Highly elastic porous graphene and a preparation method thereof

Abstract

The application provides a kind of high elasticity porous graphene and its preparation method, its preparation method can be divided into four steps assembly, first, synthesis rich same charge group graphene precursor complex, mainly utilize the bonding of oxygen-containing functional groups such as hydroxyl, carboxyl on graphene oxide, connect with charge group molecule on graphene oxide, utilize the high dispersibility precursor solution system of surplus non-bonding same charge group same repulsion characteristics;Second, by introducing heterocharge group molecule, by same and different charge group electrostatic adsorption crosslinking and flocculation, form high elasticity porous graphene oxide intermediate;Finally, by replacement reduction treatment and high temperature reduction treatment, obtain the porous graphene material with high elasticity, the high elasticity porous graphene provided by the application has high compression resilience, can be used as pressure variable device material, has high specific surface area, high active loading site, electrically conductive and other characteristics, is ideal high-performance load catalytic substrate material.

Description

Technical Field

[0001] This invention relates to the field of graphene technology, specifically to a highly elastic porous graphene and its preparation method. Background Technology

[0002] Graphene is an emerging two-dimensional material with excellent mechanical, thermal, and electrical properties, showing great promise for applications in electronic devices, thermal management, and new energy fields. Graphene materials mainly exist in three forms: powder, film, and porous graphene. Porous graphene, due to its lightweight, porous structure, high specific surface area, high load-bearing capacity, and high conductivity, is an ideal material for seawater desalination, photoelectric and thermal conversion, high-performance catalysis, sound insulation, and heat insulation. The over-exploitation and consumption of fossil fuels such as coal and oil have led to severe air pollution, water pollution, and energy shortages. Due to its unique physicochemical properties, porous graphene is the most promising functional substrate material for solving these problems. Among these, graphene aerogel is the most typical porous graphene material; however, the demanding preparation conditions and high cost of graphene aerogel, coupled with the inability to mass-produce it, greatly limit its application. While graphene films have a simple fabrication process, they are formed by stacking two-dimensional graphene sheets, resulting in low porosity, small specific surface area, and few active loading sites, making it difficult to achieve the unique properties of porous graphene materials. Furthermore, the large-scale production of graphene aerogels is still under development. To meet the application requirements of porous graphene materials, there is an urgent need to find intermediate transitional materials based on graphene films and graphene aerogels. These materials must be low-cost, have a simple fabrication process, and possess a highly elastic porous graphene material and its fabrication method. Summary of the Invention

[0003] The purpose of this invention is to provide a low-cost and simple method for preparing porous graphene materials, the specific steps of which are as follows: S1. Graphene oxide deionized water solution is uniformly dispersed in a deionized water solution rich in cationic groups and allowed to stand at 50-90℃ for 2-24 hours to obtain solution A. The purpose of this step is to synthesize a graphene precursor complex rich in homogeneous charged groups. This mainly utilizes the bonding effect of oxygen-containing functional groups such as hydroxyl and carboxyl groups on graphene oxide to attach charged group molecules to graphene oxide. The high-dispersion precursor solution system is obtained by utilizing the homogeneous repulsion property of the abundant non-bonded homogeneous charged groups.

[0004] S2. Add molecules containing anionic groups to solution A and keep it at 50-90℃ for 10-24 hours to obtain solution B. The purpose of this step is to introduce charged group molecules of opposite polarity to those in step S1, and form a highly elastic porous graphene oxide intermediate through electrostatic adsorption crosslinking and flocculation of the opposite charged groups.

[0005] S3. Use anhydrous ethanol containing 0.1-5% hydrazine hydrate to slowly replace the deionized water in solution B, followed by drying. The replacement process plays a role in partial reduction and shaping, preventing the cross-linked and flocculated graphene oxide blocks from collapsing after filtration.

[0006] S4. Reduce the dried sample under an inert atmosphere at 200-1100℃ to obtain highly elastic porous graphene.

[0007] Furthermore, the solid content of the graphene oxide aqueous solution is 0.01%-2.0%, and the mass fraction of the deionized aqueous solution containing cationic groups is 0.01%-1.0%. Controlling the solid content of the graphene oxide aqueous solution to 0.01%-2.0% is to allow for the subsequent disordered cross-linking between graphene sheets to form a porous structure. If the solid content is greater than 2.0%, dense packing of graphene sheets will occur. Self-assembled dense packing is a sheet-like stacking, which cannot form the desired porous structure.

[0008] Furthermore, the cationic group is one or more of a metal cation and an amino group. Preferably, the metal cation is a multivalent ion, such as Cu. 2+ Fe 3+ wait.

[0009] Furthermore, the anionic group is one or more of a carboxyl group and a sulfonic acid group.

[0010] Furthermore, the temperature of the anhydrous ethanol solution containing 0.1-5% hydrazine hydrate is 50-70℃. If the temperature of the anhydrous ethanol solution containing 0.1-5% hydrazine hydrate is less than 50℃, the hydrazine hydrate ethanol solution will have a slower permeation rate and a lower degree of reduction during the displacement reduction process, thus affecting the elasticity of the final product. If the solution temperature is greater than 70℃, the higher the temperature, the more energy the ethanol molecules gain, and the greater and more intense the disordered movement. Exceeding the boiling point will also cause violent volatilization, which is not conducive to static precipitation and will cause the sample to form a flocculent precipitate, which is not conducive to shaping.

[0011] Furthermore, the specific method of slowly replacing the deionized water in solution B with anhydrous ethanol containing 0.1-5% hydrazine hydrate is bottom-up displacement, which allows for a more stable replacement of the deionized water in solution B.

[0012] Further, step S1 specifically involves: using graphene oxide cake as a solute and deionized water as a solution to prepare a graphene oxide solution with a solid content of 0.01%-2.0%; adding 0.01-1.0% of a cationic group-rich solvent to the graphene oxide solution; stirring and dispersing; and allowing it to stand at 50-90℃ for 2-24 hours to obtain solution A.

[0013] Furthermore, the cationic solvent is an amine-rich solvent, preferably one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0014] Furthermore, step S2 specifically involves: using molecules containing anionic groups as solutes and deionized water as a solution, preparing a solvent rich in anionic groups with a solid content of 0.01-1.0%, and slowly adding it to solution A under stirring conditions, and continuing to keep it at 50-90℃ for 10-24 hours to obtain solution B.

[0015] A second object of the present invention is to provide a highly elastic porous graphene prepared according to any of the methods described above.

[0016] The beneficial effects of this invention are as follows: The highly elastic porous graphene prepared by this invention uses graphene oxide with oxygen-containing groups and common molecules rich in cationic groups as raw materials. The raw materials are simple and readily available. The preparation process involves relatively simple environmental conditions such as temperature and humidity. Compared with the traditional graphene aerogel preparation process, this process is simple and inexpensive, and can be mass-produced on a large scale.

[0017] The highly elastic porous graphene material provided by this invention is a porous graphene intermediate between graphene film and graphene aerogel. It has high compression resilience and can be used as a material for voltage converters. It has high specific surface area, high active loading sites, and conductivity, making it an ideal high-performance supported catalytic substrate material. It has a porous structure and can be applied to multiple fields such as supported catalysis, filtration, sound insulation, and heat insulation. Implementation

[0018] The technical solution will now be clearly and completely described in conjunction with embodiments of the present invention. Obviously, the embodiments described below are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The more detailed description of the embodiments of the present invention below is not intended to limit the scope of the claimed invention, but is merely for illustrative purposes and does not limit the description of the features and characteristics of the invention, to propose the best mode for carrying out the invention, and is sufficient to enable those skilled in the art to implement the invention. However, it should be understood that various modifications and variations can be made without departing from the scope of the invention as defined by the appended claims. The detailed description should be considered illustrative only, not restrictive, and any such modifications and variations will fall within the scope of the invention 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 the present invention or the application field of the present invention.

[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 invention pertains; the terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention; 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 the present invention clearer, a detailed description will be given below in conjunction with specific embodiments.

[0022] The following are specific embodiments and comparative examples. Example 1

[0023] A method for preparing a highly elastic porous graphene material includes the following steps: S1. Synthesis of a precursor rich in charged groups: Using graphene oxide cake as the solute and deionized water as the solution, a homogeneous graphene oxide slurry with a solid content of 0.5% was prepared by stirring and dispersing. 0.1% of a rich amine molecular solvent was added to the graphene oxide slurry; in this embodiment, tetraethylenepentamine was selected as the solvent, and dispersion treatment was performed. Dispersion methods included, but were not limited to, stirring, milling, homogenization, and ultrasonication. In this embodiment, a digital disperser was used to stir at 1500 r / min for 10 min, and then the mixture was transferred to an 80℃ water bath and kept at that temperature for 10 h. During the standing and holding process, the benzene ring on the polyethylenepolyamine molecule underwent strong π-π conjugation with the graphene oxide, while the carboxyl groups on the edge of the graphene oxide and some of the amine groups on the tetraethylenepentamine molecule slowly underwent esterification and dehydration reactions to obtain a GO-TEPA precursor complex solution, denoted as solution A. Due to the rich amine characteristics of the precursor complex, the solute in solution A exhibited high dispersibility. S2. Electrostatic Adsorption and Cross-linking Flocculation of Different Charged Groups: Using sodium dodecylbenzenesulfonate as the solute and deionized water as the solution, a sodium dodecylbenzenesulfonate solution with a solid content of 0.2% was prepared by stirring. This solution was then slowly added to solution A under stirring and kept at 80°C for 24 hours to obtain solution B. During this process, the sulfonic acid groups on the sodium dodecylbenzenesulfonate molecules achieve electrostatic adsorption and cross-linking with the amino groups in the solution through osmosis. Simultaneously, the highly dispersed graphene oxide in the solution gradually shrinks into porous, long columnar graphene oxide blocks.

[0024] S3. Using a bottom-up, top-down method, slowly replace the water in the solution with anhydrous ethanol containing 1% hydrazine hydrate over 30 minutes. The temperature of the replacement solution is 55°C. After completion, the solution is removed by a simple vacuum filtration process. The replacement process serves to partially reduce and solidify the solution, preventing the cross-linked and flocculated graphene oxide blocks from collapsing after filtration. The solution is then transferred to a forced-air drying oven to dry the solvent. S4. Transfer the sample obtained in step S2 to a muffle furnace and hold it at 200℃ for 2 hours, then reduce it at 600℃ under an inert atmosphere for 2 hours. After the high-temperature reduction is complete, allow it to cool naturally to room temperature. During this process, the 3D graphene oxide block undergoes further high-temperature reduction, generating a large amount of gas. The contracted porous structure expands and rebounds, resulting in a porous graphene sample with highly elastic graphene-like aerogel. The target sample obtained in step S4 was cut into a cylindrical sample with a height of 2 cm, and then subjected to a compression-rebound test. Two metal plates were used as clamps to hold the sample. A low-voltage DC power supply was applied to form a series circuit between the upper and lower metal clamps and the sample. The initial height was 2 cm, and the compression ratio was set to 50% (compression height 1 cm). When the sample reversibly rebounded, the series circuit remained open, and the test continued. When the sample experienced irreversible fatigue rebound, the sample could not contact the upper clamp, the series circuit was open, and the test automatically stopped while recording the number of repeated compression-rebound cycles. The sample obtained in Example 1 maintained a 100% reversible rebound rate after 7825 repeated compression-rebound tests. Comparative Example 1

[0025] A highly elastic porous graphene and its preparation method are disclosed. The raw materials and methods are the same as in Example 1, except that in step S1, a uniform slurry of graphene oxide with a solid content of 2.5% is prepared. It was found that due to the high solid content of the graphene oxide slurry, self-assembly and dense stacking of graphene sheets occurred. The self-assembly and dense stacking was a sheet-like stacking rather than a porous disordered arrangement. Therefore, it was impossible to obtain porous long columnar graphene oxide blocks in step S2. Comparative Example 2

[0026] A highly elastic porous graphene and its preparation method are described. The raw materials and methods are the same as in Example 1, except that in step S3, deionized water is used instead of anhydrous ethanol containing 1% hydrazine hydrate for replacement. It was found that after filtration, the sample exhibited structural collapse and cracking, and the sample could not be tested. This was attributed to the fact that deionized water did not have the effect of initial reduction and shaping. Comparative Example 3

[0027] A highly elastic porous graphene and its preparation method are disclosed. The raw materials and methods are the same as in Example 1, except that in step S3, anhydrous ethanol of 1% hydrazine hydrate at 25°C is used for replacement. It was found that the expansion and rebound effect after high-temperature reduction was poor. The sample began to show fatigue after more than 5210 compression and rebound tests and could not achieve reversible rebound. This is attributed to the slow penetration rate of the hydrazine hydrate ethanol solution at room temperature, which resulted in low reduction and shaping of the outer layer and a low degree of reduction on the inner side. Comparative Example 4

[0028] A highly elastic porous graphene and its preparation method are disclosed. The raw materials and methods are the same as in Example 1, except that in step S3, anhydrous ethanol in 1% hydrazine hydrate at 80°C is used for replacement. It was found that porous long columnar graphene oxide blocks could not be obtained in step S2. This is because the temperature is too high and the disordered movement of ethanol molecules is too intense, which is not conducive to the static precipitation of the sample.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing highly elastic porous graphene, characterized in that, Includes the following steps: S1. A deionized water solution of graphene oxide with a solid content of 0.01%-2.0% is uniformly dispersed in a deionized water solution rich in cationic groups, and allowed to stand at 50-90℃ for 2-24 hours to obtain solution A, wherein the cationic groups are amine groups. S2. Add molecules containing anionic groups to solution A and keep it at 50-90℃ for 10-24 hours to obtain solution B. The anionic groups are one or more of carboxyl groups and sulfonic acid groups. S3. Use anhydrous ethanol containing 0.1-5% hydrazine hydrate at a temperature of 50-70℃ to slowly replace the deionized water in solution B, followed by drying. S4. Reduce the dried sample under an inert atmosphere at 200-1100℃ to obtain highly elastic porous graphene.

2. A method for preparing highly elastic porous graphene as described in claim 1, characterized in that, The mass fraction of the deionized aqueous solution containing the cationic group is 0.01-1.0%.

3. A method for preparing highly elastic porous graphene as described in claim 1, characterized in that, The specific method for slowly replacing the deionized water in solution B with anhydrous ethanol containing 0.1-5% hydrazine hydrate is bottom-up drainage.

4. A method for preparing highly elastic porous graphene as described in claim 1, characterized in that, Step S1 specifically involves: using graphene oxide cake as a solute and deionized water as a solvent to prepare a graphene oxide solution with a solid content of 0.01%-2.0%; adding a deionized aqueous solution rich in cationic groups with a mass fraction of 0.01-1.0% to the graphene oxide solution; stirring and dispersing; and allowing it to stand at 50-90℃ for 2-24 hours to obtain solution A.

5. A method for preparing highly elastic porous graphene as described in claim 4, characterized in that, The cationic groups in the deionized aqueous solution rich in cationic groups are amine groups, and the substances providing the amine groups are one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

6. A method for preparing highly elastic porous graphene as described in claim 1, characterized in that, Step S2 specifically involves: using molecules containing anionic groups as solutes and deionized water as solvents to prepare a solution rich in anionic groups with a solid content of 0.01-1.0%, which is then slowly added to solution A under stirring conditions. The solution is then kept at 50-90°C and allowed to stand for 10-24 hours to obtain solution B.

7. A highly elastic porous graphene, characterized in that, Prepared according to the method of any one of claims 1-6.