KR20090067920A - Expanded graphite oxide and a method for preparing the same - Google Patents

Abstract

An expanded graphite oxide and a method for preparing the same are provided, wherein a gap between layers of the expanded graphite oxide is expanded by dyes with heat resistance inserted between the layers, and the expanded gap between the layers is not reduced even after heat treatment. A method for preparing an expanded graphite oxide comprises the steps of: oxidizing raw material graphite with an oxidizer to prepare graphite oxide; and bringing the graphite oxide and dyes into contact with each other. The contact process is performed by adding the graphite oxide in a dye solution. The graphite oxide is added in the dye solution in a state that the graphite oxide is water-dispersed into a basic solution with a pH value of 9 or more. The method further comprises the step of heat-treating the graphite brought into contact with the dyes in an inert atmosphere. The dyes have a thermal decomposition temperature of higher than 200 deg.C.

Description

Expanded graphite oxide and a method for preparing the same

The present invention relates to expanded graphite oxide and a method for producing the same, and more particularly, to expanded graphite oxide in which a dye is inserted between carbon network graphene of graphite oxide and a method for producing the same.

Graphite oxide is a reaction product obtained by reacting graphite in concentrated liquid of concentrated nitric acid or concentrated sulfuric acid and potassium chlorate for a long time. Graphite oxide is a layered graphite having a layered structure formed by the penetration of oxygen or the like between the carbon network planes (grpahene). In the dried state, the interplanar distance of the graphite oxide is about 0.6 nm or more. The graphite oxide may insert a volatile molecule such as sulfuric acid or nitric acid between the carbon network planes and then expand the gap between the carbon network planes by the pressure when the molecules are vaporized. Since the expanded graphite oxide has an increased spacing between carbon network planes, the expanded graphite oxide may have a lower density, and thus may be applied to battery material applications such as hydrogen storage materials, fuel cell separators, and capacitors.

In order to use the expanded graphite oxide as a battery material, various hydrophilic functional groups existing on the graphite surface must be removed. Therefore, a heat treatment process for removing the functional groups is required. However, when the expanded graphite oxide is heat treated, the spacing between the carbon network planes is contracted again.

Expanded graphite oxide having a layered structure and including a dye interposed between the layers is provided. Preparing raw graphite by oxidizing raw graphite with an oxidant; And

There is provided a method for producing expanded graphite oxide comprising the step of contacting the graphite with the dye.

Hereinafter, expanded graphite oxide according to a preferred embodiment of the present invention and a manufacturing method thereof will be described in more detail.

Expanded graphite oxide according to an embodiment of the present invention has a layered structure and includes a dye interposed between the layers. The term dye is used herein to include organic compounds used as dyes, metal salts of organic compounds used as dyes, and / or hydrates thereof. Dyes are generally heat-resistant compounds that retain color without being easily degraded or vaporized even at the high temperature heat treatments involved in the dyeing process. In addition, dyes are generally bulky in molecular size. Therefore, it is suitable for use as a compound to be intercalated between the expanded graphite oxide of the present invention. The expanded graphite oxide is enlarged between layers by a dye having heat resistance intercalated between layers, and the enlarged interlayer gap does not decrease even after heat treatment.

According to another embodiment of the present invention, the thermal decomposition temperature of the dye is preferably more than 200 ℃. When the pyrolysis temperature of the dye is 200 ° C. or less, the dye may be decomposed at a heat treatment temperature of 200 ° C. or more, and thus it may be difficult to maintain an interlayer gap of graphite oxide. The pyrolysis temperature is the temperature at which the derivative value of the slope of the mass change is the largest when measured using a thermogravimetric analysis.

According to another embodiment of the present invention, the dye is preferably present in the form of a monomer. That is, it is suitable for achieving the object of the present invention that the dye is present in a single molecule form. However, this does not exclude the presence of the dye in oligomeric or polymeric form.

According to another embodiment of the present invention, the dye may be a disodium salt of basocuproindisulfonic acid (bathocuproinedisulfonic acid disodium salt, B1125), coumarin 343, methylene blue (methylene blue, C ₁₆ H ₁₈ ClN ₃ S) It is preferably at least one compound selected from the group consisting of Brilliant cresyl blue (C ₁₇ H ₂₁ ClN ₄ O) and lucigenin (bis-N-methylacridinum nitrate).

The amount of the dye inserted into the expanded graphite oxide is preferably 10% to 80% by weight of the total weight of the graphite oxide as the dye is inserted. The above content ranges are suitable for achieving the object of the present invention.

According to another embodiment of the present invention, it is preferable that the interlayer spacing d ₀₀₂ of the carbon network plane (graphene) of the expanded graphite oxide is 0.8 nm or more, and more preferably 0.8 to 1.5 nm. However, the interlayer spacing is not necessarily limited to the above range, and may be appropriately adjusted within the range to achieve the object of the present invention if it is 0.8 nm or more. The larger the interlayer spacing of the expanded graphite oxide is, the more space is secured.

According to another embodiment of the present invention, the method for producing expanded graphite oxide includes preparing graphite oxide by oxidizing raw graphite with an oxidizing agent; And contacting the graphite with the dye. When the oxidized graphite is in contact with the dye, fuel is inserted into the interlayers of the carbon network planes of the graphite to extend the interlayer spacing.

According to another embodiment of the present invention, the contacting is preferably performed by adding graphite oxide to the dye solution, but is not necessarily limited to this method, and is a method used in the art as a method by which the dye may contact graphite oxide. If it is available. In addition, the oxidized graphite is preferably added to the dye solution in the form of water dispersed in a basic solution of pH 9 or more. Although the said pH range will not be specifically limited if it is 9 or more, pH 9-11 are more preferable.

According to another embodiment of the present invention, the expanded graphite oxide manufacturing method further comprises the step of contacting the graphite oxide and the dye, followed by heat treatment of the graphite in contact with the dye in an inert atmosphere; The heat treatment temperature is preferably 200 ° C. or less, but is not necessarily limited to the above temperature range, and an appropriate temperature may be used as necessary. The time required for the heat treatment is preferably 2 to 20 hours, but is not necessarily limited to this range, and may be heat treated for an appropriate time as needed.

According to another embodiment of the present invention, the dye preferably has a pyrolysis temperature of more than 200 ° C., more specifically, a disodium salt of vasocuproindisulfonic acid (bathocuproine disulfonic acid disodium salt, B1125), coumarin 343 (Coumarin 343), Methylene blue (C ₁₆ H ₁₈ ClN ₃ S), Brilliant cresyl blue (C ₁₇ H ₂₁ ClN ₄ O) and lucigenin (lucigenin, bis-N-methylacridinum nitrate) It is preferred that it is at least one compound.

The raw graphite is not particularly limited as long as it is a graphite-based material, and natural graphite such as scaly graphite, earth graphite, artificial graphite such as highly oriented pyrolytic graphite (HOPG), and the like may be used.

The oxidant is preferably a mixture of a strong acid and an oxidant. The strong acid may be concentrated nitric acid, concentrated sulfuric acid, and the like, and the oxidizing agent may be hydrogen peroxide or chlorate. Specifically, the oxidizing agent may be used oxygen, hydrogen peroxide, potassium permanganate, potassium dichromate, potassium chlorate (KclO ₃ ), sodium chlorate (NaClO ₃ ) and the like.

Hereinafter, an embodiment of the expanded graphite oxide manufacturing method will be described in more detail.

First, the raw graphite and the oxidizing agent are mixed at a ratio of 1: 1 to 1:30, and then a strong acid per 1 g of the raw graphite is added at a ratio of 0.02 to 100 ml to the mixture, and the mixed solution is stirred for several hours to several tens of hours. A sufficient amount of distilled water is added to the stirred mixture to neutralize it, and the graphite oxide is separated by filtration. The separated graphite oxide is added to a NaOH aqueous solution having a pH of about 10, and then dispersed by ultrasonication to prepare a graphite oxide dispersion. On the other hand, a dye solution of 0.01 to 50% by weight is prepared. Subsequently, the graphite oxide dispersion and the dye solution are mixed, stirred for several hours to several tens of hours, and then expanded graphite oxide is separated by filtration. Thereafter, if necessary, the expanded graphite oxide is heat treated for several tens of hours in an argon atmosphere of 200 ° C. or less. On the other hand, various experimental conditions applied to the production of the expanded graphite oxide can be appropriately adjusted as necessary.

The heat-expanded expanded graphite oxide may be used as various battery materials such as hydrogen storage materials, separators, and capacitors.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to examples, but these embodiments are only for the purpose of description and should not be construed as limiting the protection scope of the present invention.

Preparation of Expanded Graphite Oxide

Comparative Example 1

Highly Oriented Pyrolytic Graphite (HOPG) and NaClO ₃ were mixed at a weight ratio of 1: 8.5. To the mixture was added concentrated nitric acid at a rate of 20 ml of concentrated nitric acid (94% by weight) per 1 g of graphite and stirred for 48 hours. 200 ml of distilled water per 100 ml of the stirred solution was added and diluted, and this dilution process was repeated four times. The diluted solution was filtered to separate graphite oxide.

Comparative Example 2

Highly Oriented Pyrolytic Graphite (HOPG) and NaClO ₃ were mixed at a weight ratio of 1: 8.5. To the mixture was added concentrated nitric acid at a rate of 20 ml of concentrated nitric acid (95% by weight) per 1 g of graphite and stirred for 24 hours. 200 ml of distilled water per 100 ml of the stirred solution was added and diluted, and this dilution process was repeated four times. The separated graphite oxide was heat treated in an argon atmosphere at 200 ° C. for 10 hours.

Example 1

Highly Oriented Pyrolytic Graphite (HOPG) and NaClO ₃ were mixed at a weight ratio of 1: 8.5. To the mixture was added concentrated nitric acid at a rate of 20 ml of concentrated nitric acid (95% by weight) per 1 g of graphite and stirred for 24 hours. 200 ml of distilled water per 100 ml of the stirred solution was added to dilute and this dilution process was repeated four times. The diluted solution was filtered to separate graphite oxide.

60 mg of the separated graphite oxide was added to 180 ml of distilled water to prepare a dispersion, and then the pH of the dispersion was adjusted to 10 by adding NaOH solution.

Meanwhile, B1125 (disodium salt of vasocuproindisulfonic acid, bathocuproinedisulfonic acid disodium salt) was dissolved in distilled water to prepare an aqueous 0.03% by weight B1125 solution.

180 ml of the 0.03 wt% B1125 (disodium salt of bathocuproinedisulfonic acid disodium salt) solution was added to 180 ml of the graphite oxide dispersion and stirred for 12 hours. The stirred mixture was filtered to separate expanded graphite oxide.

Example  2

Expanded graphite oxide was prepared in the same manner as in Example 1, except that 0.03% by weight of coumarin (Coumarin 343) aqueous solution was used instead of 0.03% by weight of B1125 aqueous solution.

Example 3

Highly Oriented Pyrolytic Graphite (HOPG) and NaClO ₃ were mixed at a weight ratio of 1: 8.5. To the mixture was added concentrated nitric acid at a rate of 20 ml of concentrated nitric acid (94% by weight) per 1 g of graphite and stirred for 24 hours. 200 ml of distilled water per 100 ml of the stirred solution was added and diluted, and this dilution process was repeated four times. The diluted solution was filtered to separate graphite oxide.

60 mg of the separated graphite oxide was added to 180 ml of distilled water to prepare a dispersion, and then the pH of the dispersion was adjusted to 10 by adding NaOH solution.

Meanwhile, B1125 (disodium salt of vasocuproindisulfonic acid, bathocuproinedisulfonic acid disodium salt) was dissolved in distilled water to prepare an aqueous 0.03% by weight B1125 solution.

180 ml of the 0.03% by weight B1125 (disodium salt of bathocuproinedisulfonic acid disodium salt) was added to 180 ml of the dispersion and stirred for 12 hours. The stirred mixture was filtered to separate expanded graphite oxide.

The separated graphite oxide was heat treated in an argon atmosphere at 200 ° C. for 10 hours.

Example 4

Except for using the 0.03% by weight coumarin (Coumarin 343) aqueous solution instead of the 0.03% by weight of B1125 aqueous solution was heat-treated in the same manner as in Example 3 to prepare expanded graphite oxide.

Determination of pyrolysis temperature of dye

A thermogravimetric analysis (ThermoGravimetric Analysis, TGA) was used for each of the disodium salts of BASCUPROIN DISulfonic acid (B1125) represented by Formula 1 and Coumarin 343 represented by Formula 2 below. The weight change with temperature was measured. As a result, the temperature at which pyrolysis occurred was 471 ° C for B1125 and 226 ° C for Coumarin 343.

<Formula 1><Formula2>

Determination of the interlayer spacing between carbon network graphenes

X-ray diffraction spectrums of the graphite oxides obtained in Comparative Examples 1 to 2 and Examples 1 to 4 were measured, and the results are shown in FIGS. 1 and 2.

1 shows the results of X-ray diffraction experiments on the graphite oxide of Comparative Example 1 and Examples 1 to 2 that were not heat treated. As shown in FIG. 1, theta (theta) values of the peaks of the graphite oxides of Examples 1 and 2 were smaller than those of the graphite oxide of Comparative Example 1.

The interlayer spacing calculated from theta values of Comparative Example 1 and Examples 1 to 2 is shown in Table 1 below. As shown in Table 1, the interlayer spacing of Examples 1 and 2 was 0.8 nm or more, but the interlayer spacing of Comparative Example 1 was 0.7 nm.

2 is an X-ray diffraction test result of the graphite oxide of Comparative Example 2 and Examples 3 to 4 subjected to a heat treatment process. As shown in FIG. 2, the theta value of the peak of the graphite oxide of Comparative Example 2 was increased compared to Comparative Example 1 of FIG. 1. On the contrary, the theta values of the graphite oxide peaks of Examples 3 to 4 decreased compared with Examples 1 to 2 of FIG.

The interlayer spacing calculated from the theta values is shown in Table 1 below. As shown in Table 1, the interlayer spacing of Examples 3 to 4 was 1.1 nm, but the interlayer spacing of Comparative Example 2 was 0.6 nm.

TABLE 1

Interplanar spacing (d ₀₀₂ ) [nm] Comparative Example 1 0.7 Comparative Example 2 0.6 Example 1 0.85 Example 2 0.83 Example 3 1.1 Example 4 1.1

As shown in Table 1, in the conventional graphite oxide without dye insertion, the interlayer spacing was 0.7 nm (Comparative Example 1), and the heat treatment was reduced to 0,6 nm (Comparative Example 2) after heat treatment.

The graphite oxide of the present invention in which the dye was inserted had an interlayer spacing of 0.8 nm or more (Examples 1 and 2), and the heat treatment increased to 1.1 nm (Examples 3 and 4) after heat treatment.

1 is an X-ray diffraction spectrum of graphite oxide prepared in Comparative Example 1, Example 1 and Example 2 of the present invention.

2 is an X-ray diffraction spectrum of graphite oxide prepared in Comparative Example 2, Example 3 and Example 4 of the present invention.

Claims (12)

Expanded graphite oxide having a layered structure, in which a dye is inserted between the layers. The expanded graphite oxide according to claim 1, wherein the pyrolysis temperature of the dye is 200 deg. 2. The expanded graphite oxide according to claim 1, wherein the dye is in monomer form. The method of claim 1, wherein the dye is bathocuproine disulfonic acid disodium salt (B1125), coumarin 343, methylene blue (methylene blue, C ₁₆ H ₁₈ ClN ₃ S), brilliant Expanded graphite oxide, characterized in that at least one compound selected from the group consisting of (Brilliant cresyl blue, C ₁₇ H ₂₁ ClN ₄ O) and lucigenin (bis-N-methylacridinum nitrate). The expanded graphite oxide according to claim 1, wherein the interlayer spacing (d ₀₀₂ ) of the expanded graphite oxide is 0.8 nm or more. The expanded graphite oxide according to claim 1, wherein the interlayer spacing (d ₀₀₂ ) of the expanded graphite oxide is 0.8 to 1.5 nm. Oxidizing the raw graphite with an oxidizing agent to prepare graphite oxide; And Contacting the graphite oxide with a dye (Dye); manufacturing method of expanded graphite oxide comprising a. 8. The process for producing expanded graphite oxide according to claim 7, wherein said contact is made by adding graphite oxide to a dye solution. The method for producing expanded graphite oxide according to claim 8, wherein the graphite oxide is added to the dye solution in the form of being dispersed in a basic solution having a pH of 9 or more. The method of claim 7, further comprising the step of heat-treating the graphite in contact with the dye in an inert atmosphere. 8. The process for producing expanded graphite oxide according to claim 7, wherein the thermal decomposition temperature of said dye is greater than 200 deg. 8. The dye according to claim 7, wherein the dye is bathocuproine disulfonic acid disodium salt (B1125), coumarin 343, methylene blue (methylene blue, C ₁₆ H ₁₈ ClN ₃ S), brilliant Method for producing expanded graphite oxide, characterized in that at least one compound selected from the group consisting of (Brilliant cresyl blue, C ₁₇ H ₂₁ ClN ₄ O) and lucigenin (bis-N-methylacridinum nitrate).

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