A device and method for preparing graphene oxide

Abstract

The invention discloses a device and method for preparing graphene oxide, and relates to the technical field of graphene preparation. In the device of the invention, a graphite material fixed at an anode is fixed in the following manner: holes are respectively perforated in the graphite material and an anode metal electrode, and a fixing bolt with a compression piece is passed through the holes of the two to fix the compression piece, the graphite material and the anode metal electrode in connection, and the compression piece is used to make the graphite material in close contact with the anode metal electrode at all locations. The method of the invention adopts the device of the invention to prepare graphene oxide, and pretreatment is performed for a period of time at a voltage lower than the formal electrolysis voltage before preparation. The invention creates confined electrolysis conditions by means of bolts and compression pieces, utilizes pretreatment to ensure that the reaction proceeds fully, avoids insufficient oxidation caused by rapid shedding, and can improve reaction efficiency and product quality. The temperature is controlled by a water bath to prevent the electrolyte from undergoing a large amount of spontaneous decomposition, which is conducive to recycling and reuse, and the product is dispersed with water, which is environmentally friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene preparation, and in particular to a device and method for preparing graphene oxide. Background Art

[0002] As an excellent carbon material, graphene has excellent mechanical, electrical, thermal and barrier properties. However, its hydrophobicity and bioincompatibility limit its application in many fields. To compensate for these shortcomings, graphene oxide (GO) has emerged as a derivative of graphene. The surface of GO has carboxylic acid functional groups, hydroxyl groups and epoxy groups, which give it good dispersibility, amphiphilicity and biocompatibility. Therefore, it is considered to be one of the most promising carbon materials in contemporary times. However, traditional graphene oxide preparation methods (such as the methods disclosed in the invention patent applications with publication numbers CN109607526A and CN108408722A) have the problem of using strong oxidants to oxidize graphite in concentrated acid. This method is simple but brings toxic and harmful gases and explosion hazards. In the article "Preparation of Few-layer Graphene Based on Electrode Exchange Exfoliation Technology and Study on Its Characteristics", the toxic and harmful DMF solvent is used in the ultrasonic process of the preparation post-treatment. Therefore, there is an urgent need to develop efficient, large-scale, low-cost and environmentally friendly graphene preparation technology to promote the further development of its application.

[0003] In recent years, electrochemical exfoliation has emerged as a novel graphene production method. During electrolysis, oppositely charged ions and mixtures are inserted into graphite electrodes, causing expansion and exfoliation of the graphite interlayers, ultimately yielding graphene. For example, invention patent applications with publication numbers CN115838168A and CN106865534A disclose electrochemical exfoliation methods. This method offers multiple advantages: abundant and inexpensive graphite raw materials; precise adjustment of voltage and current, making the exfoliation process reproducible and manageable; and electrolysis, typically performed at or near room temperature, is easily controlled. Therefore, electrochemical graphene oxidation (EGO) holds significant promise for graphene production.

[0004] However, graphene produced by conventional electrochemical methods typically has poor water solubility and dispersibility. This is because during the oxidation reaction at the anode, the graphite material is rapidly exfoliated by the electric field, generating a large number of bubbles. This causes the graphite material to fall off the electrode surface, hindering further oxidation of the graphene. This results in thicker and less consistent graphene sheets, as well as poor dispersion in aqueous solutions. This compromises product quality and severely hinders the industrial application of electrochemical exfoliation. Summary of the Invention

[0005] The object of the present invention is to provide a device and method for preparing graphene oxide to solve the problems mentioned in the above background technology.

[0006] To achieve the above-mentioned object, the present invention provides the following technical solution: a device for preparing graphene oxide, comprising a cathode and an anode disposed in an electrolytic cell filled with an electrolyte, a cathode metal electrode and an anode metal electrode disposed at the cathode and the anode, respectively, a graphite material fixed at the anode, and a power supply electrically connected to the cathode metal electrode and the anode metal electrode via a cathode wire and an anode wire, respectively, wherein the graphite material fixed at the anode is fixed in the following manner:

[0007] Holes are punched in the graphite material and the anode metal electrode respectively, and fixing bolts with a clamping piece are passed through the holes of the two to fix the clamping piece, the graphite material and the anode metal electrode. The clamping piece is used to make the graphite material in close contact with the anode metal electrode at all locations.

[0008] In a preferred embodiment, the anode metal electrode is in the form of a sheet, and the anode further includes an anode fixing member on which a threaded hole matching the fixing bolt is provided; the two sides of the anode metal electrode are in surface contact with the anode fixing member and the graphite material respectively, the pressure surface of the clamping member is in surface contact with the graphite material, and the end of the fixing bolt passes through the clamping member, the graphite material and the anode metal electrode in sequence and is threadedly connected to the threaded hole on the anode fixing member; the cathode metal electrode is also in the form of a sheet, which is arranged perpendicular to the anode metal electrode, and the intersection of the planes of the two is the center line of the cathode metal electrode.

[0009] In order to carry out larger quantities of preparation at the same time, in another preferred embodiment, the anode metal electrode is plate-shaped with multiple threaded holes or through holes formed thereon, and a set of anode assemblies is fixedly connected to each threaded hole or through hole, and each set of anode assemblies includes a clamping member, a fixing bolt and a graphite material, and the end of the fixing bolt passes through the clamping member and the graphite material in turn, and is threadedly connected to the threaded hole or passed through the through hole and then tightened with a nut, the anode metal electrode is in surface contact with the graphite material, and the pressure surface of the clamping member is in surface contact with the graphite material; the cathode metal electrode is plate-shaped or sheet-shaped, and is arranged opposite and parallel to the anode metal electrode.

[0010] In order to carry out larger-scale preparation at the same time, in another preferred embodiment, the anode metal electrode is mesh-shaped, the cathode metal electrode is hollow tubular or rod-shaped and is provided in plurality, each cathode metal electrode is inserted in a different mesh of the mesh anode metal electrode, and a plurality of through holes are provided at the edge of the mesh where each cathode metal electrode is located. The anode metal electrode is located at the periphery of the through hole and is in sheet shape, and a set of anode assemblies is fixedly connected to each through hole. Each set of anode assemblies includes a clamping piece, a fixing bolt and a graphite material, and the end of the fixing bolt passes through the clamping piece, the graphite material and the through hole in turn and is tightened with a nut. The anode metal electrode is in surface contact with the graphite material, and the pressure surface of the clamping piece is in surface contact with the graphite material; multiple mesh anode metal electrodes are provided parallel to the cathode metal electrode.

[0011] In the above three embodiments, preferably, the pressure between the graphite material and the anode metal electrode is 0.3 to 10 MPa, which is achieved by adjusting the pressure applied by the clamping member by fixing the bolt;

[0012] In addition, the sizes and shapes of the graphite material, the pressure surface of the pressing member, and the contact surface between the anode metal electrode and the graphite material match; or the outer edge of the contact point between the graphite material and the pressing member is located within the outer edge range of the pressure surface of the pressing member, and the outer edge of the contact point between the graphite material and the anode metal electrode is located within the side range of the anode metal electrode.

[0013] Preferably, the distance between the cathode metal electrode and the anode metal electrode at their closest point is the minimum distance that can be achieved while ensuring that there is no short circuit and that the local temperature does not cause a side reaction in the electrolyte.

[0014] Preferably, the electrolytic cell is a water bath electrolytic cell, which comprises an inner container and a water bath jacket wrapped around the outside of the container wall for controlling the temperature of the electrolyte.

[0015] Another technical solution provided by the present invention is a method for preparing graphene oxide, which adopts the above-mentioned device to perform chemical electrostripping preparation, and pre-treats it for a period of time at a voltage lower than the formal electrolysis voltage before preparation.

[0016] For reference, the above method may include any one or more of the following preparation conditions:

[0017] a. The electrolyte may be one or more of sulfuric acid, sulfate, persulfate, nitric acid, nitrate, perchloric acid, perchlorate, phosphoric acid, high phosphate, ferric chloride, etc., and the electrolyte concentration is preferably 0.05 to 6M;

[0018] b. The electrolyte temperature should be controlled at -10 to 30°C. When a water bath jacket is used, the temperature of the water bath jacket can be controlled;

[0019] c. The materials of the cathode metal electrode and the anode metal electrode can be common materials such as platinum, titanium, silver, palladium, etc.;

[0020] d. The power supply is in constant voltage mode. During pretreatment, the voltage range is set to 0.1-3V, and the treatment time is 5-30 minutes. During formal electrolysis, the voltage range is set to 5-20V, and the treatment time is 1-3 hours.

[0021] e. After the formal electrolysis is completed, the post-processing process is also included: the product is filtered, washed with water, and then placed in pure water for ultrasonic dispersion and assisted exfoliation. The ultrasonic power is 40 to 200 W and the ultrasonic time is 0.5 to 2 hours. After ultrasonication, a dispersed graphene aqueous solution is obtained.

[0022] Preferably, the graphene produced by the above method is 1 to 3 layers, and the graphene produced under the same conditions has the same size; and the electrolyte of the above method is recycled and reused several times without affecting the quality stability of the graphene oxide product, for example, 3 to 5 times.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The device for preparing graphene oxide compresses the graphite material and the anode metal electrode at various locations by fixing bolts, pressing parts, and perforations to form confined electrolysis conditions. It makes full use of threaded connections to ensure stable and reliable compression, effectively improving local reaction efficiency. Moreover, since the graphite material is fixed in a specific area, it avoids rapid shedding without sufficient exfoliation and oxidation during the reaction process. This method of fixing the anode and graphite material provides key support for efficient electrolysis, improves the overall preparation efficiency, and helps to prepare lower-layer and high-quality graphene, making the final product more controllable and consistent.

[0025] 2. The device for preparing graphene oxide provides a scheme for the closest possible distance between the anode and cathode metal electrodes under different implementation methods, which can make the reaction site of the graphite material close to the cathode and have excellent current density, maximize the electrolysis efficiency, help to increase the reaction speed and reduce electrolyte consumption. At the same time, the rapid reaction can reduce the probability of graphene falling off before it is fully oxidized, indirectly ensuring the consistency of the final product.

[0026] 3. This method for preparing graphene oxide utilizes an electrolysis pretreatment step to open the grain boundaries, edges, and other defect locations between graphite layers where the van der Waals forces are weak without causing the graphite to fall off, thereby achieving large-scale expansion and effective exfoliation of the microstructure of the graphite layer, ensuring that the subsequent formal electrolysis can fully react and proceed quickly, avoiding insufficient oxidation caused by rapid exfoliation, and helping to optimize the efficiency of the electrolysis process and ensure product quality. At the same time, the rapid reaction can reduce the probability of graphene falling off due to insufficient oxidation, thereby indirectly ensuring the consistency of the final product.

[0027] 4. The device and method for preparing graphene oxide can use pure water as a solvent for ultrasonic post-treatment of the prepared graphene oxide product, which is different from other electrochemical preparations that use toxic and harmful solvents such as DMF; the use of a water-bath jacketed electrolytic cell to control the temperature not only helps to improve the stability of the reaction, but also shortens the reaction time on the basis of the efficient conduct of the above-mentioned electrolytic reaction. At the same time, under the low-temperature reaction conditions of the water bath, the electrolyte does not undergo large-scale spontaneous decomposition, which can reduce the consumption of the electrolyte and facilitate the repeated reuse of the electrolyte. The entire preparation scheme has low consumption, no pollution, and is green and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1A schematic diagram of the device structure of the first embodiment provided by the present invention;

[0029] Figure 2 for Figure 1 Exploded view of the electrode structure in the structure shown;

[0030] Figure 3 A schematic diagram of the electrode structure of the second embodiment provided by the present invention;

[0031] Figure 4 for Figure 3 An enlarged side view of the structure shown;

[0032] Figure 5 for Figure 3 A physical diagram of the anode portion of the structure shown;

[0033] Figure 6 A schematic diagram of the electrode structure of the third embodiment provided by the present invention;

[0034] Figure 7 for Figure 6 A partially enlarged schematic diagram of the structure shown;

[0035] Figure 8 for Figure 6 Actual picture of the anode of the structure shown;

[0036] Figure 9 for Figure 6 A schematic diagram of the three-dimensional structure of the structure shown;

[0037] Figure 10 This is an electron microscope image of the product obtained in Example 1;

[0038] Figure 11 This is an atomic force microscope image of the product obtained in Example 1;

[0039] Figure 12 This is the ultraviolet spectrum absorption test graph of Example 2;

[0040] Figure 13 The three electrolysis results of Example 3 are compared with electron microscope images;

[0041] Figure 14 is a line graph showing changes in electrolyte concentration in Example 4;

[0042] Figure 15 This is an electron microscope image of the product obtained in Example 5;

[0043] Figure 16 This is an electron microscope image of the product obtained in Example 6.

[0044] In the figure: 1. Water bath electrolytic cell; 2. Electrolyte; 3. Anode fixing member; 4. Cathode metal electrode; 5. Pressing member; 6. Fixing bolt; 7. Graphite material; 8. Anode metal electrode; 9. Anode wire; 10. Cathode wire; 11. Power supply. DETAILED DESCRIPTION

[0045] A device for preparing graphene oxide includes a cathode and an anode arranged in an electrolytic cell filled with an electrolyte 2, a cathode metal electrode 4 and an anode metal electrode 8 respectively provided at the cathode and the anode, a graphite material 7 fixed at the anode, and a power supply 11 electrically connected to the cathode metal electrode 4 and the anode metal electrode 8 via a cathode wire 10 and an anode wire 9, respectively. The graphite material 7 fixed at the anode is fixed in the following manner:

[0046] Holes are punched in the graphite material 7 and the anode metal electrode 8 respectively, and a fixing bolt 6 with a clamping piece 5 is passed through the holes of the two to fix the clamping piece 5, the graphite material 7 and the anode metal electrode 8. The clamping piece 5 is used to make the graphite material 7 in close contact with the anode metal electrode 8 at all locations.

[0047] The purpose of the present invention using a clamping member 5 and a fixing bolt 6 to compress the graphite material 7 and the anode metal electrode 8 is to create a new physically confined electrolysis condition, make full use of the threaded connection, and ensure that the device remains stable and reliable during operation. The unique advantage of this confined structure is that the graphite material 7 is confined to a specific area between the clamping member 5 and the anode metal electrode 8, so that the graphite material 7 can be in close contact with the anode metal electrode 8 at all locations, effectively improving the local reaction efficiency. And because the graphite material 7 is fixed in a specific area, it avoids the situation where it falls off quickly without being fully stripped and oxidized during the reaction process, which helps to prepare graphene with a lower number of layers and high quality, making the final product more controllable and consistent. The above is only the core point of the present invention, which will be further explained in the following more preferred structure.

[0048] See Figure 1 、 2 In a preferred embodiment, the anode metal electrode 8 is in the form of a sheet, and the anode further includes an anode fixing member 3, on which a threaded hole matching the fixing bolt 6 is formed; the two sides of the anode metal electrode 8 are in surface contact with the anode fixing member 3 and the graphite material 7 respectively, and the pressure surface of the clamping member 5 is in surface contact with the graphite material 7, and the end of the fixing bolt 6 passes through the clamping member 5, the graphite material 7 and the anode metal electrode 8 in sequence and is threadedly connected to the threaded hole on the anode fixing member 3.

[0049] See Figure 3-5In order to prepare a larger amount at the same time, in another preferred embodiment, the anode metal electrode 8 is plate-shaped and has multiple threaded holes or through holes on it. A set of anode components is fixedly connected to each threaded hole or through hole. Each set of anode components includes a clamping piece 5, a fixing bolt 6 and a graphite material 7. The end of the fixing bolt 6 passes through the clamping piece 5 and the graphite material 7 in turn, and is threadedly connected to the threaded hole or passed through the through hole and then tightened with a nut. The anode metal electrode 8 is in surface contact with the graphite material 7, and the pressure surface of the clamping piece 5 is in surface contact with the graphite material 7.

[0050] See Figure 6-9 In order to carry out larger-scale preparation at the same time, in another preferred embodiment, the anode metal electrode 8 is mesh-shaped, the cathode metal electrode 4 is hollow tubular or rod-shaped and is provided in plurality, each cathode metal electrode 4 is inserted in a different mesh of the mesh anode metal electrode 8, and a plurality of through holes are provided at the edge of the mesh where each cathode metal electrode 4 is located. The anode metal electrode 8 is located at the periphery of the through hole and is in sheet shape. A set of anode assemblies is fixedly connected to each through hole, and each set of anode assemblies includes a clamping member 5, a fixing bolt 6 and a graphite material 7. The end of the fixing bolt 6 passes through the clamping member 5, the graphite material 7 and the through hole in turn and is tightened with a nut. The anode metal electrode 8 is in surface contact with the graphite material 7, and the pressure surface of the clamping member 5 is in surface contact with the graphite material 7; a plurality of mesh anode metal electrodes 8 are provided parallel to the cathode metal electrode 4.

[0051] In the above three embodiments, it is preferred that the pressure at each location between the graphite material 7 and the anode metal electrode 8 is 0.3 to 10 MPa, which is achieved by adjusting the pressure applied by the clamping member 5 by the fixing bolt 6; the clamping member 5 and the anode fixing member 3 are preferably made of polytetrafluoroethylene, polycarbonate, polyimide, polyether ketone, etc. that are resistant to high temperature, acid and alkali, and corrosion, or the same inert metal raw material as the electrode can be used. The fixing method of the cathode metal electrode 4 can be the same as that of the anode, using a corresponding cathode fixing member. The fixing method of the anode metal electrode 8 and the cathode metal electrode 4 to the electrolytic cell is a well-known technology and will not be repeated here. In order to make the pressure at each location more balanced, the perforation on the graphite material 7 can be located in the middle thereof, and the fixing bolt 6 is also preferably provided in the middle of the clamping member 5;

[0052] In addition, the graphite material 7 can be made of flake graphite, expanded graphite, graphite paper, graphite plate, etc.; the graphite material 7 can be a planar structure such as square or circular; optionally, the sizes and shapes of the graphite material 7, the pressure surface of the pressing member 5, and the contact surface between the anode metal electrode 8 and the graphite material 7 are matched; or the outer edge of the contact point between the graphite material 7 and the pressing member 5 can be located within the outer edge range of the pressure surface of the pressing member 5, and the outer edge of the contact point between the graphite material 7 and the anode metal electrode 8 can be located within the side range of the anode metal electrode 8, that is, the pressure provided by the fixing bolt 6 can be transmitted to all parts of the graphite material 7 through the pressing member 5, and all parts of the graphite material 7 can be effectively clamped between the pressing member 5 and the anode metal electrode 8. In the above-mentioned scheme with the anode fixing member 3, it should be clear that the anode fixing member 3 and the pressing member 5 are only distinguished in name, and both actually provide a compressive force. Therefore, it can be expected that the graphite material 7 can be clamped between the anode fixing member 3 and the anode metal electrode 8, and the effect is equivalent;

[0053] The locking method using the fixing bolt 6 in the present invention is that the thread can provide sufficient positive pressure, which can be calculated according to the following formula:

[0054] Torque = torque * thread diameter

[0055] Pressure / torque = 3.14*thread diameter / pitch

[0056] Pressure = 3.14*torque / pitch

[0057] Assuming the traditional pitch P = 0.35mm, the thread diameter d = 1.6mm

[0058] When torque = 1.2kg*cm*f, pressure = 3.14*1.2*9.8 / 0.035 = 1055N (about 108kg)

[0059] It can be seen that the positive pressure provided by the fixing bolt 6 is very sufficient. Compared with a direct frontal pressing structure such as a press, the use of the fixing bolt 6 to apply pressure can ensure that the graphite material 7 can fully contact with the clamp, thereby ensuring that the graphite raw material is in full contact with the electrode, forming a local micro-hot zone.

[0060] Specifically, the pressure between the graphite material 7 and the anode metal electrode 8 should be controlled within the range of 0.3 to 10 MPa. Since the pressing member 5, the graphite material 7 and the anode metal electrode 8 are pressed layer by layer, it is easy to achieve this by simply controlling the pressure transmitted from the fixing bolt 6 to the pressing member 5. However, according to the above calculations, it is not difficult to see that the size of the graphite material 7 of the present invention is slightly limited (30 cm 2 Below, generally can be controlled within 10cm 2 Below, the better one is 2cm including the through hole area 2And it is a circular solution), of course, it is not difficult to think of a solution with multiple holes through multiple bolts, but the best is still a small range confinement formed by a single bolt and a pressing member 5, and thus forming a Figure 3-9 The parallel electrostripping implementation method is adopted, because this small-scale confinement is most capable of controlling the reaction conditions at various locations of the graphite material 7 to be more consistent.

[0061] In a preferred embodiment, the distance between the cathode metal electrode 4 and the anode metal electrode 8 at their closest point is the minimum distance that ensures no short circuit and that the local temperature does not cause a side reaction in the electrolyte. In different embodiments, the distance between the electrodes cannot be too close, mainly because if it is too close, the peeled graphene material will accumulate, posing a risk of internal short circuit in the circuit. On the other hand, if the electrodes are too close, the local electrolyte heat may rise, exceeding the optimal reaction temperature, causing a side reaction in the electrolyte. The electrode distance cannot be too far, because if it is too far, the overall reaction internal resistance will increase and the electrolysis efficiency will decrease.

[0062] For specific reference, please refer to the above Figure 1 and 2 In the embodiment, the cathode metal electrode 4 can also be sheet-shaped and arranged perpendicular to the anode metal electrode 8, and the intersection of the two planes is the center line of the cathode metal electrode 4. Since the graphite material 7 is covered on both sides, the actual side is the reaction surface, especially the side between the cathode and cathode. Therefore, the vertical arrangement can enable the side of the graphite material 7 to react to the cathode metal electrode 4 to have a larger current density. Specifically, the distance between the two can be controlled to 2 cm. This layout is intended to improve the electrolysis efficiency under the confined mode of the present invention, making the reaction during the electrolysis process more rapid and effective.

[0063] In the above Figure 3-5 In the embodiment, the cathode metal electrode 4 can be in the form of a plate or sheet, and is preferably arranged opposite and parallel to the anode metal electrode 8. For reference, the distance between the two can be controlled to be 5 cm;

[0064] In the above Figure 6-9 In the embodiment, the minimum distance from the cathode metal electrode 4 to the anode metal electrode 8 is preferably controlled to be above 1 cm.

[0065] In the above schemes, the electrolytic cell is preferably a water bath electrolytic cell 1, which includes an internal container and a water bath jacket wrapped around the outside of the container wall, which can conveniently control the temperature of the electrolyte 2. Of course, an ordinary electrolytic cell can also be placed in a temperature control device such as a water bath. Controlling the temperature within an appropriate range can reduce the degree of spontaneous decomposition of the electrolyte, help provide an appropriate working temperature, and ensure the stability of the electrolysis process. At the same time, by effectively controlling the temperature, it is helpful to recycle and reuse the electrolyte, which is in line with the concept of green environmental protection.

[0066] The above-mentioned device is used for chemical electrostripping preparation. It is preferred to pre-treat for a period of time with a voltage lower than the formal electrolysis voltage before preparation. The purpose of this step is to open the grain boundaries, edges and other defect locations between the graphite layers where the van der Waals forces are weak without causing the graphite to fall off, thereby achieving large-scale expansion and effective exfoliation of the microstructure of the graphite layer, ensuring that the subsequent formal electrolysis can react fully and proceed quickly, which is beneficial to optimizing the efficiency of the electrolysis process and ensuring product quality.

[0067] In addition, for reference, the above method may include any one or more of the following preparation conditions:

[0068] a. The electrolyte may be one or more of sulfuric acid, sulfate, persulfate, nitric acid, nitrate, perchloric acid, perchlorate, phosphoric acid, high phosphate, ferric chloride, etc., and the electrolyte concentration is preferably 0.05 to 6M;

[0069] b. The electrolyte temperature should be controlled at -10 to 30°C. When a water bath jacket is used, the temperature of the water bath jacket can be controlled;

[0070] c. The materials of the cathode metal electrode and the anode metal electrode can be made of inert metal materials such as platinum, titanium, silver, palladium, etc. that can be used for electrochemical stripping to prepare graphene oxide;

[0071] d. The power supply is preferably in constant voltage mode. During pretreatment, the voltage range is set to 0.1-3V, and the treatment time is 5-30 minutes. During formal electrolysis, the voltage range is set to 5-20V, and the treatment time is 1-3 hours.

[0072] e. After the formal electrolysis is completed, the post-finishing process is also included: the product is filtered (such as suction filtration, filter press, etc.), and it is placed in pure water for ultrasonication to play the role of dispersion and auxiliary exfoliation. The ultrasonic power should be 40-200W, and the ultrasonic time should be 0.5-2h. After ultrasonication, a graphene aqueous solution with good dispersion is obtained.

[0073] The graphene obtained by the above method can be effectively controlled to 1 to 3 layers, and under the same conditions, the size of the graphene obtained by the method of the present invention can be kept consistent even in different batches; and the electrolyte of the method of the present invention can be recycled and reused several times without affecting the quality stability of the graphene oxide product, for example, 3 to 5 times, as shown in the following examples.

[0074] Example 1

[0075] use Figure 1 and 2The device shown uses double titanium electrodes as the positive and negative metal electrodes, 1 mol / L sodium sulfate solution as the electrolyte, the clamp material is polytetrafluoroethylene, the size is 1*2 cm, the graphite raw material is graphite paper and cut into corresponding shapes and clamped with bolts and pressure blocks to maintain the confined state, the tightening degree of the bolts is adjusted to make the pressure between the graphite material and the anode metal electrode at each point about 4 MPa, and the direction of the electrode is adjusted so that the side of the graphite raw material is facing the cathode metal electrode. The water bath temperature is set to 10 ° C. The constant voltage mode of 1V is used in the pretreatment stage, and the electrolysis time is 20 minutes. After 20 minutes, the voltage is switched to 15V, and the electrolysis time is 2 hours. After the electrolysis is completed, the graphene oxide solution is cleaned with pure water through a filter press and placed in pure water for ultrasonic treatment, such as Figure 10 As shown, under the electron microscope, it was found that the size of graphene oxide remained consistent, all around 10 microns, and the sample had good consistency. Figure 11 The atomic force microscope image of graphene oxide was obtained, and it can be seen that the number of layers is 1 to 2.

[0076] Example 2

[0077] use Figure 1 and 2 The device shown uses double platinum electrodes as the positive and negative metal electrodes, 1.5 mol / L potassium sulfate solution as the electrolyte, the clamp material is polytetrafluoroethylene, the size is 1*2 cm, the graphite raw material is graphite paper and cut into corresponding shapes and clamped with bolts and pressure blocks to maintain the confined state, the tightening degree of the bolts is adjusted to make the pressure between the graphite material and the anode metal electrode at all points about 0.3 MPa, and the direction of the electrode is adjusted so that the side of the graphite raw material is facing the cathode metal electrode. The water bath temperature is set to 20°C. The pretreatment stage adopts a constant voltage mode of 2V, and the electrolysis time is 10 minutes. After 10 minutes, the voltage is switched to 10V, and the electrolysis time is 1 hour. During the formal electrolysis process, 5 ml of electrolyte is taken every 10 minutes, and the graphene oxide in it is cleaned with pure water through a filtration instrument, and configured into a graphene oxide aqueous solution. The ultraviolet spectrum is tested, and the six groups of test results are shown in the figure. Figure 12 The results showed that all groups of data generated characteristic peaks at 265nm (the absorption value only represents the concentration of the solution and has no effect on the research results), and the samples had good consistency.

[0078] Example 3

[0079] use Figure 1 and 2The apparatus shown uses a double palladium electrode as the anode and cathode metal electrodes, and a 1 mol / L ammonium persulfate solution as the electrolyte. The fixture is made of polytetrafluoroethylene and measures 1 x 2 cm. The graphite raw material is made of graphite paper cut into a corresponding shape and clamped with bolts and a clamp to maintain confinement. The bolts are tightened to maintain a pressure of approximately 10 MPa at all points between the graphite material and the anode metal electrode. The electrodes are oriented so that the side of the graphite raw material faces the cathode metal electrode. The water bath temperature is set to 0°C. The pretreatment phase uses a constant voltage mode of 3V, and the electrolysis time is 20 minutes. After 10 minutes, the voltage is switched to 15V, and the electrolysis time is 1 hour. After the electrolysis is completed, the ammonium persulfate electrolyte and graphene oxide in the electrolytic cell are separated by filtration. The graphene oxide is rinsed with pure water and subjected to ultrasonic treatment in pure water. The separated ammonium persulfate electrolyte is then subjected to the same electrolysis process as the first step, for a second electrolysis. After the second electrolysis, repeat the above steps to collect the graphene oxide after the second electrolysis, collect the ammonium persulfate electrolyte after the second electrolysis, perform the third electrolysis and collect the graphene oxide. The graphene oxide after the three electrolysis was observed under an electron microscope, see Figure 13 The size of the three graphene oxides remained consistent, all around 5 microns, and the samples had good consistency, indicating that the consistency of different batches of products under the same conditions was comparable, and that the recycling and reuse of the electrolyte for several times did not affect the quality stability of the graphene oxide products.

[0080] Example 4

[0081] use Figure 1 and 2 The apparatus shown uses dual titanium electrodes as the anode and cathode metal electrodes, and a 1 mol / L sodium persulfate solution as the electrolyte. The fixture is made of polytetrafluoroethylene and measures 1 x 2 cm. The graphite raw material is made of graphite paper cut into a corresponding shape and clamped with bolts and a clamp to maintain confinement. The bolts are tightened to maintain a pressure of approximately 5 MPa at all points between the graphite material and the anode metal electrode. The electrodes are oriented so that the side of the graphite raw material faces the cathode metal electrode. The water bath temperature is set to 0°C. During the pretreatment phase, a constant voltage of 2 V is used, and the electrolysis lasts for 20 minutes. After 10 minutes, the voltage is switched to 20 V, and the electrolysis lasts for 1 hour. After the electrolysis is completed, the sodium persulfate electrolyte and graphene oxide in the electrolytic cell are separated by filtration. The graphene oxide is then rinsed with pure water. The separated sodium persulfate electrolyte is then analyzed by UV spectroscopy, and the concentration is determined using the Ludwig-Beer law. The collected separated sodium persulfate electrolyte is repeated with the first electrolysis step, and the next electrolysis is carried out, and the process is repeated until the concentration of the sodium persulfate solution decreases significantly. The results of the number of electrolysis times and the sodium persulfate concentration after electrolysis are as follows: Figure 14 As shown in the figure, after the first seven electrolysis cycles, the electrolyte concentration only decreased slightly, making it suitable for recycling and reuse.

[0082] Example 5

[0083] use Figure 3-5 The device shown uses platinum electrodes as the positive and negative metal electrodes with a size of 5*10cm, and a 1mol / L potassium sulfate solution as the electrolyte. The graphite raw material is graphite paper and cut into a circle and clamped with bolts and large gaskets to maintain the confined state. The size of the graphite paper and the large gasket is φ6*16mm. The tightening degree of the bolts is adjusted so that the pressure between the graphite material and the anode metal electrode is about 10Mpa. The water bath temperature is set to 10℃. The constant voltage mode of 1V is used in the pretreatment stage, and the electrolysis time is 20min. After 20min, the voltage is switched to 15V, and the electrolysis time is 2h. After the electrolysis is completed, the graphene oxide solution is cleaned with pure water through a filter press and placed in pure water for ultrasonic treatment, and observed under an electron microscope, as shown Figure 15 As shown, the size of graphene oxide remains consistent, all around 5 microns, and the sample has good consistency.

[0084] Example 6

[0085] use Figure 6-9 The device shown uses titanium electrodes as the positive and negative metal electrodes and clamps, the cathode uses a hollow electrode with a size of φ40mm, and a 1.5mol / L sodium sulfate solution as the electrolyte. The graphite raw material uses graphite paper and is cut into a circle and clamped with bolts and large gaskets to maintain a confined state. The size of the graphite paper and the large gasket is φ8*20mm. The tightening degree of the bolts is adjusted so that the pressure between the graphite material and the anode metal electrode is about 10Mpa. The water bath temperature is set to 0℃. The constant voltage mode of 2V is used in the pretreatment stage, and the electrolysis time is 10min. After 10min, the voltage is switched to 10V, and the electrolysis time is 1h. After the electrolysis is completed, the graphene oxide solution is cleaned with pure water through a filter press, placed in pure water for ultrasonic treatment, and observed under an electron microscope, as shown Figure 16 As shown, the size of graphene oxide remains consistent, all around 3 microns, and the sample has good consistency.

[0086] The above six embodiments demonstrate that the few-layer graphene oxide products produced by the apparatus and method provided by the present invention have good consistency, the electrolyte can be reused multiple times, the reaction speed is fast, and it is easy to control and achieve large-scale production, which broadens the development path of electrochemical exfoliation to prepare graphene oxide.

[0087] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims.

[0088] Any matters not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. A device for preparing graphene oxide, comprising a cathode and an anode arranged in an electrolytic cell containing an electrolyte (2), a cathode metal electrode (4) and an anode metal electrode (8) respectively provided at the cathode and the anode, a graphite material (7) fixed at the anode, and a power source (11) electrically connected to the cathode metal electrode (4) and the anode metal electrode (8) via a cathode wire (10) and an anode wire (9), respectively, wherein: The graphite material (7) fixed at the anode is fixed in the following manner: Holes are respectively punched in the graphite material (7) and the anode metal electrode (8), and a fixing bolt (6) with a pressing member (5) is passed through the holes of the two to fix the pressing member (5), the graphite material (7) and the anode metal electrode (8) together, and the pressing member (5) is used to make the graphite material (7) closely contact the anode metal electrode (8) at all locations; When the anode metal electrode (8) is in the form of a plate, a plurality of threaded holes or through holes are provided on it, and a set of anode components is fixedly connected to each threaded hole or through hole, and each set of anode components includes a clamping member (5), a fixing bolt (6) and a graphite material (7), and the end of the fixing bolt (6) passes through the clamping member (5) and the graphite material (7) in turn, is threadedly connected to the threaded hole or passes through the through hole and is tightened with a nut, the anode metal electrode (8) is in surface contact with the graphite material (7), and the pressure surface of the clamping member (5) is in surface contact with the graphite material (7); the cathode metal electrode (4) is in the form of a plate or sheet, and is arranged opposite and parallel to the anode metal electrode (8); When the anode metal electrode (8) is mesh-shaped, the cathode metal electrode (4) is hollow tubular or rod-shaped and is provided in plurality. Each cathode metal electrode (4) is inserted into a different mesh of the mesh anode metal electrode (8). A plurality of through holes are provided at the edge of the mesh where each cathode metal electrode (4) is located. The anode metal electrode (8) is located at the periphery of the through hole and is in sheet shape. A set of anode assemblies is fixedly connected to each through hole. Each set of anode assemblies includes a clamping member (5), a fixing bolt (6) and a graphite material (7). The end of the fixing bolt (6) passes through the clamping member (5), the graphite material (7) and the through hole in turn and is tightened with a nut. The anode metal electrode (8) is in surface contact with the graphite material (7), and the pressure surface of the clamping member (5) is in surface contact with the graphite material (7). The mesh anode metal electrode (8) is provided in plurality parallel to the cathode metal electrode (4).

2. A device for preparing graphene oxide according to claim 1, characterized in that: The pressure at each location between the graphite material (7) and the anode metal electrode (8) is between 0.3 and 10 MPa, which is achieved by adjusting the pressure applied by the pressing member (5) by fixing the bolt (6); The sizes and shapes of the graphite material (7), the pressure surface of the pressing member (5), and the contact surface between the anode metal electrode (8) and the graphite material (7) are matched; or the outer edge of the contact point between the graphite material (7) and the pressing member (5) is located within the outer edge range of the pressure surface of the pressing member (5), and the outer edge of the contact point between the graphite material (7) and the anode metal electrode (8) is located within the side range of the anode metal electrode (8).

3. The device for preparing graphene oxide according to claim 1, wherein: The distance between the cathode metal electrode (4) and the anode metal electrode (8) at their closest points is the minimum distance under the condition of ensuring that there is no short circuit and that the local temperature does not cause a side reaction in the electrolyte.

4. The device for preparing graphene oxide according to claim 1, wherein: The electrolytic cell is a water bath electrolytic cell (1), which comprises an internal container and a water bath jacket wrapped around the outside of the container wall, and is used to control the temperature of the electrolyte (2).

5. A method for preparing graphene oxide, characterized in that: The chemical electrostripping preparation is performed using the device described in any one of claims 1 to 4, and the material is pretreated for a period of time at a voltage lower than the formal electrolysis voltage before the preparation.

6. The method according to claim 5, characterized in that Include any one or more of the following preparation conditions: The electrolyte includes one or more of sulfuric acid, sulfate, persulfate, nitric acid, nitrate, perchloric acid, perchlorate, phosphoric acid, perphosphate, and ferric chloride, and the electrolyte concentration is 0.05 to 6M; The electrolyte temperature is controlled at -10 to 30°C; The cathode metal electrode and the anode metal electrode are made of platinum, titanium, silver or palladium; The power supply is in constant voltage mode. During pretreatment, the voltage range is set to 0.1-3V, and the treatment time is 5-30 minutes. During formal electrolysis, the voltage range is set to 5-20V, and the treatment time is 1-3 hours. After the formal electrolysis is completed, the post-finishing process is also included: the product is filtered, washed with water, and then placed in pure water for ultrasonic dispersion and assisted exfoliation. The ultrasonic power is 40 to 200 W, and the ultrasonic time is 0.5 to 2 hours. After ultrasonication, a dispersed graphene aqueous solution is obtained.

7. The method according to claim 5 or 6, characterized in that: The graphene prepared by the method has 1 to 3 layers, the graphene prepared under the same conditions has the same size, and the electrolyte can be recycled and reused several times without affecting the quality stability of the graphene oxide product.

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