KR20200018019A - Method for low defective graphene oxide using antioxidant and graphene oxide thereby - Google Patents

Abstract

The present invention relates to a method for producing low defectivity graphene oxide using an oxidation stabilizer and the low defectivity graphene oxide produced by the method and, more specifically, to a graphene oxide producing method comprising: a step (a) of producing oxidation stabilizer solution by adding acid solution and an oxidation stabilizer into a reactor and stirring the same; a step (b) of adding graphite and potassium permanganate (KMnO_4) into a reactor including the oxidation stabilizer solution, and performing an oxidation reaction therein; a step (c) of obtaining a product containing graphene oxide by adding and stirring hydrogen peroxide (H_2O_2) after adding distilled water to the reactant; and a step (d) of washing and drying the product. The present invention produces low defectivity graphene oxide in which residual binding is reduced after the reduction of graphene oxide while maintaining the size of a graphene oxide sheet by suppressing the formation of a ketone group (C=O) which is a non-reducible defect formed during an oxidation process in a graphene oxide producing process.

Description

TECHNICAL FIELD OF THE INVENTION A method for producing low defect graphene oxide using an oxidative stabilizer and a graphene oxide produced thereby

The present invention relates to a method for producing graphene oxide, and more particularly to a method for producing low defect graphene oxide using an oxidative stabilizer.

Graphene has a lot of researches on the manufacture of graphene thin film for the application of various electronic products due to the excellent electrical conductivity, thermal conductivity and mechanical properties.

The graphene thin film may be manufactured by a physical method and a chemical method, and the graphene manufacturing method using the chemical method is an oxidation-reduction reaction. The graphite is chemically oxidized by exfoliation of graphite. Use the principle of separating it into a pin sheet.

Graphene oxide made by a general Hummer's method has oxygen functional groups such as ketone group (C = O), carboxyl group (C = O-O-H), hydroxy group (-OH) and ether group (C-O-C). These oxygen functional groups act as dispersing mechanisms that form charges and impart electrostatic repulsion between the layers of graphite, which are reversibly reduced through the reduction process and return to the lattice of graphene.

In the case of using an oxidation-reduction reaction, it is easy to prepare graphene sheets from graphite through oxidation, but since it is difficult to achieve a perfect reduction reaction, the dispersion stability of the exfoliated graphene is degraded and reagglomeration occurs due to the reduction reaction. There is a problem that damage to the graphene sheet occurs.

Korean Patent Registration No. 10-1844644

In view of the above, an object of the present invention is to provide a low-defect graphene oxide production method using an oxidation stabilizer that can produce low-defect graphene oxide from graphite by a significantly improved yield by using an oxidation stabilizer in the process of preparing graphene oxide. And it provides a graphene oxide produced thereby.

The object of the present invention is not limited to the above-mentioned objects.

Graphene oxide production method of the present invention for achieving the above object, (a) the step of preparing an oxidation stabilizer solution by putting an acid solution and an oxidation stabilizer in the reactor, stirring, (b) a reactor containing the oxidation stabilizer solution Step of oxidizing the graphite and potassium permanganate (KMnO ₄ ) in the reaction, (c) After the distilled water is added to the reaction of the step (b), hydrogen peroxide (H ₂ O ₂ ) is added and stirred to include graphene oxide (D) washing and drying the product to obtain graphene oxide powder.

The oxidation stabilizer may be any one selected from boric acid, sulfur trioxide, acetic acid, and phosphoric acid.

In the step (a), the oxidant stabilizer solution may include 5 wt% to 15 wt% oxidative stabilizer based on 100 wt% of the acid solution.

In the step (a), while maintaining the temperature of the reactor below 10 ℃, the acid solution and the oxidizing stabilizer by stirring at 50 to 200rpm to prepare an oxidizing stabilizer solution.

The acid solution may be a sulfuric acid or a mixture containing any one or more of phosphorus pentoxide (P ₂ O ₅ ) and potassium thiosulfate (K ₂ S ₂ O ₈ ) in sulfuric acid.

The step (b) may be stirred for 6 hours to 24 hours at a stirring speed of 50 to 200 rpm while maintaining the temperature of the reactor at 30 to 70 ℃.

The graphite has a particle size of 50 μm to 850 μm.

If the size of the graphite particles is less than 50㎛, it is difficult to disperse during the manufacturing process is not formed smoothly, and if the size of the graphite particles exceeds 850㎛, due to the size of large particles It is not preferable because the oxidation reaction and subsequent processes are time-consuming and expensive, and the formation of graphene oxide is not performed properly.

Therefore, it is preferable to use graphite having the particle size range set out above, and more preferably, an average particle size of 300 μm can be used.

In the step (c), the temperature of the reactor is lowered to 10 ° C. or lower, and distilled water is slowly added dropwise to the reaction product for 1 to 3 hours, and then, hydrogen peroxide (H ₂ O ₂ ) is added thereto, followed by stirring. You can.

The step (d) comprises washing the product with an aqueous hydrochloric acid solution, putting the washed product in a vacuum desiccator and vacuum drying the product, and the product having undergone the first washing and drying step. It may comprise a second washing and drying step of washing with acetone, the washed product is put in a vacuum desiccator and vacuum dried to obtain a graphene oxide powder.

The graphene oxide production method of the present invention may further comprise the step of preparing a graphene oxide dispersion by dispersing the graphene oxide is dried in water after the step of washing and vacuum drying the graphene oxide in water.

The present invention can also produce low-defect graphene oxide by the method for producing graphene oxide described above.

Graphene oxide manufacturing method using the oxidation stabilizer according to the present invention to maintain the size of the sheet of graphene oxide by inhibiting the formation of the ketone group (C = O), which is a non-reduced defect formed during the oxidation process in the graphene oxide manufacturing process While there is an effect that can produce a low defect graphene oxide that reduces residual bonds after reduction of graphene oxide.

1 is a flow chart of a graphene oxide manufacturing method using an oxidation stabilizer according to an embodiment of the present invention.
Figure 2 is a schematic diagram showing the difference between the oxidation reaction of graphene oxide with or without the introduction of an oxidative stabilizer.
3 is an X-ray photoelectron spectroscopy (XPS) analysis result of graphene oxide prepared using an oxidative stabilizer according to Comparative Example 1. FIG.
4 is an X-ray photoelectron spectroscopy (XPS) analysis result of graphene oxide prepared using an oxidative stabilizer according to Example 1 of the present invention.
5 is a scanning electron microscope (SEM) analysis result of graphene oxide prepared according to Comparative Example 1 of the present invention.
6 is a scanning electron microscope (SEM) analysis result of graphene oxide prepared according to Example 1 of the present invention.

The graphene oxide production method of the present invention will be described in more detail with reference to the accompanying drawings. However, this is by way of example, and those skilled in the art to which the present invention pertains may be embodied in many different forms, not limited to what is described herein.

Graphene oxide production method of the present invention is carried out using a modified hummer's method as shown in Figure 1, (a) step of preparing an oxidant stabilizer solution (S100), (b) the addition of graphite and potassium permanganate into the oxidant stabilizer solution oxidation reaction To perform the step (S200), (c) adding distilled water and hydrogen peroxide water to the reactants after the step (b) in turn and stirring to obtain a product containing graphene oxide (S300), (d) the product To wash and vacuum drying step (S400).

The step (a) of preparing an oxidant stabilizer solution (S100) comprises adding an acid solution and an oxidant stabilizer to the reactor and stirring to prepare an oxidant stabilizer solution, while lowering the temperature of the reactor to 10 ° C. or lower and maintaining the temperature. By stirring at 50 to 200rpm can be prepared an oxidative stabilizer solution.

In the step (a) (S100), the oxidative stabilizer includes 5 wt% to 15 wt% based on 100 wt% of the acid solution.

If the oxidizing stabilizer solution contains less than 5 wt% of the oxidizing stabilizer based on 100% by weight of the acid solution, the content of the oxidizing stabilizer is low, and thus the effect of the oxidizing stabilizer is insignificant, and the formation of the ketone group (C = O) is not inhibited. If the amount of the oxidation stabilizer exceeds 15% by weight, the content of the acid solution is relatively low, thereby preventing the reaction of potassium permanganate (KMnO ₄ ) and the acid solution added in the subsequent process, thereby preventing the formation of graphene oxide.

The acid solution may be a mixture containing sulfuric acid or any one or more of phosphorus pentoxide (P ₂ O ₅ ) and potassium thiosulfate (K ₂ S ₂ O ₈ ) in sulfuric acid, but is not necessarily limited thereto, graphite Any acid solution usually used in the step of oxidative peeling may be used.

The oxidation stabilizer may be any one selected from boric acid, sulfur trioxide, acetic acid and phosphoric acid, and preferably boric acid may be used.

(B) performing an oxidation reaction (S200) is a step of oxidizing and adding graphite and potassium permanganate (KMnO ₄ ) to a reactor containing an oxidizing stabilizer solution prepared through step (a) (S100). Oxidation reaction is an oxidation exfoliation process in which graphene is peeled off from graphite into a monolayer to produce graphene oxide.

In step (b), the graphite and potassium permanganate are added to the oxidant stabilizer solution and stirred at a stirring speed of 50 to 200 rpm for 6 to 24 hours while maintaining the temperature of the reactor at 30 to 70 ° C. Here, the degree of oxidation of graphite can be controlled by the reaction time.

(c) obtaining the product containing graphene oxide (S300) is a process for terminating the oxidation reaction of the step (b) (S300), after the distilled water is added to the reactants, the hydrogen peroxide solution is added and stirred To obtain a product containing graphene oxide.

Specifically, step (c) (S300) is to lower the temperature of the reactor to 10 ℃ or less, slowly dropping distilled water to the reactant for 1 hour to 3 hours, and then 20 to 40% by weight of hydrogen peroxide water reactant It is added and stirred to obtain a product containing graphene oxide. Of distilled water to be added here may be added to part 100 to 1,000 parts by weight in the potassium permanganate (KMnO ₄₎ 100 parts by weight burul based, hydrogen peroxide may be added in an amount of 50 to 150 by weight, the potassium permanganate (KMnO ₄₎ 100 parts by weight burul reference have.

(D) washing and vacuum drying the product (S400) is a process of washing and drying the product containing the obtained graphene oxide, in one embodiment, the product is washed with an aqueous hydrochloric acid solution, and the washed product The first washing and drying step of placing in a vacuum desiccator and vacuum drying, and the product after the first washing and drying step are washed with acetone, the washed product is put in a vacuum desiccator and vacuum dried to oxidize It is preferable to perform the second washing and drying step to obtain the graphene powder, but is not limited thereto, and the first washing and drying step and the second washing and drying step may be repeated as many times as necessary.

In the step (d), the process of washing with the aqueous hydrochloric acid solution or acetone in step (S400) may be washed through the process of separating and recovering the graphene oxide prepared by a method such as centrifugation by putting hydrochloric acid aqueous solution or acetone in the product. Can be.

Then, the graphene oxide powder formed through the step (d) (S400) is dispersed in water at a desired concentration to prepare a graphene oxide dispersion and use it.

Figure 2 is a schematic diagram showing the difference in the oxidation reaction of the graphene oxide with or without the introduction of an oxidizing stabilizer in the graphene oxide manufacturing process of the present invention. As shown in FIG. 2, graphene oxide prepared by a conventional modified hummer's method without using an oxidative stabilizer is condensation-polymerized with a hydroxyl group (-OH) on the surface of graphene oxide formed during oxidation. C = O), but when an oxidative stabilizer is used, the oxidative stabilizer is bonded to the hydroxy group to prevent the hydroxy group from condensation polymerization to form a ketone group.

Therefore, the graphene oxide manufacturing method using the oxidation stabilizer according to the present invention to suppress the formation of the ketone group (C = O), which is a non-reduced defect formed during the oxidation process in the production of graphene oxide to produce a low defect graphene oxide It can be seen that.

Hereinafter will be described in more detail through experiments using examples and comparative examples in order to determine the effect on the oxidation stabilizer used in the graphene oxide production method of the present invention.

<Example 1>

Put 450 mL of sulfuric acid and 50 mL of boric acid as oxidizing stabilizer together, and then circulate cooling water at 0 ° C to reduce the temperature of the reactor to 10 ° C or below, and prepare an oxidizing stabilizer solution at a stirring speed of 150rpm. . 3 g of graphite and 18 g of potassium permanganate were added to the prepared oxidative stabilizer solution, and the reaction was stirred for 18 hours at 180 rpm while maintaining the temperature of the reactor at 50 ° C. Then, the reactor temperature was lowered to 10 ° C. or lower for completion of the oxidation reaction, and 400 mL of distilled water was slowly added dropwise to the reaction over about 2 hours, and then 35% by weight of hydrogen peroxide solution until a golden slurry was obtained. Add 10 mL. The product containing graphene oxide was washed with 10% HCl, vacuum dried in a desiccator for 3 days, the dried product was washed again with acetone, and vacuum dried in a desiccator for 3 days to obtain final graphene oxide. Prepare a powder.

Comparative Example 1

Comparative Example 1 was prepared in the same manner as in Example 1 except that no oxidation stabilizer was used to prepare graphene oxide.

3 and Table 1 below show the results of X-ray photoelectron spectroscopy (XPS) analysis of graphene oxide prepared using an oxidative stabilizer according to Comparative Example 1, and FIG. 4 and Table 2 below. X-ray photoelectron spectroscopy (XPS) analysis results of graphene oxide prepared using an oxidative stabilizer according to Example 1 of the present invention.

Comparative Example 1 Peak position (eV) % C-C 284.565 36.60 C-O 286.765 54.69 C = O 287.865 5.65 -COOH 288.965 3.06

Example 1 Peak position (eV) % C-C 284.684 39.21 C-O 286.867 55.43 C = O 287.984 2.59 -COOH 289.084 2.77

Comparing FIGS. 3 to 4 with Tables 1 to 2, the bonding ratio of the ketone group (C = O), which is a nonreducible defect of the oxygen functional group, in the graphene oxide of Comparative Example 1 was represented by 5.65%, Example 1 The bond ratio of ketone group (C = O) in graphene oxide is 2.59%, and the bond ratio of ketone group in graphene oxide prepared using an oxidative stabilizer is reduced by about 2 times. And FIG. 6 shows the results of observing the graphene oxide prepared according to Comparative Example 1 and Example 1 with a scanning electron microscope (SEM), respectively, as shown in FIG. By preventing the cutting of the graphene oxide sheet can be confirmed that there is an effect that can maintain the graphene sheet size even after the oxidation reaction.

Claims (11)

(a) adding an acid solution and an oxidant stabilizer to the reactor and stirring to prepare an oxidant stabilizer solution;
(b) oxidizing graphite and potassium permanganate (KMnO ₄ ) in a reactor containing the oxidant stabilizer solution;
(c) adding distilled water to the reaction of step (b), adding hydrogen peroxide (H ₂ O ₂ ) and stirring to obtain a product including graphene oxide; And
(d) a washing and drying step of washing and vacuum drying the product to obtain graphene oxide powder. The method of claim 1,
The oxidation stabilizer is a graphene oxide manufacturing method, characterized in that any one selected from boric acid (boric acid), sulfur trioxide (sulfur trioxide), acetic acid (acetic acid) and phosphoric acid (phosphoric acid). The method of claim 1,
In the step (a), the oxidation stabilizer solution, the graphene oxide manufacturing method, characterized in that it comprises 5 to 15% by weight oxidizing stabilizer based on 100% by weight of the acid solution. The method of claim 1,
In step (a),
While maintaining the temperature of the reactor below 10 ℃, stirring the acid solution and the oxidation stabilizer at 50 to 200rpm to prepare an oxide stabilizer solution, characterized in that for producing an oxidation stabilizer solution. The method of claim 1,
The acid solution is a method for producing graphene oxide, characterized in that the mixture containing any one or more of sulfuric acid or phosphoric pentoxide (P ₂ O ₅ ) and potassium thiosulfate (K ₂ S ₂ O ₈ ). The method of claim 1,
Step (b) is,
Graphene oxide production method characterized in that the stirring for 6 to 24 hours at a stirring speed of 50 to 200rpm while maintaining the temperature of the reactor at 30 to 70 ℃. The method of claim 1,
The graphite is a graphene oxide manufacturing method, characterized in that the particle size of 50 to 850㎛. The method of claim 1,
In step (c),
After lowering the temperature of the reactor to 10 ℃ or less, distilled water is added dropwise to the reaction for 1 hour to 3 hours, hydrogen peroxide (H ₂ O ₂ ) is added and stirred to react the graphene oxide manufacturing method . The method of claim 1,
In step (d),
Washing the product with an aqueous hydrochloric acid solution, placing the washed product in a vacuum desiccator, and vacuum drying the first product; And
A second washing and drying step of washing the product passed through the first washing and drying step with acetone, putting the washed product into a vacuum desiccator and vacuum drying to obtain graphene oxide powder. Graphene oxide production method. The method of claim 1,
After washing and vacuum drying the graphene oxide,
Dispersing the graphene oxide in water to prepare a graphene oxide dispersion; Graphene oxide manufacturing method comprising a. Graphene oxide prepared by the manufacturing method according to any one of claims 1 to 10.

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