WO2020009421A1

WO2020009421A1 - Method for producing graphite oxide and graphene oxide in eco-friendly manner by using hydroxylation reaction

Info

Publication number: WO2020009421A1
Application number: PCT/KR2019/008034
Authority: WO
Inventors: 이중희; 박옥경; 김남훈
Original assignee: 전북대학교산학협력단
Priority date: 2018-07-03
Filing date: 2019-07-02
Publication date: 2020-01-09
Also published as: KR102072914B1; KR20200004126A

Abstract

The present invention relates to an eco-friendly efficient oxidation method for producing graphite oxide (O-Gr) and high-conductivity graphene oxide (GO) by using a chemical oxidation reaction capable of introducing a hydroxyl group into a carbon crystal lattice. More specifically, instead of conducting an oxidation reaction within a strong acid solution that is typically used as a reaction solvent when producing graphite oxide from graphene, such as sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), and nitric acid (HNO₃), the oxidation method of the present invention uses deionized water (DI-water) as a reaction solvent for the oxidation reaction, and by adding graphite, sodium hydroxide, and potassium permanganate to the DI-water, induces a chemical oxidation reaction, producing O-Gr and high-conductivity GO having reduced lattice defects by using same. The oxidation method according to the present invention can dramatically decrease the processing time and costs required for the process of treating and neutralizing acidic wastewater generated from post-reaction washing/neutralization processes in O-Gr production, and thus can increase the efficiency of product production and reduce the costs thereof, providing a great advantage in the mass-production of O-Gr and GO.

Description

Eco-friendly method for producing graphite oxide and graphene oxide using hydroxide reaction

This application claims the priority of Korean Patent Application No. 10-2018-0077191, filed July 03, 2018, the entirety of which is a reference of the present application.

The present invention relates to a method for environmentally friendly production of graphite oxide and graphene oxide using a chemical oxidation reaction capable of introducing a hydroxyl group (-OH) to the surface of the carbon crystal structure, and more specifically, graphite Oxidation reaction on strong acid solutions such as sulfuric acid (H ₂ SO ₄ ), phosphoric acid (Phosphoric acid, H ₃ PO ₄ ), nitric acid (HNO ₃ ) In the oxidation reaction, the reaction solvent is used as distilled water (DI-water), and graphite, sodium hydroxide, and potassium permanganate are added to the distilled water to induce a chemical oxidation reaction to sp ² bonds between carbon and carbon. Graphite oxide (O-Gr) and a high-conductivity graphene oxide (GO) using the same to rapidly reduce the rate of crystal defects generated in the oxidation process The present invention relates to an oxidation process that is environmentally friendly and can improve production efficiency. The oxidation method according to the present invention breaks down the neutralization process time, which accounts for most of the acid wastewater treatment and graphite oxide manufacturing process time, which occur in the washing / neutralization process after the oxidation reaction required by the conventional Hummer 'method in terms of the production of graphite oxide. Can be reduced to reduce product production efficiency and cost, providing a great advantage in the industrial mass production of graphite oxide and graphene oxide.

Graphene is a two-dimensional carbon allotrope consisting of carbon-to-carbon bonds, and has excellent mechanical properties as well as low electrical resistivity and high thermal conductivity. Graphene is generally manufactured using chemical oxidation / reduction method and chemical vapor deposition method (CVD), and when the chemical vapor deposition method is used, it is possible to produce high quality graphene. Although it is difficult to industrialize mass, it has a limitation that its application is difficult in various industries. In order to manufacture graphene oxide and graphene products having cost and technical competitiveness, mass production of graphene oxide should be preceded as an essential prerequisite.

In industries that need to incorporate a large amount of graphene, the method of preparing graphene oxide or graphene using chemical oxidation / reduction method that is easy to mass-produce is compared with the method of preparing graphene using chemical vapor deposition. It is considered as a useful method in terms of productivity or price competitiveness. In general, graphene oxide reacts graphite with oxidizing agents such as potassium permanganate (KMnO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) in strong acidic solutions such as sulfuric acid, nitric acid, and phosphoric acid. After forming on the surface, the graphene oxide is prepared by applying a shear force through an ultrasonic disperser, a fine homogenizer, or the like and peeling it into a single layer or an aqueous layer. The prepared graphene oxide finally removes the oxygen functional groups formed on the surface through thermal and chemical reduction methods to finally prepare graphene.

However, the method for preparing graphene using a strong acid solution / acid mixture requires a considerably long process time in the process of neutralizing the pH of the reaction mixture to 6 to 7 while washing the acid solvent after the oxidation reaction. Since a large amount of acidic wastewater treatment process is required, additional costs are required in terms of product commercialization and wastewater treatment in terms of product commercialization, resulting in an improvement in the manufacturing cost of the product. The long neutralization process time and the problem of the large amount of wastewater treatment process will be a big consideration in terms of mass production and commercialization of graphene in the future, and it will be greatly noticed in various industries as a preliminary task that requires a technical solution in terms of manufacturing process. have. In addition, due to the acid removal / refining process that requires a long time, there is a problem that a high speed graphene oxide synthesis process is difficult to be disposed in a continuous process.

As mentioned above, various studies related to eco-friendly oxidation methods using weak acid or no acid in the process of manufacturing graphene oxide to address the problems in the manufacturing process of products in the industry have recently been greatly attracting attention. have.

Professor G. Drummond of the Center de Recherche Paul Pascal (CRPP) in France disperses natural graphite containing potassium (Potassium, K) ions intercalated onto Tetrahydrofuran (THF) to carry a negative charge. Reported the results of research on a technique for preparing a highly crystalline graphene having a reduced mixing ratio by preparing a mixed solution in which graphene is dispersed and then dispersing it in a degassed distilled water (Nature Chemistry, 2017). , C. Drummond et al., 2017, 9, 347). In this case, it is possible to prevent the graphene material bunching phenomenon between caused by bubbles present in the distilled Water hydroxide ions (OH ^-) is adsorbed by the ion bonded to the graphene surface to improve the compatibility (compatibility) with distilled water The prepared graphene was allowed to form a uniform dispersed phase on distilled water. However, this study also requires an organic pretreatment process step because of the first pretreatment on tetrahydrofuran, an organic solvent, and because of the presence of hydroxyl groups through ionic bonds, the dispersion stability is abrupt due to weak chemical bond persistence. There is a problem that can be reduced.

S. Sarkar, Ph.D., a research team at the Indian Institute of Engineering Science and Technology in India, uses a method of preparing graphite oxide without acid solution by injecting nitrogen dioxide (NO ₂ ) gas into the reactant, not acid solution. The results were reported to Chemistry Select in 2017 (Chemistry Select, S. Sarkar et al., 2017, 2, 5564). Carbon dioxide having a carbon-carbon double bond such as graphite or fullerene is dispersed in a dichloromethane (DCM) solution, followed by injection of nitrogen dioxide, so that NO ₂ ions are sp ² bonds between the carbon atoms and π-π interactions. Hydroxyl groups (-OH) and ketones (C = O) as NO ₂ H is removed during the formation of chemical bonds by action and washing in aqueous sodium hydroxide (NaOH) and hydrochloric acid (HCl) solutions Graphite oxide with groups formed on the surface was produced. In this case, however, the acid wastewater solution is generated during the reaction in the organic solution, the NO ₂ ions are injected, and the washing process is carried out, and the production cost is increased by injecting excess nitrogen dioxide into the solution. This increases, causing a problem of decreasing physical properties.

In order to shorten the process time for producing graphite oxide and graphene oxide, researches to adjust the reaction rate through strong acid and temperature control have been proposed through various methods. This leads to the problem of an additional cost for processing. Therefore, in the production of graphite oxide or graphene oxide through a chemical synthesis method, while reducing the manufacturing process time, more environmentally friendly methods are being sought.

Accordingly, the inventors of the present invention provide a method for producing an environmentally friendly graphite oxide comprising reacting an alkali ion, an oxidizing agent and a carbon source in a distilled water solution or a hydrophilic organic solvent to chemically oxidize the carbon source. It provides a method for producing high conductivity graphene oxide comprising the step of peeling through the shear stress or ultrasonic dispersion by addition to the phase and a method for producing graphene through a method of chemically reducing or thermally reducing the graphene oxide. .

The present invention provides a method for producing environmentally friendly graphite oxide comprising the following steps.

(i) chemically oxidizing the carbon source by reacting an alkali metal ion, an oxidant and a carbon source in distilled water or a hydrophilic organic solvent;

(ii) adding hydrogen peroxide to the oxidized reactant and stirring to terminate the reaction; And

(iii) washing the reactant with distilled water to produce graphite oxide.

In addition, it provides a method for producing graphene oxide comprising the following steps of the present invention.

(i) adding graphite oxide prepared by the above method to an organic solvent or distilled water; And

(ii) exfoliating graphite oxide in the organic solvent or distilled water through shear stress or ultrasonic dispersion to produce graphene oxide.

In another aspect, the present invention provides a method for producing graphene comprising the following steps.

(i) adding graphite oxide prepared by the above method to an organic solvent or distilled water;

(ii) exfoliating graphite oxide in the organic solvent or distilled water through shear stress or ultrasonic dispersion to produce graphene oxide; And

(iii) preparing graphene by adding a reducing agent to the graphene oxide.

(i) adding graphite oxide prepared by the above-mentioned preparation method onto an organic solvent or distilled water;

(iii) preparing graphene by heat treating the graphene oxide at 500 ° C. or higher.

Graphite oxide and graphene oxide prepared by the present invention is because the oxidation reaction is carried out in distilled water without using an acidic solution, the defects on the surface of the graphite oxide prepared in comparison with the oxidation reaction using a conventionally used strong acid The rate of formation can be reduced to result in the production of high conductivity graphene oxide. In addition, since no acidic solution is used as the reaction solvent, a neutralization process that takes most of the time for preparing graphene oxide is not required, and thus, a process time for producing graphite oxide can be significantly reduced. In addition, an excessive amount generated in the neutralization process Since it does not produce acidic wastewater solution, it is possible to remove industrial wastewater treatment process later. This will significantly reduce the manufacturing cost and production time of the product will provide a great advantage in terms of cost competitiveness and production process efficiency in terms of commercialization of graphene oxide.

1 illustrates a schematic diagram of an oxidation reaction of natural graphite using an oxidation reaction on distilled water according to one embodiment of the present invention.

2 shows Fourier transform infrared spectroscopy (FT-IR) analysis results of Example 1 according to an embodiment of the present invention.

Figure 3 shows the results of thermogravimetric analysis (TGA) of graphene according to Example 1 and Comparative Example 2 according to an embodiment of the present invention.

Figure 4 shows the results of confirming the change of the dispersion phase of Example 1 according to an embodiment of the present invention on distilled water and enmethylpyrrolidone (N-Methyl Pyrrolidone, NMP).

5 is GO-1 (using the graphene oxide and Hummer 'oxidation method of Example 2 prepared through a process of peeling by applying a shearing force through ultrasonic dispersion in Example 1 according to an embodiment of the present invention) Comparative Example 1) is shown through the analysis of the atomic force microscope (Atomic Force Microscope, AFM).

6 is D-band and G of GO-1 (Comparative Example 1) prepared using Example 2 and Hummer 'oxidation method prepared by exfoliating Example 1 through ultrasonic dispersion according to an embodiment of the present invention. The Raman graph shows the change in intensity ratio (I _D / I _G ) of the -band.

7 is a result of comparing the electrical conductivity of Example 1 and GO-1 (Comparative Example 1) prepared using the Hummer 'oxidation method according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described. The present invention has been described with reference to the embodiments presented in the drawings, which are described as one embodiment, whereby the technical details of the present invention and its core configuration and operation are not limited.

In general, graphene oxide is a rapid chemical oxidation method in which graphite is reacted with an oxidizing agent such as potassium permanganate (KMnO ₄ ) and hydrogen peroxide (H ₂ O ₂ ) in strong acid solutions such as sulfuric acid, nitric acid, and phosphoric acid. After the oxygen functional group is formed on the surface through the ultrasonic disperser, fine homogenizer, etc. by applying a shear force (Shear force) is produced through the process of peeling into a single layer or a water layer. However, the method for producing graphite oxide using a strong acid solution / acid mixture requires a fairly long process time in the process of neutralizing the pH of the reaction mixture to 6 to 7 while washing the acid solvent after the oxidation reaction, There is a disadvantage in that a large amount of wastewater treatment process generated in the treatment process is required. In addition, due to the acid removal / refining process that requires a long time, there is a problem that a high speed graphene oxide synthesis process is difficult to be disposed in a continuous process.

In order to overcome the above problems, in the present invention, in the method for producing graphite oxide from graphite, the chemical oxidation reaction is induced by using an aqueous solution containing alkali ions and oxidizing agent of the osmium tetroxide (OsO4) series In addition, the reaction solvent was used as distilled water (DI-water), and it was confirmed that graphite oxide could be efficiently produced by drastically reducing the production time in terms of environment-friendly and process. In the present invention, natural graphite, sodium hydroxide (NaOH) and potassium permanganate (KMnO ₄ ) were added to 50 mL of distilled water, followed by stirring at 60 ° C. for 3 days (FIG. 1). After the reaction was quenched by adding hydrogen peroxide to the oxidized graphite, the reaction was terminated, washed with distilled water and 30 wt% hydrochloric acid (HCl) aqueous solution, removing the remaining unreacted oxidant, filtration and lyophilization, and finally, graphite oxide. Was prepared.

The present invention provides a method for producing an affinity graphite oxide comprising the following steps.

(iii) preparing the graphite oxide by washing the reacted product with distilled water and an acid solution.

The alkali metal ion may be any one or more selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), barium hydroxide (BrOH) and lithium hydroxide (LiOH), preferably sodium hydroxide.

The molar concentration of the alkali metal may be 1 mol to 50 mol, preferably 10 mol to 40 mol, and most preferably 20 to 25 mol.

The oxidizing agent may be any one or more selected from the group of onium tetraoxide consisting of potassium permanganate, potassium chlorate, perchloric acid, and hydrogen peroxide, and preferably potassium permanganate.

The molar concentration of the oxidant may be 1 mol to 50 mol, preferably 10 mol to 40 mol, and most preferably 20 to 25 mol.

Chemical ion bonding between the alkali metal and hydroxyl by the oxidizing agent may form an alkali hydroxide material that generates hydroxide ions and alkali ions in an aqueous solution. In detail, the above-mentioned method can be used to form graphite between carbon and carbon atoms on a graphite surface through a chemical reaction between sodium hydroxide (NaOH) in distilled water and potassium oxidant (Potassium permanganate, KMnO ₄ ). Conversion of sp ² bonds to sp ³ bonds can form hydroxyl (Hydroxyl, -OH) functional groups. As a result of comparing the graphite oxide and natural graphite of the present invention, it was confirmed that graphite oxide containing about 15 wt% of an oxygen functional group was prepared (FIG. 3).

The carbon source may be any one selected from the group consisting of carbon nanotubes, carbon nanowires, carbon nanofibers, graphite, activated carbon, and graphene having sp ² bonds between carbon atoms, preferably graphite.

The hydrophilic organic solvent is selected from the group consisting of dimethylformamide (Dimethylformamide, DMF), ethylenepyrrolidone (N-Methyl Pyrrolidone, NMP), dimethyl sulfoxide (Dimethyl sulfoxide, DMSO) and ethanol (Ethanol, EtOH) It can be either.

In the step (i), the reaction may be performed at 40 ° C. to 80 ° C. for 1 day to 10 days, preferably at 50 ° C. to 70 ° C. for 1 day to 8 days, and more preferably The reaction may proceed for 2 to 6 days at 55 ℃ to 65 ℃.

The (ii) may be stirred for 1 minute to 120 minutes at room temperature, preferably the reaction may proceed for 1 to 60 minutes at 15 ℃ to 35 ℃, more preferably 1 at 20 ℃ to 30 ℃ The reaction may proceed for 30 minutes.

The present invention also provides a method for producing graphene oxide comprising the following steps.

Adding graphite oxide prepared by the above method to an organic solvent or distilled water; And

Graphene oxide is prepared by peeling graphite oxide in the organic solvent or distilled water through shear stress or ultrasonic dispersion.

The organic solvent may be any one or more selected from the group consisting of water, methanol, ethanol, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethylformamide, and mixtures thereof, as a hydrophilic solvent. Preferably N-methylpyrrolidone.

In the above method, when hydroxyl (-OH) group is formed while converting double bond (sp ² ) between carbon-carbon atoms constituting graphite or carbon material into single bond (sp ³ ) between carbon-carbon atoms, Accordingly, since oxygen functional groups are formed on the surface of the carbon material, dispersibility is improved in organic solvents / distilled water, and as a result, a peeling reaction is performed by a shear force applied from the outside, thereby producing graphene oxide of a single layer or a water layer. Can be. After adding the graphite oxide of the present invention to distilled water and NMP phase and proceeding a peeling process through an ultrasonic disperser for 30 minutes, the dispersibility over time was observed to show the dispersed phase even after 30 days (FIG. 4). ). In addition, the graphite oxide prepared according to the present invention was irradiated using AFM to confirm whether it is exfoliated in a hydrophilic organic solvent through ultrasonic dispersion to form graphene oxide, and as shown in FIG. It was confirmed that the eggplant was made of graphene oxide.

In order to confirm whether the graphene oxide prepared according to the present invention is reduced in defect formation rate compared to Comparative Example 1 in which the oxidation reaction proceeds under an acidic solvent, Raman spectroscopy is used between G-band and D-band. As a result of confirming the intensity ratio (I _D / I _G ), as shown in FIG. 6, it was confirmed that the I _D / I _G ratio of Example 1 showed a greatly reduced value of 0.07.

(iii) preparing graphene by adding a reducing agent to the graphene oxide.

The reducing agent may be any one or more selected from the group consisting of hydrazine, hydrazine monohydrate, acetichydrazide, sodium or potassium borohydride, N-methyl pyrrolidine and morpholine, preferably hydrazine, hydrazine monohydride It may be any one selected from the group consisting of latex and acetichydrazide, most preferably hydrazine.

The shear force rate may be 100 to 10000 rpm, preferably 500 to 10000 rpm, and most preferably 5000 to 6000 rpm.

(iii) heat-treating the graphene oxide prepared by the above method at 500 ° C or higher; It can provide a method for producing a graphene further comprising a.

The temperature range may be 500 ° C or higher, preferably 500 ° C to 1000 ° C, and more preferably 600 ° C to 800 ° C.

Since the oxidation reaction described in the embodiment of the present invention proceeds in distilled water, it will provide advantages in terms of commercialization of graphene oxide and graphene, and also greatly reduces the defect production rate of the surface occurring in the oxidation reaction process, resulting in crystallinity and Since the graphene oxide with improved electrical conductivity can be produced, it can be widely used in materials fields such as high-performance polymer composite materials as well as electrical and electronic devices.

The present invention will be described in detail through specific examples and experimental examples below. The following Examples and Experimental Examples are only examples to help understanding of the present invention, but the scope and scope of the present invention are not limited thereto.

Example 1

Preparation of Graphite Oxide

1 g of natural graphite and 23 mol of sodium hydroxide (NaOH) and potassium permanganate (KMnO ₄ ) were added to 50 mL of distilled water, followed by stirring at 60 ° C. for 3 days to proceed the oxidation reaction. After the reaction was completed, the temperature of the reactant was lowered to room temperature, hydrogen peroxide (H ₂ O ₂ ) was added, and then stirred again at room temperature for 30 minutes. The reaction mixture was rinsed with distilled water and 30 wt% hydrochloric acid (HCl) aqueous solution, the reaction residues were removed, filtered, and lyophilized to finally prepare graphite oxide. In the present invention, graphite oxide prepared in Example 1 was designated as O-Gr.

Example 2

Preparation of Graphene Oxide

Graphite oxide was prepared by exposing the graphite oxide prepared in Example 1 to distilled water or enmethylpyrrolidone (NMP) solution and applying a shear force for 30 minutes using an ultrasonic disperser to perform a peeling process. In the present invention, the graphene oxide prepared in Example 2 was specified as GO.

Comparative Example 1

Hummer ’production of graphite oxide through oxidation

1 g of natural graphite is added to 50 mL of sulfuric acid solution (H ₂ SO ₄ ) and mixed, and 6 g of potassium permanganate (KMnO ₄ ) is slowly added thereto. After the addition of the oxidizing agent, the reaction was stirred for 12 hours at 50 ° C and the temperature of the reaction vessel was decreased to room temperature. Slowly add 80 mL of distilled water to the reaction tank which lowered the temperature to room temperature. When the reaction solution is cooled to room temperature, add 200 mL of distilled water, and add 6 mL of hydrogen peroxide (H ₂ O ₂ : 35 wt% aqueous solution) until the color of the graphite oxide reaction solution turns yellow. . After stirring the yellow graphite oxide dispersion for an additional 30 minutes to confirm that the temperature is lowered to room temperature, the filter is washed with DI-water using a vacuum decompression device. Finally, 100 mL is washed with 30 wt% hydrochloric acid (HCl) aqueous solution to remove potassium permanganate residue. Finally, the obtained graphite oxide was lyophilized to produce graphite oxide. The prepared graphite oxide was subjected to a peeling process by applying shear force using an ultrasonic disperser to prepare graphene oxide. In the present invention, graphite oxide prepared through Comparative Example 1 is designated as GO-1.

Comparative Example 2

Natural graphite

Natural graphite was used as an initial material to determine the physical properties, oxidation, and absence of graphite oxide prepared by the oxidation method proposed by the present invention, and 2 was specified in the comparison to prove the results of the present invention.

Experimental Example 1

In order to confirm whether the oxygen functional group is formed by the oxidation method according to the present invention to produce a graphite oxide, it was investigated through the FT-IR results of Example 1 and is shown in FIG. As shown in FIG. 2, the characteristic peak region associated with the oxygen functional group in -C = O (1712 cm ^-1 ), -CO (1110 cm ^-1 ), -OH (3416 cm ^-1 ) was observed. Graphite oxide was produced by the oxidation method proposed in the invention.

Experimental Example 2

In order to confirm the formation and content of the oxidation functional group by the oxidation method proposed in the present invention, it was confirmed by comparing the TGA pyrolysis curves of Example 1 and Comparative Example 2, the results are shown in FIG. As can be seen in FIG. 3, in the case of pure graphite state which does not undergo oxidation reaction, 2 shows a stable pyrolysis curve up to 800 degrees. However, in Example 1 in which the oxidation reaction was performed through the present invention, the pyrolysis curve was shown from 200 degrees by the oxygen functional group, and about 15 wt% in the decomposition temperature range of the oxygen functional group is 200-500 degrees. A weight loss was shown. In connection with the results of Experimental Example 1, it was confirmed that the graphite oxide containing the oxygen functional group of about 15 wt% through the oxidation reaction proposed in the present invention. Because of the oxygen functional groups, the graphite oxide becomes hydrophilic, and is subjected to ultrasonic treatment in distilled water, whereby a single layer of graphene oxide can be easily peeled off and a very stable dispersion can be obtained.

Experimental Example 3

In order to confirm whether the graphite oxide prepared by the oxidation method proposed in the present invention exhibits dispersibility and dispersion stability in a hydrophilic solvent, Experimental Example 1 was added to distilled water and NMP, followed by a stripping process through an ultrasonic disperser for 30 minutes. After the change was confirmed a change in dispersibility with time, the confirmed result is shown in FIG. As can be seen in FIG. 4, the graphite oxide prepared in Example 1 showed a dispersed phase even after 30 days in distilled water and NMP phase. Through these results, it was confirmed that the oxidative functional groups formed on the surface of the graphite oxide produced by the present invention exhibits dispersibility on the hydrophilic solvent.

Experimental Example 4

Graphite oxide prepared by the oxidation method proposed in the present invention (Example 1) was examined using AFM to determine whether the graphene oxide was peeled off in a hydrophilic organic solvent through ultrasonic dispersion, and the confirmed results were shown in FIG. 5 is shown. As can be seen in Figure 5 it was confirmed that the case of Example 2 was made of graphene oxide having a thickness of less than about 2nm. Through the above results, it was confirmed that the graphene oxide and the mixed graphene oxide dispersion liquid can be easily prepared by the method for producing graphite oxide and the graphene oxide proposed through the present invention.

Experimental Example 5

In order to confirm whether the graphene oxide prepared by the oxidation method proposed by the present invention is reduced in the defect formation rate compared with Comparative Example 1 in which the oxidation reaction proceeds under an acidic solvent, Raman spectroscopy and G-band were used. The intensity ratio (I _D / I _G ) between the D-bands was confirmed, and the results are shown in FIG. 6 below. As can be seen from the results of FIG. 6, it was confirmed that the I _D / I _G ratio of Example 1 was significantly reduced to 0.07 compared to 1 in comparison. In connection with the Experimental Example 3, it was confirmed that by the oxidation method proposed in the present invention it is possible to produce a highly crystalline graphene oxide with a drastically reduced defect formation rate.

Experimental Example 6

In order to confirm whether the graphene oxide produced by the oxidation method proposed by the present invention has improved electrical conductivity due to the reduced structural defects, a compressed disk-type GO pellet was manufactured to provide a 4-point prove device (Keithley, 6221). DC and AC current Source, 2182A Nanovoltmeter) to investigate using (Fig. 7). Example 1 showed an electrical conductivity value of 760 ± 210 S / m improved by about 80 times or more compared to Comparative Example 1 prepared through the Hummer 'method. Through these results, it was confirmed that the highly conductive graphene oxide having greatly improved electrical conductivity through the proposed oxidation method through the present invention.

Claims

(i) chemically oxidizing the carbon source by reacting an alkali metal ion, an oxidant and a carbon source in distilled water or a hydrophilic organic solvent;

(ii) adding hydrogen peroxide to the oxidized reactant and stirring to terminate the reaction; And

(iii) washing the reactant from which the reaction is terminated to produce graphite oxide; Including

The alkali metal ion is at least one selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH) and bromine hydroxide (BrOH), and the oxidizing agent is composed of potassium permanganate, potassium chlorate, perchloric acid and hydrogen peroxide. Environmentally friendly method for producing graphite oxide, which is at least one selected from the group of nium.
The method of claim 1, wherein the hydrophilic organic solvent is any one selected from the group consisting of dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide and ethanol Environmentally friendly method for producing one or more graphite oxides.
The method of claim 1, wherein the carbon source is any one or more selected from the group consisting of carbon nanotubes, carbon nanowires, carbon nanofibers, graphite, activated carbon and graphene having sp 2 bonds between carbon atoms, environmentally friendly graphite oxide Manufacturing method.
(i) adding graphite oxide prepared by the method of any one of claims 1 to 3 onto an organic solvent or distilled water;

(ii) exfoliating graphite oxide in the organic solvent or distilled water through shear stress or ultrasonic dispersion to produce graphene oxide; And

(iii) preparing graphene by adding a reducing agent to the graphene oxide;

Including, graphene manufacturing method.
The method of claim 4, wherein the reducing agent is hydrazine, hydrazine monohydrate, acetichydrazide, sodium or potassium borohydride, trisodium citrate, and methyl diethanolamine, ethanol amine, diethanol amine, propanol amine, butanol Amine, hexanol amine, dimethylethanol amine, 2-amino-2-methyl propanol, dimethylamineborane, butylamineborane, piperidine, N-methylpiperidine, piperazine, N, N'-dimethyl Piperazine, 1-amino-4-methyl piperazine, pyrrolidine, N-methyl pyrrolidine and any one selected from the group consisting of morpholine, a method for producing graphene.
(i) adding the graphite oxide prepared by the method of any one of claims 1 to 6 onto an organic solvent or distilled water;

(ii) exfoliating graphite oxide in the organic solvent or distilled water through shear stress or ultrasonic dispersion to produce graphene oxide; And

(iii) heat treating the graphene oxide at 500 ° C. or higher to prepare graphene;

Including, graphene manufacturing method.