Graphene, transparent conductive film and preparation method and application thereof

Abstract

The application discloses graphene, a transparent conductive film and a preparation method and application thereof. The preparation method of the graphene comprises the following steps: taking a gelled carboxymethyl cellulose sodium-metal salt aqueous solution as an electrolyte, taking a graphite electrode as a cathode, and jointly constructing an electrochemical reaction system with an anode, wherein the electrolyte is formed by mixing a metal salt and carboxymethyl cellulose sodium, wetting treatment by an alcohol substance, and mixing with water; and direct current is passed through the electrochemical reaction system to perform electrolysis, a constant voltage is applied to graphite to perform stripping, and graphene is obtained. The method for preparing high-quality graphene based on the electrochemical method has the advantages of high efficiency and simple operation, and the transparent conductive film prepared by the method has good advantages in light transmission performance and conductive performance.

Description

Technical Field

[0001] This invention belongs to the field of graphene preparation technology, specifically relating to a graphene, a transparent conductive film, its preparation method and application. Background Technology

[0002] Graphene's excellent electrical, thermal, optical, and mechanical properties make it an outstanding material for electronic and optoelectronic devices; therefore, developing technologies for the large-scale, efficient production of graphene is essential. Among the many methods employed to date, the exfoliation of bulk graphite is the most common method for large-scale graphene production. Methods such as ball milling, liquid-phase ultrasonication, and shear exfoliation provide feasible approaches for producing graphene with a few defects; however, these methods are generally inefficient. In contrast, the traditional chemical oxidation method for preparing graphene oxide followed by reduction treatment greatly improves the preparation efficiency. However, because a considerable number of oxygen-containing groups and defects are left behind, this method severely damages the physical properties of graphene, which cannot be fully recovered even after reduction.

[0003] Electrochemical exfoliation for graphene preparation is a highly efficient, safe, and easy-to-operate method that has attracted widespread attention in recent years. Classified by the different working electrodes used, electrochemical graphene preparation can be divided into anodic exfoliation and cathodic exfoliation. When graphite is used as the anode, it is called anodic exfoliation, where anions intercalate, oxidize, and exfoliate the graphite; when graphite is used as the cathode, it is called cathodic exfoliation, where cations intercalate and exfoliate the graphite. To date, there has been extensive research on electrochemical graphene preparation methods. However, these methods typically use graphite as the anode in aqueous solutions, inevitably leading to a certain degree of oxidation and defects. This negatively impacts the electrical, mechanical, and thermal properties of the prepared graphene. Therefore, developing a green, efficient, and scalable method for preparing high-quality graphene remains a pressing challenge. Summary of the Invention

[0004] The main objective of this invention is to provide graphene, transparent conductive films, their preparation methods and applications, in order to overcome the shortcomings of the prior art.

[0005] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0006] This invention provides a method for preparing graphene, comprising:

[0007] An electrochemical reaction system is constructed using a gelled sodium carboxymethyl cellulose-metal salt aqueous solution as the electrolyte and a graphite electrode as the cathode, together with the anode. The electrolyte is formed by mixing a metal salt and sodium carboxymethyl cellulose, wetting it with an alcohol, and then mixing it with water.

[0008] Furthermore, the electrochemical reaction system is electrolyzed by passing a direct current through it, and a constant voltage is applied to exfoliate the graphite to obtain graphene.

[0009] The present invention also provides graphene prepared by the aforementioned preparation method.

[0010] This invention also provides a method for preparing a transparent conductive thin film, comprising:

[0011] The graphite was exfoliated using the aforementioned method to obtain a mixed solution of graphene and electrolyte;

[0012] Furthermore, the mixed solution is applied to the surface of the substrate by spin coating, followed by water washing and drying to obtain a transparent conductive film.

[0013] The present invention also provides a transparent conductive film prepared by the aforementioned preparation method.

[0014] The present invention also provides the use of the aforementioned graphene or transparent conductive film in the fabrication of electronic or optoelectronic devices.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] (1) This invention provides a method for preparing high-quality graphene based on an electrochemical method, which has significant advantages of high efficiency and ease of operation:

[0017] (2) This invention provides a simple, controllable and easy-to-operate method for preparing gelled sodium carboxymethyl cellulose-metal salt aqueous solution;

[0018] (3) In the process of preparing graphene by electrochemical exfoliation, the present invention uses gelled sodium carboxymethyl cellulose-metal salt aqueous solution as electrolyte and graphite as cathode for exfoliation, which achieves a good exfoliation effect. The high-quality graphene prepared has almost no oxygen-containing groups and has high quality.

[0019] (4) The present invention provides a simple and easy-to-operate method for preparing transparent conductive films, avoiding the use of toxic and harmful organic solvents;

[0020] (5) The method for preparing high-quality graphene provided by the present invention is used to prepare transparent conductive films, which has good advantages in terms of light transmittance and conductivity. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a scanning electron microscope image of the high-quality graphene prepared in Example 1 of this invention;

[0023] Figure 2 This is a thermogravimetric analysis curve of the high-quality graphene prepared in Example 1 of this invention;

[0024] Figure 3 This is a transmittance diagram of the transparent conductive film prepared in Example 1 of the present invention at different wavelengths. Detailed Implementation

[0025] In view of the deficiencies of the prior art, the inventors of this case, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0026] Specifically, as one aspect of the technical solution of this invention, a method for preparing graphene includes:

[0027] An electrochemical reaction system is constructed using a gelled sodium carboxymethyl cellulose-metal salt aqueous solution as the electrolyte and a graphite electrode as the cathode, together with the anode. The electrolyte is formed by mixing a metal salt and sodium carboxymethyl cellulose, wetting it with an alcohol, and then mixing it with water.

[0028] Furthermore, the electrochemical reaction system is electrolyzed by passing a direct current through it, and a constant voltage is applied to exfoliate the graphite to obtain graphene.

[0029] In some preferred embodiments, the preparation method specifically includes: mixing a metal salt with sodium carboxymethyl cellulose, adding an alcohol for wetting, and then mixing it thoroughly with water under stirring to obtain a gelled sodium carboxymethyl cellulose-metal salt aqueous solution.

[0030] In some preferred embodiments, the metal salt includes any one or a combination of two or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate, but is not limited thereto.

[0031] Furthermore, the present invention selects metal salts with high solubility, and the metal salts do not exhibit strong acidity or strong alkalinity after dissolving in water.

[0032] In some preferred embodiments, the alcohol solvent includes, but is not limited to, anhydrous ethanol and / or anhydrous methanol.

[0033] In some preferred embodiments, the graphite electrode comprises a graphite sheet, but is not limited thereto.

[0034] In some preferred embodiments, the anode includes any one of a platinum electrode, an iron electrode, a copper electrode, a silver electrode, and a graphite electrode, but is not limited thereto.

[0035] In some preferred embodiments, the electrolyte contains 1-20 wt% sodium carboxymethyl cellulose and the metal salt.

[0036] In some preferred embodiments, the mass ratio of the metal salt to sodium carboxymethyl cellulose is 0.5-5:0.5-5.

[0037] In some preferred embodiments, the mass ratio of the alcohol to water is 1-10:10-100.

[0038] In some preferred embodiments, the mass ratio of the graphite electrode to the electrolyte is 0.05-0.5:12-120.

[0039] In some preferred embodiments, the constant voltage is 8 to 15 V.

[0040] In some preferred embodiments, the stripping process takes 10-30 minutes.

[0041] Another aspect of the present invention provides graphene prepared by the aforementioned preparation method.

[0042] Furthermore, the graphene has 1 to 8 layers.

[0043] Furthermore, the graphene sheet diameter is 10–23 μm.

[0044] Another aspect of the present invention provides a method for preparing a transparent conductive film, comprising:

[0045] The graphite was exfoliated using the aforementioned method to obtain a mixed solution of graphene and electrolyte;

[0046] Furthermore, the mixed solution is applied to the surface of the substrate by spin coating, followed by water washing and drying to obtain a transparent conductive film.

[0047] In some preferred embodiments, the spin coating is performed at a rotation speed of 50-500 r / min.

[0048] In some preferred embodiments, the drying process is carried out at a temperature of 20–100°C.

[0049] In some preferred embodiments, the substrate material includes, but is not limited to, PET.

[0050] In some preferred embodiments, the diameter of the substrate is 1 to 100 cm.

[0051] In some preferred embodiments, the amount of the mixed solution is 0.01 to 170 g.

[0052] In some preferred embodiments, the graphene content in the mixed solution is 5–15 mg.

[0053] In some preferred embodiments, the method for preparing graphene and transparent conductive films in this invention includes:

[0054] (1) Preparation of electrolyte: First, the metal salt and sodium carboxymethyl cellulose are mixed and then anhydrous ethanol is added for wetting. Under stirring, the wetted metal salt and sodium carboxymethyl cellulose mixture is slowly added to water and stirred until uniform, thus obtaining a gelled sodium carboxymethyl cellulose-metal salt aqueous solution.

[0055] (2) Preparation of high-quality graphene: Graphite sheets were used as the working electrode (cathode) and platinum wire as the counter electrode (anode), and both were placed parallel to each other in an aqueous solution of sodium carboxymethyl cellulose-metal salt. Then, a constant voltage was applied using a DC power supply to peel off the graphite sheets until they were completely peeled off.

[0056] (3) Preparation of transparent conductive film: Take a certain amount of the mixed solution of graphene and electrolyte obtained in step (2), stir it evenly, and spin-coat it with PET as the substrate. After uniform spin coating, rinse slowly with water until sodium carboxymethyl cellulose and metal salt are completely removed (since sodium carboxymethyl cellulose and metal salt are soluble in water and graphene is hydrophobic, rinsing with water can remove sodium carboxymethyl cellulose and metal salt and retain graphene on the PET substrate). Then dry the PET substrate loaded with graphene. After completely removing the water, the transparent conductive film can be obtained.

[0057] Furthermore, the ratio of the metal salt, sodium carboxymethyl cellulose, anhydrous ethanol, and water used is 0.5-30g: 0.5-5g: 1-35g: 10-100g, respectively.

[0058] Further, the metal salt is sodium chloride, potassium chloride, sodium sulfate, or potassium sulfate. Further, in step (1), after mixing the metal salt and sodium carboxymethyl cellulose and wetting with anhydrous ethanol, the sodium carboxymethyl cellulose particles become relatively dispersed, and the particles are separated by anhydrous ethanol. This avoids clumping when dissolved in water later, allowing for rapid and uniform dispersion in water. This process can be carried out at room temperature without strict temperature control or heating. Furthermore, the metal salt can act as an additive to improve the solubility and flowability of sodium carboxymethyl cellulose, which is beneficial for subsequent preparation processes and can be easily removed by water during subsequent cleaning.

[0059] Furthermore, the ratio of the amount of graphite sheet to sodium carboxymethyl cellulose-metal salt aqueous solution is 0.01-2g: 12-170g.

[0060] Furthermore, the concentration of the sodium carboxymethyl cellulose-metal salt aqueous solution is 1%-20%.

[0061] Furthermore, the applied constant voltage is 8-15V.

[0062] Furthermore, in step (2), when the graphite sheet is used as the anode and peeled off in a non-gelled aqueous solvent, the hydroxyl radicals and oxygen radicals generated by water electrolysis will oxidize the graphite, resulting in a certain degree of oxidation and defects in the prepared graphene. Compared with other methods that use graphite as the anode and peel it off in a non-gelled aqueous solvent, this invention uses graphite as the cathode for peeling, which avoids the oxidation of graphene to a certain extent. In addition, the gelled sodium carboxymethyl cellulose-metal salt aqueous solution used as the electrolyte can wrap around the graphene, further preventing the graphene from being oxidized and damaged. At the same time, it can also avoid the premature termination of the preparation process due to premature graphene detachment.

[0063] Furthermore, the amount of the mixed solution of graphene and electrolyte used is 0.01-170g.

[0064] Furthermore, the graphene content in the mixed solution is 5–15 mg.

[0065] Furthermore, the diameter of the PET substrate is 1-100cm.

[0066] Furthermore, the spin coating speed is 50-500 r / min.

[0067] Furthermore, the drying temperature is 20-100℃.

[0068] Furthermore, in step (3), since sodium carboxymethyl cellulose and metal salts are soluble in water and graphene is hydrophobic, rinsing with water can remove sodium carboxymethyl cellulose and metal salts and retain graphene on the PET substrate.

[0069] Furthermore, in step (3), an excessive amount of gel in the mixture and high viscosity will cause uneven dispersion of graphene, resulting in uneven graphene content and uneven film thickness after spin coating. A suitable gel concentration can avoid this problem. Moreover, the specification here is "take a certain amount of the mixed solution of graphene obtained in step (2) and electrolyte, stir it evenly, and then spin coat it with PET as the substrate". Step (1) specifies the components and concentration, and this specification is "stir it evenly", so the condition of uniform spin coating can be met.

[0070] In this invention, insufficient sodium carboxymethyl cellulose (SMC) fails to adequately protect the graphene, resulting in graphene with defects and high oxygen content. Excessive SMC leads to low exfoliation efficiency. Insufficient metal salt results in incomplete and inefficient exfoliation, while excessive metal salt leads to thick and uneven graphene sheets. Insufficient voltage results in incomplete and inefficient exfoliation, while excessive voltage results in thick and uneven exfoliated graphene sheets.

[0071] The impact of sodium carboxymethyl cellulose (CMC) on the quality of the transparent conductive film in this invention: CMC helps with the film-forming properties of the conductive film. A suitable concentration of CMC allows for relatively uniform spin-coating. Graphene dispersed in CMC can also be uniformly spin-coated. After removing the CMC, the graphene can be spin-coated relatively evenly. Graphene dispersed in water or organic solvents using other methods is not easily spin-coated (it is easily flung away like water). (Too little CMC can be roughly considered like water, which will be flung away during spin-coating; too much will result in too high viscosity, making it difficult to spin-coat).

[0072] Another aspect of the present invention provides a transparent conductive film prepared by the aforementioned preparation method.

[0073] In some preferred embodiments, the light transmittance of the transparent conductive film is 75-90%.

[0074] In some preferred embodiments, the sheet resistance of the transparent conductive film is 1000–1200 Ω / sq.

[0075] In some preferred embodiments, the diameter of the transparent conductive film is 2 to 5 cm.

[0076] Another aspect of the present invention provides the use of the aforementioned graphene or transparent conductive film in the fabrication of electronic or optoelectronic devices.

[0077] The technical solution of the present invention will be further described in detail below with reference to several preferred embodiments and accompanying drawings. This embodiment is implemented on the premise of the technical solution of the invention, and provides detailed implementation methods and specific operation processes. However, the protection scope of the present invention is not limited to the following embodiments.

[0078] Unless otherwise specified, the experimental materials used in the examples below can be purchased from conventional biochemical reagent companies.

[0079] Example 1

[0080] (1) Preparation of electrolyte: First, mix 2.5g of sodium chloride and 2.5g of sodium carboxymethyl cellulose, and then add 5g of anhydrous ethanol for wetting. Slowly add the wetted sodium chloride and sodium carboxymethyl cellulose mixture to 50g of water while stirring, and continue stirring until uniform to obtain a gelled sodium carboxymethyl cellulose-sodium chloride aqueous solution. (Sodium carboxymethyl cellulose is highly hygroscopic, rapidly absorbing water and swelling upon contact, exhibiting strong adhesive properties. Therefore, when dissolved in water, it forms clumps that are wet on the outside and dry on the inside, making uniform dispersion difficult. Mixing sodium chloride and sodium carboxymethyl cellulose and wetting them with anhydrous ethanol results in relatively dispersed sodium carboxymethyl cellulose particles, with the particles separated by the ethanol. This prevents clumping during subsequent dissolution in water, allowing for rapid and uniform dispersion. This process can be carried out at room temperature without strict temperature control or heating. Furthermore, sodium chloride can act as an additive, improving the solubility and flowability of sodium carboxymethyl cellulose, which is beneficial for subsequent preparation processes and is easily removed by water during subsequent cleaning.)

[0081] (2) Preparation of high-quality graphene: 0.1g of graphite sheet was used as the working electrode (cathode), and platinum wire was used as the counter electrode (anode). Both were placed in parallel in 60g of an 8.3% sodium carboxymethyl cellulose-sodium chloride aqueous solution. Then, a constant voltage of 10V was applied by a DC power supply to peel off the graphite sheet. After 20 minutes, the graphite sheet was completely peeled off. (When graphite is used as the anode and peeled in a non-gelled aqueous solvent, the hydroxyl radicals and oxygen radicals generated by water electrolysis will oxidize the graphite, resulting in a certain degree of oxidation and defects in the prepared graphene. Compared with other methods that use graphite as the anode and peel it in a non-gelled aqueous solvent, this method uses graphite as the cathode for peeling, which avoids the oxidation of graphene to a certain extent. In addition, the gelled sodium carboxymethyl cellulose-sodium chloride aqueous solution used as the electrolyte can wrap around the graphene, further preventing the graphene from being oxidized and damaged. At the same time, it can also avoid premature termination of the preparation process due to premature graphene detachment.)

[0082] (3) Preparation of transparent conductive film: Take 1g of the mixed solution of graphene and electrolyte obtained in step (2), stir it evenly, and spin-coat it onto a PET substrate with a diameter of 3cm. The spin-coating speed is 200r / min. After uniform spin-coating, rinse slowly with water until sodium carboxymethyl cellulose and sodium chloride are completely removed (since sodium carboxymethyl cellulose and sodium chloride are soluble in water and graphene is hydrophobic, rinsing with water can remove sodium carboxymethyl cellulose and sodium chloride and retain graphene on the PET substrate). Then dry the PET substrate loaded with graphene at 65℃. After completely removing the water, the transparent conductive film is obtained. (Compared to other methods that first clean graphene and then dissolve it in an organic solvent before preparing a transparent conductive film, this method avoids the use of toxic and harmful organic solvents. The solvent is easy to remove, and only water is needed to meet the preparation requirements, reducing costs. Furthermore, the prepared transparent conductive film is more uniform and has better performance. This is because the prepared graphene is of high quality, meaning it lacks oxygen-containing groups and defects, resulting in better conductivity. Sodium carboxymethyl cellulose (CMC) helps with the film-forming properties of the conductive film; a suitable concentration of CMC allows for relatively uniform spin-coating. Graphene dispersed in CMC can also be uniformly spin-coated, and after removing the CMC, the graphene can be spin-coated relatively evenly. Other methods disperse graphene in water or organic solvents, making spin-coating difficult; it is easily scattered like water.)

[0083] Performance characterization: Taking the high-quality graphene prepared in Example 1 as an example, characterization and performance determination were performed:

[0084] Figure 1 The image shows a scanning electron microscope (SEM) image of high-quality graphene, revealing its morphological characteristics. The maximum size is approximately 23 μm, demonstrating the possibility and advantages of this method in preparing large-size, high-quality graphene. Figure 2 The thermogravimetric analysis curves for high-quality graphene are shown. Due to its hydrophobic nature and near-absence of water molecules, high-quality graphene exhibits almost no mass loss within 100℃. The total weight loss between 100℃ and 600℃ is only 2.8%, indicating that the high-quality graphene prepared by this method has extremely low oxidation and virtually no oxygen-containing functional groups, thus demonstrating its high quality. Figure 3 The figure shows the transmittance of the transparent conductive film at different wavelengths. As can be seen from the figure, the transmittance increases with increasing wavelength, reaching a high of 86.1% at 550 nm, corresponding to a sheet resistance of 1054 Ω / sq. This indicates that the high-quality graphene produced by this method, when used to prepare a transparent conductive film, exhibits good transmittance and conductivity. The performance characterization data of the prepared transparent conductive film are shown in Table 2.

[0085] Comparative Example 1

[0086] The method is basically the same as in Example 1, except that anhydrous ethanol was not used to wet the mixture of sodium chloride and sodium carboxymethyl cellulose. The amounts of each raw material and the reaction conditions are shown in Table 1, and the performance characterization data of the prepared film are shown in Table 2.

[0087] Comparative Example 2

[0088] The method is basically the same as in Example 1, except that a non-constant voltage of 8-15V was applied by a DC power supply to peel off the graphite sheets during the preparation of graphene. The amounts of each raw material and the reaction conditions are shown in Table 1, and the performance characterization data of the prepared film are shown in Table 2.

[0089] Comparative Example 3

[0090] The method is the same as in Example 1, except that a constant voltage of 5V is applied by a DC power supply; the amount of each raw material and the reaction conditions are shown in Table 1; and the performance characterization data of the prepared film are shown in Table 2.

[0091] Comparative Example 4

[0092] The method is the same as in Example 1, except that a constant voltage of 20V is applied by a DC power supply; the amount of each raw material and the reaction conditions are shown in Table 1; and the performance characterization data of the prepared film are shown in Table 2.

[0093] Comparative Example 5

[0094] The method is the same as in Example 1, except that the content of carboxymethyl cellulose and metal salt in the electrolyte is 25 wt%, the amount of each raw material and the reaction conditions are shown in Table 1, and the performance characterization data of the prepared film are shown in Table 2.

[0095] Example 2

[0096] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0097] Example 3

[0098] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0099] Example 4

[0100] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0101] Example 5

[0102] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0103] Example 6

[0104] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0105] Example 7

[0106] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0107] Example 8

[0108] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0109] Example 9

[0110] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0111] Example 10

[0112] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0113] Example 11

[0114] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0115] Example 12

[0116] The method is the same as in Example 1. The amounts of each raw material and the reaction conditions are shown in Table 1. The performance characterization data of the prepared thin film are shown in Table 2.

[0117] Table 1. Amounts and reaction conditions of each raw material in Examples 1-12 and Comparative Examples 1-5.

[0118]

[0119]

[0120] Table 2. Performance characterization data of the thin films prepared in Examples 1-12 and Comparative Examples 1-5.

[0121]

[0122] Table 2 shows that, as seen in Examples 1-5, insufficient sodium carboxymethyl cellulose in the electrolyte fails to adequately protect the graphene, resulting in graphene with defects and oxygen content; excessive sodium carboxymethyl cellulose leads to low exfoliation efficiency. Insufficient metal salts result in incomplete exfoliation and low efficiency; excessive metal salts lead to thicker graphene sheets. Examples 6-8 show that a low proportion of carboxymethyl cellulose and metal salts in the electrolyte leads to lower current density, insufficient exfoliation, and inadequate protection of the graphene, resulting in graphene with defects and oxygen content; a high proportion of carboxymethyl cellulose and metal salts in the electrolyte increases current density and leads to thicker graphene sheets. Examples 9-10 show that a high ratio of graphite electrode to electrolyte leads to insufficient exfoliation and thicker sheets. Examples 11-12 show that a reduced ratio of graphite electrode to electrolyte slightly decreases current density, but the impact is minimal; the main effect is electrolyte waste. In Comparative Example 1, the absence of sodium carboxymethyl cellulose in the electrolyte fails to adequately protect the graphene, resulting in graphene with defects and oxygen content. In Comparative Example 2, the use of a non-constant voltage leads to poor stability during exfoliation, resulting in low-quality graphene. In Comparative Examples 3-4, excessively low voltage leads to incomplete exfoliation and low efficiency, while excessively high voltage results in thicker exfoliated graphene sheets. In Comparative Example 5, the high proportion of carboxymethyl cellulose and metal salts in the electrolyte increases the current density, resulting in thicker exfoliated graphene sheets. Table 2 shows that transparent conductive films prepared from graphene with fewer layers and larger dimensions exhibit higher light transmittance, better conductivity, and lower sheet resistance; while transparent conductive films prepared from graphene with more layers and smaller dimensions have lower light transmittance, poorer conductivity, and higher sheet resistance. Furthermore, the inventors of this invention also conducted experiments with other raw materials, processes, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained satisfactory results in all cases.

[0123] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for preparing graphene, characterized in that, include: An electrochemical reaction system is constructed using a gelled sodium carboxymethyl cellulose (CCMC)-metal salt aqueous solution as the electrolyte and a graphite electrode as the cathode, together with the anode. The preparation method of the gelled CCMC-metal salt aqueous solution includes: uniformly mixing the metal salt and CCMC, adding an alcohol for wetting, and then thoroughly mixing with water under stirring to obtain the gelled CCMC-metal salt aqueous solution; the total content of CCMC and metal salt in the electrolyte is 1-20 wt%; the mass ratio of metal salt to CCMC is 0.5-5:0.5-5: Furthermore, the electrochemical reaction system is electrolyzed by passing a direct current through it, and a constant voltage is applied to exfoliate the graphite to obtain graphene; wherein the constant voltage is 8~15V.

2. The preparation method according to claim 1, characterized in that: The metal salt includes any one or a combination of two or more of sodium chloride, potassium chloride, sodium sulfate, and potassium sulfate.

3. The preparation method according to claim 1, characterized in that: The alcohols include anhydrous ethanol and / or anhydrous methanol.

4. The preparation method according to claim 1, characterized in that: The graphite electrode comprises a graphite sheet; And / or, the anode includes any one of a platinum electrode, an iron electrode, a copper electrode, a silver electrode, and a graphite electrode.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the alcohol to water is 1-10:10-100; And / or, the mass ratio of the graphite electrode to the electrolyte is 0.05-0.5:12-120.

6. The preparation method according to claim 1, characterized in that: The stripping process takes 10-30 minutes.

7. A method for preparing a transparent conductive thin film, characterized in that, include: The graphene is prepared by exfoliating graphite using the method described in any one of claims 1-6 to obtain a mixed solution of graphene and electrolyte. Furthermore, the mixed solution is applied to the surface of the substrate by spin coating, followed by water washing and drying to obtain a transparent conductive film.

8. The preparation method according to claim 7, characterized in that: The spin coating is performed at a speed of 50-500 r / min; and / or the drying process is carried out at a temperature of 20-100℃.

9. The preparation method according to claim 7, characterized in that: The substrate material includes PET.

10. The transparent conductive film prepared by the method according to any one of claims 7-9, characterized in that: The transparent conductive film has a light transmittance of 75-90%; a sheet resistance of 1000-1200 Ω / sq; and a diameter of 2-5 cm.

11. Use of the transparent conductive film of claim 10 in the fabrication of electronic or optoelectronic devices.

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