A method for preparing graphene nanosheets by electrochemical cathode exfoliation and the application of graphene nanosheets.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- DALIAN INSTITUTE OF CHEMICAL PHYSICS CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2022-08-09
- Publication Date
- 2026-05-26
AI Technical Summary
In existing electrochemical cathode exfoliation methods, graphite flakes are prone to detaching from the electrode, resulting in insufficient exfoliation, low exfoliation rate, and difficulty in preparing high-quality graphene.
Electrochemical cathode exfoliation is performed inside a conductive cylindrical tube, using conductive materials to form a confined space to maintain electrical contact between graphite microsheets, thus preparing graphene nanosheets through electrochemical intercalation exfoliation.
This method enables the efficient preparation of high-quality graphene nanosheets, avoiding the problem of graphite microsheet detachment in traditional methods. It is simple to operate, low in cost, and suitable for applications such as supercapacitors, batteries, and conductive inks.
Smart Images
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Abstract
Description
Technical Field
[0001] This application relates to a method for preparing graphene nanosheets by electrochemical cathode exfoliation and the application of graphene nanosheets, belonging to the field of controllable preparation technology of graphene materials. Background Technology
[0002] Few-layer high-quality graphene (less than 10 layers) possesses high electrical conductivity, chemical and thermodynamic stability, and excellent electrical properties, making it highly promising for emerging applications such as micro / nanoelectronics, energy storage, and catalysis. Among various methods for synthesizing graphene, electrochemical exfoliation is a relatively rapid, simple, and high-throughput intercalation-assisted exfoliation method. Anodic exfoliation of graphene has been widely reported, but it is known to induce oxidation or other doping reactions, thereby introducing defects on the graphene surface.
[0003] Graphene prepared by cathode exfoliation (especially in aqueous solutions) exhibits minimal surface oxidation, making it a superior method for producing high-quality graphene. However, a common problem with existing electrochemical cathode exfoliation processes is that insufficiently exfoliated graphite flakes easily detach from the graphite electrode. This loss of electrical contact halts the electrochemical intercalation and exfoliation reaction, resulting in low graphene exfoliation yields. Encasing the graphite electrode in paraffin wax within a confined space, allowing the detached graphite flakes to maintain electrical contact and continue exfoliation, is a practical method (ACS Appl Mater Interfaces, 2017, 39, 34456). However, this method, applied to anodic electrochemical exfoliation, suffers from the inability of brittle paraffin wax to withstand the expansion pressures generated during prolonged electrochemical exfoliation. Summary of the Invention
[0004] This patent proposes a method for preparing graphene nanosheets by electrochemical cathode exfoliation within a confined space. A conductive cylindrical tube is used to form a confined space, and graphene nanosheets are synthesized in one step by electrochemical cathode exfoliation of graphite.
[0005] The purpose of this invention is to overcome the problem of insufficient peeling caused by the loss of electrical contact when graphite microsheets are peeled from electrodes. The method of this invention is simple, easy to scale up, and can be used to produce high-quality pure graphene.
[0006] One aspect of this application provides a method for preparing graphene nanosheets by electrochemical cathode exfoliation in an aqueous solution. The graphene nanosheets prepared by this method exhibit excellent chemical properties and can be widely used in supercapacitors, batteries, conductive inks and other fields.
[0007] The method for preparing graphene nanosheets by electrochemical cathode exfoliation includes the following steps:
[0008] Graphite powder is placed inside a conductive cylindrical tube that is closed at one end, serving as an electrochemical cathode; a conductive material is used as an electrochemical anode; wherein the graphite powder is electrically connected to the conductive cylindrical tube.
[0009] An electrochemical circuit is formed by the electrolyte, the electrochemical anode, and the electrochemical cathode, wherein the electrolyte comprises a solution of a soluble salt containing a large cation and / or a solution of a base containing a large cation;
[0010] A cell voltage is applied between the electrochemical cathode and the electrochemical anode to electrochemically exfoliate graphite and obtain the graphene nanosheets.
[0011] In this application, a soluble salt or alkali containing a large cation is used as the electrolyte for exfoliation. Graphite, as a raw material, is placed inside a conductive cylindrical tube and fully contacts the tube through electrode clamps, thus forming the cathode. A conductive material serves as the counter electrode, connected to the positive electrode of a DC power supply. An appropriate cell voltage is applied for electrochemical exfoliation. The graphene or graphite flakes exfoliated from the graphite electrode gradually accumulate within the cylindrical tube, building a new conductive network to ensure the continued electrochemical exfoliation reaction. The exfoliated product is washed, ultrasonically dispersed to obtain a graphene slurry, and then dried to obtain graphene powder.
[0012] Soluble salts or alkaline electrolytes refer to salts or bases of any concentration that are electrochemically inert to the anode and the conductive tube. The cations of the salts or bases used must be large enough to disrupt the van der Waals forces between the graphite layers, or to accompany the gas evolution reaction between the graphite layers.
[0013] The round tube used is open and can be made of conductive material, or it can be achieved by coating the inner surface of a non-conductive tube with conductive material, or by attaching conductive foil to the inner surface of a non-conductive tube.
[0014] Optionally, the graphite powder is selected from at least one of natural flake graphite powder, artificial graphite powder, and microcrystalline graphite powder.
[0015] Optionally, the conductive material is selected from at least one of graphite, platinum, gold, silver, nickel, aluminum, and glassy carbon. The conductive material is one that does not undergo electrochemical corrosion in the electrolyte in use.
[0016] Optionally, the soluble salt of the large cation is selected from at least one of sodium sulfate, potassium hexafluorophosphate, and sodium tetrafluoroborate;
[0017] The base of the large cation is selected from at least one of potassium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.
[0018] Optionally, the concentration of the soluble salt of the large cation or the base of the large cation in the electrolyte is 0.01 mol / L to 15 mol / L.
[0019] Optionally, the concentration of the soluble salt of the large cation or the base of the large cation in the electrolyte is 1 mol / L to 10 mol / L.
[0020] Optionally, the concentration of the soluble salt of the large cation or the base of the large cation in the electrolyte is independently selected from any value among 0.01 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 5 mol / L, 7 mol / L, 10 mol / L, 12 mol / L, and 15 mol / L, or any range between any two of the above points.
[0021] Optionally, the reaction temperature for the electrochemical stripping is 1–100°C.
[0022] Optionally, the reaction time for the electrochemical stripping is 1 min to 24 h.
[0023] Optionally, the reaction temperature for the electrochemical stripping is 5–50°C.
[0024] Optionally, the reaction temperature for the electrochemical stripping is independently selected from any value among 1°C, 10°C, 30°C, 50°C, 80°C, and 100°C, or any range between any two of the above.
[0025] Optionally, the reaction time for the electrochemical stripping is independently selected from any value among 1 min, 10 min, 30 min, 45 min, 1 h, 6 h, 12 h, 18 h, and 24 h, or any range between any two of the above points.
[0026] Optionally, the tank voltage is 2 to 30V.
[0027] Optionally, the tank voltage is independently selected from any value among 2V, 6V, 8V, 10V, 15V, 20V, 25V, and 30V, or any range between any two of the above.
[0028] Optionally, the method further includes:
[0029] After electrochemical exfoliation of graphite, the exfoliated product is washed and ultrasonically dispersed to obtain graphene slurry, which is then dried to obtain the graphene nanosheets.
[0030] Optionally, the washing method is vacuum filtration or centrifugal washing.
[0031] Optionally, the drying method is at least one of natural drying, heat drying, vacuum drying, and freeze drying.
[0032] Optionally, the graphene nanosheets have a diameter of 0.5–20 μm.
[0033] Optionally, the surface oxygen content of the graphene nanosheets is <6 at.
[0034] Optionally, the solvent for ultrasonic dispersion is selected from at least one of dimethylformamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide.
[0035] Optionally, the ultrasonic dispersion time is 5 to 12 hours.
[0036] This application describes a method for preparing graphene by electrochemical cathode exfoliation in a conductive cylindrical tube, achieved through the following steps: Graphite material is placed inside a conductive metal tube as the cathode, and a conductive material acts as the anode. A certain voltage is applied in an aqueous or organic electrolyte medium. The graphite expands due to electrochemical intercalation and begins to fill the tube, forming a secondary electrode within the tube for further exfoliation. The reaction continues, with optimized reaction time. The expanded and exfoliated graphite is collected and thoroughly washed to remove solvent residue. This is further dispersed in an organic solvent using gentle ultrasonication. The electrolyte in these steps can be any electrolyte capable of achieving electrochemical exfoliation of graphite.
[0037] Another aspect of this application is to provide an application of graphene nanosheets prepared by the above method in supercapacitors, batteries, and conductive inks.
[0038] The beneficial effects that this application can produce include:
[0039] (1) The preparation method of this invention avoids the disadvantage of insufficiently peeled graphite microsheets easily detaching from the electrode and stopping the peeling process in the traditional electrochemical cathode stripping process; it is a method for preparing graphene nanosheets with simple equipment, convenient operation, mild conditions, good repeatability, low cost and easy process scale-up. The product obtained by this invention has high quality, good performance and wide range of applications.
[0040] (2) This invention prepares few-layer graphene nanosheets by enclosing a graphite electrode within a confined conductive circular tube, using it as a cathode, and performing electrochemical exfoliation. This preparation method ensures that the graphite microsheets exfoliated from the electrode are confined within the designated circular tube space, thus maintaining conductive contact in the electrolyte. This allows the exfoliation reaction to continue, extending the electrochemical exfoliation process and ultimately yielding high-quality few-layer graphene. The prepared graphene has potential applications in energy storage and manufacturing of electronic components. Attached Figure Description
[0041] Figure 1 This is a schematic diagram of an apparatus for preparing graphene by electrochemical cathode exfoliation of graphite materials in a conductive circular tube.
[0042] Figure 2 This is a transmission electron microscope (TEM) image of the graphene nanosheets prepared in Example 1.
[0043] Figure 3 This is a high-resolution transmission electron microscope (TEM) image of the graphene nanosheets prepared in Example 1.
[0044] Figure 4 This is the Raman spectrum of the graphene nanosheets prepared in Example 1.
[0045] Figure 5 This is the X-ray photoelectron spectroscopy (XPS) spectrum of the graphene nanosheets prepared in Example 1.
[0046] in:
[0047] 1. Anode; 2. Graphite cathode; 3. Electrolyte; 4. Electrolysis system; 5. Conductive tube; 6. Alligator clips connecting the graphite electrode and the conductive tube. Detailed Implementation
[0048] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.
[0049] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.
[0050] The analysis method in the embodiments of this application is as follows:
[0051] TEM testing and analysis were performed using a JEM-2100 transmission electron microscope.
[0052] HRTEM analysis was performed using a JEM-2100 transmission electron microscope.
[0053] Raman spectroscopy analysis was performed using a LabRAM HR800 spectrometer.
[0054] XPS analysis was performed using X-ray photoelectron spectroscopy (model EscaLab 250Xi).
[0055] Example 1
[0056] Add 20 mL of potassium hydroxide aqueous solution (1 mol / L) to the electrolytic cell. Then, connect a platinum sheet electrode (2.5 cm × 2.5 cm) to the positive terminal of a DC power supply. Use alligator clips to fill a 0.5 cm diameter copper tube with graphite powder and connect it to the negative terminal of the DC power supply, immersing the graphite electrode and platinum sheet electrode in the electrolyte solution (separation device as follows). Figure 1 As shown, the platinum electrode is completely immersed, while the graphite electrode is immersed no more than 0.2 cm at a time. 2A 6V tank voltage was applied, and after the power was turned on, the graphite electrode began to expand. After several minutes, the expanded graphite micro-flakes gradually filled the copper tube. The exfoliation was stopped after 30 minutes at 25°C. The reaction product was thoroughly washed with high-purity water and ethanol, then dispersed in DMF solution and sonicated in a cold water bath for 1 hour. TEM and HRTEM images of the exfoliated graphene are shown below. Figure 2 and Figure 3 ,like Figure 2 As shown, large-scale graphene sheet structures were obtained; as Figure 3 As shown, the obtained graphene is multi-layered; Raman spectroscopy data shows an ID / IG value of 0.22 (as shown). Figure 4 (As shown).
[0057] XPS analysis was performed on the graphene obtained in Example 1, and the results are as follows: Figure 5 ,from Figure 5 It can be seen that its C1S peak does not show obvious splitting, indicating that the oxygen content is extremely low and the graphene product is of high quality.
[0058] Comparative Example 1
[0059] Add 20 mL of sodium sulfate aqueous solution (7 mol / L) to the electrolytic cell. Then, connect a platinum sheet electrode (2.5 cm × 2.5 cm) to the positive terminal of the DC power supply. Use alligator clips to hold graphite paper (2 cm × 4 cm) in a 2 cm diameter plastic tube lined with copper foil and connect it to the negative terminal of the DC power supply, immersing the graphite electrode and platinum sheet electrode in the electrolyte solution (separation device as follows). Figure 1 As shown, the platinum electrode is completely immersed, while the graphite electrode is immersed no more than 0.2 cm at a time. 2 An 8V tank voltage was applied, and the graphite electrode began to expand after the power was turned on. After a few minutes, the expanded graphite micro-sheets gradually filled the copper tube. The peeling was stopped after 45 minutes at 35°C. The reaction product was thoroughly washed with high-purity water and ethanol, and then dispersed in DMF solution and sonicated in a cold water bath for 1 hour.
[0060] Comparative Example 2
[0061] Add 30 mL of a 0.5 mol / L potassium hydroxide aqueous solution to the electrolytic cell. Then, connect a platinum electrode (2.5 cm × 2.5 cm) to the positive terminal of a DC power supply. Use alligator clips to hold a graphite paper (3 cm × 4 cm) inside a copper tube and connect it to the negative terminal of the DC power supply, immersing both the graphite electrode and the platinum electrode in the electrolyte solution (using a stripping device such as...). Figure 1 As shown, the platinum electrode is completely immersed, while the graphite electrode is immersed no more than 0.2 cm at a time. 2A 2V cell voltage was applied, and the copper tube was peeled for 10 minutes at room temperature. Then, a 6V cell voltage was applied, and the copper tube was peeled for 30 minutes at room temperature at 25°C. After the power was turned on, the graphite electrode began to expand. After a few minutes, the expanded graphite micro-flakes gradually filled the copper tube. The peeling was stopped after 40 minutes. The reaction product was thoroughly washed with high-purity water and ethanol, and then dispersed in DMF solution and sonicated in a cold water bath for 1 hour.
[0062] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.
Claims
1. A method for preparing graphene nanosheets by electrochemical cathode exfoliation, characterized in that, Includes the following steps: Graphite powder is placed inside a conductive cylindrical tube that is closed at one end, serving as an electrochemical cathode; this ensures that the graphite flakes peeled off from the electrode are confined within the designated cylindrical tube space, thereby maintaining conductive contact in the electrolyte and allowing the peeling reaction to continue. A conductive material is used as the electrochemical anode; wherein the graphite powder is electrically connected to the conductive cylindrical tube; An electrochemical circuit is formed by the electrolyte, the electrochemical anode, and the electrochemical cathode, wherein the electrolyte comprises a solution of a soluble salt containing a large cation and / or a solution of a base containing a large cation; A cell voltage is applied between the electrochemical cathode and the electrochemical anode to electrochemically exfoliate graphite and obtain the graphene nanosheets.
2. The method according to claim 1, characterized in that, The graphite powder is selected from at least one of natural flake graphite powder, artificial graphite powder, and microcrystalline graphite powder.
3. The method according to claim 1, characterized in that, The conductive material is selected from at least one of graphite, platinum, gold, silver, nickel, aluminum, and glassy carbon.
4. The method according to claim 1, characterized in that, The soluble salt of the large cation is selected from at least one of sodium sulfate, potassium hexafluorophosphate, and sodium tetrafluoroborate. The base of the large cation is selected from at least one of potassium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.
5. The method according to claim 1, characterized in that, In the electrolyte, the concentration of the soluble salt of the large cation or the base of the large cation is 0.01 mol / L to 15 mol / L.
6. The method according to claim 1, characterized in that, In the electrolyte, the concentration of the soluble salt of the large cation or the base of the large cation is 1 mol / L to 10 mol / L.
7. The method according to claim 1, characterized in that, The reaction temperature for the electrochemical stripping is 1~100℃; The reaction time for the electrochemical stripping is 1 min to 24 h.
8. The method according to claim 1, characterized in that, The reaction temperature for the electrochemical stripping is 5~50℃.
9. The method according to claim 1, characterized in that, The voltage of the slot is 2~30V.
10. The method according to claim 1, characterized in that, The method further includes: After electrochemical exfoliation of graphite, the exfoliated product is washed and ultrasonically dispersed to obtain graphene slurry, which is then dried to obtain the graphene nanosheets.
11. The method according to claim 10, characterized in that, The washing method is vacuum filtration or centrifugal washing.
12. The method according to claim 10, characterized in that, The drying method is at least one of natural drying, heat drying, vacuum drying, and freeze drying.
13. The method according to claim 1, characterized in that, The graphene nanosheets have a diameter of 0.5 ~ 20 µm.
14. The method according to claim 1, characterized in that, The surface oxygen content of the graphene nanosheets is <6 at.
15. The method according to claim 10, characterized in that, The solvent for ultrasonic dispersion is selected from at least one of dimethylformamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide; The ultrasonic dispersion time is 5 min to 12 h.