CN103626167A - Preparation method for graphene - Google Patents

Abstract

The invention discloses a preparation method of graphene, which comprises the following steps: 1) adding graphite into concentrated sulfuric acid and dispersing it, and then sequentially adding potassium permanganate and sodium nitrate; 2) adding distilled water, stirring evenly, and then adding hydrogen peroxide to obtain Bright yellow reaction system A; 3) adjust the pH of reaction system A to 6, and ultrasonically disperse for 2 to 5 hours to obtain a dispersion system; 4) add a high boiling point organic solvent and a reducing agent to the dispersion system, and stir for 5 to 10 hours to obtain Reaction system B; 5) The reaction system B was left to stand and separated, and the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain the obtained product. The preparation method of graphene of the present invention saves graphite oxide filtration, washing, drying and other steps, saves a lot of separation time and washing water, has the advantages of time saving, labor saving, water saving, pollution reduction, low cost and large amount of preparation The advantages.

Description

A kind of preparation method of graphene

technical field

The invention belongs to the technical field of graphene materials, and relates to a preparation method of graphene.

Background technique

Graphene is a hexagonal honeycomb two-dimensional structure composed of a single layer of ^sp2 carbon atoms. Its structure can be decomposed into zero-dimensional fullerene, curled to form one-dimensional carbon nanotubes, and superimposed to form three-dimensional graphite. Each carbon atom of graphene is connected to other three carbon atoms through a σ bond to form a six-membered ring structure. These CC bonds make the graphene sheet have excellent structural rigidity; at the same time, each carbon atom contributes an unbonded π Electrons, these π electrons form π orbitals in the direction parallel to the graphite layer, endowing graphene with good electrical conductivity, thermal conductivity, extraordinary specific surface area, Young's modulus and fracture strength, which are also comparable to carbon nanotubes, and also have Some unique properties, such as a series of properties such as perfect quantum tunneling effect, half-integer quantum Hall effect, never-disappearing conductivity, and cheap. It is precisely because graphene materials have so many unique properties that they have aroused great research interests of scientists in different fields such as physics, chemistry, and materials, and also make graphene play an important role in the fields of electronics, information, energy, materials, and biomedicine. application prospects.

At present, the preparation methods of graphene mainly include mechanical exfoliation method, epitaxial growth method, epitaxy method, vapor phase deposition method and redox method. The mechanical exfoliation method is a method of exfoliating graphene sheets from the surface of bulk graphite crystals by mechanical force. The raw materials of this method are easy to obtain, the operation is relatively simple, and the synthesized graphene has high purity and fewer defects, but this method is time-consuming and labor-intensive. The yield is low and not suitable for large-scale production. The epitaxial growth method removes Si by heating single crystal 6H-SiC, and decomposes graphene sheets on the surface of single crystal SiC. Separated, it is difficult to manufacture graphene in large quantities. The epitaxy method uses the atomic structure of the growth substrate to "plant" graphene. The thickness of graphene prepared by this method is often uneven, and the interaction between graphene and the substrate will affect the characteristics of graphene. Chemical vapor deposition is a process technology in which the reacting substances react chemically under relatively high temperature and gaseous conditions, and the generated solid substances are deposited on the surface of the heated solid substrate to obtain solid materials. This method is the most widely used method for large-scale preparation of semiconductor thin film materials in industry, and it is also an effective way to prepare graphene. It can be used to prepare large-area electronic devices (such as electrodes, displays, etc.). Commercial application provides an effective way, but at this stage, high cost, complicated process and precise control of processing conditions restrict the development of this method.

Redox method (including oxidation-modification-reduction method) is divided into Standenmaier method, Brodie method and Hummers method, among which Hummers method is widely used. There are two chemical reactions involved in this method: 1) treating graphite with a strong protonic acid to form a graphite interlayer compound, and then adding a strong oxidant to oxidize it; 2) reducing the graphene oxide after separation, the more effective chemical Reductant reduction. Graphene prepared by the redox method is low in cost, easy to operate, and large in output. It is most likely to achieve large-scale preparation of graphene, and it is also convenient for further modification, processing, and molding of graphene. This method can prepare a large number of single-layer graphite for people. Alkenes offer hope. However, the separation of the product of this method is difficult, a large amount of water is used for washing, and the entire preparation process is lengthy, so the efficiency is low and the environment is not friendly. These unfavorable factors limit the large-scale preparation of graphene and its application research.

Contents of the invention

The purpose of the present invention is to provide a kind of efficient, environment-friendly preparation method of graphene.

In order to achieve the above object, the technical solution adopted in the present invention is: a kind of preparation method of graphene, comprises the following steps:

1) Under stirring conditions, add 1 weight part of graphite into concentrated sulfuric acid and disperse it, then add 3 weight parts of potassium permanganate and 0.5 weight part of sodium nitrate in sequence, and continue stirring for 2 to 5 hours to obtain a mixture;

2) Heat the mixture obtained in step 1) to 30-50°C, keep it warm for 1 hour, add 45 parts by weight of distilled water, continue to heat up to 95°C, and react for 1-2 hours, then add 70 parts by weight of deionized water to keep the temperature 70-90°C, stir evenly and add 5-8 parts by weight of hydrogen peroxide to obtain bright yellow reaction system A;

3) Under stirring conditions, adjust the pH of the reaction system A obtained in step 2) to 6, then raise the temperature to 90-100°C, and ultrasonically disperse for 2-5 hours to obtain a dispersion system;

4) Cool the dispersion system obtained in step 3) to 80°C, add a high-boiling point organic solvent, and then add 15-50 parts by weight of a reducing agent, heat up to reflux temperature, and stir for 5-10 hours to obtain a reaction system B;

5) The reaction system B obtained in step 4) was allowed to stand for stratification, and after the water layer was removed, the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain the final product.

The graphite described in step 1) is natural flake graphite with a particle size greater than 300 mesh.

The amount of concentrated sulfuric acid described in step 1) is: 1g of graphite dispersed in 25ml of concentrated sulfuric acid.

The temperature of the concentrated sulfuric acid is 5-15°C.

The method for adjusting the pH of the reaction system A in step 3) is: adding sodium carbonate to the reaction system A.

The high-boiling organic solvent described in step 4) is toluene, xylene, monochlorobenzene, ethylbenzene or tetralin.

The addition amount of the high boiling point organic solvent is: the volume of the high boiling point organic solvent and the dispersion system is 1:2-4.

The reducing agent in step 4) is hydrazine, hydroquinone, sodium borohydride, citric acid, vitamin C or ethylenediamine.

The preparation method of graphene of the present invention utilizes the principle that graphene oxide is highly hydrophilic and easy to disperse in water, and the principle that reduced graphene is hydrophobic and easy to disperse in organic solvents is directly reduced in the graphite oxide system, eliminating the need for Graphite oxide filtration, washing, drying and other steps save a lot of separation time and washing water, and have the advantages of time saving, labor saving, water saving, pollution reduction, low cost and large amount of preparation.

Description of drawings

Fig. 1 is the SEM figure of the obtained Graphene of embodiment 2;

Fig. 2 is the SEM figure of the graphene obtained in embodiment 5.

Detailed ways

The present invention will be further described below in combination with specific embodiments.

Example 1

The preparation method of the graphene of the present embodiment, comprises the following steps:

1) Under the condition of mechanical stirring, disperse 1g of natural flake graphite (>300 mesh) in 25ml of concentrated sulfuric acid at a temperature of 5°C, then slowly add 3g of potassium permanganate and 0.5g of sodium nitrate in sequence, and stir for reaction 2 hours, a mixture is obtained;

2) Heat the mixture obtained in step 1) to 30°C, keep it warm for 1 hour, slowly add 45g of distilled water, control the speed of adding water to raise the temperature to 95°C, keep mechanical stirring for 1 hour, then add 70g of deionized water to maintain the temperature at 70°C, after stirring evenly, add 5g of hydrogen peroxide to obtain a bright yellow reaction system A;

3) Under stirring conditions, add sodium carbonate to the reaction system A obtained in step 2) to adjust the pH of the reaction system A to 6, then raise the temperature to 95°C, ultrasonically disperse in an ultrasonic device, and react for 2 hours to obtain a dispersion system;

4) Cool the dispersion system obtained in step 3) to 80 °C, add toluene and 15 g of hydrazine whose volume is 1/4 of the volume of the dispersion system, raise the temperature to reflux temperature, and perform a reduction reaction for 5 hours under vigorous stirring to obtain a reaction system B;

5) The reaction system B obtained in step 4) was allowed to stand and layered, and after removing the water layer, the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain graphene.

Example 2

The preparation method of the graphene of the present embodiment, comprises the following steps:

1) Under the condition of mechanical stirring, disperse 1g of natural flake graphite (>300 mesh) in 25ml of concentrated sulfuric acid at a temperature of 10°C, then slowly add 3g of potassium permanganate and 0.5g of sodium nitrate in sequence, and stir for 3 hours, a mixture is obtained;

2) Heat the mixture obtained in step 1) to 35°C, keep it warm for 1 hour, slowly add 45g of distilled water, control the speed of adding water to raise the temperature to 95°C, keep mechanical stirring for 1 hour, then add 70g of deionized water to maintain the temperature to 80°C, after stirring evenly, add 5g of hydrogen peroxide to obtain a bright yellow reaction system A;

3) Under stirring conditions, add sodium carbonate to the reaction system A obtained in step 2) to adjust the pH of the reaction system A to 6, then raise the temperature to 90°C, ultrasonically disperse in an ultrasonic machine, and react for 3 hours to obtain a dispersion system;

4) Cool the dispersion system obtained in step 3) to 80°C, add toluene and 20 g of hydrazine whose volume is 1/3 of the volume of the dispersion system, raise the temperature to the reflux temperature, and carry out the reduction reaction for 8 hours under vigorous stirring to obtain the reaction system B;

5) The reaction system B obtained in step 4) was allowed to stand and layered, and after removing the water layer, the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain graphene.

Example 3

The preparation method of the graphene of the present embodiment, comprises the following steps:

1) Under the condition of mechanical stirring, disperse 1g of natural flake graphite (>300 mesh) in 25ml of concentrated sulfuric acid at a temperature of 15°C, then slowly add 3g of potassium permanganate and 0.5g of sodium nitrate in sequence, and stir for 3 hours, a mixture is obtained;

2) Heat the mixture obtained in step 1) to 50°C, keep it warm for 1 hour, slowly add 45g of distilled water, control the speed of adding water to raise the temperature to 95°C, keep mechanical stirring for 2 hours, then add 70g of deionized water to maintain the temperature at 90°C, after stirring evenly, add 6g of hydrogen peroxide to obtain a bright yellow reaction system A;

3) Under stirring conditions, add sodium carbonate to the reaction system A obtained in step 2) to adjust the pH of the reaction system A to 6, then raise the temperature to 95°C, ultrasonically disperse in an ultrasonic device, and react for 4 hours to obtain a dispersion system;

4) Cool the dispersion system obtained in step 3) to 80°C, add xylene and 20g sodium borohydride whose volume is 1/2 of the volume of the dispersion system, raise the temperature to reflux temperature, and carry out the reduction reaction for 8 hours under vigorous stirring to obtain the reaction System B;

5) The reaction system B obtained in step 4) was allowed to stand and layered, and after removing the water layer, the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain graphene.

Example 4

The preparation method of the graphene of the present embodiment, comprises the following steps:

1) Under the condition of mechanical stirring, disperse 1g of natural flake graphite (>300 mesh) in 25ml of concentrated sulfuric acid at a temperature of 15°C, then slowly add 3g of potassium permanganate and 0.5g of sodium nitrate in sequence, and stir for 5 hours, a mixture is obtained;

2) Heat the mixture obtained in step 1) to 45°C, keep it warm for 1 hour, slowly add 45g of distilled water, control the speed of adding water to raise the temperature to 95°C, keep mechanical stirring for 1.5 hours, then add 70g of deionized water to maintain the temperature to 70°C, after stirring evenly, add 8g of hydrogen peroxide to obtain a bright yellow reaction system A;

3) Under stirring conditions, add sodium carbonate to the reaction system A obtained in step 2) to adjust the pH of the reaction system A to 6, then raise the temperature to 95°C, ultrasonically disperse in an ultrasonic device, and react for 5 hours to obtain a dispersion system;

4) Cool the dispersion system obtained in step 3) to 80°C, add chlorobenzene and 20g vitamin C whose volume is 1/2 of the volume of the dispersion system, raise the temperature to reflux temperature, and carry out the reduction reaction for 10 hours under vigorous stirring to obtain the reaction system B;

5) The reaction system B obtained in step 4) was allowed to stand and layered, and after removing the water layer, the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain graphene.

Example 5

The preparation method of the graphene of the present embodiment, comprises the following steps:

1) Under the condition of mechanical stirring, disperse 1g of natural flake graphite (>300 mesh) in 25ml of concentrated sulfuric acid at a temperature of 5°C, then slowly add 3g of potassium permanganate and 0.5g of sodium nitrate in sequence, and stir for reaction 2 hours, a mixture is obtained;

2) Heat the mixture obtained in step 1) to 45°C, keep it warm for 1 hour, slowly add 45g of distilled water, control the speed of adding water to raise the temperature to 95°C, keep mechanical stirring for 1.5 hours, then add 70g of deionized water to maintain the temperature to 70°C, after stirring evenly, add 7g of hydrogen peroxide to obtain a bright yellow reaction system A;

3) Under stirring conditions, add sodium carbonate to the reaction system A obtained in step 2) to adjust the pH of the reaction system A to 6, then raise the temperature to 95°C, ultrasonically disperse in an ultrasonic device, and react for 5 hours to obtain a dispersion system;

4) Cool the dispersion system obtained in step 3) to 80°C, add tetralin and 50g of ethylenediamine whose volume is 1/4 of the volume of the dispersion system, raise the temperature to reflux temperature, and carry out the reduction reaction under strong stirring for 10 hours, Obtain reaction system B;

5) The reaction system B obtained in step 4) was allowed to stand and layered, and after removing the water layer, the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain graphene.

Experimental example

In this experimental example, the graphene obtained in Example 2 and Example 5 was detected by a scanning electron microscope, and the results are shown in Figures 1 and 2. As can be seen from Figures 1 and 2, the obtained graphene sheet of the method of the present invention has a larger area and a smaller thickness.

In the preparation method of graphene of the present invention, due to the adoption of a two-phase (water phase, organic phase) system, the graphene after reduction is immediately transferred to the organic phase, completely separated from the inorganic matter in the water phase, and only a few minutes are needed after separation. Pure graphene can be obtained by washing and filtering for only one time; while the prior art requires 4-5 days.

Claims (8)

1. a preparation method of graphene, is characterized in that: comprise the following steps: 1) Under stirring conditions, add 1 weight part of graphite into concentrated sulfuric acid and disperse it, then add 3 weight parts of potassium permanganate and 0.5 weight part of sodium nitrate in sequence, and continue stirring for 2 to 5 hours to obtain a mixture; 2) Heat the mixture obtained in step 1) to 30-50°C, keep it warm for 1 hour, add 45 parts by weight of distilled water, continue to heat up to 95°C, and react for 1-2 hours, then add 70 parts by weight of deionized water to keep the temperature 70-90°C, stir evenly and add 5-8 parts by weight of hydrogen peroxide to obtain bright yellow reaction system A; 3) Under stirring conditions, adjust the pH of the reaction system A obtained in step 2) to 6, then raise the temperature to 90-100°C, and ultrasonically disperse for 2-5 hours to obtain a dispersion system; 4) Cool the dispersion system obtained in step 3) to 80°C, add a high-boiling point organic solvent, and then add 15-50 parts by weight of a reducing agent, heat up to reflux temperature, and stir for 5-10 hours to obtain a reaction system B; 5) The reaction system B obtained in step 4) was allowed to stand for stratification, and after the water layer was removed, the organic layer was washed with deionized water until sulfate ions were free, filtered and freeze-dried to obtain the final product. 2. The preparation method of graphene according to claim 1, characterized in that: the graphite in step 1) is natural flake graphite with a particle size greater than 300 mesh. 3. The preparation method of graphene according to claim 1, characterized in that: the amount of concentrated sulfuric acid in step 1) is: 1g of graphite dispersed in 25ml of concentrated sulfuric acid, and the above amount can be adjusted in proportion. 4. The method for preparing graphene according to claim 1 or 3, characterized in that: the temperature of the concentrated sulfuric acid is 5-15°C. 5. The preparation method of graphene according to claim 1, characterized in that: the method for adjusting the pH of the reaction system A in step 3) is: adding sodium carbonate to the reaction system A. 6. The method for preparing graphene according to claim 1, characterized in that: the high-boiling organic solvent in step 4) is toluene, xylene, chlorobenzene, ethylbenzene or tetralin. 7. The method for preparing graphene according to claim 1 or 6, characterized in that: the amount of the high-boiling organic solvent added is: the volume of the high-boiling organic solvent and the dispersion system is 1:2-4. 8 . The method for preparing graphene according to claim 1 , wherein the reducing agent in step 4) is hydrazine, hydroquinone, sodium borohydride, citric acid, vitamin C or ethylenediamine.

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