CN103935989A - Method for preparing graphene by means of flammable solvent reduction - Google Patents

Abstract

A method for preparing graphene by reducing a flammable solvent is to dry graphite oxide; place dry graphite oxide powder in a reaction vessel, ignite it with a combustion aid after impregnating the flammable solvent, and reduce the graphite oxide; after burning, naturally cool down to At room temperature, high-quality graphene is obtained. The invention has the advantages of being simple and practical, cost-effective, high-quality and mass-producible.

Description

A kind of method that flammable solvent reduction prepares graphene

technical field

The invention belongs to a method for preparing graphene, in particular to a process for preparing high-quality graphene by thermally reducing graphite oxide.

Background technique

In the last 30 years, the allotropes of carbon—fullerenes and carbon nanotubes—have attracted extensive attention due to their excellent electronic and mechanical properties and excellent solvent dispersibility. In 1985, Koroto, Curl and Smalley discovered zero-dimensional fullerene (fullerene), prompting researchers to have a strong interest in nanocarbon materials. Then in 1991, Iijima discovered a one-dimensional carbon nanotube (carbon nanotube), which further ignited the research boom of carbon-based nanoparticles. It was not until 2004 that Geim et al. from the University of Manchester in the United Kingdom used a very simple micromechanical exfoliation method to peel off and observe single-layer graphene crystals, which caused a new round of "carbon" craze in the scientific community (Novoselov K S et al. Science , 2004, 306, 666). In 2010, Geim et al. received the Nobel Prize in Physics for this. Graphene is a two-dimensional periodic honeycomb lattice structure composed of carbon six-membered rings. Its C-C bond length is about 0.142 nm. It can be bent and wrapped into zero-dimensional fullerenes and rolled into one-dimensional carbon nanotubes. Or stacked into three-dimensional graphite (graphite), which is also the basic unit of other graphite materials (Geim A K et al. Modern Physics, 2007, 8, 35).

The theoretical specific surface area of graphene is as high as 2630 m ² /g, and its light weight has outstanding thermal conductivity (5000 Wm-1K-1), Young's modulus (1100 GPa) and fracture strength (125 GPa) comparable to single-walled comparable to carbon nanotubes (Moon I K et al. Nature, 2010, 1, 1). Compared with expensive carbon nanotubes and fullerenes, the main raw material of graphene (graphite) is readily available and cheap. These excellent properties and unique nanostructures have made graphene the focus of widespread attention in recent years, and it has broad application prospects in many fields. For example, graphene can be used to make supercapacitors, transistors, integrated circuits, gas sensors, lithium batteries, catalyst supports, reinforcing fillers, etc.

For many years, people have been exploring high-quality, high-yield and low-cost graphene preparation methods. At present, there are four commonly used preparation methods: micromechanical exfoliation method (Novoselov K S et al. Science, 2004, 306, 666), graphene oxide reduction method (Yang S J et al. Carbon, 2013, 53, 73), epitaxial growth (Borovikov V et al. Progress in Physics, 2009, 80,12) and chemical vapor deposition (Reina A et al. Nano Letters, 2009,9,1). Although micromechanical exfoliation is a simple method for preparing graphene, which is very useful for theoretical research in the laboratory, it is time-consuming and laborious, the size is difficult to precisely control, and the repeatability is poor, making it difficult to produce and apply it on a large scale. Epitaxial growth method and chemical vapor deposition method are also a more potential method. However, the equipment used in these two methods is expensive and difficult to produce continuously; it has always been a challenge to prepare graphene with large area and uniform thickness and its excellent electrical properties. The graphite oxide reduction method is currently considered to be an effective method for preparing graphene in batches. In this method, graphite powder is strongly oxidized first; then deoxidized by different methods such as reducing solvent method or thermal expansion method to prepare graphene with low oxygen content. The advantage of this method is that the raw materials of graphite powder used are easy to obtain, the preparation process is simple, and graphene can be prepared in batches. The disadvantage is that during the reduction process of graphite oxide, the loss of the high-temperature furnace is large (thermal expansion method), and impurities are introduced (reduction solvent method); and the quality of the graphene produced is low, and there are many structural defects, which cause the characteristics of graphite to be significantly reduced. The physical, chemical and mechanical properties of alkenes limit its further wide application.

Contents of the invention

Aiming at the deficiencies in the prior art, the object of the present invention is to provide a simple, practical, cost-effective, high-quality and mass-producible method for preparing graphene by reduction of flammable solvents.

In the present invention, in the state of graphite oxide powder or block, a combustible solvent is added to uniformly disperse and infiltrate, and different concentrations of oxygen are introduced in the normal pressure environment, and the graphite oxide powder infiltrated by the combustible solvent is ignited in the reaction chamber. Graphite is quickly reduced in the flame generated by the flammable solvent, and at the same time, the lattice defects are repaired by the plasma in the flame, and collected through the collection container to obtain high-quality graphene.

The method for preparing graphene of the present invention comprises the steps:

(1) Graphite oxide is dried;

(2) Put the dry graphite oxide powder in the reaction container, ignite it with a combustion aid after impregnating the flammable solvent, and reduce the graphite oxide;

(3) After the combustion is over, cool down to room temperature naturally to obtain high-quality graphene.

The invention is to reduce the graphene oxide by introducing the flame generated by the combustion aid oxygen in a combustible solvent system. The method of exfoliating and reducing graphite oxide at high temperature, so there is no specific limitation on graphite oxide, any graphite oxide obtained from oxidized graphite can be used in the present invention. Preferably, the graphite oxide described in the present invention is obtained by strong oxidation of graphite, and the surface layer and sides of the oxidized graphite are loaded with a large number of oxygen-containing groups, that is, graphite oxide. In the prior art, the preparation methods of graphite oxide mainly include three oxidation methods: Brodie method, Hummers method or Staudenmaier method.

Preferably, the preparation method of graphite oxide is preferably selected from any one of Brodie method, Hummers method or Staudenmaier method.

The drying method of graphite oxide is a method well known to those skilled in the art, such as spray drying, low temperature freeze drying, vacuum heating drying, normal pressure heating drying and the like. The present invention does not limit the means of drying, and all methods that can obtain dry graphite oxide can be used in the present invention.

The graphite oxide powder particle size of the present invention is 1-500 μm, more preferably 1-200 μm, particularly preferably 1-100 μm.

The graphite oxide reduction described in the present invention needs to be carried out in a flammable solvent system, and the temperature and plasma generated by the flame are used to strip and reduce graphite oxide, remove most of the oxygen-containing functional groups in graphite oxide, and repair the structure in graphene at the same time defects, thereby effectively reducing and exfoliating graphite oxide. The combustion enhancer of the present invention is a mixed gas or air of different concentrations of oxygen gas and nitrogen, and the volume percentage of oxygen in the mixed gas is 21%-100%, more preferably 21%-50%, especially preferably 21%-30% ;

The flammable solvent of the present invention is a liquid that can be ignited at normal temperature, including various flammable liquids, which are respectively primary flammable liquids: acetone, methanol, acetaldehyde, benzene, ethanol, gasoline, etc.; secondary flammable liquids : butenol, acetic acid, butyl acetate, turpentine, kerosene, etc.; tertiary flammable liquids: propylenediamine, nonanol, ethyl caproate, diethylenetriamine; quaternary flammable liquids: dioctyl adipate, Dibutyl phthalate, dioctyl phthalate, etc. Further preferred are primary flammable liquids: acetone, methanol, acetaldehyde, benzene, ethanol, gasoline, etc.; secondary flammable liquids: butenol, acetic acid, butyl acetate, turpentine, kerosene, etc.; particularly preferably a flammable Sexual liquids, including acetone, methanol, acetaldehyde, benzene, ethanol, etc.

In order to achieve high temperature resistance (300-2000°C) and a closed reaction vessel that can be fed with a combustion enhancer under normal pressure, the reaction vessel described in the present invention can be used by those skilled in the art according to their own professional knowledge and related information, and according to actual conditions. Make a selection. The heating method of the high temperature resistant reaction furnace of the present invention can be selected from resistance heating, induction heating and the like. Preferably, the high-temperature reaction furnace in the present invention is selected from any one of a reactor and a calciner, more preferably a reactor.

The atomic ratio of the carbon element and the oxygen element of the graphene prepared by the present invention is 6-50, such as 6, 10, 14, 36, 41, 50, etc., and the atomic ratio of the carbon element and the oxygen element of the graphene is controlled to 8 -50, further control 8-20. The specific surface area of graphene is 400-1600 m ² /g, such as 300, 680, 800, 890, 910, 970, 1060, 1350, 1600 m ² /g, etc. The conductivity of graphene is 400-1200 S/m, such as 200, 305, 440, 560, 680, 720, 860, 1100 S/m, etc.

The graphene prepared by the present invention is used for energy storage active materials, preferably for hydrogen storage, lithium ion batteries, supercapacitors or fuel cells, as well as nanoelectronic devices, high frequency circuits, photon sensors, gene electronic sequencing and noise reduction.

The method provided by the invention has a simple preparation process, each node in the process can be precisely controlled, can realize efficient and high-quality reduction of graphene oxide materials, and solve the problems of environmental pollution, incomplete reduction, and reduction time in the prior art. Waiting question.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The present invention burns and reduces graphite oxide under normal pressure and repairs defects, has low energy consumption and can better remove oxygen-containing functional groups in graphene oxide, and at the same time repair structural defects in graphene, thereby producing high-quality graphite alkene;

(2) The process of the present invention avoids the use of a large number of toxic chemical reagents and high-power heating equipment, has little environmental pollution, and is suitable for the reduction of various graphene oxide powders prepared by various methods;

(3) The reduction time of the present invention is short, the reduction is thorough, the operation is simple, and the conditions are easy to control;

(4) The present invention can achieve high-efficiency and high-quality reduction of graphene oxide materials, and the ratio of C/O is at least 6. According to the difference in reaction temperature, time and residual amount of oxidizing gas, the oxygen-containing functional groups can be completely removed in theory ;

(5) The specific surface area of the graphene material provided by the present invention is significantly higher than the graphene prepared by the prior art.

Description of drawings

Figures 1a-c are scanning electron micrographs of reduced graphene in Examples 1, 4, and 10 of the present invention, respectively.

Detailed ways

In order to facilitate understanding of the present invention, the present invention enumerates the following examples. It should be clear to those skilled in the art that the embodiments are only for helping to understand the present invention, and should not be regarded as specific limitations on the present invention.

Example 1:

First, graphite oxide was prepared according to the Hummers method, and graphite oxide blocks were obtained after vacuum drying. After crushing and sieving, 50-150 μm graphite oxide powder is obtained. Weigh 100 mg of graphite oxide, add enough absolute ethanol to fully impregnate for 2 minutes, place it in the reactor, pass through the oxygen/nitrogen mixed gas with an oxygen content of 73% (volume percentage), and ignite the sample through the ignition device. The sample is combusted with the assistance of oxygen, and the temperature is naturally cooled to room temperature after the combustion reaction is completed. The graphene material obtained after reduction has a specific surface area of 1200 m ² /g and an electrical conductivity of 900 S/m. Before reduction, the atomic ratio of carbon and oxygen in graphite oxide (C/O ratio) is only 1.6. After reduction, due to the removal of a large number of oxygen-containing functional groups, the C/O ratio increases to 10.41.

Example 2

Firstly, graphite oxide was prepared according to the Staudenmaier method, graphite oxide powder was obtained after freeze-drying, and graphite oxide powder of 80-200 μm was obtained by sieving. Weigh 100 g of the graphite oxide powder, add enough butenyl alcohol solvent to fully impregnate for 20 min, and place it in the reactor. Introduce an oxygen/nitrogen mixed gas with an oxygen content of 29% (volume percentage), seal the reactor and ignite the sample through an ignition device. The sample is combusted with the assistance of a high-oxygen combustion aid, and the temperature is naturally cooled to room temperature after the combustion is completed. The graphene material obtained after reduction has a specific surface area of 700 m ² /g and an electrical conductivity of 650 S/m. The atomic ratio of carbon and oxygen in graphite oxide before reduction (C/O ratio) is only 1.52. After reduction, the C/O ratio increased to 8 due to the removal of most of the oxygen-containing functional groups.

Example 3

First prepare graphite oxide according to the Brodie method, obtain graphite oxide powder after spray drying, and obtain 1-100 μm graphite oxide powder by sieving. Weigh 500 g of the graphite oxide powder, add enough propylenediamine solvent to fully impregnate for 62 min, and place in the reactor. Introduce a mixed gas of oxygen/nitrogen with an oxygen content of 35% (volume percentage) to support combustion, and ignite the sample through an ignition device. The sample is combusted with the assistance of a high-oxygen combustion aid, and the temperature is naturally cooled to room temperature after the combustion is completed. The specific surface area of the obtained graphene material after reduction is 1600 m ² /g, and the electrical conductivity is 1000 S/m. The atomic ratio of carbon and oxygen in graphite oxide before reduction (carbon-to-oxygen atomic ratio C/O) is only 1.41. After reduction, the C/O was increased to 18 due to the removal of a large number of oxygen-containing functional groups.

Example 4

First, graphite oxide was prepared according to the Hummers method, graphite oxide powder was obtained after spray drying, and graphite oxide powder of 100-300 μm was obtained by sieving. Weigh 310 g of the graphite oxide powder, add enough diethylenetriamine solvent to impregnate for 38 min, and place it in the reactor. Introduce a mixed gas containing 62% (volume percent) oxygen/nitrogen, and ignite the sample through the ignition device. The sample is combusted with the assistance of a high-oxygen combustion aid, and the temperature is naturally cooled to room temperature after the combustion is completed. The graphene material obtained after reduction has a specific surface area of 650 m ² /g and an electrical conductivity of 490 S/m. The carbon and oxygen atomic ratio (C/O ratio) of graphene oxide before reduction is only 1.63. After reduction, the C/O ratio increased to 9 due to the removal of a large number of oxygen-containing functional groups.

Example 5

Firstly, graphite oxide was prepared according to the Staudenmaier method, heated and dried under normal pressure to obtain graphite oxide block, then crushed to obtain graphite oxide powder, and then crushed and sieved to obtain 200-350 μm graphite oxide powder. Weigh 50 g of the graphene oxide powder, add enough dioctyl adipate solvent to impregnate for 15 min, and place it in the reactor. Introduce a 20% oxygen/nitrogen mixed gas to support combustion, and ignite the sample through the ignition device. It burns at high temperature and cools down to room temperature naturally after burning. The graphene material obtained after reduction has a specific surface area of 900 m ² /g and an electrical conductivity of 500 S/m. The carbon and oxygen atomic ratio (C/O ratio) of graphene oxide before reduction is only 1.56. After reduction, the C/O ratio increased to 8.6 due to the removal of a large number of oxygen-containing functional groups.

Embodiment 6:

First, graphite oxide was prepared according to the Hummers method, and graphite oxide blocks were obtained after vacuum drying. 1-80 μm graphite oxide powder is obtained by crushing and sieving. Weigh 10 g of graphite oxide and place it in the reactor, add sufficient methanol to fully impregnate it for 48 min, then transfer it to the reactor for ignition, and pass a mixed gas of oxygen content of 35% oxygen/nitrogen under normal pressure environment conditions, through The ignition device ignites the sample. The sample is combusted with the assistance of oxygen, and the temperature is naturally cooled to room temperature after the reaction is completed. The graphene material obtained after reduction has a specific surface area of 1200 m ² /g and an electrical conductivity of 765 S/m. Before reduction, the atomic ratio of carbon and oxygen in graphite oxide (C/O ratio) was only 1.6. After reduction, the C/O ratio increased to 11 due to the removal of a large number of oxygen-containing functional groups.

Example 7

First, prepare graphite oxide according to the Staudenmaier method, obtain graphite oxide powder after spray drying, and obtain 20-120 μm graphite oxide powder by sieving. Weigh 200 g of the graphite oxide powder, add enough gasoline solvent to impregnate for 50 min, and place it in the reactor . Introduce a mixed gas of oxygen/nitrogen with an oxygen content of 62%, and ignite the sample through an ignition device. The sample is combusted with the assistance of a high-oxygen combustion aid, and the temperature is naturally cooled to room temperature after the combustion is completed. The graphene material obtained after reduction has a specific surface area of 923 m ² /g and an electrical conductivity of 670 S/m. The carbon and oxygen atomic ratio (C/O ratio) of graphene oxide before reduction is only 1.63. After reduction, the C/O ratio increased to 20 due to the removal of a large number of oxygen-containing functional groups.

Example 8

Firstly, graphite oxide was prepared according to the Staudenmaier method, graphite oxide block was obtained after vacuum drying, and graphite oxide powder of 1-100 μm was obtained by crushing and screening. Weigh 2 g of the graphene oxide powder, add enough acetone solvent to impregnate for 3 min, and place it in the reactor. Introduce air to support combustion, and ignite the sample through the ignition device. It burns at high temperature and cools down to room temperature naturally after burning. The graphene material obtained after reduction has a specific surface area of 860 m ² /g and an electrical conductivity of 500 S/m. The carbon and oxygen atomic ratio (C/O ratio) of graphene oxide before reduction is only 1.56. After reduction, the C/O ratio increased to 13 due to the removal of a large number of oxygen-containing functional groups.

Example 9

Firstly, graphite oxide was prepared according to the Hummers method, and graphite oxide powder was obtained after freeze-drying. After sieving, 100-400 μm graphite oxide powder is obtained. Weigh 3 g of graphite oxide powder, add enough benzene to fully impregnate it for 4 min, place it in the reactor, pass air into it to support combustion, and ignite the sample through the ignition device. The sample is combusted with the assistance of air, and the temperature is naturally cooled to room temperature after the combustion reaction is completed. The graphene material obtained after reduction has a specific surface area of 500 m ² /g and an electrical conductivity of 930 S/m. Before reduction, the atomic ratio of carbon and oxygen in graphite oxide (C/O ratio) was only 1.62. After reduction, due to the removal of a large number of oxygen-containing functional groups, the C/O ratio increased to 11.21.

Example 10

Firstly, graphite oxide was prepared according to the Hummers method, and graphite oxide powder was obtained after freeze-drying. 1-150 μm graphite oxide powder is obtained by sieving. Weigh 5 g of graphite oxide, add enough kerosene to fully impregnate it for 20 min, then place it in the reactor, feed a 20% oxygen/nitrogen mixed gas to support combustion, and ignite the sample through the ignition device. The sample is combusted with the assistance of oxygen, and the temperature is naturally cooled to room temperature after the combustion reaction is completed. The graphene material obtained after reduction has a specific surface area of 600 m ² /g and an electrical conductivity of 900 S/m. Before reduction, the atomic ratio of carbon and oxygen in graphite oxide (C/O ratio) was only 1.46. After reduction, due to the removal of a large number of oxygen-containing functional groups, the C/O ratio increased to 7.52.

Example 11

Firstly, graphite oxide was prepared according to the Hummers method, and graphite oxide blocks were obtained after being heated and dried under normal pressure. After crushing and sieving, 150-350 μm graphite oxide powder is obtained. Weigh 200 mg of graphite oxide, add enough acetaldehyde to fully impregnate it for 8 minutes, place it in the reactor, pass air into it to support combustion, and ignite the sample through the ignition device. The sample is combusted with the assistance of air, and the temperature is naturally cooled to room temperature after the combustion reaction is completed. The graphene material obtained after reduction has a specific surface area of 410 m ² /g and an electrical conductivity of 430 S/m. Before reduction, the atomic ratio of carbon and oxygen in graphite oxide (C/O ratio) was only 1.48. After reduction, due to the removal of a large number of oxygen-containing functional groups, the C/O ratio increased to 6.21.

The applicant declares that the present invention illustrates the detailed process equipment and process flow of the present invention through the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, that is, it does not mean that the present invention must rely on the above-mentioned detailed process equipment and process flow process can be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc., all fall within the scope of protection and disclosure of the present invention.

Claims (16)

1. a method for Graphene is prepared in combustible solvent reduction, it is characterized in that comprising the steps:

Graphite oxide is dried;

To be dried graphite oxide powder and be placed in reaction vessel, after combustible solvent dipping, ignite with ignition dope, make graphite oxide reduction;

After burning finishes, be naturally cooled to room temperature, obtain high-quality graphene.

2. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 1, and the preparation method who it is characterized in that described step (1) graphite oxide is selected from any one in Brodie method, Hummers method or Staudenmaier method.

3. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 1, it is characterized in that described step (1) drying means for spraying is dry, frozen drying, vacuum and heating drying or normal heating dry.

4. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 1, it is characterized in that described step (2) graphite oxide powder footpath is 1-500 μ m.

5. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 4, it is characterized in that described step (2) graphite oxide powder footpath is 1-200 μ m.

6. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 5, it is characterized in that described step (2) graphite oxide powder footpath is 1-100 μ m.

7. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 1, it is characterized in that the described ignition dope of described step (2) is mixed gas or the air of oxygen and nitrogen, and in mixed gas, oxygen volumn concentration is 21%-100%.

8. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 7, it is characterized in that the described ignition dope of described step (2) is mixed gas or the air of oxygen and nitrogen, and in mixed gas, oxygen volumn concentration is 21%-50%.

9. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 8, it is characterized in that the described ignition dope of described step (2) is mixed gas or the air of oxygen and nitrogen, and in mixed gas, oxygen volumn concentration is 21%-30%.

10. the method for Graphene is prepared in a kind of combustible solvent reduction as claimed in claim 1, it is characterized in that the described combustible solvent of described step (2) is for being respectively one-level inflammable liquid: acetone, methyl alcohol, acetaldehyde, benzene, ethanol or gasoline; Secondary inflammable liquid: butenol, acetic acid, butylacetate, turps or kerosene; Three grades of flammable liquids: propylene diamine, nonyl alcohol, ethyl hexanoate or Diethylenetriamine; Level Four flammable liquid: adipic acid dioctyl ester, phthalic acid dibutyl ester or dioctyl phthalate.

The method of Graphene is prepared in 11. a kind of combustible solvent reduction as claimed in claim 10, it is characterized in that described step (2) combustible solvent is one-level inflammable liquid: acetone, methyl alcohol, acetaldehyde, benzene, ethanol or gasoline; Secondary inflammable liquid: butenol, acetic acid, butylacetate, turps or kerosene.

The method of Graphene is prepared in 12. a kind of combustible solvent reduction as claimed in claim 11, it is characterized in that described step (2) combustible solvent is acetone, methyl alcohol, acetaldehyde, benzene or ethanol.

The method of Graphene is prepared in 13. a kind of combustible solvent reduction as claimed in claim 1, it is characterized in that described reactor is high temperature resistant 300-2000 DEG C, and under normal pressure, can pass into the closed reaction vessel of ignition dope.

Product prepared by the method for Graphene is prepared in 14. a kind of combustible solvent reduction as described in claim 1-13 any one, it is characterized in that the carbon of product Graphene and the atomic ratio of oxygen element are 6-50, and specific surface area is 400-1600m ²/ g, specific conductivity is 400-1200S/m.

Product prepared by the method that Graphene is prepared in 15. a kind of combustible solvent reduction as claimed in claim 14, is characterized in that the carbon of product Graphene and the atomic ratio of oxygen element are 8-50.

Product prepared by the method that Graphene is prepared in 16. a kind of combustible solvent reduction as claimed in claim 15, is characterized in that the carbon of product Graphene and the atomic ratio of oxygen element are 8-20.