Preparation method of graphene aerogel

Abstract

The invention discloses a preparation method of graphene aerogel, which comprises the following steps: preparing a graphene oxide solution with the solid content of 0.5-1%, mixing a reducing agent with the graphene oxide solution, mixing the graphene oxide solution accounting for 99.5-99.9% of the mass of the total system, mixing the reducing agent accounting for 0.1-0.5% of the mass of the total system, and uniformly stirring to obtain the graphene aerogel. Uniformly stirring and dispersing to obtain a graphene hydrogel precursor; putting a plurality of cotton ropes into the graphene hydrogel precursor, performing heating treatment in a high-pressure state, keeping the cotton ropes in a vertical state in the high-pressure heating treatment process, and naturally cooling to normal temperature after the treatment is finished, so as to obtain graphene hydrogel; soaking the graphene hydrogel in a 10%-100% ethanol water solution to remove impurities; and carrying out freeze drying treatment on the graphene hydrogel from which the impurities are removed, so as to obtain the graphene aerogel. According to the scheme, when the graphene aerogel is prepared, fine cotton ropes are added, so that the graphene aerogel has certain supporting force in the preparation process, and the problems of drying cracking, shrinkage and collapse are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of new graphene materials, and in particular relates to a method for preparing graphene aerogel. Background Art

[0002] Graphene aerogel is a new type of nanomaterial with high specific surface area, excellent conductivity and mechanical properties. Its special feature is that it combines the excellent properties of graphene with the lightweight porous structure of aerogel, making it a hot spot for research and application in many fields. The characteristics of graphene aerogel mainly include: 1. Ultra-lightweight and high porosity: Graphene aerogel has extremely low density while maintaining a high degree of pore structure, which makes them unique in energy absorption and catalyst carriers. 2. High conductivity: Thanks to the intrinsic properties of graphene, graphene aerogel exhibits good conductivity and is suitable for electronic devices, sensors and energy storage. 3. Excellent mechanical properties: Despite its light weight, graphene aerogel exhibits good mechanical strength and toughness, and can withstand large deformation without being easily damaged. 4. High specific surface area: A large number of open pores and a huge specific surface area are conducive to adsorption, catalytic reactions and sensing applications.

[0003] Graphene aerogel has a wide range of applications, mainly concentrated in the following areas: 1. Energy storage and conversion: As an electrode material for supercapacitors and lithium-ion batteries, its high conductivity and large specific surface area are used to improve energy storage efficiency. 2. Environmental protection: Due to its strong adsorption capacity, it can be used for water purification to remove heavy metal ions, organic pollutants, etc., and can also be used as a gas adsorption material. 3. Sensors and electronic devices: High sensitivity and fast response make graphene aerogel suitable as a substrate for a variety of sensors such as pressure, humidity, and gas. 4. Biomedicine: Its porous structure and biocompatibility make it potentially applicable in drug delivery, tissue engineering, and biological detection. 5. Aerospace: Due to its light weight and high strength, graphene aerogel can be used as an ideal structural material or thermal management material in spacecraft.

[0004] However, in the preparation process of traditional aerogels, problems such as drying cracking, shrinkage and collapse often occur. This limits the application of graphene aerogels to a certain extent. Through experiments and research, it is found that the cracking phenomenon is generally caused by the following reasons: 1. Volume shrinkage caused by the loss of water inside the aerogel during the drying process; 2. The drying rates of various parts of the aerogel during the drying process are inconsistent; 3. The volatilization of the solvent leads to the concentration of the solute, resulting in cracking. The causes of collapse are generally: 1. Volume shrinkage caused by the loss of water during the drying process leads to collapse; 2. The arrangement density of the gel microstructure affects the degree of shrinkage. Based on the existing technology, how to improve the yield of large-scale preparation of graphene aerogels has become a technical problem that needs to be solved urgently by technicians in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method that can solve the problems of cracking and collapse of graphene aerogels during large-scale preparation. In this solution, fine cotton ropes are added during the preparation of graphene aerogels, so that the graphene aerogels have a certain supporting force during the preparation process, solving the problems of drying cracking, shrinkage and collapse. The specific technical solution is as follows: A method for preparing a graphene aerogel comprises the following steps: preparing a graphene oxide solution with a solid content of 0.5%-1%, mixing a reducing agent with the graphene oxide solution, wherein the mass percentage of the graphene oxide solution in the total system is 99.5%-99.9%, and the mass percentage of the reducing agent in the total system is 0.1%-0.5%, and stirring and dispersing the mixture uniformly to obtain a graphene hydrogel precursor; placing a plurality of cotton ropes in the graphene hydrogel precursor, and performing a heating treatment under a high pressure state, wherein the cotton ropes are kept in a vertical state during the high pressure heating treatment, and naturally cooling the mixture to room temperature after the treatment is completed to obtain a graphene hydrogel; soaking the graphene hydrogel in a 10%-80% ethanol aqueous solution to remove impurities; and freeze-drying the graphene hydrogel after the impurities are removed to obtain a graphene aerogel.

[0006] In a further technical solution, the graphene oxide solution is prepared by mixing graphene oxide cake and deionized water in a mass ratio of 1:10.

[0007] In a further technical solution, the reducing agent is selected from one of sodium hydroxide, glucose and polyethylene glycol.

[0008] In a further technical solution, the reducing agent is ethylene glycol, and the mass percentage of the reducing agent is 1%-10%.

[0009] In a further technical solution, in the stirring and dispersing step, the stirring rate is set at 300-400 r / min, and the stirring and dispersing time is 10-20 min.

[0010] In a further technical solution, a graphene hydrogel precursor is poured into a reactor, one end of a plurality of cotton ropes is fixed on the inner wall of a reactor cover, the reactor cover is closed, and the cotton ropes are placed in the graphene hydrogel precursor in a vertical state. The reactor cover and the reactor are locked and closed and then placed in an oven. The reaction temperature of the oven is adjusted to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, it is ensured that the water in the reactor does not boil during the reaction. After reacting for 10-60 minutes, the reactor is naturally cooled to room temperature to obtain a graphene hydrogel.

[0011] In a further technical solution, the graphene hydrogel is immersed in an ethanol aqueous solution with a mass percentage greater than 10% to remove impurities, and the immersion time is 12-24 hours.

[0012] In a further technical solution, the graphene hydrogel precursor needs to be filtered through a sieve before being subjected to high pressure heating treatment, and the mesh number of the sieve is 200-3000 meshes.

[0013] In a further technical solution, in the freeze-drying step, the graphene hydrogel that has been soaked in ethanol or ethanol aqueous solution is placed in a freeze drying box for freeze drying, and the freeze drying time is 48h-72h.

[0014] In a further technical solution, the temperature of the freeze-drying treatment is -18°C.

[0015] Compared with the prior art, the technical effects achieved by the present invention are as follows: The present invention provides a mass production method for preparing large-area graphene aerogels. While preparing aerogels using a method similar to a hydrothermal method, a thin cotton rope is vertically placed in a solution. During the reaction, the cotton rope provides support for graphene oxide. When graphene oxide forms a three-dimensional network structure, it can cling to the cotton rope, thereby enhancing the structural strength of the aerogel and avoiding the problems of collapse and cracking, thereby being able to prepare large-area aerogels. Compared with aerogels prepared in a traditional way, the finished aerogels obtained by the present invention can effectively solve the problems of cracking and collapse, so that large-area aerogels can be prepared on a large scale, and meet the applications in the fields of environmental remediation, sensing, heat insulation, sound insulation, wave absorption, aerospace, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is an appearance diagram of the graphene aerogel prepared in Example 1; Figure 2 This is an appearance picture of the graphene aerogel prepared in Comparative Example 1; Figure 3 This is the appearance picture of the graphene aerogel prepared in Comparative Example 2. DETAILED DESCRIPTION

[0017] The content of the present invention is further described below in conjunction with specific examples, but it should not be construed as limiting the present invention. If not specifically indicated, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art, and there is no specific restriction on their sources, and they can be purchased in the market or prepared according to conventional methods well known to those skilled in the art.

[0018] Unless explicitly stated otherwise, throughout the specification and claims, the term “comprise” or variations such as “include” or “comprising”, etc., will be understood to include the stated elements or components but not to exclude other elements or components.

[0019] The technical solution of the present invention is described below by specific embodiments. It should be understood that one or more steps mentioned in the present invention do not exclude the existence of other methods and steps before and after the combination step, or other methods and steps can be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and does not limit the order of arrangement of each method or limit the scope of implementation of the present invention. The change or adjustment of the relative relationship thereof can also be regarded as the scope of implementation of the present invention without substantial changes in the technical content.

[0020] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents. Example 1

[0021] A method for preparing graphene aerogel comprises the following steps: 1. Weigh 30.67g of graphene oxide cake (solid content of 50%±3%), use deionized water as solvent, mix 2900g of deionized water and graphene oxide cake, prepare a graphene oxide solution with a solid content of 0.5%, and add polyethylene glycol (reducing agent) to the prepared graphene oxide solution. The amount of reducing agent added accounts for 0.1% by mass of the total system.

[0022] 2. The mixed solution prepared in step 1 is dispersed by a stirring device, the stirring rate is set at 400 r / min, and the stirring and dispersing time is 20 min, until the graphene oxide cake is completely dissolved to obtain a graphene hydrogel precursor.

[0023] 3. Filter the graphene oxide and polyethylene glycol solution that have been fully stirred in step 2 with a 200-mesh sieve, then pour the filtered solution into a reactor, and fix several cotton threads on the reactor cover with rivets, cover the reactor cover, and place the cotton rope in the graphene hydrogel precursor in a vertical state. After the reactor cover and the reactor are locked tightly, place them in an oven, turn on the oven for heating treatment, adjust the reaction temperature of the oven to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, ensure that the water in the reactor does not boil during the reaction. After reacting for 60 minutes, naturally cool to room temperature to obtain a graphene hydrogel.

[0024] 4. Soak the graphene hydrogel obtained in step 3 in a 10% by mass ethanol aqueous solution to remove impurities for 16 hours; freeze-dry the graphene hydrogel after impurities are removed at a temperature of -18°C for 48 hours to obtain a graphene aerogel. Figure 1 shown. Example 2

[0025] A method for preparing graphene aerogel comprises the following steps: 1. Weigh 60g of graphene oxide cake (solid content of 50%±3%), use deionized water as solvent, mix 2900g of deionized water and graphene oxide cake, prepare a graphene oxide solution with a solid content of 1%, and add polyethylene glycol (reducing agent) to the prepared graphene oxide solution. The amount of reducing agent added accounts for 0.5% by mass of the total system.

[0026] 2. The mixed solution prepared in step 1 is dispersed by a stirring device, the stirring rate is set at 400 r / min, and the stirring and dispersing time is 20 min, until the graphene oxide cake is completely dissolved to obtain a graphene hydrogel precursor.

[0027] 3. Filter the graphene oxide and polyethylene glycol solution that have been fully stirred in step 2 with a 500-mesh sieve, then pour the filtered solution into a reactor, and fix several cotton threads on the reactor cover with rivets, cover the reactor cover, and place the cotton rope in the graphene hydrogel precursor in a vertical state. After the reactor cover and the reactor are locked tightly, place them in an oven, turn on the oven for heating treatment, adjust the reaction temperature of the oven to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, ensure that the water in the reactor does not boil during the reaction. After reacting for 60 minutes, naturally cool to room temperature to obtain a graphene hydrogel.

[0028] 4. Soak the graphene hydrogel obtained in step 3 in a 30% by mass ethanol aqueous solution to remove impurities for 12 hours; freeze-dry the graphene hydrogel after impurities removal at a freeze-drying temperature of -18°C for 48 hours to obtain a graphene aerogel. Example 3

[0029] A method for preparing graphene aerogel comprises the following steps: 1. Weigh 30.67g of graphene oxide cake (solid content of 50%±3%), use deionized water as solvent, mix 2900g of deionized water and graphene oxide cake, prepare a graphene oxide solution with a solid content of 0.5%, and add polyethylene glycol (reducing agent) to the prepared graphene oxide solution. The amount of reducing agent added accounts for 0.5% by mass of the total system.

[0030] 2. The mixed solution prepared in step 1 is dispersed by a stirring device, the stirring rate is set at 400 r / min, and the stirring and dispersing time is 10-20 min, until the graphene oxide cake is completely dissolved to obtain a graphene hydrogel precursor.

[0031] 3. Filter the graphene oxide and polyethylene glycol solution that have been fully stirred in step 2 with a 1000-mesh sieve, then pour the filtered solution into a reactor, and fix several cotton threads on the reactor cover with rivets, cover the reactor cover, and place the cotton rope in the graphene hydrogel precursor in a vertical state. After the reactor cover and the reactor are locked tightly, place them in an oven, turn on the oven for heating treatment, adjust the reaction temperature of the oven to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, ensure that the water in the reactor does not boil during the reaction. After reacting for 60 minutes, naturally cool to room temperature to obtain a graphene hydrogel.

[0032] 4. Soak the graphene hydrogel obtained in step 3 in a 10% by mass ethanol aqueous solution to remove impurities for 16 hours; freeze-dry the graphene hydrogel after impurities removal at a freeze-drying temperature of -18°C for 48 hours to obtain graphene aerogel. Example 4

[0033] A method for preparing graphene aerogel comprises the following steps: 1. Weigh 30.67g of graphene oxide cake (solid content of 50%±3%), use deionized water as solvent, mix 2900g of deionized water and graphene oxide cake, prepare a graphene oxide solution with a solid content of 0.5%, and add polyethylene glycol (reducing agent) to the prepared graphene oxide solution. The amount of reducing agent added accounts for 1% by mass of the total system.

[0034] 2. The mixed solution prepared in step 1 is dispersed by a stirring device, the stirring rate is set at 400 r / min, and the stirring and dispersing time is 10-20 min, until the graphene oxide cake is completely dissolved to obtain a graphene hydrogel precursor.

[0035] 3. Filter the graphene oxide and polyethylene glycol solution that have been fully stirred in step 2 with a 200-mesh sieve, then pour the filtered solution into a reactor, and fix several cotton threads on the reactor cover with rivets, cover the reactor cover, and place the cotton rope in the graphene hydrogel precursor in a vertical state. After the reactor cover and the reactor are locked tightly, place them in an oven, turn on the oven for heating treatment, adjust the reaction temperature of the oven to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, ensure that the water in the reactor does not boil during the reaction. After reacting for 60 minutes, naturally cool to room temperature to obtain a graphene hydrogel.

[0036] 4. Soak the graphene hydrogel obtained in step 3 in a 10% by mass ethanol aqueous solution to remove impurities for 16 hours; freeze-dry the graphene hydrogel after impurities removal at a freeze-drying temperature of -18°C for 48 hours to obtain graphene aerogel. Example 5

[0037] A method for preparing graphene aerogel comprises the following steps: 1. Weigh 30.67 g of graphene oxide cake (solid content of 50% ± 3%), use deionized water as solvent, mix 2900 g of deionized water and graphene oxide cake, prepare a graphene oxide solution with a solid content of 0.5%, and add polyethylene glycol (reducing agent) to the prepared graphene oxide solution.

[0038] 2. The mixed solution prepared in step 1 is dispersed by a stirring device, the stirring rate is set at 400 r / min, and the stirring and dispersing time is 10-20 min, until the graphene oxide cake is completely dissolved to obtain a graphene hydrogel precursor.

[0039] 3. Filter the graphene oxide and polyethylene glycol solution that have been fully stirred in step 2 with a 800-mesh sieve, then pour the filtered solution into a reactor, and fix several cotton threads on the reactor cover with rivets, cover the reactor cover, and place the cotton rope in the graphene hydrogel precursor in a vertical state. After the reactor cover and the reactor are locked tightly, place them in an oven, turn on the oven for heating treatment, adjust the reaction temperature of the oven to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, ensure that the water in the reactor does not boil during the reaction. After reacting for 60 minutes, naturally cool to room temperature to obtain a graphene hydrogel.

[0040] 4. Soak the graphene hydrogel obtained in step 3 in a 10% by mass ethanol aqueous solution to remove impurities for 16 hours; freeze-dry the graphene hydrogel after impurities removal at a freeze-drying temperature of -18°C for 48 hours to obtain graphene aerogel.

[0041] Comparative Example 1 A method for preparing graphene aerogel comprises the following steps: 1. Weigh 30.67g of graphene oxide cake (solid content of 50%±3%), use deionized water as solvent, mix 2900g of deionized water and graphene oxide cake, prepare a graphene oxide solution with a solid content of 0.5%, and add polyethylene glycol (reducing agent) to the prepared graphene oxide solution. The amount of reducing agent added accounts for 0.1% by mass of the total system.

[0042] 2. The mixed solution prepared in step 1 is dispersed by a stirring device, the stirring rate is set at 400 r / min, and the stirring and dispersing time is 10-20 min, until the graphene oxide cake is completely dissolved to obtain a graphene hydrogel precursor.

[0043] 3. Filter the graphene oxide and polyethylene glycol solution that have been fully stirred in step 2 with a 200-mesh sieve, then pour the filtered solution into the reactor, cover the reactor cover, lock the reactor cover and the reactor tightly, and place them in an oven. Turn on the oven for heating treatment. The reaction temperature of the oven is adjusted to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, ensure that the water in the reactor does not boil during the reaction. After reacting for 60 minutes, naturally cool to room temperature to obtain a graphene hydrogel.

[0044] 4. Soak the graphene hydrogel obtained in step 3 in a 10% by mass ethanol aqueous solution to remove impurities for 16 hours; freeze-dry the graphene hydrogel after impurities removal at a freeze-drying temperature of -18°C for 48 hours, and the aerogel is not formed. Figure 2 shown.

[0045] The difference between Comparative Example 1 and Example 1 is that no cotton rope was used as support during the preparation process of Comparative Example 1. The aerogel prepared in the end was not formed. After analysis, it was believed that due to the lack of support of the cotton rope, there was a lack of objects to cling to when the graphene oxide self-assembled to form a three-dimensional network, so the aerogel could not be formed in the end.

[0046] Comparative Example 2 A method for preparing graphene aerogel comprises the following steps: 1. Weigh 30.67g of graphene oxide cake (solid content of 50%±3%), use deionized water as solvent, mix 2900g of deionized water and graphene oxide cake, prepare a graphene oxide solution with a solid content of 0.5%, and add polyethylene glycol (reducing agent) to the prepared graphene oxide solution. The amount of reducing agent added accounts for 0.1% by mass of the total system.

[0047] 2. The mixed solution prepared in step 1 is dispersed by a stirring device, the stirring rate is set at 400 r / min, and the stirring and dispersing time is 10-20 min, until the graphene oxide cake is completely dissolved to obtain a graphene hydrogel precursor.

[0048] 3. Filter the graphene oxide and polyethylene glycol solution that have been fully stirred in step 2 with a 200-mesh sieve, then pour the filtered solution into a reactor, and fix several cotton threads on the reactor cover with rivets, cover the reactor cover but do not lock it, and place the cotton rope in the graphene hydrogel precursor in a vertical state, turn on the oven for heating treatment, adjust the reaction temperature of the oven to above 160°C, and the temperature and pressure in the reactor are consistent with those in the oven. After reacting for 60 minutes, naturally cool to room temperature to obtain graphene hydrogel.

[0049] 4. Soak the graphene hydrogel obtained in step 3 in a 10% by mass ethanol aqueous solution to remove impurities for 16 hours; freeze-dry the graphene hydrogel after impurities removal at a temperature of -18°C for 48 hours to obtain a partially formed graphene aerogel, which exhibits severe collapse and cracking. Figure 3 shown.

[0050] The difference between Comparative Example 2 and Example 1 is that during the preparation process, the pressure in the reactor is the same as that in the oven. After analysis, it is believed that during the reaction process, since the pressure and temperature in the reactor are the same as those in the oven, the graphene hydrogel in the reactor boils more violently after being heated to 100°C. The boiling phenomenon is not conducive to the assembly and molding of the graphene aerogel. Finally, the graphene aerogel obtained according to the preparation method of Comparative Example 2 had serious collapse and cracking problems.

Claims

1. A method for preparing graphene aerogel, characterized in that: A graphene oxide solution with a solid content of 0.5%-1% is prepared, a reducing agent is mixed with the graphene oxide solution, wherein the mass percentage of the graphene oxide solution in the total system is 99.5%-99.9%, and the mass percentage of the reducing agent in the total system is 0.1%-0.5%, and the mixture is stirred and dispersed uniformly to obtain a graphene hydrogel precursor; several cotton ropes are placed in the graphene hydrogel precursor, and subjected to a heating treatment under high pressure, during which the cotton ropes are kept in a vertical state, and naturally cooled to room temperature after the treatment is completed to obtain a graphene hydrogel; the graphene hydrogel is immersed in a 10%-80% ethanol aqueous solution to remove impurities; and the graphene hydrogel after the impurities are removed is freeze-dried to obtain a graphene aerogel.

2. The method for preparing a graphene aerogel according to claim 1, characterized in that: The graphene oxide solution is prepared by mixing graphene oxide cake and deionized water.

3. The method for preparing a graphene aerogel according to claim 1, characterized in that: The reducing agent is selected from one of sodium hydroxide, glucose and polyethylene glycol.

4. The method for preparing a graphene aerogel according to claim 3, characterized in that: The reducing agent is ethylene glycol.

5. The method for preparing a graphene aerogel according to claim 1, characterized in that: In the stirring and dispersing step, the stirring rate is set at 300-400 r / min and the stirring and dispersing time is 10-20 min.

6. The method for preparing a graphene aerogel according to claim 1, characterized in that: Pour the graphene hydrogel precursor into the reactor, fix one end of several cotton ropes on the inner wall of the reactor cover, cover the reactor cover, and place the cotton ropes in the graphene hydrogel precursor in a vertical state. After the reactor cover and the reactor are locked tightly, they are placed in an oven. The reaction temperature of the oven is adjusted to above 160°C, and the temperature in the reactor is greater than 100°C. At the same time, ensure that the water in the reactor does not boil during the reaction. After reacting for 10-60 minutes, naturally cool to room temperature to obtain graphene hydrogel.

7. The method for preparing a graphene aerogel according to claim 1, characterized in that: The graphene hydrogel is immersed in an ethanol aqueous solution with a mass percentage greater than 10% to remove impurities, and the immersion time is 12-24 hours.

8. The method for preparing a graphene aerogel according to claim 1, characterized in that: The graphene hydrogel precursor needs to be filtered through a sieve before being subjected to high pressure heating treatment, and the mesh number of the sieve is 200-3000 meshes.

9. The method for preparing a graphene aerogel according to claim 1, characterized in that: In the freeze-drying step, the graphene hydrogel that has been soaked in ethanol or ethanol aqueous solution is placed in a freeze drying box for freeze drying, and the freeze drying time is 48h-72h.

10. The method for preparing a graphene aerogel according to claim 9, characterized in that: The freeze-drying temperature was -18°C.

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