CN111017915A

CN111017915A - Method for preparing graphene from graphite

Info

Publication number: CN111017915A
Application number: CN201811179420.5A
Authority: CN
Inventors: 张龙; 王欣
Original assignee: Changchun University of Technology
Current assignee: Changchun University of Technology
Priority date: 2018-10-10
Filing date: 2018-10-10
Publication date: 2020-04-17

Abstract

The invention relates to the technical field of graphene preparation, in particular to a method for preparing graphene from graphite, which comprises the following steps of adding a conductive agent aqueous solution and crystalline flake graphite with certain volume concentration into an electrochemical reactor provided with graphite or metal electrodes, wherein the mass/volume ratio of the graphite to the conductive agent is 1 (10-50), and simultaneously introducing 5-30 mA direct current and a certain flow of air into a reaction system for 1-20 h; then taking out the materials of the system, filtering and washing, and grinding the obtained filter cake after vacuum drying to obtain a graphene powder product; under proper treatment conditions, 1-10 layers of graphene products can be obtained; the method disclosed by the invention is mild in preparation conditions and simple in process, adopts an inorganic salt aqueous solution as a conductive solution, does not need to add other strong acid or alkali solution with strong oxidizing property, 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.

Description

Method for preparing graphene from graphite

Technical Field

The invention relates to the technical field of graphene preparation, in particular to a method for preparing graphene from graphite.

Background

Carbon elements are widely distributed on the earth, and not only are important elements indispensable to the construction of living bodies, but also many carbon materials having specific properties can be formed. Both fullerenes discovered in 1985 and carbon nanotubes discovered in 1991 have been an important frontier area of scientific research and innovation. In 2004, scientists k.s.novoseov and a.k.geem et al reported a novel carbon material-graphene, which is a monolayer of graphite with single carbon atoms connected to each other, for the first time in the journal of SciencePersp²The 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 can move freely and at high speed in the crystal, so that graphene has good conductivity. Meanwhile, graphene also has a plurality of other excellent properties, such as large theoretical specific surface area, excellent light transmittance and high Young modulus. In addition, theoretical studies on the energy band structure of graphene indicate that it is a zero-bandgap semiconductor material, and it is shown that the valence band occupied by electrons and the conduction band occupied by holes intersect at the fermi level (K and K') in the graphene structure, and that both are completely symmetrical about these two points. Research also shows that the thickness of the single-layer graphene is only the diameter of carbon atoms, about 0.335nm, but the strength is more than 100 times higher than that of steel, so that the graphene is the thinnest and hardest two-dimensional material known at present and is known as a new material for changing the world. The special two-dimensional structure and the numerous advantages of the graphene endow the graphene with wide application prospects. In addition, the novel graphene derivative is prepared by changing the spatial configuration, regulating and controlling the electronic structure, performing functional treatment and the like, and has extremely important significance for comprehensively utilizing a plurality of excellent properties of graphene and realizing commercial application.

Since the discovery of graphene in 2004, the research on the preparation of large-scale and high-quality graphene has been the target pursued by technologists. Heretofore, methods for producing graphene have been greatly developed, and they are mainly classified into a micro-mechanical exfoliation method, an oxidation-dispersion-reduction method, an epitaxial growth method, a chemical vapor deposition method, and the like.

Graphene prepared by a micro-mechanical stripping method can reach the micron level, and has the defects of low yield, time and labor waste, poor repeatability and difficulty in realizing large-scale preparation; although the oxidation, dispersion and reduction method is simple and convenient to operate and low in cost, inorganic strong protonic acid or organic reagent is not needed in the preparation process, so that the environment is polluted; 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, and the produced graphene sheet is often uneven in thickness and high in cost, and industrialization is not easy to realize; the chemical vapor deposition method is a method in which reactants are chemically reacted under a gaseous condition to generate a solid substance and deposit the solid substance on the surface of a heating substrate to obtain a target product, but a sample obtained by the method has uneven thickness, the carbon layer characteristics are affected by adhesion between the sample and a substrate, and the production process requires high temperature and harsh conditions and is not suitable for mass production.

OH radical as the most common and important one of the radicals, its oxidation potential being 2.8V, second only to F₂The catalyst has very high reaction rate constant and electrophilicity of negative charge, short survival life, and oxidation characteristic of non-selectivity, can react with almost all kinds of substances, and is a main body of many free radical oxidation reactions. OH radicals oxidize mainly the dissolved inorganic and organic species by four pathways, electron transfer, dehydrogenation, addition and self-quenching. At present, the generation method of OH radicals is mainly a pulse radiation decomposition method, an ozone method, a Fenton type, a Haber-Weiss reaction, an electrochemical method, and the like. The existing generation mode of hydroxyl free radicals has the defects of high energy consumption, need of using harmful and dangerous auxiliary agents and the like. Aiming at the difficulty in production of hydroxyl radicals, the method adopts an inorganic salt solution as a solvent, adds raw material graphite as a catalyst into the solvent, and simultaneously continuously and efficiently prepares the hydroxyl radicals under the action of air, thereby providing a premise for industrial application of the radicals.

Disclosure of Invention

Technical problem to be solved

Aiming at the problems, the invention aims to find a convenient, efficient, green and clean method for preparing graphene from graphite by applying hydroxyl radicals to the process of preparing graphene from layered graphite.

(II) technical scheme

In order to achieve the purpose, the invention is realized by the following technical scheme:

a method of preparing graphene from graphite, comprising the steps of:

(1) adding a conductive agent aqueous solution and crystalline flake graphite with a certain concentration into an electrochemical reactor provided with graphite or metal electrodes, and introducing a certain direct current and a certain flow of air into a reaction system to strip for a certain time;

(2) and then taking out the materials of the reaction system, sequentially filtering and washing, and grinding the obtained filter cake after vacuum drying to obtain the graphene product.

Preferably, the mass/volume ratio of the graphite to the aqueous solution of the conductive agent in the step (1) is 1 (10-50).

Preferably, the conductive agent in the step (1) is conductive inorganic salt, and the mass concentration of the conductive agent solution is 1.0-10.0%.

Preferably, the conductive inorganic salt is sodium chloride or potassium chloride.

Preferably, the direct current intensity applied in the step (1) is 5-100 mA, the air flow is 0.5-2.0L/h, and the stripping time is 1-20 h.

Preferably, the product obtained in the step (2) when the number of graphene layers is 1-3 can be used for preparing an electrode material, a graphene composite or a graphene composite material.

(III) advantageous effects

When the hydroxyl radical oxidation-electric stripping synergistic preparation method is adopted to prepare the graphene, on one hand, the hydroxyl radical shows strong oxidation property, has oxidation effect on raw material graphite to open graphite interlayer spacing, and simultaneously generates synergistic effect with current to stripping of graphite, so that the efficient preparation of the graphene is achieved; on the other hand, the natural crystalline flake graphite is used as a raw material and is also a catalyst for generating hydroxyl radicals, green, clean and efficient preparation of the hydroxyl radicals and graphene is realized, the utilization rate of the raw material is high, and the process is simple. In addition, the invention adopts inorganic salt solution as solvent, and does not use acid or alkali solution with strong oxidizing property, thereby having little corrosion to equipment and no pollutant discharge; the catalyst graphite is simultaneously used as a raw material, and is free from separation, economic and environment-friendly.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.

FIG. 1 is an XRD pattern of a product of example 1 of the present invention;

FIG. 2 is a TEM image of a product in example 1 of the present invention;

FIG. 3 is a Raman spectrum of the product of example 1 of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

adding 2.0g of crystalline flake graphite into a 5% volume concentration aqueous solution of a conductive agent, keeping the air inlet flow at 1.0L/h, and preparing for 5h under the action of 30mA direct current intensity. And then, carrying out suction filtration on the prepared solution, drying in vacuum, and grinding to obtain graphene powder. The XRD, TEM and Raman spectra of the product are shown in figures 1, 2 and 3 respectively.

As can be seen from fig. 1 and 3, the product has a diffraction angle corresponding to a characteristic peak of graphene and a characteristic raman spectrum of graphene, which indicates that the graphene can be successfully prepared by the method of the present invention. As shown in fig. 2, the TEM image of the product shows that the graphene is a uniform lamellar layer. The thickness of the graphene prepared by the embodiment is about 3nm, the number of layers of the peeled graphene product is 3, and the graphene product with better quality is prepared.

Example 2:

adding 4.0g of crystalline flake graphite into a 10% volume concentration aqueous solution of a conductive agent, keeping the air inflow at 1.5L/h, and preparing for 5h under the action of direct current intensity of 10 mA. And then, carrying out suction filtration on the prepared solution, drying in vacuum, and grinding to obtain graphene powder.

The characteristic diffraction angle 2 theta of the natural crystalline flake graphite is about 27 degrees and 54 degrees, and the diffraction angle corresponding to the XRD characteristic peak of the product shown in the example is basically the same as that of the natural crystalline flake graphite by comparing with the XRD spectrum of the natural crystalline flake graphite, which indicates that the product has the same carbon-based material component and the same internal carbon atom or molecular structure form as the natural crystalline flake graphite. According to TEM detection, the graphite material was exfoliated into uniform lamellar graphene. The product has a characteristic Raman spectrum peak of the graphene, which shows that the graphene is successfully prepared by the method. The graphene prepared in this example was examined with an atomic force microscope, and the number of layers was 4.

Example 3:

adding 2.0g of crystalline flake graphite into a conductive agent aqueous solution with the volume concentration of 8%, keeping the air inflow at 1.0L/h, and preparing for 20h under the action of direct current intensity of 10 mA. And then, carrying out suction filtration on the prepared solution, drying in vacuum, and grinding to obtain graphene powder.

The product has a characteristic XRD spectrogram absorption peak and a Raman spectrogram peak of the graphene through detection, and the method is proved to successfully prepare the graphene. According to TEM detection, the graphite raw material is stripped into uniform lamellar graphene. The number of graphene layers of the product of this example was 5 as measured by atomic force microscopy.

Example 4:

adding 6.0g of crystalline flake graphite into a 6% volume concentration conductive agent aqueous solution, keeping the air inlet flow at 1.0L/h, and preparing for 10h under the action of direct current intensity of 10 mA. And then, carrying out suction filtration on the prepared solution, drying in vacuum, and grinding to obtain graphene powder.

XRD and Raman spectrum detection show that the product has a characteristic XRD spectrogram absorption peak and a Raman spectrum peak of graphene, and the method provided by the invention successfully prepares the graphene. The TEM examination shows that the graphite raw material is stripped into uniform lamellar graphene. And detecting the number of the stripped graphene product to be 7 by using an atomic force microscope.

Example 5:

4.0g of crystalline flake graphite is added into a 1.0 volume percent aqueous solution of a conductive agent, the air inflow is kept at 1.0L/h, and the preparation is carried out for 5h under the action of 10mA direct current intensity. And then, carrying out suction filtration on the prepared solution, drying in vacuum, and grinding to obtain graphene powder.

XRD and Raman spectrum detection prove that the graphene is successfully prepared by the method. The TEM examination shows that the graphite raw material is stripped into uniform lamellar graphene. And detecting the number of the stripped graphene layers to be 10 by using an atomic force microscope.

Example 6:

4.0g of crystalline flake graphite is added into a 5.0 volume percent aqueous solution of a conductive agent, the air inflow is kept at 2.0L/h, and the preparation is carried out for 5h under the action of 10mA direct current intensity. And then, carrying out suction filtration on the prepared solution, drying in vacuum, and grinding to obtain graphene powder.

XRD and Raman spectrum detection show that the graphene is successfully prepared in the example. TEM detection shows that the raw material graphite is peeled into uniform lamellar graphene. And detecting the number of the stripped graphene product to be 5 by using an atomic force microscope.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

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

1. A method for preparing graphene from graphite is characterized by comprising the following steps:

2. The method of claim 1, wherein the graphene is prepared from graphite: the mass/volume ratio of the graphite to the aqueous solution of the conductive agent in the step (1) is 1 (10-50).

3. The method of claim 1, wherein the graphene is prepared from graphite: in the step (1), the conductive agent is conductive inorganic salt, and the mass concentration of the conductive agent solution is 1.0-10.0%.

4. The method of claim 3, wherein the graphene is prepared from graphite: the conductive inorganic salt is sodium chloride or potassium chloride.

5. The method of claim 1, wherein the graphene is prepared from graphite: the direct current intensity applied in the step (1) is 5-100 mA, the air flow is 0.5-2.0L/h, and the stripping time is 1-20 h.

6. The method of claim 1, wherein the graphene is prepared from graphite: and (3) preparing an electrode material, a graphene compound or a graphene composite material by using the product with 1-3 graphene layers in the step (2).