbon materials based on attapulgite and their application in supercapacitors. The method utilizes attapulgite crystals as a porous material template, waste cooking oil and recycled egg white as carbon and nitrogen sources, and mixes the three materials before preparing N-doped porous carbon materials through carbonization-alkaline-acid combined etching. When used in supercapacitors, these materials exhibit excellent specific capacitance and have the advantages of low cost, simple preparation method, and environmental friendliness.
[0005] Technical solution: On one hand, the present invention provides a method for preparing N-doped porous carbon materials based on attapulgite, comprising the following steps:
[0006] S1: Mix the recycled egg white with the waste cooking oil evenly to obtain a mixture; add attapulgite clay to the mixture, stir evenly, and let stand; then heat to 600~800℃ under nitrogen protection for carbonization for 2~3 hours to obtain a black powder.
[0007] S2: Mix the black powder with NaOH solution, heat at 100~180℃ for 5~10 h, filter, wash with water, and dry to obtain alkaline etched carbon material;
[0008] S3: The alkaline etched carbon material is placed in the dilute HF solution, stirred, filtered, washed with water, and dried to obtain an N-doped porous carbon material based on attapulgite.
[0009] Furthermore, in S1, the mass ratio of the recycled egg white to the waste cooking oil is 1:1 to 4.
[0010] Furthermore, in S1, the solid-liquid mass ratio of the attapulgite clay to the mixture is 1:1~2.
[0011] Furthermore, in S1, the settling time is 5-6 hours.
[0012] Furthermore, in S2, the solid-liquid mass ratio of the black powder to the NaOH solution is 20%.
[0013] Furthermore, the concentration of the NaOH solution is 2.5~4 mol / L.
[0014] Furthermore, in S2, the alkaline solution obtained by filtration can be recycled and used to synthesize zeolite, silica, etc.
[0015] Furthermore, in S3, the solid-liquid ratio of the alkaline etched carbon material to the dilute HF solution is 20%.
[0016] Furthermore, the concentration of the dilute HF solution is 5-10%.
[0017] Preferably, in step S3, the stirring time is 2-3 hours.
[0018] On the other hand, the present invention provides an application of an attapulgite-based N-doped porous carbon material prepared by any of the above methods in a supercapacitor.
[0019] The synthesis principle of this invention is as follows: Waste oil and recycled egg white are mixed evenly and added to attapulgite clay. The liquid mixture enters the internal pores of the attapulgite, covering the surface of the attapulgite fibers. Under nitrogen protection, carbonization forms carbon material. Simultaneously, the nitrogen element from the egg white protein dops the carbon. Treatment with NaOH solution under heating dissolves the silicon and aluminum components in the attapulgite. Residual mineral components and alkali-stable associated quartz can be removed by dissolving in dilute HF acid, yielding nitrogen-doped porous carbon material for use as an electrode material in supercapacitors. After removing the porous attapulgite template, the resulting carbon material has a hollow porous structure. The introduction of nitrogen from the egg white protein improves the electrode performance of the material. The combined alkali-dilute HF acid etching recovers most of the mineral components and completely removes residues, obtaining a relatively pure carbon material, avoiding the problem of large amounts of waste liquid requiring treatment after direct HF etching. The raw materials are mainly natural minerals and recycled materials, resulting in low cost and a green and environmentally friendly preparation process.
[0020] Beneficial Effects: This invention utilizes inexpensive clay minerals as templates and waste from the catering and food processing industries as a carbon source to prepare N-doped porous carbon superelectric materials. Combined with a green etching method, it achieves economical and green preparation of N-doped porous carbon materials. Compared with existing technologies, the specific beneficial effects are as follows:
[0021] Waste cooking oil and recycled egg whites are carbonized at high temperatures and used as electrode materials for supercapacitors. This method is inexpensive and achieves the reuse of waste. At the same time, the carbonization of egg whites into carbon materials can also provide nitrogen elements for the modification and doping of carbon materials.
[0022] A mixture of waste cooking oil and recycled egg white seeps into the pores of attapulgite, solidifies at high temperature, and carbonizes into carbon material. After etching away the mineral template, the resulting carbon material replicates the porous structure of the mineral, which is beneficial for the storage of sodium ions.
[0023] Alkaline etching of attapulgite yields an alkaline solution that can be recycled and used to synthesize products such as zeolite and silica. However, when etching with HF acid alone, the etching solution is difficult to recover. Alkaline etching alone is insufficient to completely remove attapulgite and impurity quartz. By using a combination of alkali and HF acid etching, not only are mineral components recovered, but the concentration of HF acid used is also lower, allowing for long-term use. This increases HF utilization, making it a green and economical approach that is also more environmentally friendly. Attached Figure Description
[0024] Figure 1 The XRD pattern of the N-doped porous carbon material prepared in Embodiment 1 of the present invention;
[0025] Figure 2 This is a SEM image of the N-doped porous carbon material prepared in Embodiment 1 of the present invention.
[0026] Figure 3The electrode performance of the N-doped porous carbon material prepared in Embodiment 1 of the present invention is shown. Detailed Implementation
[0027] The present invention will now be described in detail with reference to the embodiments.
[0028] Implementation method 1:
[0029] The recycled egg white and waste cooking oil were mixed evenly at a mass ratio of 1:1. Then, attapulgite clay was added at a solid-liquid mass ratio of 1:1, stirred evenly, and allowed to stand for 5 hours. The mixture was then transferred to a porcelain crucible and heated to 700℃ for 2 hours under nitrogen protection to obtain a black powder. The black powder was added to a 2.5 mol / L NaOH solution at a solid-liquid mass ratio of 20%, transferred to a reaction vessel, and heated at 180℃ for 5 hours to remove the attapulgite mineral components through alkaline etching. The mixture was then filtered, washed with water, and dried to obtain alkaline etched carbon material (the alkaline solution obtained from filtration can be recycled and used to synthesize zeolite, silica, and other products). The alkaline etched carbon material was then transferred to a 5% dilute HF solution at a solid-liquid mass ratio of 20%, stirred for 3 hours to further remove residual mineral components and impurities such as quartz. The mixture was then filtered, washed with water, and dried to obtain N-doped porous carbon material.
[0030] Figure 1 The XRD pattern of the N-doped porous carbon material shows the disappearance of the attapulgite characteristic peaks and the appearance of a peak with a domed shape in the 2θ range of 20–30°, indicating that it is an amorphous carbon material. The characteristic peak at 2θ 43° is a characteristic peak of graphitized carbon material. In addition, a small amount of quartz peaks remain in the material. Figure 2 The image shows an SEM image of an N-doped porous carbon material, which reveals that the carbon material still retains the morphology of attapulgite fibers. Figure 3 To assess its electrode performance as a capacitor electrode material, it exhibits a specific capacitance of 338.8 F / g at a current density of 0.5 A / g. In comparison, carbon materials obtained using only alkaline etching have a specific capacitance of 143 F / g, carbon materials obtained using only HF etching have a specific capacitance of 238 F / g, and carbon materials obtained using a combined alkaline-HF etching process have a specific capacitance of 308 F / g. Introducing nitrogen (N) increases the specific capacitance of N-doped porous carbon to 339 F / g, demonstrating its promising application potential in supercapacitors.
[0031] Implementation Method 2:
[0032] The recycled egg white and waste cooking oil were mixed evenly at a mass ratio of 1:2. Then, attapulgite clay was added at a solid-liquid mass ratio of 1:1.2, stirred evenly, and allowed to stand for 5 hours. The mixture was then transferred to a porcelain crucible and heated to 600℃ for 3 hours under nitrogen protection to obtain a black powder. The black powder was added to a 3 mol / L NaOH solution at a solid-liquid mass ratio of 20%, transferred to a reaction vessel, and heated at 150℃ for 6 hours to remove the attapulgite mineral components through alkaline etching. The mixture was then filtered, washed with water, and dried to obtain alkaline etched carbon material (the alkaline solution obtained from filtration can be recycled and used to synthesize zeolite, silica, and other products). The alkaline etched carbon material was then transferred to a 6% dilute HF solution at a solid-liquid mass ratio of 20%, stirred for 2.5 hours to further remove residual mineral components and impurities such as quartz. The mixture was then filtered, washed with water, and dried to obtain an N-doped porous carbon material with a specific capacitance of 328 F / g.
[0033] Implementation Method 3:
[0034] The recycled egg white and waste cooking oil were mixed evenly at a mass ratio of 1:3. Then, attapulgite clay was added at a solid-liquid mass ratio of 1:1.5, stirred evenly, and allowed to stand for 5 hours. The mixture was then transferred to a porcelain crucible and heated to 750°C for 2.5 hours under nitrogen protection to obtain a black powder. The black powder was added to a 3.5 mol / L NaOH solution at a solid-liquid mass ratio of 20%, transferred to a reaction vessel, and heated at 120°C for 8 hours to remove the attapulgite mineral components through alkaline etching. The mixture was then filtered, washed with water, and dried to obtain alkaline etched carbon material (the alkaline solution obtained from filtration can be recycled and used to synthesize zeolite, silica, and other products). The alkaline etched carbon material was then transferred to an 8% dilute HF solution at a solid-liquid mass ratio of 20%, stirred for 2.5 hours, and further removed residual mineral components and impurities such as quartz. The mixture was then filtered, washed with water, and dried to obtain an N-doped porous carbon material with a specific capacitance of 315 F / g.
[0035] Implementation Method 4:
[0036] The recycled egg white and waste cooking oil were mixed evenly at a mass ratio of 1:4. Then, attapulgite clay was added at a solid-liquid mass ratio of 1:2. The mixture was stirred evenly, allowed to stand for 5 hours, and then transferred to a porcelain crucible. Under nitrogen protection, it was heated to 800℃ for 2 hours to carbonize and obtain a black powder. The black powder was added to a 4 mol / L NaOH solution at a solid-liquid mass ratio of 20%, transferred to a reaction vessel, and heated at 100℃ for 10 hours to remove the attapulgite mineral components through alkaline etching. The mixture was then filtered, washed with water, and dried to obtain alkaline etched carbon material (the alkaline solution obtained from filtration can be recycled and used to synthesize zeolite, silica, and other products). The alkaline etched carbon material was then transferred to a 10% dilute HF solution at a solid-liquid mass ratio of 20%, stirred for 2 hours, and the residual mineral components and impurities (quartz) were further removed. The mixture was then filtered, washed with water, and dried to obtain N-doped porous carbon material with a specific capacitance of 308 F / g.
[0037] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing N-doped porous carbon materials based on attapulgite, characterized in that, Includes the following steps: S1: Mix the recycled egg white with waste cooking oil evenly to obtain a mixture; add attapulgite clay to the mixture, stir evenly, and let stand; then heat to 600~800℃ under nitrogen protection for carbonization for 2~3 h to obtain black powder; wherein, the egg white carbonization is carbon material, and can also provide N element to modify and dope carbon material. S2: Mix the black powder with NaOH solution, heat at 100~180℃ for 5~10 h, filter, wash with water, and dry to obtain alkaline etched carbon material; S3: The alkaline etched carbon material is placed in a dilute HF solution, stirred, filtered, washed with water, and dried to obtain an N-doped porous carbon material based on attapulgite.
2. The method for preparing N-doped porous carbon material based on attapulgite according to claim 1, characterized in that: In S1, the mass ratio of the recycled egg white to the waste cooking oil is 1:1~4; In S1, the solid-liquid mass ratio of the attapulgite clay to the mixture is 1:1~2.
3. The method for preparing N-doped porous carbon material based on attapulgite according to claim 1, characterized in that: In S1, the settling time is 5-6 hours.
4. The method for preparing N-doped porous carbon material based on attapulgite according to claim 1, characterized in that: In S2, the solid-liquid mass ratio of the black powder to the NaOH solution is 20%.
5. A method for preparing N-doped porous carbon material based on attapulgite according to claim 4, characterized in that: The concentration of the NaOH solution is 2.5~4 mol / L.
6. The method for preparing N-doped porous carbon material based on attapulgite according to claim 1, characterized in that: In S2, the alkaline solution obtained by filtration can be recycled and used to synthesize zeolite and silica.
7. The method for preparing N-doped porous carbon material based on attapulgite according to claim 1, characterized in that: In S3, the solid-liquid ratio of the alkaline etched carbon material to the dilute HF solution is 20%.
8. The method for preparing N-doped porous carbon material based on attapulgite according to claim 7, characterized in that: The concentration of the dilute HF solution is 5-10%.
9. A method for preparing N-doped porous carbon material based on attapulgite according to claim 1, characterized in that: In S3, the stirring time is 2-3 hours.
10. The application of the attapulgite-based N-doped porous carbon material prepared by the method according to any one of claims 1-9 in supercapacitors.