Method for preparing graphene sponge
By synthesizing three-dimensional porous zinc oxide from the bottom up and combining it with chemical vapor deposition to prepare graphene sponges, the problem of insufficient specific surface area and pore volume of graphene materials in traditional methods has been solved, realizing efficient and low-cost preparation of graphene sponges suitable for supercapacitors.
Patent Information
- Application Number
- CN202511174532.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-11
- Publication Date
- 2025-11-18
AI Technical Summary
Existing technologies for preparing three-dimensional graphene materials suffer from problems such as small specific surface area, low bulk density, limited pore volume, difficulty in template removal, high cost, and harsh heat treatment temperatures, which affect their application in supercapacitors.
A three-dimensional porous zinc oxide substrate was synthesized using a bottom-up approach. Graphene sponge was then prepared by chemical vapor deposition. Acetylene was used as the carbon source, and the template was removed by etching with HCl and HF to obtain a graphene sponge with high specific surface area and pore volume.
This method simplifies the preparation process, reduces costs, increases the specific surface area and pore volume of graphene sponges, makes them suitable for supercapacitors, and is pollution-free, overcoming the shortcomings of traditional methods.
Smart Images
Figure CN120964787A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of porous carbon materials, specifically relating to a method for preparing graphene sponge. Its key feature is the use of a bottom-up approach to synthesize three-dimensional porous zinc oxide, which is then used as a substrate to prepare graphene sponge via chemical vapor deposition (CVD). Background Technology
[0002] Since the discovery of graphene, a typical two-dimensional material, in 2004, it has been a major focus of research due to its unique mechanical and chemical properties, as well as its high thermal and electrical conductivity. Notably, graphene possesses a very high specific surface area and extremely high carrier mobility, making it an ideal electrode material for electric double-layer capacitors (ECs). However, graphene exhibits strong in-plane van der Waals forces, causing it to adhere and even tend to revert to graphite. This significantly reduces its specific surface area, limiting its practical application in ECs. The most effective way to address this problem is to construct three-dimensional graphene structures. Advanced three-dimensional graphene architectures require at least two fundamental conditions: first, the three-dimensional structure should prevent the re-stacking of graphene sheets to maintain graphene's superior two-dimensional physical and chemical properties; second, the three-dimensional architecture should enable a large accessible surface area, efficient mass transfer, and high electronic conductivity, which are crucial for electrical and electrochemical devices.
[0003] Several typical three-dimensional porous graphene structures include graphene aerogels, graphene hydrogels, graphene frameworks, and graphene sponges. Researchers have synthesized graphene aerogels (J. 2D Mater., 2017, 4, 032001) and graphene hydrogels (J. ACS nano, 2010, 4, 4324) using graphene oxide as a precursor. However, the poor conductivity of graphene oxide and the fact that the synthesized three-dimensional graphene is composed of intersecting fragments lead to reduced surface area, electrical conductivity, and mechanical properties. Three-dimensional graphene prepared by chemical vapor deposition (CVD) possesses a high-conductivity monolithic structure while effectively maintaining the template shape, including the graphene framework and graphene sponge (Carbon. 2018, 135, 52). This method typically uses nickel foam as a substrate and catalyst, generally exhibiting interconnected porous structures, high electrical conductivity, and good mechanical properties. However, due to substrate limitations, the resulting three-dimensional graphene often has a small specific surface area, low bulk density, and limited pore volume, while also lacking structural diversity. Furthermore, the substrate removal and transfer process is skill-intensive and can lead to damage and leave metal and solvent residues. Therefore, we need to explore a method for synthesizing graphene sponges that is highly selective, has a low reaction temperature, and is easy to produce.
[0004] To address the shortcomings of existing technologies and the needs of research and application in this field, this invention provides a method for preparing graphene sponges. This method can shorten the synthesis time, reduce costs, is simple and easy to operate, and is pollution-free. At the same time, it overcomes the problems that common three-dimensional graphene often has a small specific surface area, low bulk density, and limited pore volume. Summary of the Invention
[0005] This invention proposes a method for preparing graphene sponges. A three-dimensional porous zinc oxide is synthesized using a bottom-up approach, and this zinc oxide is used as a substrate to prepare graphene sponges via chemical vapor deposition (CVD). This method shortens the synthesis time, reduces costs, is simple and easy to operate, and is pollution-free. The synthesized graphene sponges have promising applications in supercapacitors.
[0006] The preparation method uses three-dimensional porous ZnO obtained by high-temperature sintering of ZnO particles as a template agent and acetylene as a carbon source to synthesize graphene sponges. The ZnO sample is placed in a tube furnace, and the temperature is slowly increased to 800-950℃ in an air atmosphere and held for 2-3 hours to obtain three-dimensional porous ZnO. The synthesized three-dimensional porous ZnO sample is then placed in a CVD horizontal furnace, and the temperature is slowly increased to 400-500℃. Acetylene gas is then introduced into the furnace and held for 2-3 hours. Subsequently, a mixed solution of 1.5-2% HCl and 2.5-3% HF (by mass fraction) is used to dissolve the three-dimensional porous ZnO framework to obtain the final product.
[0007] The specific steps are as follows:
[0008] Step 1: Place 100-200mg of ZnO nanopowder into a high-temperature sintering furnace and heat it to 800-950℃ at a rate of 5-10℃ / min. Hold the temperature for 2-3 hours to obtain a three-dimensional porous ZnO template.
[0009] Step 2: The three-dimensional porous ZnO template synthesized in the previous step is then placed in a CVD horizontal furnace, and N2 is introduced for 10 minutes to remove air impurities. The temperature is then increased to 400-500℃ at a rate of 5-10℃ / min, and acetylene gas with a volume fraction of 20-30% is introduced for 2-3 hours. After natural cooling, the template is removed, and N2 is introduced throughout the process.
[0010] Step 3: Prepare 400-500 ml of 1.5-2% HCl solution. At room temperature, use a plastic bottle to stir and etch twice at a uniform speed, 2 hours each time. After etching, filter the solution under vacuum. During the filtration process, wash the solution several times with distilled water to ensure that the mixed solution is completely removed. Dry the solution in a vacuum chamber at 60-70℃ for 12 hours to obtain the final product.
[0011] The advantages of this invention are as follows: It allows for complete template removal during the preparation process at a relatively low temperature, overcoming problems such as high preparation costs, stringent heat treatment temperatures, difficulty in completely removing the template, and poor structural stability of the product. Simultaneously, it overcomes the common limitations of three-dimensional graphene, which often exhibits small specific surface area, low bulk density, and limited pore volume. The synthesized graphene sponge has promising applications in supercapacitors. This method can be extended to the preparation of other carbon materials. Attached Figure Description
[0012] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0013] Figure 1 These are scanning electron microscope images of the three-dimensional porous zinc oxide prepared in Example 1;
[0014] Figure 2 These are the N2 adsorption-desorption curves and pore size distribution diagrams of the three-dimensional porous zinc oxide prepared in Example 1;
[0015] Figure 3 This is the X-ray diffraction pattern of the graphene sponge prepared in Example 1;
[0016] Figure 4 This is a scanning electron microscope image of the graphene sponge prepared in Example 1;
[0017] Figure 5 These are transmission electron microscope images of the graphene sponge prepared in Example 1;
[0018] Figure 6 These are the N2 adsorption-desorption curves and pore size distribution diagrams of the graphene sponge prepared in Example 1;
[0019] Figure 7 This is a Raman image of the graphene sponge prepared in Example 1;
[0020] Figure 8 This is the dispersive spectrum of the graphene sponge prepared in Example 1; Detailed Implementation
[0021] Example 1:
[0022] Step 1: Place 150mg of ZnO nanopowder into a high-temperature sintering furnace and heat it to 900℃ at a rate of 5℃ / min. Hold the temperature for 3 hours to obtain a three-dimensional porous ZnO template.
[0023] Step 2: Using the synthesized three-dimensional porous ZnO as a template, N2 is introduced for 10 minutes to remove air impurities. The temperature is increased to 450℃ at a rate of 5℃ / min, and acetylene gas with a volume fraction of 20% is introduced for 3 hours. After natural cooling, the sample is removed, and N2 is introduced throughout the process.
[0024] Step 3: Prepare 400 ml of 1.5% HCl solution and etch twice at a constant speed using a plastic bottle at room temperature, each time for 2 hours. After etching, filter the solution and wash it several times with distilled water during the filtration process to ensure that the mixed solution is completely removed. Dry the solution in a vacuum chamber at 70°C for 12 hours to obtain the final product.
[0025] Example 2:
[0026] Step 1: Place 150mg of ZnO nanopowder into a high-temperature sintering furnace and heat it to 800℃ at a rate of 5℃ / min. Hold the temperature for 3 hours to obtain a three-dimensional porous ZnO template.
[0027] Step 2: Using the synthesized three-dimensional porous ZnO as a template, N2 is introduced for 10 minutes to remove air impurities. The temperature is increased to 450℃ at a rate of 5℃ / min, and acetylene gas with a volume fraction of 20% is introduced for 3 hours. After natural cooling, the sample is removed, and N2 is introduced throughout the process.
[0028] Step 3: Prepare 400 ml of 1.5% HCl solution and etch twice at a constant speed using a plastic bottle at room temperature, each time for 2 hours. After etching, filter the solution and wash it several times with distilled water during the filtration process to ensure that the mixed solution is completely removed. Dry the solution in a vacuum chamber at 70°C for 12 hours to obtain the final product.
[0029] Example 3:
[0030] Step 1: Place 150mg of ZnO nanopowder into a high-temperature sintering furnace and heat it to 850℃ at a rate of 10℃ / min. Hold the temperature for 3 hours to obtain a three-dimensional porous ZnO template.
[0031] Step 2: Using the synthesized three-dimensional porous ZnO as a template, N2 is introduced for 10 minutes to remove air impurities. The temperature is increased to 450℃ at a rate of 10℃ / min, and acetylene gas with a volume fraction of 20% is introduced for 3 hours. After natural cooling, the sample is removed, and N2 is introduced throughout the process.
[0032] Step 3: Prepare 400 ml of 1.5% HCl solution and etch twice at a constant speed using a plastic bottle at room temperature, each time for 2 hours. After etching, filter the solution and wash it several times with distilled water during the filtration process to ensure that the mixed solution is completely removed. Dry the solution in a vacuum chamber at 70°C for 12 hours to obtain the final product.
[0033] Example 4:
[0034] Step 1: Place 150mg of ZnO nanopowder into a high-temperature sintering furnace and heat it to 950℃ at a rate of 5℃ / min. Hold the temperature for 3 hours to obtain a three-dimensional porous ZnO template.
[0035] Step 2: Using the synthesized three-dimensional porous ZnO as a template, N2 is introduced for 10 minutes to remove air impurities. The temperature is increased to 450℃ at a rate of 10℃ / min, and acetylene gas with a volume fraction of 20% is introduced for 3 hours. After natural cooling, the sample is removed, and N2 is introduced throughout the process.
[0036] Step 3: Prepare 400 ml of 1.5% HCl solution and etch twice at a constant speed using a plastic bottle at room temperature, each time for 2 hours. After etching, filter the solution and wash it several times with distilled water during the filtration process to ensure that the mixed solution is completely removed. Dry the solution in a vacuum chamber at 70°C for 12 hours to obtain the final product.
[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, and variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any equivalent changes, alterations, and variations made to the above embodiments based on the implementation techniques of the present invention are within the protection scope of the present invention.
Claims
1. A method for preparing graphene sponges by obtaining a three-dimensional porous zinc oxide template using a top-down approach. Its characteristics are... The template shape can be completely preserved and the template can be completely removed during the preparation process. The method for preparing the graphene sponge is characterized by including the following specific steps: Step 1: Place 100-200mg of ZnO nanopowder into a high-temperature sintering furnace and heat it to 800-950℃ at a rate of 5-10℃ / min. Hold the temperature for 2-3 hours to obtain a three-dimensional porous ZnO template. Step 2: The three-dimensional porous ZnO template synthesized in the previous step is then placed in a CVD horizontal furnace, and N2 is introduced for 10 minutes to remove air impurities. The temperature is then increased to 400-500℃ at a rate of 5-10℃ / min, and acetylene gas with a volume fraction of 20-30% is introduced for 2-3 hours. After natural cooling, the template is removed, and N2 is introduced throughout the process. Step 3: Prepare 400-500 ml of 1.5-2% HCl solution. At room temperature, use a plastic bottle to stir and etch twice at a uniform speed, 2 hours each time. After etching, filter the solution under vacuum. During the filtration process, wash the solution several times with distilled water to ensure that the mixed solution is completely removed. Dry the solution in a vacuum chamber at 60-70℃ for 12 hours to obtain the final product.
2. The preparation method according to claim 1, characterized in that, In step one, the ZnO nanopowder has a size of less than 200 nm.
3. The preparation method according to claim 1, characterized in that, In step two, the reaction temperature range after heating is 450℃.
4. The preparation method according to claim 1, characterized in that, In step two, the volume fraction of acetylene gas is 20-30%.