A graphene oxide cake and a method for producing the same, a reduced graphene oxide film

Abstract

The application discloses a preparation method of graphene oxide material cake and belongs to the technical field of graphene material preparation. The method comprises the following steps: S1, mixing graphite and concentrated sulfuric acid under a temperature environment of-5 DEG C to 15 DEG C to obtain a precursor A; S2, adding a potassium permanganate aqueous solution to the precursor A to perform an oxidation reaction under the control of a temperature of 30 DEG C to 50 DEG C, and after the reaction is completed, performing pressure filtration to obtain a precursor B, wherein the mass ratio of the precursor A to the potassium permanganate aqueous solution is 4 to 6:1; S3, dispersing the precursor B into a sulfuric acid solution and performing pressure filtration one or more times until the filtrate is colorless to obtain a precursor C; and S4, dispersing the precursor C into an aqueous solution and performing pressure filtration one or more times to obtain a target graphene oxide material cake. The method provided by the application avoids a traditional high-temperature hydrolysis step, avoids carbon skeleton damage and introduction of a large number of structural defects caused by hydrolysis under high temperature, and provides a high-quality graphene oxide material cake.

Description

Technical Field

[0001] This invention belongs to the field of graphene material preparation technology, specifically relating to a graphene oxide cake and its preparation method, and a reduced graphene oxide film. Background Technology

[0002] Currently, the main industrial production methods for graphene oxide are the Hummers process and its modifications. The functional groups of the resulting graphene oxide are typically dominated by hydroxyl, epoxy, carboxyl, and carbonyl groups. These oxygen-containing functional groups ensure good dispersibility of graphene oxide in aqueous solutions and provide active sites for grafting and further functionalization modification. However, different types of functional groups have different effects on the film-forming properties of graphene oxide. Hydroxyl and epoxy groups, as the main functional groups on the basal surface of the sheets, can promote tight bonding and orderly stacking between adjacent sheets through hydrogen bonding, which is beneficial for forming dense, uniform films with few defects. On the other hand, carbonyl and carboxyl groups are mainly distributed at the edge of the sheets, which are prone to structural defects during their formation and carbon etching during reduction, thus adversely affecting the thermal conductivity of the reduced graphene oxide film. Therefore, controlling the relative ratio of hydroxyl and epoxy groups in graphene oxide to maximize basal surface hydrogen bonding and minimize structural interference from edge carboxyl / carbonyl groups while maintaining appropriate hydrophilicity and reactivity is crucial for obtaining reduced graphene oxide products with excellent thermal conductivity.

[0003] The typical steps of the industrial-grade improved Hummers method for preparing graphene oxide are as follows: graphite is mixed with concentrated sulfuric acid, potassium permanganate is added for oxidation, and after the oxidation reaction is completed, deionized water is added under stirring to hydrolyze and exfoliate the graphite. Finally, hydrogen peroxide is added to reduce the remaining potassium permanganate and manganese dioxide to terminate the reaction. After washing and filtration, the target graphene oxide cake is obtained. However, the high temperature of hydrolysis and the use of hydrogen peroxide will inevitably lead to the formation of carboxyl and carbonyl functional groups in the graphene oxide. Summary of the Invention

[0004] Based on one or more of the above technical problems, in a first aspect, this application provides a method for preparing graphene oxide cakes, specifically as follows: S1. Premix graphite and concentrated sulfuric acid at a temperature of -5℃ to 15℃ to obtain precursor A; S2. Control the temperature at 30~50℃, add potassium permanganate aqueous solution to precursor A to carry out oxidation reaction. After the reaction is completed, filter by pressure to obtain precursor B. The mass ratio of precursor A to potassium permanganate aqueous solution is 4~6:1. S3. Disperse precursor B in sulfuric acid solution and filter it by pressure once or multiple times until the filtrate is colorless to obtain precursor C. S4. Disperse the precursor C in an aqueous solution and filter it once or multiple times to obtain the target graphene oxide cake.

[0005] In some embodiments, in step S3, the concentration of the sulfuric acid solution used is the same as or higher than the concentration of sulfuric acid in the system after the oxidation reaction in step S2.

[0006] In some embodiments, the selected raw material graphite has a mesh size of 2000-5000 mesh, and the mesh size of the graphite is controlled by sieving.

[0007] In some embodiments, the step of ultrasonically peeling the precursor C is further included.

[0008] In some embodiments, in step S1: The concentration of concentrated sulfuric acid is 95%~99%. And / or, the mass ratio of graphite to concentrated sulfuric acid is 1:40~60. And / or, premixing is carried out under stirring conditions for 30-90 minutes.

[0009] In some embodiments, in step S2: The concentration of potassium permanganate aqueous solution is 30%~80%. And / or, the oxidation reaction takes 0.5 to 3 hours.

[0010] In some embodiments, in step S1, the premixing temperature is 0°C to 10°C, and the premixing temperature is controlled by an ice-water bath.

[0011] In some embodiments, in step S2, the oxidation reaction temperature is controlled at 35°C to 45°C, and the oxidation reaction temperature is controlled by a water bath or an oil bath.

[0012] The second aspect of this application provides a graphene oxide cake, which is prepared according to the preparation method provided in the first aspect of this application, wherein the prepared graphene oxide cake has an oxygen content of ≥35% and a CO content of ≥50%.

[0013] The third aspect of this application provides a reduced graphene oxide film, which is prepared by using graphene oxide cake prepared by the preparation method provided in the first aspect of this application or by using graphene oxide cake provided in the second aspect of this application as raw material. The graphene oxide cake is mixed with deionized water and ammonia water to form a graphene oxide slurry, which is then coated into a graphene oxide film and then thermally reduced to obtain a reduced graphene oxide film.

[0014] In some embodiments, the graphene oxide film is further subjected to a chemical reduction treatment before thermal reduction to prepare a cavity structure in the film material, and then thermally reduced to obtain a reduced graphene oxide film with a porous structure.

[0015] The beneficial effects of this application are as follows: 1. The method provided in this application avoids the traditional high-temperature hydrolysis step, avoids the destruction of the carbon skeleton and the introduction of a large number of structural defects caused by hydrolysis at high temperature, and provides a high-quality graphene oxide cake. 2. The method for preparing graphene oxide cake provided in this application removes potassium permanganate from the system in a timely manner after oxidation reaction at 30~50℃, thereby avoiding the excessive oxidation of potassium permanganate and preventing the carbon-carbon conjugated structure from transforming into carboxyl and carbonyl groups. 3. The preparation method provided in this application does not require the addition of additional modifiers, does not introduce new impurities, reduces production costs, and is simple to operate, with controllable process, making it suitable for industrial production. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the embodiments or existing methods will be described below. The accompanying drawings used in the technical description are briefly introduced. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 C1s diagram of the graphene oxide cake provided in Example 1 of this application. Figure 2 SEM image of the graphene oxide cake provided in Example 1 of this application. Figure 3 C1s diagram of the graphene oxide cake provided in Example 2 of this application. Figure 4 SEM image of the graphene oxide cake provided in Example 2 of this application. Figure 5 C1s diagram of the graphene oxide cake provided in Example 3 of this application. Figure 6 SEM image of the graphene oxide cake provided in Example 3 of this application. Figure 7 C1s plot of the graphene oxide cake provided in Comparative Example 1 of this application. Figure 8 SEM image of the graphene oxide cake provided in Comparative Example 1 of this application. Figure 9The carbon and oxygen content of the graphene oxide cakes provided in Examples 1-3 and Comparative Example 1 of this application, as well as the thermal diffusivity of the film after film formation, are considered. Detailed Implementation

[0018] The following detailed description of exemplary embodiments of this application refers to the accompanying drawings, which form part of the description, illustrating exemplary embodiments in which this application may be implemented. The more detailed description of embodiments of this application below is not intended to limit the scope of the claimed application, but is merely illustrative and does not limit the description of the features and characteristics of this application, in order to suggest the best mode for carrying out this application and sufficient to enable those skilled in the art to implement it. However, it should be understood that various modifications and variations can be made without departing from the scope of this application as defined by the appended claims. The detailed description and drawings should be considered illustrative only and not restrictive, and any such modifications and variations shall fall within the scope of this application described herein. Furthermore, the background art is intended to illustrate the current state of research and development and significance of the technology, and is not intended to limit this application or its application areas.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0021] To make the technical problems, technical solutions and advantages of this application clearer, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments.

[0022] The typical steps of the current industrial-grade modified Hummers process for preparing graphene oxide are as follows: ① Intercalation of graphite with concentrated sulfuric acid, during which a very small amount of hydroxyl groups are generated; ② Oxidation is then carried out by adding potassium permanganate, during which a large number of hydroxyl and epoxy groups are mainly generated on the basal surface, and a small amount of carboxyl and carbonyl groups are generated; ③ After the oxidation reaction is completed, deionized water is added under stirring conditions or the oxidized mixed solution is added to deionized water for high-temperature hydrolysis to exfoliate the graphite. The graphite sheets are exfoliated and oxidized more fully, and carboxyl and carbonyl groups will be generated at the edges and defects of the sheets; ④ Finally, hydrogen peroxide is added to reduce the remaining potassium permanganate and manganese dioxide to terminate the reaction, and the target graphene oxide cake is obtained by washing and filtration.

[0023] The formation of functional groups carboxyl and carbonyl groups is influenced by the following factors: ① In an acidic aqueous solution environment, permanganate, as a strong oxidizing agent, will attack the sp groups originally composed of carbon-carbon double bonds on graphene sheets. 2 In the conjugated region, the broken carbon atoms combine with oxygen, generating carboxyl and carbonyl groups at the edges of the sheets. Simultaneously, the "cutting off" of carbon atoms on the sheets also creates nano- to micron-scale voids within the graphene oxide sheets; ② The oxidizing power of permanganate in acidic aqueous solutions largely depends on the intermediate substances it is reduced to (such as Mn₂O₇, Mn...). 3+ Under high-temperature hydrolysis conditions (typically reaching 90~100℃), hydrogen peroxide can significantly accelerate the generation and diffusion rates of intermediate substances in permanganate, thereby allowing them to attack the carbon-carbon double bonds on the graphite framework more frequently, thus generating more carboxyl and carbonyl groups; ③ Although hydrogen peroxide is used as a "reducing agent" in terminating the reaction, it also has weak oxidizing properties. Some literature points out that even under relatively mild conditions, hydrogen peroxide can utilize the structural defects in graphene oxide to introduce carboxyl groups through a mild oxidation process.

[0024] The presence of irreparable lamellar voids and the abundance of carboxyl and carbonyl groups within graphene oxide can negatively impact the film-forming properties of subsequent graphene oxide films. Specifically, irreparable lamellar voids disrupt phonon propagation paths, leading to a decrease in the thermal diffusivity of the subsequently reduced graphene oxide film. Furthermore, carboxyl and carbonyl groups are removed as CO2 during subsequent thermal reduction, forming carbon etching, which can also easily generate irreparable defects, affecting the thermal conductivity of the subsequent reduced graphene oxide film.

[0025] For the above reasons, this application provides a method for preparing graphene oxide cakes, wherein the cakes prepared by this method have a high hydroxyl content, specifically including the following steps: S1. Premix graphite and concentrated sulfuric acid at a temperature of -5℃ to 15℃ to obtain precursor A. In this step, low temperature control is required to prevent thermal runaway caused by violent exothermic reaction and rapid temperature rise. The low temperature also reduces the reaction rate, giving sulfuric acid molecules enough time to slowly and orderly enter the graphite interlayer to form a stable sulfuric acid-graphite intercalation structure.

[0026] S2. At a controlled temperature of 30-50℃, potassium permanganate aqueous solution is added to precursor A for oxidation. After the reaction, the mixture is filtered to obtain precursor B. The mass ratio of precursor A to potassium permanganate aqueous solution is 4-6:1. The oxidation reaction temperature is controlled at 30-50℃ because, in the initial stage of contact between potassium permanganate and precursor A, under reaction conditions of 30-50℃, the functional groups generated on the graphene oxide sheets are mainly hydroxyl and epoxy groups. This temperature range also provides suitable reaction conditions for the strong oxidant generated by the reaction of potassium permanganate and concentrated sulfuric acid. If the temperature is below 30℃, the reactant's reactivity is insufficient, oxidation is incomplete, and the oxidation degree of the product cannot meet the requirements. If the temperature is ≥50℃, the oxidant potassium permanganate violently attacks the edges of the graphite layers, leading to excessive oxidation of carbon atoms and causing sheet defects.

[0027] S3. Disperse precursor B in sulfuric acid solution and filter it once or multiple times until the filtrate is colorless to obtain precursor C. This step involves repeatedly rinsing and filtration with sulfuric acid solution to remove residual potassium permanganate solution from precursor B.

[0028] S4. Disperse precursor C in an aqueous solution and filter it one or more times to obtain the target graphene oxide cake. This step removes excess sulfuric acid and a small amount of potassium permanganate from the precursor C through repeated rinsing with the aqueous solution.

[0029] Compared with traditional industrial-grade methods for preparing graphene oxide cakes, the method provided in this application avoids the high-temperature hydrolysis step and the introduction of hydrogen peroxide. Excess potassium permanganate is directly removed by repeated pressure filtration and washing with sulfuric acid solution.

[0030] In some embodiments, in step S3, the concentration of the sulfuric acid solution used is the same as or higher than the concentration of sulfuric acid in the system after the oxidation reaction in step S2. The purpose is to maintain the same acidic chemical environment and prevent the sulfuric acid in the system from directly contacting water or dilute sulfuric acid at high temperatures, which would cause hydrolysis and generate carboxyl and carbonyl groups.

[0031] In some embodiments, the selected raw material graphite has a mesh size of 2000-5000 mesh, which is controlled by sieving. Those skilled in the art generally believe that sufficient exfoliation to obtain thinner, more monolayer graphene oxide is a prerequisite for constructing a highly efficient thermally conductive network. In traditional methods, graphene oxide sheets are further exfoliated through high-temperature hydrolysis and then further oxidized into graphene oxide in a high-temperature environment. In this application, the oxidation efficiency of graphene oxide is controlled by controlling the size of the raw material flakes. A 2000-5000 mesh graphite raw material is selected to ensure sufficient intercalation with sulfuric acid and complete oxidation during the oxidation reaction, thereby avoiding the formation of carboxyl and carbonyl groups caused by high-temperature hydrolysis.

[0032] In some embodiments, the method further includes an ultrasonic stripping step of the precursor C. Furthermore, ultrasonic stripping is used to assist in the stripping process, thereby avoiding the formation of carboxyl and carbonyl groups caused by high-temperature hydrolysis.

[0033] In some embodiments, in step S1: The concentration of concentrated sulfuric acid is 95% to 99%, typically but not limitingly, 95%, 96%, 97%, 98%, and 99%. And / or, the mass ratio of graphite to concentrated sulfuric acid is 1:40 to 60, typically but not limitingly, the mass ratio of graphite to concentrated sulfuric acid is 1:40, 1:42, 1:44, 1:46, 1:48, 1:50, 1:52, 1:54, 1:56, 1:58, 1:60; And / or, premixing is carried out under stirring conditions for 30-90 min. Premixing under stirring conditions promotes a more complete intercalation reaction of concentrated sulfuric acid on graphite. Typical but not limiting stirring times are 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, 65 min, 70 min, 75 min, 80 min, 85 min, and 90 min.

[0034] In some embodiments, in step S2: The concentration of potassium permanganate aqueous solution is 30% to 80%, typically but not limitingly, 30%, 40%, 50%, 60%, 70%, and 80%.

[0035] And / or, the oxidation reaction time is 0.5 to 3 hours. If the oxidation time is too short, the graphite sheets will not be oxidized sufficiently. If the oxidation time is too long, the excessive action of potassium permanganate may introduce too many carboxyl groups. Typical but not limiting oxidation reaction times are 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, and 3 hours.

[0036] In some embodiments, in step S1, the premixing temperature is 0°C to 10°C, and the premixing temperature is controlled by an ice-water bath.

[0037] In some embodiments, in step S2, the oxidation reaction temperature is controlled at 35°C to 45°C, and the oxidation reaction temperature is controlled by a water bath or an oil bath.

[0038] The second aspect of this application provides a graphene oxide cake, which is prepared according to the preparation method provided in the first aspect of this application. The prepared graphene oxide cake has an oxygen content of ≥35% and a CO content of ≥50%. This graphene oxide cake achieves full oxidation and has a high hydroxyl content.

[0039] A third aspect of this application provides a reduced graphene oxide film, which is prepared using a graphene oxide cake obtained by the preparation method provided in the first aspect of this application, or using a graphene oxide cake provided in the second aspect of this application as raw material. The graphene oxide cake is mixed with deionized water and ammonia to form a graphene oxide slurry, which is then coated to form a graphene oxide film and subsequently thermally reduced to obtain a reduced graphene oxide film. The reduced graphene oxide film has excellent thermal conductivity and can be widely used in smartphones, computers, batteries, drones, high-power electronic devices, radio frequency / microwave systems, flexible electronic devices, and automotive electronics to achieve efficient heat dissipation.

[0040] In some embodiments, the graphene oxide film further includes a chemical reduction treatment before thermal reduction to prepare a porous structure within the film material, followed by thermal reduction to obtain a reduced graphene oxide film with a porous structure. The reduced graphene oxide film with a porous structure combines high thermal conductivity with flexibility. Besides its applications in the aforementioned thermal management areas, it can also be used directly as a thermal interface material or combined with silicone as a thermal interface material for chip heat dissipation.

[0041] The following are some specific examples.

[0042] The detection methods involved in the embodiments and comparative examples of this application are as follows: SEM: The method described in standard GB / Z 124.1-2025 "Nanotechnology Graphene Structure Characterization Part 1: Graphene Powder and Dispersion System" is used to visually observe the wrinkling, curling, stacking and agglomeration of GO sheets; the wrinkling feature is the typical morphology after GO oxidation and exfoliation, which can indirectly reflect the degree of exfoliation and sheet integrity.

[0043] XPS: The method described in standard GB / T 43598-2023 "Determination of Oxygen Content and Carbon-Oxygen Ratio of Nanotechnology Graphene Powder by X-ray Photoelectron Spectroscopy" reflects the surface elemental composition and the chemical bonding state of carbon: it measures the content of C and O atoms to determine the degree of GO oxidation; it separates the C1s peak to distinguish the relative content of oxygen-containing functional groups such as sp² C=C, CO, and C=O.

[0044] Thermal diffusivity: The test method described in the standard "Q / GDMR 04-2023 Thermal conductivity test by laser flash method" uses a support determined based on the thickness of the reduced graphene oxide film. Example 1

[0045] This embodiment provides a method for preparing graphene oxide cakes, including the following steps: S1. Under stirring conditions, 2500-mesh graphite powder was added to 98% concentrated sulfuric acid with a mass ratio of graphite to sulfuric acid of 1:50. The system temperature was controlled at 5±3℃ by an ice-water bath and stirred for 60 min to obtain precursor A. S2. Under stirring conditions, potassium permanganate was dissolved in water at a mass ratio of 1:1 to obtain an aqueous solution of potassium permanganate. This aqueous solution was then slowly added to precursor A at a mass ratio of 5:1. After the potassium permanganate solution was completely added, the system temperature was maintained at 40℃±3℃ using an oil bath for 2 hours. After the reaction was complete, the system was cooled to room temperature, and a sample of the resulting solution was subjected to acid-base titration to determine the acid concentration. The solution was then filtered to obtain precursor B. S3. Disperse precursor B in 83% sulfuric acid, filter under pressure, and repeat the above steps until the filtrate is colorless to obtain precursor C. S4. Disperse the precursor C in water, wash and filter three times to obtain the target graphene oxide cake.

[0046] XPS analysis was performed on the graphene oxide cake, and the results are as follows: Figure 9 As shown, its oxygen content is 35.48%, and the C1s peak is as follows. Figure 1 As shown, CO accounted for 51.09%. SME testing was conducted, and the results are as follows... Figure 2 As shown, GO exhibits a two-dimensional sheet-like structure with clear sheet outlines, a smooth surface, and few wrinkles, which is a typical exfoliated morphology of graphene oxide.

[0047] This embodiment also provides a method for preparing a reduced graphene oxide film and a reduced graphene oxide film.

[0048] The obtained graphene oxide cake was dispersed in a deionized water solution, and ammonia was added to adjust the pH to 6.2 to prepare a graphene oxide slurry with a solid content of 5%. This slurry was then coated onto a graphene oxide film using a doctor blade and dried. The graphene oxide film was then subjected to high-temperature thermal reduction to obtain a reduced graphene oxide film, whose thermal diffusivity was measured to be 914.369 mm. 2 / s .

[0049] The graphene oxide cake obtained above was dispersed in a deionized water solution, and ammonia was added to adjust the pH value to 6.2 to prepare a graphene oxide slurry with a solid content of 5%. After being coated with a doctor blade to form a film and dried to form a graphene oxide film, the graphene oxide film was immersed in a 20% hydrazine hydrate solution for chemical reduction and foaming, and then subjected to high-temperature thermal reduction to obtain a reduced graphene oxide film with a porous internal structure. Example 2

[0050] This embodiment provides a method for preparing graphene oxide cakes, including the following steps: S1. Under stirring conditions, 5000 mesh graphite powder was added to 95% concentrated sulfuric acid. The mass ratio of graphite to sulfuric acid was 1:60. The system temperature was controlled at 0±3℃ by an ice-water bath. After stirring for 60 min, precursor A was obtained. S2. Under stirring conditions, potassium permanganate was dissolved in water at a mass ratio of 2:1 to obtain an aqueous solution of potassium permanganate. This aqueous solution was then slowly added to precursor A at a mass ratio of 6:1. After the potassium permanganate solution was completely added, the system temperature was maintained at 45℃±3℃ using an oil bath for 2 hours. After the reaction was complete, the system was cooled to room temperature, and a sample of the resulting solution was subjected to acid-base titration to determine the acid concentration. The solution was then filtered to obtain precursor B. S3. Disperse precursor B in 86% sulfuric acid, filter under pressure, and repeat the above steps until the filtrate is colorless to obtain precursor C. S4. The precursor C is dispersed in water and subjected to ultrasonic exfoliation and pressure filtration, then dispersed in water again, washed and pressure filtered 3 times to obtain the target graphene oxide cake.

[0051] XPS analysis was performed on the graphene oxide cake, and the results are as follows: Figure 9 As shown, its oxygen content is 35.89%, and the C1s peak is as follows. Figure 3 As shown, CO accounted for 54.95%. SME testing was conducted, and the results are as follows... Figure 4 As shown, GO exhibits a two-dimensional sheet-like structure with clear sheet outlines, a smooth surface, and few wrinkles, which is a typical exfoliated morphology of graphene oxide.

[0052] This embodiment also provides a method for preparing a reduced graphene oxide film and a reduced graphene oxide film.

[0053] The obtained graphene oxide cake was dispersed in a deionized water solution, and ammonia was added to adjust the pH to 6.2 to prepare a graphene oxide slurry with a solid content of 5%. This slurry was then coated with a doctor blade, dried, and finally subjected to high-temperature thermal reduction to obtain a reduced graphene oxide film. The thermal diffusivity of the reduced graphene oxide film was measured to be 930.408 mm. 2 / s .

[0054] The graphene oxide cake obtained above was dispersed in a deionized water solution, and ammonia was added to adjust the pH value to 6.2 to prepare a graphene oxide slurry with a solid content of 5%. The slurry was coated with a doctor blade to form a film and dried to form a graphene oxide film. The graphene oxide film was then immersed in a 30% hydrazine hydrate solution for chemical reduction and foaming, followed by high-temperature thermal reduction to obtain a reduced graphene oxide film with a porous internal structure. Example 3

[0055] This embodiment provides a method for preparing graphene oxide cakes, including the following steps: S1. Under stirring conditions, 5000 mesh graphite powder was added to 95% concentrated sulfuric acid. The mass ratio of graphite to sulfuric acid was 1:40. The system temperature was controlled at 8±3℃ by an ice-water bath. After stirring for 90 min, precursor A was obtained. S2. Under stirring conditions, potassium permanganate was dissolved in water at a mass ratio of 1:2 to obtain an aqueous solution of potassium permanganate. This aqueous solution was then slowly added to precursor A at a mass ratio of 4:1. After the potassium permanganate solution was completely added, the system temperature was maintained at 35℃±3℃ using a water bath for 1.5 hours. After the reaction was complete, the solution was cooled to room temperature. A sample of the reaction solution was then subjected to acid-base titration to determine the acid concentration. Precursor B was obtained by pressure filtration. S3. Disperse precursor B in 80% sulfuric acid, filter under pressure, and repeat the above steps until the filtrate is colorless to obtain precursor C. S4. Disperse the precursor C in water, wash and filter five times to obtain the target graphene oxide cake.

[0056] XPS analysis was performed on the graphene oxide cake, and the results are as follows: Figure 9 As shown, its oxygen content is 35.41%, and the C1s peak is as follows. Figure 5 As shown, CO accounts for 51.59%. SME testing was performed, and the results are as follows. Figure 6 As shown, GO exhibits a two-dimensional sheet-like structure with clear sheet outlines, a smooth surface, and few wrinkles, which is a typical exfoliated morphology of graphene oxide.

[0057] This embodiment also provides a method for preparing a reduced graphene oxide film and a reduced graphene oxide film.

[0058] The obtained graphene oxide cake was dispersed in a deionized water solution, and ammonia was added to adjust the pH to 6.2 to prepare a graphene oxide slurry with a solid content of 5%. This slurry was then coated with a doctor blade to form a graphene oxide film, which was subsequently dried. The graphene oxide film was then subjected to high-temperature thermal reduction to obtain a reduced graphene oxide film. The thermal diffusivity of the obtained reduced graphene oxide film was measured to be 810.168 mm.2 / s.

[0059] The graphene oxide cake obtained above was dispersed in a deionized water solution, and ammonia was added to adjust the pH value to 6.2 to prepare a graphene oxide slurry with a solid content of 5%. After being coated with a doctor blade to form a film and dried to form a graphene oxide film, the graphene oxide film was immersed in a 25% hydrazine hydrate solution for chemical reduction and foaming, and then subjected to high-temperature thermal reduction to obtain a reduced graphene oxide film with a porous internal structure. Comparative Example 1

[0060] This embodiment provides a method for preparing graphene oxide cakes, including the following steps: S1. Under stirring conditions, 5000-mesh graphite powder was added to 95% concentrated sulfuric acid, with a mass ratio of graphite to sulfuric acid of 1:60. The system temperature was controlled at 0±3℃ by an ice-water bath, and the mixture was stirred for 60 minutes to obtain precursor A. S2. Under stirring conditions, potassium permanganate was dissolved in water at a mass ratio of 2:1 to obtain an aqueous solution of potassium permanganate. This aqueous solution was then slowly added to precursor A at a mass ratio of 6:1. After the potassium permanganate solution was completely added, the system temperature was maintained at 45℃±3℃ using an oil bath, and the reaction was allowed to proceed for 2 hours. After the reaction was complete, the mixture was cooled to room temperature to obtain precursor B'. S3. Slowly add precursor B' to deionized water at a mass ratio of 1.5:1. Perform high-temperature hydrolysis for 3 hours, then add H2O2 to terminate the reaction at a mass ratio of 12:1. Filter by pressure to obtain precursor D.

[0061] S4. The precursor D is dispersed sequentially into 3% dilute sulfuric acid and water, and washed and filtered three times to obtain the target graphene oxide cake.

[0062] XPS analysis was performed on the graphene oxide cake, and the results are as follows: Figure 9 As shown, its oxygen content is 34.65%, and the C1s peak is as follows. Figure 7 As shown, CO accounted for 44.30%. SME testing was conducted, and the results are as follows... Figure 8 As shown, GO exhibits a two-dimensional sheet-like structure with clear sheet outlines, a smooth surface, and few wrinkles, which is a typical exfoliated morphology of graphene oxide.

[0063] This embodiment also provides a method for preparing a reduced graphene oxide film and a reduced graphene oxide film.

[0064] The obtained graphene oxide cake was dispersed in a deionized water solution, and ammonia was added to adjust the pH to 6.2 to prepare a graphene oxide slurry with a solid content of 5%. This slurry was then coated with a doctor blade to form a graphene oxide film, which was subsequently dried. The graphene oxide film was then subjected to high-temperature thermal reduction to obtain a reduced graphene oxide film. The thermal diffusivity of the obtained reduced graphene oxide film was measured to be 683.88 mm. 2 / s .

[0065] It should be noted that the proportions of raw materials and the preparation process not mentioned above can be referred to existing technologies, and will not be elaborated here.

[0066] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0067] Although this application has been illustrated and described with reference to certain preferred embodiments thereof, those skilled in the art should understand that various changes in form and detail may be made thereto without departing from the spirit and scope of this application.

Claims

1. A method for preparing graphene oxide cake, characterized in that, Includes the following steps: S1. Premix graphite and concentrated sulfuric acid at a temperature of -5℃ to 15℃ to obtain precursor A; S2. Control the temperature at 30~50℃, add potassium permanganate aqueous solution to precursor A to carry out oxidation reaction. After the reaction is completed, filter by pressure to obtain precursor B. The mass ratio of precursor A to potassium permanganate aqueous solution is 4~6:

1. S3. Disperse precursor B in sulfuric acid solution and filter it by pressure once or multiple times until the filtrate is colorless to obtain precursor C. S4. Disperse the precursor C in an aqueous solution and filter it once or multiple times to obtain the target graphene oxide cake.

2. A method for preparing graphene oxide cake according to claim 1, characterized in that, In step S3, the concentration of the sulfuric acid solution is the same as or higher than the concentration of sulfuric acid in the system after the oxidation reaction in step S2.

3. A method for preparing graphene oxide cake according to claim 1, characterized in that, The graphite has a mesh size of 2000-5000 mesh, which is controlled by sieving.

4. A method for preparing graphene oxide cake according to claim 1, characterized in that, It also includes the step of ultrasonically peeling off the precursor C.

5. A method for preparing graphene oxide cake according to claim 1, characterized in that, In step S1: The concentration of concentrated sulfuric acid is 95%~99%. And / or, the mass ratio of graphite to concentrated sulfuric acid is 1:40~60. And / or, premixing is carried out under stirring conditions for 30-90 minutes.

6. A method for preparing graphene oxide cake according to claim 1, characterized in that, In step S2: The concentration of potassium permanganate aqueous solution is 30%~80%. And / or, the oxidation reaction takes 0.5 to 3 hours.

7. A method for preparing graphene oxide cake according to claim 1, characterized in that, In step S1, the premixing temperature is 0℃~10℃, and the premixing temperature is controlled by an ice-water bath. In step S2, the oxidation reaction temperature is controlled at 35℃~45℃, and the oxidation reaction temperature is controlled by a water bath or an oil bath.

8. A graphene oxide cake, characterized in that, The graphene oxide cake is prepared by any of the preparation methods described in claims 1 to 7, wherein the oxygen content of the graphene oxide cake is higher than 35% and the CO content is greater than 50%.

9. A reduced graphene oxide film, characterized in that, The graphene oxide cake prepared by the method described in claims 1 to 7 or the graphene oxide cake provided in claim 8 is used as raw material. The graphene oxide cake is mixed with deionized water and ammonia water to prepare a graphene oxide slurry, which is then coated into a graphene oxide film and then thermally reduced to obtain a reduced graphene oxide film.

10. A reduced graphene oxide film according to claim 9, characterized in that, Before thermal reduction, the graphene oxide film also includes a chemical reduction treatment to prepare a cavity structure in the film material, and then undergoes thermal reduction to obtain a reduced graphene oxide film with a porous structure.

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