KR101408040B1 - Expanded graphite oxide and a method for preparing the same - Google Patents

Abstract

The present invention discloses expanded graphite oxide having a layered structure in which a dye is interposed between the layers.

Graphite oxide

Description

Expanded graphite oxide and a method for preparing same

The present invention relates to an expanded graphite oxide and a method for producing the same, and more particularly to an expanded graphite graphite having a dye inserted between graphenes of graphite oxide and a method for producing the graphite oxide.

Graphite oxide is a reaction product obtained by reacting graphite for a long time in a mixture of concentrated nitric acid or concentrated sulfuric acid and potassium chlorate. Graphite oxide is a layered graphite having a layered structure formed by penetration of oxygen and the like between the grphenes. The planar distance of the graphite oxide in the dried state is about 0.6 nm or more. The oxidized graphite can be expanded by inserting volatile molecules such as sulfuric acid or nitric acid between the carbon nanotubes and then between the carbon nanotubes by the pressure when the molecules are vaporized. Since the expanded graphite oxide has an increased spacing between the carbon net planes, the density of the expanded graphite oxide is lowered and can be applied to battery material applications such as a hydrogen storage material, a separator for a fuel cell, and a capacitor.

In order to use the expanded graphite oxide as a battery material, various hyrdrophilic functional groups present 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 space between the carbon net planes contracts again.

There is provided an expanded graphite oxide having a layered structure and containing a dye intercalated between the layers. The method of manufacturing a graphite sheet according to claim 1, wherein the graphite oxide is oxidized with an oxidizing agent to prepare graphite oxide. And

And bringing the dye into contact with the oxidized graphite.

Hereinafter, expanded oxidized graphite according to a preferred embodiment of the present invention and a method for producing the same will be described in detail.

The 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 mean an organic compound used as a dye, a metal salt of an organic compound used as a dye, and / or a hydrate thereof. Dyestuffs are generally highly heat-resistant compounds that maintain their color without being easily decomposed or vaporized during the high-temperature heat treatment that accompanies the dyeing process. Dyes are also generally bulky in molecular size. Therefore, it is suitable to be used as a compound to be intercalated between layers of expanded graphite oxide of the present invention. The expanded graphite oxide has an increased interlayer spacing due to the dye having heat resistance inserted between the layers and does not reduce the enlarged interlayer spacing even after the heat treatment.

According to another embodiment of the present invention, the thermal decomposition temperature of the dye is preferably higher than 200 ° C. If the thermal decomposition temperature of the dye is 200 ° C or less, the dye may be decomposed at a heat treatment temperature of 200 ° C or more, so that the interlayer spacing of graphite oxide may not be maintained. The pyrolysis temperature is the temperature at which the derivative of the mass change gradient is 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 exists in the form of a single molecule. However, it does not exclude that the dye is present in an oligomer or polymer form.

According to another embodiment of the present invention, the dye is selected from the group consisting of bathocuproinedisulfonic acid disodium salt (B1125), Coumarin 343, methylene blue (C ₁₆ H ₁₈ ClN ₃ S) , Brilliant cresyl blue (C ₁₇ H ₂₁ ClN ₄ O), and bis-N-methylacridinum nitrate.

The content of the dye inserted in the expanded graphite oxide is preferably 10% to 80% by weight of the total weight of graphite oxide in the state in which the dye is inserted. The content range is suitable for achieving the object of the present invention.

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

According to another embodiment of the present invention, there is provided a method of manufacturing expanded graphite oxide, comprising the steps of: preparing oxidized graphite by oxidizing raw graphite with an oxidizing agent; And contacting the dye with the oxidized graphite. When the oxidized graphite and the dye are in contact with each other, fuel is inserted between the layers of the carbon nanotube planes of the graphite to expand the interlayer spacing.

According to another embodiment of the present invention, it is preferable that the contact is made by adding graphite oxide to the dye solution, but it is not necessarily limited to such a method, and a method in which a dye can be contacted with graphite oxide, It can be used. Further, it is preferable that the oxidized graphite is added to the dye solution in an aqueous dispersion form in a basic solution having a pH of 9 or more. The pH range is not particularly limited as long as it is 9 or more, but a pH of 9 to 11 is more preferable.

According to another embodiment of the present invention, it is preferable that the method further comprises the step of contacting the graphite with the dye and then heat-treating the graphite in contact with the dye in an inert atmosphere. The heat treatment temperature is preferably 200 ° C or lower, but is not necessarily limited to the temperature range, and an appropriate temperature may be used if necessary. The time required for the heat treatment is preferably from 2 to 20 hours, but is not limited thereto, and the heat treatment can be performed for a suitable time as necessary.

According to another embodiment of the present invention, the dye preferably has a pyrolysis temperature higher than 200 ° C, more specifically, a bathocuproinedisulfonic acid disodium salt (B1125), Coumarin 343, Selected from the group consisting of methylene blue (C ₁₆ H ₁₈ ClN ₃ S), Brilliant cresyl blue (C ₁₇ H ₂₁ ClN ₄ O), and lucigenin (bis-N-methylacridinum nitrate) It is preferably one or more compounds.

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

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

Hereinafter, one embodiment of the method for producing the expanded graphite oxide will be described in more detail.

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

The heat-treated and expanded expanded graphite oxide may be used as various battery materials such as a hydrogen storage material, a separator, and a capacitor.

Preferred embodiments of the invention will now be described in more detail by way of example, but these embodiments are for purposes of illustration only and are not to be construed as limiting the scope of protection of the invention.

Manufacture of expanded graphite oxide

Comparative Example 1

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

Comparative Example 2

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

Example 1

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

60 mg of the separated graphite 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.

On the other hand, B1125 (bathocuproinedisulfonic acid disodium salt) was dissolved in distilled water to prepare a 0.03 wt% B1125 aqueous solution.

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

Example  2

Expanded graphite was prepared in the same manner as in Example 1, except that 0.03 wt% Coumarin 343 aqueous solution was used instead of 0.03 wt% B1125 aqueous solution.

Example 3

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

60 mg of the separated graphite 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.

On the other hand, B1125 (bathocuproinedisulfonic acid disodium salt) was dissolved in distilled water to prepare a 0.03 wt% B1125 aqueous solution.

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

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

Example 4

The expanded graphite oxide was heat-treated in the same manner as in Example 3 except that 0.03 wt% Coumarin 343 aqueous solution was used in place of the 0.03 wt% aqueous B1125 aqueous solution.

Measurement of pyrolysis temperature of dye

Thermogravimetric analysis (TGA) was used for each of bathocuproinedisulfonic acid disodium salt (B1125) represented by the following formula (1) and Coumarin 343 represented by the following formula (2) And the change of weight with temperature was measured. As a result, the temperature at which pyrolysis occurred was 471 ° C for B1125 and 226 ° C for Coumarin 343.

&Lt; Formula 1 >< EMI ID =

Interlayer spacing measurement between annealed planes (graphenes)

X-ray diffraction spectra of the graphite oxide obtained in Comparative Examples 1 to 2 and Examples 1 to 4 were measured, and the results are shown in Figs. 1 and 2. Fig.

Fig. 1 shows X-ray diffraction results of graphite oxide of Comparative Example 1 and Examples 1 and 2 which were not heat-treated. As shown in Fig. 1, the values of theta (theta, [theta]) of graphite oxide graphite of Examples 1 and 2 were smaller than those of graphite oxide of Comparative Example 1.

Table 1 shows the interlayer spacings calculated from the set values of Comparative Example 1 and Examples 1 and 2. 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.

FIG. 2 shows X-ray diffraction results of graphite oxide of Comparative Example 2 and Examples 3 and 4 which have been heat-treated. As shown in FIG. 2, the setta value of the peak of graphite oxide of Comparative Example 2 was increased as compared with Comparative Example 1 of FIG. On the other hand, the theta value of the oxidized graphite peaks in Examples 3 to 4 was smaller than those in Examples 1 and 2 in Fig.

Table 1 shows the interlayer spacing calculated from the theta value. 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, the conventional graphite oxide having no dye inserted therein had an interlayer spacing of 0.7 nm (Comparative Example 1), and the spacing after heat treatment was reduced to 0,6 nm (Comparative Example 2).

The graphite oxide of the present invention having the dye incorporated therein has an interlayer spacing of 0.8 nm or more (Examples 1 and 2), and after the heat treatment, the spacing increased to 1.1 nm (Examples 3 and 4).

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

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

Claims (12)

Expanded graphite having a layered structure and dye interposed between the layers. The expanded graphite according to claim 1, wherein the dye has a pyrolysis temperature of more than 200 ° C. The expanded graphite according to claim 1, wherein the dye is present in the form of a monomer. The method of claim 1 wherein the disodium salt of the indicator acid wherein the dye in Lancet COOP (bathocuproinedisulfonic acid disodium salt, B1125), coumarin 343 (Coumarin 343), methylene blue _{(methylene blue, C 16 H 18} ClN 3 S), brilliant Characterized in that the graphite is at least one compound selected from the group consisting of Brilliant cresyl blue (C ₁₇ H ₂₁ ClN ₄ O) and 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. A process for producing expanded graphite oxide according to any one of claims 1 to 6, Oxidizing raw graphite with an oxidizing agent to prepare graphite oxide; And And contacting the oxidized graphite with a dye (Dye). 8. The process for producing expanded graphite oxide according to claim 7, wherein the contact is made by adding graphite oxide to the dye solution. The process for producing expanded graphite oxide according to claim 8, wherein the graphite oxide is added to the dye solution in a form of water-dispersed in a basic solution having a pH of 9 or more. 8. 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 the dye is higher than 200 deg. The method of claim 7, wherein the disodium salt of the indicator acid wherein the dye in Lancet COOP (bathocuproinedisulfonic acid disodium salt, B1125), coumarin 343 (Coumarin 343), methylene blue _{(methylene blue, C 16 H 18} ClN 3 S), brilliant Wherein the at least one compound is at least one compound selected from the group consisting of Brilliant cresyl blue (C ₁₇ H ₂₁ ClN ₄ O) and bis-N-methylacridinum nitrate.

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