CN113173579B - Macroscopic quantity preparation method of graphene - Google Patents
Macroscopic quantity preparation method of graphene Download PDFInfo
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- CN113173579B CN113173579B CN202010517161.3A CN202010517161A CN113173579B CN 113173579 B CN113173579 B CN 113173579B CN 202010517161 A CN202010517161 A CN 202010517161A CN 113173579 B CN113173579 B CN 113173579B
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- C01B32/00—Carbon; Compounds thereof
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Abstract
The invention relates to the field of preparation of high-performance carbon-based materials, in particular to a high-efficiency green method for macroscopic preparation of graphene by taking layered graphite (or expanded graphite) as a raw material. At normal temperature, mixing layered graphite or expanded graphite with a dispersant aqueous solution, stripping under the action of hydroxyl radicals generated by electrochemical reaction of air and water in a system, filtering and separating out precipitates after the stripping is finished, and washing and microwave drying to obtain a graphene product. The number of layers of the graphene product obtained by the method is 1-7, wherein the percentage of 1-3 layers is 85%, the conductivity of the graphene product exceeds 300S/cm, and the highest yield of the graphene product is 98%. The filtrate can be reused in subsequent preparation processes. The method disclosed by the invention adopts normal-temperature preparation, is simple in process, does not need to consume strong acid or alkali solution with strong oxidizing property or organic solvent (only power and air are consumed), has a good stripping effect of the layered graphite, is good in quality of a graphene product, is green and environment-friendly in process, and is a graphene preparation method with an industrial application prospect.
Description
Technical Field
The invention relates to the field of preparation of high-performance carbon-based materials, in particular to a high-efficiency green method for macroscopic preparation of graphene by taking layered graphite as a raw material.
Background
Carbon elements are widely distributed on the earth, and not only are important elements constituting organisms, but also many carbon materials having special properties are formed. The first report in the journal of Science by british scientists k.s.novoseov and a.k.geim et al in 2004 of a novel carbon material, graphene (graphene), which is a monolayer of carbon atoms passing through sp2The hybridized orbitals form a two-dimensional planar material with a hexagonal lattice honeycomb structure, and carbon atoms are connected through sigma bonds. In graphene, each carbon atom has an unbound electron, which is free to move at high speed (up to one third of the speed of light) in the crystal, and thus exhibits excellent conductivity. Meanwhile, the graphene also has high theoretical specific surface area (2630 m)2·g-1) Excellent light transmittance (97.7%), Young's modulus (1.0 TPa) and other excellent performances. The thickness of the single-layer graphene is only 0.335nm, but the strength of the single-layer graphene is more than 100 times higher than that of steel, and the single-layer graphene is the thinnest two-dimensional material with the highest strength discovered at present and is known as a new material for changing the world. At present, graphene shows in the fields of microcircuits, energy storage, heat conduction materials and high-performance composite materialsThe method has attractive application prospect, so that the realization of the commercial production of the graphene has extremely important practical significance.
Since the discovery of graphene in 2004, the research on the preparation technology and equipment of large-scale and high-quality graphene has been the target pursued by the field technologists and the industry. To date, various methods of preparing graphene have been developed, including a micro mechanical exfoliation method, a physical exfoliation method, a redox method, a liquid phase exfoliation method, an epitaxial growth method, a chemical vapor deposition method, and the like.
The mechanical exfoliation method generally uses highly oriented thermally cracked graphite as a starting material. The graphene is "torn" directly from the graphite by a simple application of force to overcome the weak van der waals forces between the graphite sheets. Geim et al used this method for the first time to exfoliate from highly oriented thermally cracked graphite and observed a monolayer of graphene. Subsequently, j.c. meyer et al prepared single layer graphene by rubbing graphite on a solid surface. Knieke et al wet-milled graphite powder at room temperature and successfully prepared single-layer and multi-layer graphene using a mechanical exfoliation method. During grinding, in order to prevent graphene agglomeration, an anionic surfactant, namely sodium dodecyl sulfate, needs to be added for dispersing graphene sheets. The size of the graphene prepared by the micro-mechanical stripping method can reach micron level, but the product has low yield and poor process repeatability, and large-scale preparation is difficult to realize.
The oxidation-dispersion-reduction method is the most widely used graphene preparation method at present. Graphite is generally used as a raw material, graphite oxide is prepared by a Hummers method, a Brodie method or a Staudenmaier method, the graphite oxide is stripped by external force (such as ultrasonic) to obtain graphene oxide, and finally the graphene oxide is reduced to graphene by a reducing agent. It was found that oxidant concentration and oxidation time have a large effect on the size and thickness of the graphene sheets. The reducing agent is hydrazine hydrate, NaBH4, hydroquinone, pure hydrazine, glucose, vitamins, benzyl alcohol, strong base (KOH, NaOH), pyrrole, etc. The method has simple operation and low cost, and needs no strong inorganic protonic acid (such as fuming HNO)3Concentrated H2SO4Phosphoric acid, etc.) or organic reagents, the post-treatment of the process is complicated, and the cycle is complicatedThe environmental negative effect is large.
The epitaxial growth method is to seed a layer of graphene with the same crystal orientation as the growth substrate on a single crystal substrate. De Heer et al epitaxially grown graphene on SIC (0001) single crystal surfaces by heating the SIC surfaces. Emtsev and Norimatsu heat-treat the 4H-SiC substrate at 1500-2000 deg.C in ultra-high vacuum and argon atmosphere to sublimate the silicon atoms on the surface of the substrate, while the rest of the C atoms are gathered on the surface of the substrate to form graphene. The graphene sheets produced by the method are often uneven in thickness and high in cost, and industrialization is not easy to realize.
Chemical Vapor Deposition (CVD) is a method in which reactants are chemically reacted in a gaseous state to deposit a solid substance formed on the surface of a thermal substrate, and the resultant is further processed to obtain a target product. The starting materials are mostly organic gases (such as ethylene, methane and the like) or liquids (such as ethanol) and solids (such as sucrose, camphor and the like), carbon sources can be gradually decomposed into carbon atoms in a high-temperature reaction and deposited on a metal substrate to gradually grow into continuous graphene. Single-or multi-layered graphene was prepared by this method, both by b.h.hong et al, university of korea adult university, and by j.kong et al, university of labor, Massachusetts. The graphene product prepared by the method has uneven thickness, the adhesion between the graphene product and the substrate influences the property of the product, and meanwhile, the production process requires high temperature and harsh conditions, so that the graphene product is not suitable for mass production.
Disclosure of Invention
Aiming at the practical problems of large pollution, high energy consumption, complex production process, high cost, difficult large-scale production and the like of the existing graphene preparation method, the invention provides an efficient green method for preparing graphene on a large scale by using layered graphite or expanded graphite as a raw material.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for preparing graphene from graphite comprises the steps of mixing layered graphite or expanded graphite with a dispersant aqueous solution at normal temperature, stripping under the action of hydroxyl radicals generated by electrochemical reaction of air and water in a system, filtering and separating out precipitates after stripping is finished, and washing with water and drying with microwaves to obtain a graphene product. The filtrate was simply processed for use in the next preparation.
The mass-volume ratio of the laminar graphite to the dispersant aqueous solution is 1:5-20, preferably 1: 6-10; wherein the concentration of the dispersant in the dispersant water solution is 0.5-5.0% (wt), preferably 0.8-2.4%.
The dispersing agent is an ionic surfactant with a conductive function and a dispersing function.
The dispersant is one or more of polyaspartic acid sodium, sodium carboxymethylcellulose and octadecyl propyl hydroxy sulfobetaine.
The layered graphite is flake graphite or expanded graphite with the particle size of 80-1000 meshes.
The electrochemical reaction generates hydroxyl radicals in a hydroxyl radical generator, a graphite electrode or a composite metal oxide is used as an electrode, air is introduced, direct current is applied, and raw material layered graphite or expanded graphite is used as a catalyst. Wherein, the flow rate of the air is 5.0L/h-15L/h, the current is 0.5-15.0A, and the stripping time is 3-10 h. Preferably 8-12L/h of air flow, 5-13A of current intensity and 5-8h of stripping time
And filtering the solid-liquid mixture obtained after the stripping reaction to obtain a filter cake, washing the filter cake with tap water, and carrying out microwave vacuum drying, grinding and crushing on the filter cake to obtain the graphene product.
And drying the washed filter cake for 5-15min under vacuum microwave at the vacuum degree of-0.08-0.05 MPa and the temperature of 40-70 ℃.
The invention has the beneficial effects that:
according to the method, at normal temperature, strong acid or alkali solution with strong oxidizing property or organic solvent is not needed, only electricity and air are consumed, and the specific surfactant is used for carrying out hydroxyl radical stripping on the layered graphite, so that the graphene product with high yield (98%) and good quality is obtained, and the preparation process is mild in condition, green and environment-friendly, and is a graphene preparation method with an industrial application prospect; the method specifically comprises the following steps:
1) the invention realizes the Kg-level macroscopic preparation of the graphene under the conditions of room temperature and mild conditions.
2) In the preparation process, air and water are converted into hydroxyl radicals by utilizing the combined action of air, water, an environment-friendly conductive dispersant, current and catalyst graphite, so that the high-efficiency graphite stripping is realized, the yield of the graphene is up to 98%, the proportion of 2-3 layers of products in the product is up to 85%, and the maximum number of layers of the whole product is 7.
3) The auxiliary agent and material adopted in the process are non-corrosive and harmless to the environment. And the dispersant solution in the process is recycled, so that the green, safe and environment-friendly performance of the process is ensured.
4) The used environment-friendly dispersing agent has the functions of dispersing and conducting, can ensure the effective generation of hydroxyl free radicals in the process, and can effectively realize the dispersion of raw materials and inhibit the aggregation of products.
5) The process has high efficiency, the product yield is high (up to 98 percent), the product quality is good, and the method is an efficient, economic and green method for macro preparation of the graphene.
Drawings
FIG. 1 is an SEM photograph of a product of example 1 of the present invention
FIG. 2 is a Raman image of the product of example 1 of the present invention.
Detailed Description
The following examples are presented to further illustrate embodiments of the present invention, and it should be understood that the embodiments described herein are for purposes of illustration and explanation only and are not intended to limit the invention.
The number of layers of the graphene product obtained by the method is 1-7, wherein the percentage of 1-3 layers is 85%, the conductivity of the graphene product exceeds 300S/cm, and the highest yield of the graphene product is 98%. The filtrate can be reused in subsequent preparation processes. The method disclosed by the invention adopts normal-temperature preparation, is simple in process, does not need to add other strong acid or alkali solution with strong oxidizing property (only power and air are consumed), is good in stripping effect of the layered graphite, is good in quality of the graphene product, is green and environment-friendly in process, and is a graphene preparation method with industrial application prospect.
According to the invention, the standard analysis methods of graphene products such as infrared, Raman, electron microscope, XRD, four-probe method and atomic force method are adopted to analyze the structure, properties and performance of the graphene product.
Example 1
Adding 1.0Kg of crystalline flake graphite and 6.0Kg of aqueous solution of polyaspartic acid sodium with the mass concentration of 1.0% into a 20L hydroxyl radical generator, introducing air to keep the air flow at 5.0L/h, and carrying out a stripping reaction for 3h under the action of 5A direct current intensity. And then carrying out suction filtration on the prepared solution, washing the solution with distilled water, carrying out microwave drying for 10 minutes at 40 ℃ under the vacuum degree of-0.05 MPa, and grinding the graphene powder. Obtaining 952g of graphene product (see figure 1), wherein the yield of the product graphene is 95.2%, the number of layers of the product is 1-3 layers of 85%, 3-5 layers of 17%, and 5-7 layers of 8.0%.
The conductivity measured by the four-probe method was 375.2S/cm.
Example 2
Adding 1.0Kg of crystalline flake graphite and 6.0Kg of sodium carboxymethylcellulose aqueous solution with the mass concentration of 2.0% into a 20L hydroxyl radical generator, introducing air to keep the air flow at 10.0L/h, and carrying out a stripping reaction for 10h under the action of the direct current intensity of 12A. And then carrying out suction filtration on the prepared solution, washing the solution with distilled water, carrying out microwave drying for 8 minutes at the vacuum degree of-0.08 MPa and the temperature of 60 ℃, and grinding the graphene powder. 980g of graphene product is obtained, the yield of the graphene product is 98.0%, the number of layers of the product by the atomic force method is 1-3, 88%, 3-5, 15% and 5-7, 7.0%.
The conductivity was 385.2S/cm as measured by the four-probe method.
Example 3
Adding 1.0Kg of crystalline flake graphite and 12.0Kg of octadecyl propyl hydroxy sulfobetaine aqueous solution with the mass concentration of 0.8 percent into a 20L hydroxyl radical generator, introducing air to keep the air flow at 10.0L/h, and carrying out a stripping reaction for 10h under the action of a direct current intensity of 12A. And then carrying out suction filtration on the prepared solution, washing the solution with distilled water, carrying out microwave drying for 8 minutes at 50 ℃ under the vacuum degree of-0.08 MPa, and grinding the graphene powder. 980g of graphene product is obtained, the yield of the product graphene is 96.7%, the number of layers of the product by the atomic force method is 1-3, 87%, 3-5, 18% and 5-7, 5.0%.
The conductivity was 572.8S/cm as measured by the four-probe method.
Example 4: preparation process the dispersion is reused.
The filtrate obtained in the preparation process of example 1 is used in the next preparation process after the corresponding surfactant concentration is adjusted. The graphene preparation was carried out under the same conditions as in inventive example 1, and the obtained product graphene yield was 95.0%, the product layer number distribution was 1-3 layers 86%, 3-5 layers 17%, 5-9 layers 7.0%, and the conductivity of the product was 380.6S/cm, indicating that the reuse of the dispersion in the process did not affect the product quality and the peeling efficiency.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (6)
1. A method for preparing graphene from graphite is characterized by comprising the following steps: at normal temperature, mixing layered graphite or expanded graphite with a dispersant aqueous solution, stripping under the action of hydroxyl radicals generated by electrochemical reaction of air and water in a system, filtering and separating out precipitates after the stripping is finished, and washing and microwave drying to obtain a graphene product;
the dispersant is one or more of polyaspartic acid sodium, sodium carboxymethylcellulose and octadecyl propyl hydroxy sulfobetaine;
the electrochemical reaction generates hydroxyl radicals in a hydroxyl radical generator, a graphite electrode or a composite metal oxide is used as an electrode, air is introduced, direct current is applied, and raw material layered graphite or expanded graphite is used as a catalyst; wherein, the flow rate of the air is 5.0L/h-15L/h, the current is 0.5-15.0A, and the stripping time is 3-10 h.
2. The method for preparing graphene according to the graphite of claim 1, wherein: the particle size of the lamellar graphite or the expanded graphite is 80-1000 meshes.
3. The method for preparing graphene according to the graphite of claim 1, wherein: the mass ratio of the laminar graphite to the dispersant aqueous solution is 1: 5-20; wherein the concentration of the aqueous solution of the dispersant is 0.5 wt% -5.0 wt%.
4. The method for preparing graphene according to the graphite of claim 1, wherein: and filtering the solid-liquid mixture obtained after the stripping reaction to obtain a filter cake, washing the filter cake with tap water, and carrying out microwave vacuum drying, grinding and crushing to obtain the graphene product.
5. The method for preparing graphene according to the graphite of claim 4, wherein: and drying the washed filter cake for 5-15min under vacuum microwave at the vacuum degree of-0.08-0.05 MPa and the temperature of 40-70 ℃.
6. The method for preparing graphene according to the graphite of claim 4, wherein: the filtrate was simply processed for use in the next preparation.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102807213A (en) * | 2012-08-30 | 2012-12-05 | 中国科学院苏州纳米技术与纳米仿生研究所 | Method for electrochemically preparing graphene |
| KR20160002009A (en) * | 2014-06-30 | 2016-01-07 | 주식회사 멕스플로러 | Graphene nanosheets, graphene powder, graphene ink, graphene substrate, and method for manufacturing the graphene nanosheets |
| CN111017915A (en) * | 2018-10-10 | 2020-04-17 | 长春工业大学 | Method for preparing graphene from graphite |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102807213A (en) * | 2012-08-30 | 2012-12-05 | 中国科学院苏州纳米技术与纳米仿生研究所 | Method for electrochemically preparing graphene |
| KR20160002009A (en) * | 2014-06-30 | 2016-01-07 | 주식회사 멕스플로러 | Graphene nanosheets, graphene powder, graphene ink, graphene substrate, and method for manufacturing the graphene nanosheets |
| CN111017915A (en) * | 2018-10-10 | 2020-04-17 | 长春工业大学 | Method for preparing graphene from graphite |
Non-Patent Citations (2)
| Title |
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| Xin Wang et al..Green and facile production of high-quality graphene from graphite by the combination of hydroxyl radicals and electrical exfoliation in different electrolyte systems.《RSC Advances》.2019,第9卷 * |
| 石墨衍生物的绿色制备技术及应用;王欣;《中国优秀博硕士论文全文数据库（博士）工程科技I辑》;20200215;第4.2.2节以及第4.4节 * |
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