A method for preparing graphene from graphite oxide

Abstract

The application discloses a method for preparing graphene from graphite oxide, and belongs to the technical field of graphene preparation. The method comprises the following steps: (1) dispersing graphite oxide into a certain amount of deionized water to obtain a graphite oxide dispersion liquid, adding an auxiliary reducing agent into the graphite oxide dispersion liquid, and uniformly stirring to obtain a mixture; (2) performing rapid mechanical stirring on the mixture obtained in the step (1), and performing cyclic liquid phase shearing dispersion on the stirred mixture; (3) performing cyclic pressure filtration on the material obtained in the step (2) to achieve the purpose of liquid phase dispersion and peeling; and cleaning with deionized water during the cyclic pressure filtration; and (4) performing spray drying on the solution obtained in the step (3) to obtain the graphene. The application realizes acid-free, environment-friendly graphene production, low production cost and high quality.

Description

Technical Field

[0001] This invention relates to the field of graphene preparation technology, and specifically to a method for preparing graphene from graphite oxide. Background Technology

[0002] Graphene is a novel nanomaterial with a single-layer sheet-like structure composed of carbon atoms. It is a two-dimensional carbon atom crystal with a thickness of only one atom. Its basic structural unit is the most stable six-membered benzene ring among organic materials, making it the most ideal two-dimensional nanomaterial currently available. Since British scientists successfully isolated graphene in the laboratory in 2004, its unique hexagonal honeycomb-like two-dimensional crystal structure composed of sp2 hybrid orbitals has given it numerous excellent properties in optics, electricity, mechanics, and thermal aspects. These superior properties make graphene a promising candidate for applications in many fields, including new energy, energy storage, electronic devices, composite materials, biomedicine, and national defense, attracting widespread attention and becoming a current research focus.

[0003] The preparation of graphene is a prerequisite for graphene research and application. Currently, common methods for graphene preparation include mechanical exfoliation, redox methods, epitaxial growth, chemical vapor deposition (CVD), and electrochemical exfoliation. Among these, the redox method is one of the most widely used methods for graphene preparation. Due to the increased oxygen-containing functional groups in graphene oxide, it not only possesses a large specific surface area but also exhibits hydrophilicity. Graphene oxide is inexpensive, has abundant raw material sources, and enables large-scale graphene preparation.

[0004] However, the redox method uses large amounts of strong acids and oxidants, resulting in environmental problems due to the need to treat large quantities of acid. Therefore, some researchers have turned to liquid-phase exfoliation, but this method still faces challenges such as difficulty finding suitable solvents, long ultrasonic treatment times, and low concentrations. Korean researchers (J. Mater. Chem. C, 2015, 3, 7105) used NMMO, an environmentally friendly and non-toxic material with similar surface tension and high polarity to graphite, as the exfoliating solvent for graphite powder. They produced water-soluble solid graphene powder by ultrasonically treating graphite in an NMMO solution, followed by dilution, decantation, filtration, centrifugation, and drying. However, the entire experimental process requires sophisticated equipment, resulting in low graphene yields and limiting the industrial application of graphene. Using aromatic compounds as exfoliating agents to exfoliate graphite powder effectively separates graphene sheets, yielding large quantities of graphene in a short time. However, the aromatic compounds used as exfoliating solvents are toxic and can cause serious environmental pollution.

[0005] Currently, graphene is mainly prepared by high-temperature thermal reduction and hydrazine-based reducing agents. However, both methods have their drawbacks. The first method involves high reaction temperatures and requires sophisticated equipment; the second method uses hydrazine-based reducing agents, which are toxic and dangerous, and the reaction time is long, making it unsuitable for large-scale production and application. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing graphene from graphite oxide. This method addresses the issue that deep intercalation of graphite oxide requires strong oxidants or physical exfoliation, by employing liquid-phase shearing and pressure filtration techniques. After exfoliation and delamination of graphite oxide in the liquid phase, it is reduced to graphene with the assistance of vitamin C. This method avoids the environmental problems of redox methods, the low efficiency of physical exfoliation, the high cost and low yield of epitaxy and CVD growth methods, and the generation of harmful substances by electrochemical exfoliation methods. It achieves acid-free and environmentally friendly graphene production with low production costs and high quality.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing graphene from graphite oxide, the method comprising the following steps:

[0009] (1) Disperse graphite oxide in a certain amount of deionized water to obtain graphite oxide dispersion. Add an auxiliary reducing agent to the graphite oxide dispersion and stir evenly to obtain a mixture.

[0010] (2) The mixture obtained in step (1) is subjected to rapid mechanical stirring, and the stirred mixture is subjected to circulating liquid phase shear dispersion;

[0011] (3) The material obtained after step (2) is subjected to circulating pressure filtration to achieve liquid phase dispersion and stripping; deionized water is used for cleaning during circulating pressure filtration.

[0012] (4) The material obtained after step (3) is spray-dried to obtain the graphene.

[0013] In step (1) above, the mass ratio of graphite oxide to water in the graphite oxide dispersion is (0.002~0.01):1; the weight of the auxiliary reducing agent is 2~12% of the weight of graphite oxide.

[0014] In step (1) above, the auxiliary reducing agent is vitamin C (VC).

[0015] In step (2) above, the mechanical stirring time is 15 min to 1 h;

[0016] In step (2) above, the circulating liquid phase shear dispersion is accomplished by a glass reactor and a grinding pump. The glass reactor is equipped with a feeding pipe and a discharging pipe, both of which are connected to the grinding pump to form a circulation loop. A discharging valve and a circulation pump are provided on the liquid-liquid pipeline, and a circulation pump is also provided on the feeding pipe. When the discharging valve is opened, the mixture flows into the grinding pump under the action of the circulation pump and is ground, and then returns to the glass reactor through the feeding pipe, thereby realizing the circulating liquid phase shear dispersion of the mixture.

[0017] In step (2) above, the circulating liquid phase shear dispersion time is 20 min to 3 h.

[0018] In step (3) above, a pressure filter tank is used for circulating pressure filtration. During circulating pressure filtration, deionized water is added to the pressure filter tank for cleaning until the pH value of the solution is neutral.

[0019] In step (3) above, the pressure for circulating pressure filtration is 0.2-0.5 MPa.

[0020] The above step (4) is carried out in a centrifugal spray dryer with an inlet air temperature of 150-170℃ and an outlet air temperature of 100-120℃.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. This invention is the first to use liquid-phase shearing, pressure filtration, and VC reduction to prepare graphene from graphite oxide. The production process avoids the environmental problems associated with strong acids and strong oxidants. At the same time, liquid-phase shearing and pressure filtration enable continuous production. Compared with existing large-scale redox methods, the controllability of production process parameters is more refined, the quality is more controllable and stable, and the cost is lower than that of existing large-scale graphene preparation.

[0023] 2. Liquid phase shearing and liquid phase pressure filtration are relatively simple preparation processes for peeling and dispersion. This invention uses inexpensive and readily available graphite oxide as raw material. The liquid phase shearing, pressure filtration and vitamin C-assisted peeling method of this invention has the advantages of being environmentally friendly, having low production costs and high quality. Attached Figure Description

[0024] Figure 1 XRD analysis of graphite oxide.

[0025] Figure 2 XRD analysis of graphene.

[0026] Figure 3 XRD analysis of natural graphite. Detailed Implementation

[0027] To further understand the present invention, the present invention is described below with reference to examples. However, the examples are only for further illustrating the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention.

[0028] In the following embodiments, the circulating liquid phase shear dispersion is accomplished by a glass reactor and a grinding pump. The glass reactor is equipped with a feeding pipeline and a discharging pipeline, both of which are connected to the grinding pump to form a circulation loop. A discharging valve and a circulation pump are provided on the liquid-liquid pipeline, and a circulation pump is also provided on the feeding pipeline. When the discharging valve is opened, the mixture flows into the grinding pump under the action of the circulation pump and is ground, and then returns to the glass reactor through the feeding pipeline, thereby realizing the circulating liquid phase shear dispersion of the mixture.

[0029] Example 1:

[0030] The process of preparing graphene using graphene oxide in this embodiment is as follows:

[0031] (1) Take 10L of water and put it into a 10L glass reactor. Weigh 50g of graphite oxide powder and add it to the 10L glass reactor to obtain a graphite oxide dispersion. Turn on the stirrer in the glass reactor and stir for 5min. Weigh 5g of VC and add it to the 10L glass reactor, and continue stirring for another 10min. The experimental conditions for this dispersion process are a stirring speed of 250rpm and a temperature of room temperature.

[0032] (2) After step (1) is completed, connect the drain and feed lines of the 10L glass reactor to the grinding pump, open the drain valve of the 10L glass reactor, and start the grinding pump. After the mixture circulates in the grinding pump for 1 hour, close the drain valve of the 10L glass reactor and stop grinding.

[0033] (3) Pour the mixture obtained from the circulating liquid phase shear dispersion in step (2) into a 30L pressure filter tank, and add deionized water to the filter tank at the same time. Start the pressure filter and set the pressure value to 0.3MPa. Continue the pressure filter operation for 1 hour. Stop the operation when the deionized water reaches neutrality.

[0034] (4) After step (3) is completed, place the resulting mixture in a stirring container and dry it with a centrifugal spray dryer to remove water. The spray dryer has an inlet air temperature of 160°C and an outlet air temperature of 110°C. It can be stored at room temperature.

[0035] The obtained graphene samples were characterized by XRD. Figure 1 The X-ray diffraction-XRD analysis of graphite oxide raw material shows that graphite oxide has a characteristic diffraction peak near 11.68°. Figure 2The XRD pattern of the prepared graphene sample is shown. Compared with graphene oxide, the graphene sample treated with cyclic liquid phase shearing and pressure filtration does not have obvious characteristic diffraction peaks near 13.1°, while a relatively broad diffraction peak appears near 24.7°. Figure 3 XRD analysis of natural graphite showed a distinct diffraction peak around 26.7°. This indicates that graphene oxide powder was reduced to graphene under conditions of liquid-phase shearing, pressure filtration, and assisted VC reduction.

[0036] Example 2:

[0037] The process of preparing graphene using graphene oxide in this embodiment is as follows:

[0038] (1) Take 30L of water and put it into a 50L glass reactor. Weigh 150g of graphite oxide powder and add it to the 50L glass reactor to obtain a graphite oxide dispersion. Start stirring in the glass reactor for 10 minutes. Weigh 12g of VC and add it to the 50L glass reactor, and continue stirring for another 20 minutes. The experimental conditions for this dispersion process are a stirring speed of 250rpm and a temperature of room temperature.

[0039] (2) After step (1) is completed, connect the drain and feed lines of the 50L glass reactor to the special grinding pump, open the drain valve of the 50L glass reactor, and start the grinding pump. After the mixture circulates in the grinding pump for 3 hours, close the drain valve of the 50L glass reactor and stop grinding.

[0040] (3) Pour the mixture obtained from the circulating liquid phase shear dispersion in step (2) into a 100L pressure filter tank, and add deionized water to the filter tank at the same time. Start the pressure filter and set the pressure value to 0.3MPa. Continue the pressure filter operation for 3 hours. Stop the operation when the deionized water reaches neutrality.

[0041] (4) After step (3) is completed, place the resulting mixture in a stirring container and dry it with a centrifugal spray dryer to remove water. The spray dryer has an inlet air temperature of 160°C and an outlet air temperature of 110°C. It can be stored at room temperature.

[0042] The graphene sample prepared in this embodiment was characterized by XRD, which showed that graphene oxide powder was reduced to graphene under the conditions of liquid phase shearing, pressure filtration and assisted VC reduction.

Claims

1. A method of preparing graphene from graphite oxide, characterized by: The method includes the following steps: (1) Graphite oxide is dispersed in a certain amount of deionized water to obtain a graphite oxide dispersion. An auxiliary reducing agent is added to the graphite oxide dispersion and stirred evenly to obtain a mixture. The mass ratio of graphite oxide to water in the graphite oxide dispersion is (0.002~0.01):

1. The weight of the auxiliary reducing agent is 2~12% of the weight of the graphite oxide. (2) The mixture obtained in step (1) is subjected to rapid mechanical stirring, and the stirred mixture is subjected to circulating liquid phase shear dispersion. The circulating liquid phase shear dispersion is accomplished by a glass kettle and a grinding pump. The glass kettle is equipped with a feeding pipe and a discharging pipe. Both the feeding pipe and the discharging pipe are connected to the grinding pump to form a circulation loop. A discharging valve and a circulation pump are provided on the discharging pipe, and a circulation pump is also provided on the feeding pipe. When the discharging valve is opened, the mixture flows into the grinding pump under the action of the circulation pump and is ground. It then returns to the glass kettle through the feeding pipe, thereby realizing the circulating liquid phase shear dispersion of the mixture. (3) The material obtained after step (2) is subjected to circulating pressure filtration to achieve liquid phase dispersion and stripping; deionized water is used for cleaning during circulating pressure filtration. (4) The material obtained after step (3) is spray-dried to obtain the graphene.

2. The method of claim 1, wherein: In step (1), the auxiliary reducing agent is vitamin C (VC).

3. The method of claim 1, wherein: In step (2), the mechanical stirring time is 15 min to 1 h.

4. The method of claim 1, wherein the graphene is prepared from graphite oxide. In step (2), the circulating liquid phase shear dispersion time is 20 min to 3 h.

5. The method of claim 1, wherein the graphene is prepared from graphite oxide. In step (3), a pressure filter tank is used for circulating pressure filtration. During circulating pressure filtration, deionized water is added to the pressure filter tank for cleaning until the pH value of the solution is neutral.

6. The method of claim 5, wherein the graphene is prepared from the graphite oxide. In step (3), the pressure for circulating pressure filtration is 0.2-0.5 MPa.

7. The method of claim 1, wherein the graphene is prepared from graphite oxide. Step (4) is carried out in a centrifugal spray dryer with an inlet air temperature of 150-170℃ and an outlet air temperature of 100-120℃.

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