Method for preparing graphene by stripping graphite through electrochemical anode intercalation
By employing an electrochemical method of pre-intercalation and secondary exfoliation, combined with dilute sulfuric acid and anion insertion, the problems of graphite electrode consumption and poor product uniformity were solved, enabling efficient and safe large-scale production of high-quality graphene.
Patent Information
- Application Number
- CN202511218411.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-28
- Publication Date
- 2025-12-19
AI Technical Summary
Existing electrochemical exfoliation technologies suffer from problems such as severe consumption of graphite electrodes, poor product uniformity, and high reagent hazard, making it difficult to achieve low-cost, large-scale production of high-quality graphene.
H+ is introduced in the pre-intercalation stage, and the graphite layers are initially opened by soaking in dilute sulfuric acid. Combined with the insertion of anions, a double intercalation effect is formed. After the first exfoliation, the anode is replaced with a platinum sheet to provide a stable electric field for the second exfoliation, which reduces the consumption of graphite electrodes and improves the uniformity of the product. At the same time, a mixed solution of dilute sulfuric acid and other salts is used to reduce the sulfuric acid concentration and reduce the risk.
This improved the exfoliation efficiency and product uniformity of graphene, reduced the consumption of graphite electrodes and the hazards of reagents, simplified the process operation, and enabled the low-cost preparation of high-quality graphene.
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Figure CN121158771A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of graphene preparation technology, specifically to a method for preparing graphene by electrochemical anodic intercalation and exfoliation of graphite. Background Technology
[0002] Graphene is a type of poly(phosphorus) 2 Graphene is a material composed of hybridized carbon atoms tightly packed into a single-layer, two-dimensional honeycomb lattice structure. It possesses excellent optical, electrical, and mechanical properties and holds significant promise for applications in materials science, micro / nano fabrication, energy, biomedicine, and drug delivery, and is considered a revolutionary material for the future. However, achieving the green, non-toxic, pollution-free, low-cost, and large-scale preparation of high-quality, defect-free graphene remains a challenge. Electrochemical exfoliation is a novel method for graphene preparation developed in recent years. It primarily involves using an electric field to drive the insertion of dissimilar charged ions and mixtures into a graphite electrode, causing expansion and exfoliation of the interlayer of graphite to obtain graphene. The main advantages of this method are: precise control of voltage and current; reproducibility and operability of the graphite exfoliation process; and electrolysis typically occurring at or near room temperature. Therefore, electrochemical exfoliation of graphene shows promise as a low-cost, large-scale technology for producing high-quality graphene.
[0003] However, existing electrochemical stripping technologies still have the following shortcomings:
[0004] (1) Severe consumption of graphite electrodes: In traditional methods, graphite is always used as the anode. During electrolysis, it is prone to excessive oxidation or peeling, resulting in low electrode utilization and a large amount of graphite debris mixed in the product.
[0005] (2) Poor product uniformity: The ion insertion process is easily affected by uneven electric field distribution, resulting in excessive stripping in some areas and insufficient stripping in others.
[0006] (3) High risk of reagents: In order to improve the ion migration rate, traditional electrolytes often use high-concentration sulfuric acid, which is highly corrosive, increasing equipment maintenance costs and posing safety hazards. Summary of the Invention
[0007] The purpose of this invention is to overcome at least one of the defects in the prior art by providing a method for preparing graphene through electrochemical anodic intercalation and exfoliation of graphite. In the pre-intercalation stage of this invention, H+ is introduced through immersion in dilute sulfuric acid. + The initial separation of graphite layers creates space for subsequent anion insertion; in the first exfoliation stage, the electric field drives the anions (such as SO42-) in the electrolyte. 2- VO3 - It rapidly migrates towards the graphite anode and deeply inserts into the initially expanded interlayer space, further widening the interlayer spacing, and interacts with H. +The double intercalation effect is formed by the cooperation, which greatly reduces the binding of van der Waals force; after the first peeling, the anode is replaced by a platinum plate, at this time, there are some peeled graphite layers in the electrolyte, the platinum plate anode can provide a continuous and uniform electric field, avoiding the excessive consumption of the graphite electrode as the anode, and at the same time, the second peeling of the multi-layer graphite layers which are not completely peeled off is carried out, so as to further separate them and improve the layer uniformity of the product;
[0008] The object of the application can be achieved by the following technical solutions:
[0009] The method comprises the following steps:
[0010] S1, pre-intercalation: the graphite electrode is subjected to pre-intercalation treatment to obtain an intercalated and expanded graphite electrode;
[0011] S2, first peeling: the expanded graphite is used as an anode, a platinum plate is used as a cathode, and the graphite electrode is placed in an electrolyte and powered to complete the first peeling;
[0012] S3, second peeling: the anode is replaced by a platinum plate, and the second peeling is carried out again, and the obtained graphene slurry is filtered and washed to obtain a graphene product.
[0013] In S1, the graphite electrode is a battery graphite rod, graphite paper, graphite foil or pencil core. The size of the graphite electrode is (0.5-1.5) cm x (0.5-1.5) cm x (3-6) cm. The pre-intercalation treatment of the graphite electrode comprises: soaking the graphite electrode in a dilute sulfuric acid solution, and then ultrasonic treatment to obtain an intercalated and expanded graphite electrode.
[0014] In S2, the electrolyte can be selected from: dilute sulfuric acid; or a mixed solution of dilute sulfuric acid and lye; or a mixed solution of dilute sulfuric acid, metal sulfate and ammonium metavanadate. The metal sulfate is copper sulfate or ferrous sulfate. Among them, the molar concentration ratio of the mixed solution containing dilute sulfuric acid, copper sulfate and ammonium metavanadate is (0.01-0.07):(0.01-0.05):(0.01-0.03), and the best is 0.05:0.03:0.02. In addition, the molar concentration ratio of the mixed solution containing dilute sulfuric acid and potassium hydroxide is (0.2-0.5):(0.05-0.2), and the best is 0.3:0.1.
[0015] In S2, the first peeling is powered as follows: first, apply a voltage of 1-3V to wet the graphite electrode for 5-10min, then increase the voltage to 5-15V for peeling, and the peeling time is 30-60min.
[0016] In S3, the second peeling is carried out, the anode is replaced by a platinum sheet, and the peeling is continued for 20-40 min at 8-12 V; the obtained graphene mixed solution is subjected to suction filtration and washing to obtain high-purity graphene.
[0017] Compared with the prior art, the present application has the following advantages:
[0018] (1) The present application provides a method for preparing graphene by electrochemical anode intercalation peeling of graphite, which realizes the preparation of graphene through secondary peeling. The first peeling utilizes the intercalation expansion of the graphite electrode itself, and the van der Waals force between the graphite layers is destroyed by changing the voltage gradient. The second peeling maintains a stable electric field by a platinum electrode, avoids the consumption of the graphite electrode, and improves the peeling efficiency and product uniformity.
[0019] (2) The present application provides a method for preparing graphene by electrochemical anode intercalation peeling of graphite, which reduces the sulfuric acid concentration to less than 30% of the traditional method by compounding sulfuric acid salt with ammonium metavanadate, reduces the use of hazardous chemicals, and realizes environmentally friendly preparation.
[0020] (3) The present application provides a method for preparing graphene by electrochemical anode intercalation peeling of graphite, which adopts "low-voltage wetting + high-voltage peeling" two stages in the first peeling, and adopts constant voltage in the second peeling, which can accurately control the number of graphene layers (5-5 layers) without complex feedback system, and simplifies the process operation. BRIEF DESCRIPTION OF DRAWINGS
[0021] Figure 1 It is a schematic diagram of the electrochemical peeling process of the present application;
[0022] Figure 2 It is the infrared spectrum of the graphene samples prepared in Examples 1-3 of the present application.
[0023] Figure 3 It is the Raman spectrum of the graphene samples prepared in Examples 1-3 of the present application.
[0024] Figure 4 It is the SEM image of the graphene prepared in Example 1 of the present application.
[0025] Figure 5 It is the SEM image of the graphene prepared in Example 3 of the present application.
[0026] Figure 6 It is the TEM image of the graphene prepared in Example 3 of the present application.
[0027] Figure 7 It is a comparison chart of peeling efficiency, speed and yield of the graphene prepared in Examples 1-3 of the present application. DETAILED DESCRIPTION
[0028] The application will be described in detail below with reference to the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.
[0029] The application provides a method for preparing graphene by electrochemical anode intercalation and exfoliation of graphite, which comprises the following steps:
[0030] S1, graphite electrodes are subjected to pre-intercalation treatment to obtain intercalation expanded graphite electrodes;
[0031] S2, the intercalation expanded graphite electrodes in S1 are used as anodes, platinum sheet electrodes are used as cathodes, the anodes and the cathodes are put into an electrolyte, and electricity is passed to perform first exfoliation;
[0032] S3, the anodes in S2 are replaced by platinum sheet electrodes, electricity is passed to perform second exfoliation, and a graphene mixture is obtained, and the graphene mixture after exfoliation is filtered and washed to obtain a graphene material.
[0033] In some embodiments of the application, in S1, the pre-intercalation treatment of the graphite electrodes comprises: the graphite electrodes are soaked in a dilute sulfuric acid solution and then subjected to ultrasonic treatment to obtain intercalation expanded graphite electrodes.
[0034] In some embodiments of the application, in S2, the electrolyte is dilute sulfuric acid.
[0035] In some embodiments of the application, in S2, the electrolyte is a mixed solution of dilute sulfuric acid and lye.
[0036] In some embodiments of the application, in S2, the electrolyte is a mixed solution of dilute sulfuric acid, metal sulfate and ammonium metavanadate.
[0037] In some embodiments of the application, the metal sulfate is copper sulfate or ferrous sulfate.
[0038] In some embodiments of the application, in S2, the electrolyte is a mixed solution containing dilute sulfuric acid, copper sulfate and ammonium metavanadate, and the molar concentration ratio of dilute sulfuric acid, copper sulfate and ammonium metavanadate is (0.01-0.07):(0.01-0.05):(0.01-0.03).
[0039] In some embodiments of the application, in S2, the electrolyte is a mixed solution containing dilute sulfuric acid and potassium hydroxide, and the molar concentration of sulfuric acid and potassium hydroxide is (0.2-0.5):(0.05-0.2).
[0040] In some embodiments of the present application, in S2, the first-time power supply for peeling is specifically as follows: 1-3V voltage is applied to wet the graphite electrode for 5-10min, and then the voltage is increased to 5-15V for peeling, and the peeling time is 30-60min.
[0041] In some embodiments of the present application, in S3, the second-time power supply for peeling is specifically as follows: 8-12V voltage is applied for peeling, and the peeling time is 20-40min.
[0042] In some embodiments of the present application, in S1, the graphite electrode is a battery graphite rod, graphite paper, graphite foil or pencil core.
[0043] In some embodiments of the present application, in S1, the particle size of the graphite electrode is (0.5-1.5)cm×(0.5-1.5)cm×(3-6)cm.
[0044] Embodiment 1
[0045] The embodiment provides a method for preparing graphene by electrochemical anode intercalation peeling of graphite, and a specific process is shown in Figure 1 The method comprises the following steps:
[0046] 1. Pre-intercalation treatment: the waste battery graphite rod is washed with deionized water for 3 times to remove surface impurities, and then the graphite rod is cut into an electrode size of 1cm×1cm×5cm. The cut graphite electrode is immersed in a 0.1M dilute sulfuric acid solution for 2h, so that H + The graphite layers are initially inserted to achieve pre-expansion; and after the immersion, ultrasonic treatment is performed for 30min to further strengthen the interlayer intercalation effect, so that the graphite electrode with intercalation expansion is finally obtained.
[0047] 2. Electrolyte preparation: 6g of concentrated sulfuric acid with a mass fraction of 98% is slowly added into 250mL of deionized water for dilution, and the electrolyte is prepared by stirring.
[0048] 3. Electrolytic peeling:
[0049] Primary peeling: the graphite electrode with intercalation expansion is used as an anode, and a platinum electrode is used as a cathode. The anode and the cathode are immersed in the above electrolyte, and are placed in a 25℃ constant-temperature water bath environment to maintain stable reaction temperature. 2.5V voltage is applied to wet the graphite electrode for 10min, so that the electrolyte is driven by low voltage to fully contact the electrode surface, and local dry areas are avoided to affect the uniformity of peeling. Then, the voltage is increased to 10V for peeling, and the peeling is continued for 40min. The van der Waals force between the graphite layers is destroyed by the voltage gradient change, and the primary peeling is realized.
[0050] Second stripping: the anode in the electrolyte after the first stripping is replaced by platinum electrode, the cathode is still platinum electrode, and the electrolyte system is maintained. Apply 10V constant voltage for second stripping, last 30min. Maintain stable electric field through platinum anode to avoid further consumption of graphite electrode, while second stripping of graphite layers not completely separated in the first stripping.
[0051] 4. Product collection: filter the electrolyte after the second stripping, wash the solid with deionized water for 3 times, vacuum dry at 60℃ for 12h, get graphene powder 0.471g, stripping efficiency 92.58%, speed 0.31g / h.
[0052] Example 2
[0053] This example provides a method for preparing graphene by electrochemical anode intercalation stripping of graphite, the specific process is shown in Figure 1 , which comprises the following steps:
[0054] 1. Pre-intercalation treatment: wash the graphite foil 3 times to remove surface impurities, then put the cut graphite electrode into 0.2M dilute sulfuric acid for 1.5h, so that H + preliminary intercalation between graphite layers to achieve pre-expansion; after soaking, ultrasonic treatment for 20min to further strengthen the intercalation effect between layers, finally get the intercalated and expanded graphite electrode.
[0055] 2. Electrolyte preparation: weigh 6g of 98% mass fraction concentrated sulfuric acid, slowly drop into 250mL of 30% mass fraction potassium hydroxide solution as electrolyte, and mix uniformly by magnetic stirring to get the electrolyte.
[0056] 3. Electrolytic stripping:
[0057] First stripping: the intercalated and expanded graphite electrode is used as anode, and platinum electrode is used as cathode, the anode and cathode are immersed in the above electrolyte, and the reaction temperature is maintained stable in 25℃ constant temperature water bath environment. First apply 3V voltage to wet the graphite electrode for 5min, drive the electrolyte to fully contact the electrode surface by low voltage to avoid local dry area affecting the uniformity of stripping; then increase the voltage to 15V for stripping, last 30min, destroy the van der Waals force between graphite layers by voltage gradient change to realize first stripping.
[0058] Second stripping: the anode in the electrolyte after the first stripping is replaced by platinum electrode, the cathode is still platinum electrode, and the electrolyte system is maintained. Apply 10V constant voltage for second stripping, last 30min. Maintain stable electric field through platinum anode to avoid further consumption of graphite electrode, while second stripping of graphite layers not completely separated in the first stripping.
[0059] 4. Product collection: filter the electrolyte after the second stripping, wash the solid with deionized water for 3 times, vacuum dry at 60℃ for 12h, obtain graphene powder 0.467g, stripping efficiency 91.75%, speed 0.34g / h, yield 51.93%.
[0060] Example 3
[0061] The present embodiment provides a method for preparing graphene by electrochemical anodic intercalation and exfoliation of graphite, and the specific process is shown in Figure 1 The method comprises the following steps:
[0062] 1. Pre-intercalation treatment: wash the graphite foil for 3 times to remove surface impurities, then put the cut graphite electrode into 0.2M dilute sulfuric acid for 1.5h, so that H + The graphite layers are initially inserted between the layers to achieve pre-expansion; after soaking, ultrasonic treatment is performed for 20min to further strengthen the intercalation effect between the layers, and finally an intercalated and expanded graphite electrode is obtained.
[0063] 2. Electrolyte preparation: uniformly mix dilute sulfuric acid, copper sulfate solution, ferrous sulfate solution, manganese sulfate solution, zinc sulfate solution and ammonium metavanadate by magnetic stirring to obtain an electrolyte.
[0064] Among them, the concentration of dilute sulfuric acid, copper sulfate solution, ferrous sulfate solution, manganese sulfate solution and zinc sulfate solution is 0.02M, and the concentration of ammonium metavanadate is 0.002M.
[0065] 3. Electrolytic stripping:
[0066] First stripping: using the intercalated and expanded graphite electrode as the anode and the platinum sheet electrode as the cathode, immerse the anode and cathode in the above electrolyte, and place them in a 25℃ constant temperature water bath environment to maintain stable reaction temperature. First, apply a voltage of 3V to wet the graphite electrode for 5min, and then apply a voltage of 15V for 30min to strip the graphite electrode. Through the change of voltage gradient, the van der Waals force between the graphite layers is destroyed, and the first stripping is realized.
[0067] Second stripping: replace the anode in the electrolyte after the first stripping with a platinum sheet electrode, keep the cathode as a platinum sheet electrode, and maintain the electrolyte system unchanged. Apply a constant voltage of 10V for the second stripping for 30min. Through the platinum anode, a stable electric field is maintained to avoid further consumption of the graphite electrode, and the second stripping of the graphite layers that have not been completely separated in the first stripping is performed.
[0068] 4. Product collection: filter the electrolyte after the second stripping, wash the solid with deionized water for 3 times, vacuum dry at 60 DEG C for 12h, obtain graphene powder 0.48g, stripping efficiency 94.37%, speed 55.97g / h, yield 55.97%.
[0069] Figure 2 For the infrared spectrum of the graphene sample prepared in examples 1-3, compared with example 1 and example 2, the characteristic peak of graphene stripped in example 3 is wider and the intensity is weaker, which indicates that the quality of graphene stripped by using the sulfate mixed solution is higher.
[0070] Figure 3 a is the Raman spectrum of the graphene sample prepared in examples 1-3, I D / I G is the lowest, indicating that the graphene has the least defects in the system; I 2D / I G of the graphene sample prepared in example 3 is the highest, which proves that the graphene has the least layers stripped in the system. Figure 3 b is the Raman spectrum of the graphene sample prepared in example 3 under different water bath temperature conditions, with the increase of temperature, I D / I G gradually decreases, indicating that with the increase of temperature, the defects of the graphene sample decrease, I 2D / I G first decreases and then increases, and the number of layers of the graphene decreases after increasing with the increase of temperature. It can be seen that by adjusting the type of electrolyte, the defect density and the number of layers of the graphene can be accurately controlled to meet the needs of different application scenarios.
[0071] Figure 4 is the SEM image of the intercalated and expanded graphite electrode obtained in example 1, Figure 5 is the SEM image of the graphene sample obtained in example 3. Figure 4 and Figure 5 The sample in the picture has obvious wrinkles, which indicates that the gas produced in the stripping process has a good boosting effect on the expansion and peeling of the graphite layer. At the same time, Figure 4 The sample edge of the sample in the picture is bent, and the gap between the graphite layers can be clearly observed, which indicates that the graphene prepared in example 3 has fewer layers and larger interlayer spacing than the graphene prepared in example 1.
[0072] Figure 6 is the TEM image of the graphene sample obtained in example 3, the sample in the picture has high transparency, and the number of layers can be clearly observed, which indicates that the graphene prepared in example 3 has fewer layers, about 3-5 layers.
[0073] In summary, in the pre-intercalation stage, H +, preliminary support between the graphite layers, create space for subsequent anion insertion; a first exfoliation stage, the electric field drives the anion (such as SO4 2- , VO3 - ) in the electrolyte quickly migrates to the graphite anode, and deeply inserts into the interlayer which has been preliminarily expanded, further expands the interlayer spacing, and forms a "double intercalation effect" with H + , greatly reducing the constraint of van der Waals force; after the first exfoliation, the anode is replaced with a platinum plate, at this time there are some exfoliated graphite layers in the electrolyte, and the platinum plate anode can provide a sustained and uniform electric field, avoiding the excessive consumption of the graphite electrode as the anode, while performing a second exfoliation on the multi-layer graphite layers that have not been completely exfoliated, further promoting their separation and improving the uniformity of the number of layers of the product; in addition, the present application also reduces the amount of sulfuric acid by using various sulfate salts or other salts instead of sulfuric acid, which can not only ensure a high quality of graphene, but also reduce the use of hazardous chemicals.
[0074] The above is only a preferred embodiment of the present application, and is not intended to limit the other forms of the present application. Any skilled person in the art can use the disclosed technical content to make changes or modifications to equivalent embodiments. However, any simple modification, equivalent change and modification made to the above embodiments without departing from the technical solution of the present application, and in accordance with the technical essence of the present application, still falls within the protection scope of the present application.
Claims
1. A method for preparing graphene by electrochemical anodic intercalation and exfoliation of graphite, characterized in that, The method comprises the following steps: S1, the graphite electrode is subjected to pre-intercalation treatment to obtain an intercalated and expanded graphite electrode; S2, the intercalated and expanded graphite electrode in S1 is used as an anode, a platinum electrode is used as a cathode, the anode and the cathode are placed in an electrolyte, and electricity is supplied to complete the first peeling; S3, the anode in S2 is replaced with a platinum electrode, electricity is supplied to perform the second peeling, a graphene mixture is obtained, and the graphene mixture obtained after the peeling is completed is filtered and washed to obtain a graphene material.
2. The method of claim 1, wherein the method is characterized by: In S1, the pre-intercalation treatment of the graphite electrode comprises: soaking the graphite electrode in a dilute sulfuric acid solution and then performing ultrasonic treatment to obtain an intercalated and expanded graphite electrode.
3. The method of claim 1, wherein the method is characterized by: In S2, the electrolyte is at least one of the following: ① dilute sulfuric acid; ② a mixed solution of dilute sulfuric acid and lye; ③ a mixed solution of dilute sulfuric acid, a metal sulfate, and ammonium metavanadate.
4. The method according to claim 3, wherein the metal sulfate is copper sulfate or ferrous sulfate.
5. The method of claim 1, wherein the electrolyte in S2 is a mixture of dilute sulfuric acid, copper sulfate, and ammonium metavanadate. The molar concentration ratio of the dilute sulfuric acid, copper sulfate, and ammonium metavanadate is (0.01-0.07):(0.01-0.05):(0.01-0.03).
6. The method of claim 1, wherein the electrolyte in S2 is a mixture of dilute sulfuric acid and potassium hydroxide. The molar concentration ratio of the sulfuric acid and potassium hydroxide is (0.2-0.5):(0.05-0.2).
7. The method according to claim 1, wherein in S2, the electricity supply for the first peeling specifically comprises: first applying a voltage of 1-3 V to wet the graphite electrode for 5-10 min, and then increasing the voltage to 5-15 V to perform peeling, and the peeling time is 30-60 min.
8. The method according to claim 1, wherein in S3, the electricity supply for the second peeling specifically comprises: applying a voltage of 8-12 V to perform peeling, and the peeling time is 20-40 min.
9. The method according to claim 1, wherein in S1, the graphite electrode is a battery graphite rod, graphite paper, graphite foil, or a pencil core.
10. The method according to claim 1, wherein in S1, the size of the graphite electrode is (0.5-1.5) cm×(0.5-1.5) cm×(3-6) cm.