Method for electrochemically preparing graphene oxide

Abstract

The invention relates to the field of graphene oxide preparation, in particular to a method for electrochemically preparing graphene oxide. The preparation method comprises the following steps: firstly, pretreating a graphite plate; then adopting a dual-electrode system, taking the pretreated graphite plate as a working electrode, taking a platinum sheet as a counter electrode, taking an organic sulfonic acid solution as an electrolyte solution, applying positive potential to the working electrode, and performing electrochemical oxidation stripping on the graphite plate to obtain high-quality graphene oxide; in the pretreatment, a graphite plate is used as a working electrode, a platinum sheet is used as a counter electrode, an alkaline solution is used as an electrolyte solution, and positive potential is applied to the working electrode; the treated graphite plate is not cleaned and is directly used for subsequent electrooxidation stripping. The method is convenient to operate, does not need heating, is high in safety, prepares the graphene oxide with high oxygen content and less than or equal to 5 layers by using the electrolyte with low concentration and weak acidity, and is green, environment-friendly and high in stripping yield.

Description

Technical Field

[0001] The invention belongs to the field of graphene oxide preparation, and particularly relates to a method for electrochemically preparing graphene oxide. Background Art

[0002] Graphene oxide was initially used as a precursor for the synthesis of large amounts of graphene. In recent years, it has attracted increasing attention due to its unique physical and chemical properties and broad application prospects. Graphene oxide is very different from graphene. Graphene only contains SP 2 Hybridized carbon atoms, while graphene oxide contains not only SP 2 Hybridized carbon atoms, part of the carbon-carbon double bonds are interrupted by oxygen-containing functional groups, becoming SP 3 Hybridization: The surface of graphene oxide contains a large number of functional groups, such as -OH, -COOH, -O-, etc. These functional groups make graphene oxide sheets highly hydrophilic and can be well dispersed in water. In addition, the presence of oxygen-containing functional groups makes graphene oxide easy to modify and interact with other materials, which makes graphene oxide widely used in supercapacitors, lithium batteries, fuel cells, biomedicine, and catalysis.

[0003] Generally speaking, graphene oxide is synthesized by exfoliation of graphite oxide. There are three main methods for synthesizing graphene oxide: Brodie method, Staudenmaier method and Hummers method. All three methods are to oxidize graphite by mixing graphite with a strong oxidant to obtain graphene oxide of different thicknesses. Both the Brodie method and the Staudenmaier method use KClO3 and concentrated nitric acid, which poses an explosion risk and produces toxic and harmful gases (such as NO x and ClO2). The most commonly used Hummers method uses a large amount of concentrated sulfuric acid and KMnO4 to ensure the full oxidation of graphite, and the highly active Mn2O7 intermediate also has the risk of violent explosion under high temperature conditions. All three methods will inevitably cause serious pollution to the environment and produce metal ion impurities on the graphene oxide flakes. For example, after the oxidation reaction, the Hummers method needs to use a large amount of water to remove excess concentrated sulfuric acid and KMnO4, thereby producing a large amount of wastewater containing mixed acid and heavy metal ions, and Mn can be detected on the prepared GO flakes. 2+ Moreover, the oxidation time of these three methods ranges from a few hours to hundreds of hours, which is very time-consuming. Although the use of strong oxidants K2FeO4 and concentrated H2SO4 can shorten the oxidation time to about 1 hour, the use of more oxidation mixtures will produce greater pollution.

[0004] In recent years, electrochemical processes have been widely used in the synthesis of graphene due to their environmental friendliness, high efficiency and relatively low cost. Studies have shown that graphene with a C / O ratio of 25.3 and a mobility of 405 cm-1 can be synthesized in a few seconds by electrochemical exfoliation of graphene foil. 2 ·V -1 s -1 High-quality graphene. Inspired by these studies, researchers have tried to synthesize graphene oxide by electrochemical oxidation of various graphite materials, such as pencil leads, graphite rods, and graphite sheets. However, the electrolysis process of water / solvent during the reaction exacerbates the expansion and stratification of graphite materials, which results in invalid current supply or short circuit before the desired electrochemical oxidation process is achieved. Therefore, the degree of oxidation and exfoliation of the product is low, which is very different from the graphene oxide synthesized by the above-mentioned traditional chemical oxidation method. Although the electrochemical graphene oxidation product can reach a lower C / O atomic ratio of 2.2, that is, the oxygen content is higher, it is mainly oxidized at the edge of the graphene, the degree of oxidation is not uniform, and the actual yield is low. Tian et al. designed and used an electrochemical Tee-cell device to try to ensure that the current can evenly cover all graphite sheets to achieve efficient preparation of graphene oxide, but the reaction time is long, and the highest C / O only reaches 3.0 after 48 hours of reaction. Pei et al. prepared graphene oxide using concentrated sulfuric acid as an electrolyte. This method used concentrated sulfuric acid to pre-intercalate graphite, thereby effectively inhibiting the water oxidation reaction under high voltage, allowing graphite to be rapidly oxidized and exfoliated under high potential. This method is more than 100 times faster than the Hummers method for preparing graphene oxide. In addition, other studies have shown that graphene oxide can also be quickly electrochemically oxidized and exfoliated in concentrated nitric acid or a mixed solution of nitric acid and sulfuric acid. However, since the electrolyte used in this method is extremely acidic, it has a great impact on the health of the workers; at the same time, a large amount of water is required in the process of cleaning the concentrated acid, which consumes a lot of water resources and produces a large amount of acidic wastewater, which is not environmentally friendly.

[0005] Therefore, there is an urgent need to solve the technical problems of low oxidation degree, large number of layers, low safety, environmental pollution and low exfoliation yield in the electrochemical preparation of graphene oxide. Summary of the invention

[0006] The invention aims to solve the technical problems of low oxidation degree, large number of layers, low safety, environmental pollution and low stripping yield in electrochemical preparation of graphene oxide.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for electrochemically preparing graphene oxide, which comprises the following steps:

[0008] The graphite plate is pretreated, and a double-electrode system is used, with the pretreated graphite plate as the working electrode, the platinum sheet as the counter electrode, and the organic sulfonic acid solution as the electrolyte solution. By applying a positive potential to the working electrode, the graphite plate is electrochemically oxidized and exfoliated to obtain high-quality graphene oxide;

[0009] The pretreatment adopts a dual-electrode system, with a graphite plate as a working electrode, a platinum sheet as a counter electrode, an alkaline solution as an electrolyte solution, a positive potential is applied to the working electrode, and the treated graphite plate is directly used for subsequent electro-oxidation stripping.

[0010] The beneficial effects of the present invention are that the method provided by the present invention is easy to operate, does not require heating, and is highly safe. A low-concentration, weakly acidic electrolyte is used to prepare graphene oxide with a high oxygen content and a layer number of ≤5 layers. The preparation method is green and environmentally friendly, and the exfoliation yield is high, and it is expected to realize large-scale industrial production of graphene oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a scanning electron microscope image of graphene oxide prepared in Example 1;

[0012] Figure 2 is a transmission electron microscopy image of graphene oxide prepared in Example 1;

[0013] Figure 3 is the Raman image of the graphene oxide prepared in Example 1;

[0014] Figure 4 This is the X-ray photoelectron spectrum of the graphene oxide prepared in Example 1.

[0015] Figure 5 This is an atomic force microscope image of the graphene oxide prepared in Example 1. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] A first aspect of the present invention provides a method for electrochemically preparing graphene oxide, comprising the following steps:

[0018] The graphite plate is pretreated, and a double-electrode system is adopted, with the pretreated graphite plate as the working electrode, the platinum sheet as the counter electrode, and the organic sulfonic acid solution as the electrolyte solution. A positive potential is applied to the working electrode to obtain high-quality graphene oxide;

[0019] The pretreatment adopts a dual-electrode system, with a graphite plate as a working electrode, a platinum sheet as a counter electrode, an alkaline solution as an electrolyte solution, a positive potential is applied to the working electrode, and the treated graphite plate is directly used for subsequent electro-oxidation stripping.

[0020] In the present invention, the inventors found that a large number of hydroxyl radicals or oxygen radicals can be inserted between the graphite sheets by pre-treating the graphite sheets with an alkaline solution of a certain concentration. On the one hand, such a pre-treatment method can increase the distance between the graphite layers. When the graphite sheets are quickly transferred to the sulfonic acid electrolyte for electrochemical oxidation and stripping, the gaseous substances such as O2 generated by electro-oxidation provide sufficient stripping force, so that the graphite layers can be efficiently stripped. On the other hand, the insertion of a large number of oxygen-containing free radicals provides an oxygen source for the large-scale generation of oxidation defects on graphene, so that the graphite layers are loaded with a large number of oxygen-containing functional groups such as hydroxyl groups and carboxyl groups on the surface while stripping, so that the graphene has good hydrophilicity.

[0021] According to the present invention, the pretreatment time is 5-30 minutes.

[0022] According to the present invention, the electrolyte solution is at least one of a methane sulfonic acid solution, an ethane sulfonic acid solution, and a propane sulfonic acid solution;

[0023] Wherein, the alkaline solution is potassium hydroxide solution or sodium hydroxide solution.

[0024] According to the present invention, the electrochemical oxidation stripping time is 4-10 hours.

[0025] According to the present invention, the concentration of the alkaline solution in the electrolyte is 0.5-2M;

[0026] Wherein, the concentration of the organic sulfonic acid in the electrolyte is 0.5-2M.

[0027] According to the present invention, the thickness of the graphite plate material is 0.5-1 mm.

[0028] According to the present invention, the distance between the working electrode and the counter electrode is 1-5 cm.

[0029] According to the present invention, during the electrochemical oxidation stripping process, the positive potential applied to the working electrode is 5-10V.

[0030] According to the present invention, the method further comprises: filtering and separating the mixed solution obtained by oxidation stripping, and ultrasonically cleaning, centrifugally separating, and vacuum drying the solid product.

[0031] According to the present invention, in the ultrasonic cleaning, the ultrasonic power operating frequency is 35-53KHz, the ultrasonic time is 10-30min, and the ultrasonic temperature is 0-30°C.

[0032] According to the present invention, the centrifugal speed of the centrifugal separation is 5000-12000 r / min; the centrifugal time is 5-15 min.

[0033] According to the present invention, the vacuum drying temperature is 50-80° C. and the vacuum drying time is 6-36 hours.

[0034] Test Method

[0035] The C / O atomic ratio of graphene oxide was measured by X-ray photoelectron spectroscopy.

[0036] The technical scheme of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Obviously, the embodiments described herein are only some embodiments of the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments implemented by ordinary technicians in this field without making creative improvements belong to the protection scope of the present invention.

[0037] Embodiment 1:

[0038] Weigh 20g of sodium hydroxide and dissolve it in 500mL of deionized water to obtain a 1M sodium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*0.5mm graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode and pretreat the graphite plate for 15 minutes. Measure 32.44mL of 99.5% methanesulfonic acid, add deionized water to prepare 500mL of solution to obtain a 1M methanesulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0039] The reaction time is 5h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 2.7, and the yield of few-layer graphene oxide (≤5 layers) is 87%.

[0040] The graphene oxide powder prepared in Example 1 was tested by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Figure 1 This is a scanning electron microscope image. It can be seen from the image that graphene oxide is almost transparent and has many wrinkles, which proves the successful preparation of a large number of few-layer graphene oxide. Figure 2 This is a transmission electron microscope image, from which we can see that graphene oxide has a wrinkled structure and a structure with fewer layers. Figure 3 This is a Raman image. It can be seen from the image that graphene oxide with more oxygen defects was successfully prepared. Figure 4 This is an X-ray photoelectron spectrum. It can be seen from the figure that the prepared graphene oxide has more oxidation defects, which is consistent with the Raman spectrum data. Figure 5 This is an AFM image, from which we can see that a single layer of graphene oxide was successfully prepared.

[0041] Embodiment 2:

[0042] Weigh 20g of sodium hydroxide particles and dissolve them in 500mL of deionized water to obtain a 1M sodium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*1mm graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode and pretreat the graphite plate for 15 minutes. Measure 32.44mL of 99.5% methanesulfonic acid, add deionized water to prepare 500mL of solution to obtain a 1M methanesulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0043] The reaction time is 9h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 2.8, and the yield of few-layer graphene oxide (≤5 layers) is 78%.

[0044] Embodiment 3:

[0045] Weigh 28g of potassium hydroxide particles and dissolve them in 500mL of deionized water to obtain a 1M potassium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*0.5mm graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10v to the working electrode and pretreat the graphite plate for 15min. Measure 32.44mL of 99.5% methanesulfonic acid, add deionized water to prepare 500mL of solution to obtain a 1M methanesulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10v to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0046] The reaction time is 5h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 2.7, and the yield of few-layer graphene oxide (≤5 layers) is 84%.

[0047] Embodiment 4:

[0048] Weigh 10g of sodium hydroxide particles and dissolve them in 500mL of deionized water to obtain a 0.5M sodium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*0.5mm graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode and pretreat the graphite plate for 15 minutes. Measure 32.44mL of 99.5% methanesulfonic acid, add deionized water to prepare 500mL of solution, and obtain a 1M methanesulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0049] The reaction time is 7h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 3.1, and the yield of few-layer graphene oxide (≤5 layers) is 81%.

[0050] Embodiment 5:

[0051] Weigh 20g of sodium hydroxide particles and dissolve them in 500mL of deionized water to obtain a 1M sodium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*0.5mm graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode and pretreat the graphite plate for 15 minutes. Measure 40.77mL of 95% ethane sulfonic acid, add deionized water to prepare 500mL of solution to obtain a 1M ethane sulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0052] The reaction time is 7h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 3.1, and the yield of few-layer graphene oxide (≤5 layers) is 73%.

[0053] Embodiment 6:

[0054] Weigh 20g of sodium hydroxide particles and dissolve them in 500mL of deionized water to obtain a 1M sodium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*0.5mm graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode and pretreat the graphite plate for 15 minutes. Measure 47.75mL of 99.0% propane sulfonic acid, add deionized water to prepare 500mL of solution, and obtain a 1M propane sulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0055] The reaction time is 8h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 3.0, and the yield of few-layer graphene oxide (≤5 layers) is 70%.

[0056] Embodiment 7:

[0057] Weigh 20g of sodium hydroxide particles and dissolve them in 500mL of deionized water to obtain a 1M sodium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*0.5mm graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode and pretreat the graphite plate for 15 minutes. Measure 16.22mL of 99.5% methanesulfonic acid, add deionized water to prepare 500mL of solution, and obtain a 0.5M methanesulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0058] The reaction time is 8h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 3.3, and the yield of few-layer graphene oxide (≤5 layers) is 80%.

[0059] Embodiment 8:

[0060] Weigh 20g of sodium hydroxide particles and dissolve them in 500mL of deionized water to obtain a 1M sodium hydroxide solution. Add an appropriate amount of the above solution to the electrolytic cell, use a 1.5cm*2.5cm*0.5mm high graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode and pretreat the graphite plate for 15 minutes. Measure 64.88mL of 99.5% methanesulfonic acid, add deionized water to prepare 500mL of solution to obtain a 2M methanesulfonic acid solution. Add an appropriate amount of the above solution to the electrolytic cell, use the pretreated graphite plate as the working electrode, a platinum sheet as the counter electrode, and a distance of 3cm between the two electrodes. Apply a positive voltage of 10V to the working electrode to achieve electrochemical oxidation stripping of the graphite plate.

[0061] The reaction time is 4h, the graphite plate is completely oxidized and peeled off, and a mixed solution of graphene oxide and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene oxide is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene oxide powder is collected. The C / O is 2.7, and the yield of few-layer graphene oxide (≤5 layers) is 81%.

[0062] Comparative Example 1:

[0063] A 1M methanesulfonic acid solution was prepared and added to the electrolytic cell. A 1.5cm*1.5cm*0.5mm graphite foil was used as the working electrode and a platinum foil was used as the counter electrode. The distance between the two electrodes was 3cm. A positive voltage of 10V was applied to the working electrode to achieve electrochemical exfoliation of graphite.

[0064] The reaction time is 1200s, the graphite is completely peeled off, and a mixed solution of graphene and electrolyte is obtained. The mixed solution is separated by vacuum filtration, and the obtained solid is ultrasonically cleaned with water and ethanol, with an ultrasonic frequency of 35Hz, a time of 60min, a temperature of 30℃, and a centrifugal separation at a speed of 8000r / min; the centrifugal time is 5min. The cleaned graphene is placed in a vacuum oven for drying, the drying temperature is 60℃, the drying time is 12h, and the obtained graphene powder is collected. The C / O is 15.6, and the yield of few-layer graphene (≤5 layers) is 82%.

[0065] Table 1 shows the peeling time and C / O atomic ratio of graphene oxide prepared in Examples 1-8 and Comparative Example 1.

[0066] Table 1

[0067] serial number Stripping time (h) Yield (%) C / O Example 1 5 87 2.7 Example 2 9 78 2.8 Example 3 5 84 2.7 Example 4 7 80 3.1 Example 5 7 73 3.1 Example 6 8 70 3.0 Example 7 8 80 3.3 Example 8 4 81 2.7 Comparative Example 1 1200s 82 15.6

[0068] It can be seen from Examples 1-15 and Comparative Example 1 that the graphene oxide prepared by the preparation method of the present invention has a low C / O atomic ratio, a greatly improved degree of oxidation, and a high yield is guaranteed.

[0069] The method of the present invention uses an electrochemical method to oxidatively exfoliate graphite to prepare graphene oxide, avoiding the use of high-concentration strong acids and strong oxidants in traditional methods, and is a safe, efficient and green preparation method. After pretreatment with sodium hydroxide solution, methanesulfonic acid solution is used as an electrolyte solution for oxidative exfoliation, which not only greatly reduces the exfoliation time, but also avoids the appearance of metal ion impurities on the surface of graphene oxide, and the prepared graphene oxide has a small number of layers and a high degree of oxidation. It is of great significance to improve the industrial application of preparing graphene oxide by exfoliating graphite by electrochemical methods.

[0070] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and inventive concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for electrochemically preparing graphene oxide, characterized in that The following steps are involved: The graphite plate is pretreated, and a double-electrode system is used, with the pretreated graphite plate as the working electrode, the platinum sheet as the counter electrode, and the organic sulfonic acid solution as the electrolyte solution. By applying a positive potential to the working electrode, the graphite plate is electrochemically oxidized and exfoliated to obtain high-quality graphene oxide; The pretreatment adopts a dual-electrode system, with a graphite plate as a working electrode, a platinum sheet as a counter electrode, an alkaline solution as an electrolyte solution, and a positive potential applied to the working electrode; the treated graphite plate is directly used for subsequent electro-oxidation stripping.

2. The method according to claim 1, characterized in that The pretreatment time is 5-30 min.

3. The method according to claim 1, characterized in that The electrolyte solution is at least one of a methane sulfonic acid solution, an ethane sulfonic acid solution, and a propane sulfonic acid solution; Wherein, the alkaline solution is potassium hydroxide solution or sodium hydroxide solution.

4. The method according to claim 1, characterized in that: The electrochemical oxidation stripping time is 4-10h.

5. The method according to claim 1, characterized in that The concentration of the alkaline solution in the electrolyte is 0.5-2M; Wherein, the concentration of the organic sulfonic acid in the electrolyte is 0.5-2M.

6. The method according to claim 1, characterized in that The thickness of the graphite sheet material is 0.5-1mm.

7. The method according to claim 1, characterized in that The distance between the working electrode and the counter electrode was 1-5 cm.

8. The method according to claim 1, characterized in that During the electrochemical oxidation stripping process, the positive potential applied to the working electrode is 5-10V.

9. The method according to claim 1, characterized in that: The method also includes: filtering and separating the mixed solution obtained by oxidation stripping, ultrasonic cleaning, centrifugal separation, and vacuum drying the solid product. During the ultrasonic cleaning, the ultrasonic power operating frequency is 35-53KHz; the ultrasonic time is 10-30min; the ultrasonic temperature is 0-30°C; the centrifugal speed of the centrifugal separation is 5000-12000r / min; the centrifugal time is 5-15min; the vacuum drying temperature is 50-80°C; and the vacuum drying time is 6-36h.

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