KR20120139034A - Tuning method of interlayer spacing in graphene oxide composites for hydrogen storage - Google Patents

Abstract

PURPOSE: An interlayer controlling method of graphene oxide and a hydrogen storing graphene oxide complex treated by the method are provided to control the interlayer space of graphene oxide by injecting carbon dioxide gas into graphene oxide under room temperature and medium high pressure. CONSTITUTION: An interlayer controlling method of graphene oxide includes the following steps: graphene oxide is prepared on the basis of chemical exfoliation method by using graphite powder; and carbon dioxide is injected into the graphene oxide under room temperature and a medium high pressure to control the interlayer space of the graphene oxide. The chemical exfoliation process includes a process in which graphite oxide is mechanically stirred in the mixed solution of an acid solution and an oxidizer solution for 12 to 24 hours. [Reference numerals] (AA) Embodiment 5

Description

Method of interlayer control of graphene oxide and graphene oxide composites for hydrogen storage treated by the same

The present invention relates to an interlayer control method of graphene oxide and to a graphene oxide composite for hydrogen storage treated by the same, and more particularly, to prepare graphene oxide through a chemical exfoliation method using graphite powder, The present invention relates to a method for controlling the interlayer of graphene oxide by injecting carbon dioxide into a fin oxide at a high pressure at room temperature, and to a graphene oxide composite having an improved hydrogen storage amount.

Hydrogen can be manufactured using water or organic materials as raw materials, and is recycled back to water after use, and there is no fear of depletion of resources. Concerns about environmental pollution because almost no pollutants are generated except for very small amounts of NOx during combustion. Hydrogen energy using this has attracted attention as the energy source with the highest utilization of alternative energy among future clean energy sources.

In order for this hydrogen energy to be used as a future energy source, growth of technology classified into three stages of hydrogen production, storage, and application is required. Currently, hydrogen production technology has achieved some targets, but hydrogen storage technology has yet to achieve US energy. It is not meeting the target amount suggested by the US DOE. In 2009, the US DOE revised its technical target for vehicle hydrogen storage significantly. The target for hydrogen storage technology is 5.5 wt.% (Room temperature, 100 bar). In particular, in order to convert various vehicles using gasoline or diesel into hydrogen energy vehicles, a large amount of hydrogen must be stored safely and conveniently in the vehicle, and thus hydrogen storage technology is absolutely essential among three stage technologies.

The hydrogen storage methods developed to date include hydrogen storage alloys, liquid hydrogen storage methods, and gaseous hydrogen storage methods. The types of hydrogen storage mediums are activated carbon and activated carbon fibers, which are porous carbon materials, and recently attracted great attention as hydrogen storage media. Carbon nanotubes and graphite nanofibers, graphene and graphene oxide, porous metal-organic frameworks (NOFs), metal hydrides, complex chemical hydrates, and the like.

The most efficient hydrogen storage method ever developed is the hydrogen storage alloy. However, hydrogen storage alloys can safely store hydrogen at a pressure of 20-40 atm or less at room temperature, but have a problem in that they are heavier in weight, expensive, and inferior to gasoline or diesel in hydrogen storage capacity. In addition, the gaseous hydrogen storage method or the liquid hydrogen storage method has a small hydrogen storage amount and there is a risk of explosion at room temperature.

Due to the above problems, a hydrogen storage method using a carbon material has been studied. Although carbon material is composed of a single element, there is a variety of bonds and forms, and has various characteristics such as chemical stability, electrical and thermal conductivity, high strength, high modulus, and biocompatibility, and at the same time, lightweight and resource Because of its abundance, it is suitable as a hydrogen storage medium.

In addition, recently, a graphite having a layered structure in which each layer is coupled with weak van der Waals forces as a material present in abundance in nature has been studied as a high-efficiency hydrogen storage medium. Graphite, which is characterized by its layered structure, can easily form layered compounds because various atoms, molecules, and ions can be intercalated, and rapid heat treatment of layered compounds has improved layered structure, dispersibility, and reaction specific surface area. There is this. In addition, graphene oxide, which is in the spotlight as a precursor of graphene, is highly expected as a medium capable of storing high capacity hydrogen because the interlayer structure of graphite can be controlled according to oxidation treatment conditions and kinds of interlayer inserts.

Therefore, the present inventors have made diligent efforts to develop innovative high capacity hydrogen storage materials. As a result, the present inventors have prepared graphene oxide by chemical exfoliation method using conventional commercially available graphite powder, and used carbon dioxide in the prepared graphene oxide at room temperature. It was confirmed that the hydrogen storage ability of the graphene oxide composite prepared by controlling the interlayer of graphene oxide by injection with pressure, and the present invention was improved significantly.

An object of the present invention is to prepare a graphene oxide through a chemical exfoliation method using a graphite powder, and to control the interlayer spacing of graphene oxide by injecting carbon dioxide gas into the prepared graphene oxide at a high pressure at room temperature. to provide.

In addition, by using the graphene oxide with the interlayer spacing is adjusted to provide a graphene oxide composite for hydrogen storage in which the weight is very light and the pore diameter suitable for hydrogen molecules is expressed in large quantities.

In order to achieve the above object, the present invention is to prepare a graphene oxide by chemical exfoliation method using a graphite powder, and to control the interlayer of the graphene oxide by injecting carbon dioxide gas into the prepared graphene oxide at room temperature at high pressure. Provide a way to.

The present invention also provides a graphene oxide composite for hydrogen storage in which the weight of the graphene oxide is adjusted to the interlayer spacing and the processing diameter suitable for hydrogen molecules is expressed in large quantities.

According to the present invention as described above, by providing a method for controlling the interlayer of graphene oxide compared to the conventionally developed graphene oxide, the hydrogen is very light weight and a large amount of pore diameter suitable for hydrogen molecules, the hydrogen storage for significantly improved hydrogen storage It has the effect of providing a graphene oxide complex.

In addition, the graphene oxide with the interlayer spacing adjusted by the manufacturing method may be provided not only in a hydrogen storage medium but also in an active material for an electrode material and a semiconductor of an electrochemical device of a lithium secondary battery or a capacitor.

1 is a TEM photograph of the hydrogen storage graphene oxide composite prepared in the present invention.

Hereinafter, the present invention will be described in detail.

The present invention provides a method for preparing graphene oxide by chemical exfoliation using graphite powder, and controlling the interlayer of graphene oxide by injecting carbon dioxide gas into the prepared graphene oxide at a high pressure at room temperature.

Specifically, the present invention comprises the steps of (1) preparing graphene oxide by chemical exfoliation method using graphite powder; (2) controlling the interlayer of graphene oxide by injecting carbon dioxide gas into the prepared graphene oxide at a high pressure at room temperature; and characterized in that it comprises a.

In the present invention, the process of preparing the graphene oxide by chemical exfoliation method using the graphite powder in step (1) is sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ), phosphoric acid (H ₃ PO ₄ ) And at least one acid solution selected from hydrochloric acid (HCl), aqueous potassium permanganate solution (KMnO ₄ ? NH ₂ O), aqueous potassium thiosulfate solution (K ₂ S ₂ O ₈ ? NH ₂ O), and aqueous sodium hypochlorite solution (NaClO). It is preferable to react the mixed solution of at least one oxidant solution selected from (aq)) through mechanical stirring for 12 to 24 hours.

Graphene oxide prepared in step (1) is further oxidized through hydrogen peroxide, it is preferable to wash several times with hydrochloric acid. The washing process is to remove the excess metal salt used in the oxidation process of the graphene oxide present in the graphene oxide, which is washed again several times with distilled water and separated using a centrifuge, It is characterized by completely drying for 6 to 24 hours, preferably 12 hours at 120 ° C or more.

In addition, the step of controlling the interlayer of the graphene oxide by injecting carbon dioxide gas into the graphene oxide prepared in the step (2) at room temperature at a medium pressure, after putting the graphene oxide in a stainless chamber, remaining in the chamber at 200 ℃ After degassing for 6 to 24 hours until the pressure is 10 ⁻³ torr or less, it is preferable to proceed with a pretreatment to cool to room temperature.

In addition, the carbon dioxide gas at room temperature in the step (2) is preferably injected in the range of 1 to 100 bar, more preferably 5 to 50 bar. The injection rate of carbon dioxide gas is preferably 0.1 to 100 cc / min, more preferably 2 to 10 cc / min. Carbon dioxide gas injection at too low a pressure makes it difficult for carbon dioxide gas to be injected at interlayer intervals of graphene oxide, while carbon dioxide gas injection at too high pressures induces deformation in the structure of graphene oxide itself, thus making it suitable pores suitable for hydrogen molecules. It is not preferable because it inhibits the expression of cervix.

In addition, in the step (2), the process of performing interlayer control of graphene oxide by injecting carbon dioxide gas at a high pressure at room temperature is carried out from inert gases such as N ₂ , He, Ar, etc., in addition to carbon dioxide gas, from NH ₃ , O ₂ , SOx, All active gases such as NOx can be used.

The present invention also provides a graphene oxide composite for hydrogen storage in which a light weight and a large diameter of a processing diameter suitable for hydrogen molecules are prepared using graphene oxide having an interlayer spacing controlled according to the above method.

The hydrogen storage graphene oxide composites having greatly improved hydrogen storage amount may have a specific surface area of 100 to 500 m 2 / g and a total pore volume of 0.5 to 2.5 cm 3 / g depending on treatment conditions.

In addition, the graphene oxide composite significantly improved hydrogen storage amount produced according to the present invention is characterized in that it has a hydrogen storage value of 0.5 to 5.0 wt.%.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by those skilled in the art that these examples are for illustrative purposes only and that the scope of the present invention is not construed as being limited by these examples.

Measurement example  One. Grapina Oxide  Surface observation of the complex

The surface of the graphene oxide composite after interlayer control using carbon dioxide gas of graphene oxide was observed through a transmission electron microscope (JEM2100F, JEOL, Japan).

Measurement example  2. Grapina Oxide  Pore structure characteristics of the composite

The pore structure of the graphene oxide composite prepared by adjusting the interlayer of graphene oxide by injecting carbon dioxide gas at a high pressure at room temperature is about 0.1 g of a sample under 77 K liquid nitrogen atmosphere, and the adsorption amount of nitrogen gas is used as an adsorbate. Measured. Pretreatment of the sample is degassed for about 12 hours at 200 ℃ until the residual pressure in the sample is below 10 ^-3 torr, and after nitrogen isothermal adsorption test, P / P ₀ (P: partial pressure; P ₀ : saturated vapor pressure) The BET specific surface area was calculated | required using the slope of a straight line after BET parameter conversion about the adsorption amount of this about 0.1-0.3. Also, the total pore volume is P / P ₀ Was obtained based on the amount adsorbed at.

Measurement example  3. Grapina Oxide  Hydrogen storage of the composite

In order to measure the hydrogen storage of the prepared graphene oxide composite, each sample was degassed at 200 ° C. for 6 hours while maintaining a residual pressure of 10 ⁻³ torr or lower, and then 25 ° C. using BEL-HP (BEL Japan). Hydrogen storage was measured at 100 atmospheres. The hydrogen storage measurement method was a step-by-step method, and the average sample volume was 0.1 g.

Example  One.

After attaching 1 g of graphite powder to a mixed solution of sulfuric acid and phosphoric acid at 50 ° C, a large amount of potassium permanganate was added and mechanically stirred for 12 hours or more. The graphene oxide prepared above was cooled to room temperature, and then further oxidized by adding hydrogen peroxide. In addition, in order to completely remove the metal salt remaining in the graphene oxide used in the oxidation process, it was washed several times using hydrochloric acid solution. The washed graphene oxide was prepared by washing 1-2 times in distilled water, separating the graphene oxide through a centrifuge and completely drying at 120 ° C. for at least 12 hours. The prepared graphene oxide was injected with carbon dioxide gas at an injection rate of 3 cc / min at room temperature, finally injected to 5 bar, and then degassed.

The graphene oxide composite prepared as described above was washed 1-2 times in distilled water, completely dried at 120 ° C. for at least 12 hours, and then stored in a desiccator.

Example  2.

After attaching 1 g of graphite powder to a mixed solution of sulfuric acid and phosphoric acid at 50 ° C, a large amount of potassium permanganate was added and mechanically stirred for 12 hours or more. The graphene oxide prepared above was cooled to room temperature, and then further oxidized by adding hydrogen peroxide. In addition, in order to completely remove the metal salt remaining in the graphene oxide used in the oxidation process, it was washed several times using hydrochloric acid solution. The washed graphene oxide was prepared by washing 1-2 times in distilled water, separating the graphene oxide through a centrifuge and completely drying at 120 ° C. for at least 12 hours. The prepared graphene oxide was injected with carbon dioxide gas at an injection rate of 5 cc / min at room temperature, and finally injected up to 10 bar, followed by degassing.

The graphene oxide composite prepared as described above was washed 1-2 times in distilled water, completely dried at 120 ° C. for at least 12 hours, and then stored in a desiccator.

Example  3.

After attaching 1 g of graphite powder to a mixed solution of sulfuric acid and phosphoric acid at 50 ° C, a large amount of potassium permanganate was added and mechanically stirred for 12 hours or more. The graphene oxide prepared above was cooled to room temperature, and then further oxidized by adding hydrogen peroxide. In addition, in order to completely remove the metal salt remaining in the graphene oxide used in the oxidation process, it was washed several times using hydrochloric acid solution. The washed graphene oxide was prepared by washing 1-2 times in distilled water, separating the graphene oxide through a centrifuge and completely drying at 120 ° C. for at least 12 hours. The prepared graphene oxide was injected with carbon dioxide gas at an injection rate of 10 cc / min at room temperature, and finally injected up to 20 bar, followed by degassing.

The graphene oxide composite prepared as described above was washed 1-2 times in distilled water, completely dried at 120 ° C. for at least 12 hours, and then stored in a desiccator.

Example  4.

After attaching 1 g of graphite powder to a mixed solution of sulfuric acid and phosphoric acid at 50 ° C, a large amount of potassium permanganate was added and mechanically stirred for 12 hours or more. The graphene oxide prepared above was cooled to room temperature, and then further oxidized by adding hydrogen peroxide. In addition, in order to completely remove the metal salt remaining in the graphene oxide used in the oxidation process, it was washed several times using hydrochloric acid solution. The washed graphene oxide was prepared by washing 1-2 times in distilled water, separating the graphene oxide through a centrifuge and completely drying at 120 ° C. for at least 12 hours. The prepared graphene oxide was injected with carbon dioxide gas at an injection rate of 3 cc / min at room temperature, finally injected to 30 bar, and then degassed.

The graphene oxide composite prepared as described above was washed 1-2 times in distilled water, completely dried at 120 ° C. for at least 12 hours, and then stored in a desiccator.

Example  5.

After attaching 1 g of graphite powder to a mixed solution of sulfuric acid and phosphoric acid at 50 ° C, a large amount of potassium permanganate was added and mechanically stirred for 12 hours or more. The graphene oxide prepared above was cooled to room temperature, and then further oxidized by adding hydrogen peroxide. In addition, in order to completely remove the metal salt remaining in the graphene oxide used in the oxidation process, it was washed several times using hydrochloric acid solution. The washed graphene oxide was prepared by washing 1-2 times in distilled water, separating the graphene oxide through a centrifuge and completely drying at 120 ° C. for at least 12 hours. The prepared graphene oxide was injected with carbon dioxide gas at an injection rate of 3 cc / min at room temperature, and finally injected up to 40 bar, followed by degassing.

The graphene oxide composite prepared as described above was washed 1-2 times in distilled water, completely dried at 120 ° C. for at least 12 hours, and then stored in a desiccator.

Example  6.

After attaching 1 g of graphite powder to a mixed solution of sulfuric acid and phosphoric acid at 50 ° C, a large amount of potassium permanganate was added and mechanically stirred for 12 hours or more. The graphene oxide prepared above was cooled to room temperature, and then further oxidized by adding hydrogen peroxide. In addition, in order to completely remove the metal salt remaining in the graphene oxide used in the oxidation process, it was washed several times using hydrochloric acid solution. The washed graphene oxide was prepared by washing 1-2 times in distilled water, separating the graphene oxide through a centrifuge and completely drying at 120 ° C. for at least 12 hours. The prepared graphene oxide was injected with carbon dioxide gas at an injection rate of 3 cc / min at room temperature, and finally injected to 50 bar, followed by degassing.

The graphene oxide composite prepared as described above was washed 1-2 times in distilled water, completely dried at 120 ° C. for at least 12 hours, and then stored in a desiccator.

Example  7.

The process was performed in the same manner as in Example 5, but a graphene oxide composite was prepared by injecting ammonia gas.

Example  8.

The process was performed in the same manner as in Example 5, but a graphene oxide composite was prepared by injecting nitrogen dioxide gas.

Comparative example  One.

After attaching 1 g of graphite powder to a mixed solution of sulfuric acid and phosphoric acid at 50 ° C, a large amount of potassium permanganate was added and mechanically stirred for 12 hours or more. The graphene oxide prepared above was cooled to room temperature, and then further oxidized by adding hydrogen peroxide. In addition, in order to completely remove the metal salt remaining in the graphene oxide used in the oxidation process, it was washed several times using hydrochloric acid solution. The washed graphene oxide was prepared by washing 1-2 times in distilled water, separating the graphene oxide through a centrifuge and completely drying at 120 ° C. for at least 12 hours.

Graphene oxide prepared as described above was stored in a desiccator.

Table 1 and Table 2 below are the results showing the pore structure characteristics and hydrogen adsorption amount of the graphene oxide composite interlayer controlled as prepared above.

In the present invention, the graphene oxide controlled by the intercalation by injecting carbon dioxide gas into the prepared graphene oxide at room temperature at a medium pressure has a specific surface area of 35 m ² / g (Comparative Example 1) up to 420 m ² / g (Example 6 Increased to).

In addition, it can be seen that the total pore volume is increased by about 21 times from 0.09 cm ³ / g (Comparative Example 1) to 1.92 cm ³ / g (Example 6). As a result, it was confirmed that the hydrogen storage value was improved by 11.7 times as compared with Comparative Example 1 as the pore characteristics developed by interlayer control of graphene oxide (Example 5). In addition, carbon dioxide injection using excessive pressure induced a deformation of the structure of graphene oxide itself, resulting in a decrease in hydrogen storage value (Example 6).

As described above, specific portions of the contents of the present invention have been described in detail, and for those skilled in the art, these specific techniques are merely preferred embodiments, and the scope of the present invention is not limited thereto. Will be obvious. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (7)

(1) preparing graphene oxide by chemical exfoliation using graphite powder;
(2) controlling the interlayer of graphene oxide by injecting carbon dioxide gas into the prepared graphene oxide at normal pressure at room temperature; interlayer control method of graphene oxide comprising a.
The method of claim 1,
In the step (1), the process of preparing graphene oxide using a chemical separation method using graphite powder is sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ), phosphoric acid (H ₃ PO ₄ ) and hydrochloric acid (HCl). In at least one acid solution and potassium permanganate solution (KMnO ₄ ? NH ₂ O), aqueous potassium thiosulfate solution (K ₂ S ₂ O ₈ ? NH ₂ O), and aqueous sodium hypochlorite solution (NaClO (aq)). Method for controlling the interlayer of graphene oxide, characterized in that for reacting the mixed solution of at least one oxidizing agent selected by 12 to 24 hours through mechanical stirring.
The method of claim 1,
In the step (2), the graphene oxide is put in a stainless chamber, degassed for 6 to 24 hours until the residual pressure in the chamber becomes less than 10 ^-3 torr at 200 ° C, and then a pretreatment process of cooling to room temperature is performed. Method of controlling the interlayer of graphene oxide, characterized in that.
The method of claim 1,
The carbon dioxide gas is injected at room temperature in the range of 1 to 100 bar, and the injection speed is an interlayer control method of graphene oxide, characterized in that 2 to 10cc / min.
Graphene oxide composite for hydrogen storage using the graphene oxide interlayer controlled by the method of claim 1.
6. The method of claim 5,
The graphene oxide composite for hydrogen storage has a specific surface area of 100 to 500 m 2 / g, hydrogen storage graphene oxide composite characterized in that it has a total pore volume of 0.5 to 2.5 cm 3 / g. 6. The method of claim 5,
The hydrogen storage graphene oxide composite is a hydrogen storage graphene oxide composite, characterized in that having a hydrogen storage value of 0.5 to 5.0 wt.%.

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