KR20120131361A - Surface modification method of graphite-powder treated with phosphoric acid impregnation and manufacturing method of high efficient adsorbents for hydrogen storage - Google Patents

Abstract

PURPOSE: A surface modification method of graphite powder, the graphite-powder, and graphite powder-based adsorbent for hydrogen storage including the same are provided to modify the surface of graphite powder by using the chemical impregnation of phosphoric acid. CONSTITUTION: A surface modification method of graphite powder includes the following steps: graphite powder is washed; the washed graphite powder is treated with strong acid at room temperature, and an oxidizer is added into the treated graphite powder to be modified; and the surface of the graphite powder is functionalized by chemical impregnation of phosphoric acid. The concentration of phosphoric acid solution for the chemical impregnation of the phosphoric acid is in a range between 0.01 and 20M. The strong acid is selected from a group including sulfuric acid, nitric acid, and hydrochloric acid. [Reference numerals] (AA) Comparative example 1; (BB) Example 3; (CC,DD) Intensity(cps); (EE,FF) Binding energy(eV)

Description

Surface modification method of graphite powder using phosphate impregnation and manufacturing method of adsorbent for high efficiency hydrogen storage using the graphite powder {Surface modification method of graphite-powder treated with phosphoric acid impregnation and manufacturing method of high efficient adsorbents for hydrogen storage}

The present invention relates to a graphite powder surface modification method and to a surface-modified graphite powder, and more particularly, to modify the graphite powder using a concentrated acid and oxidant solution, and chemically impregnating the modified graphite powder with a phosphate solution. The present invention relates to a graphite powder surface modification method and to a graphite powder having a very light weight and a high hydrogen affinity point.

As the industry develops rapidly, the interests of developed countries in the development of next-generation energy sources are exploding in an attempt to replace fossil fuels that are depleted worldwide. In addition, the development of clean renewable energy sources is urgent as carbon dioxide gas, methane gas and the like cause global environmental problems such as ozone layer destruction, global warming, and acid rain caused by greenhouse gas emissions.

As a next-generation energy source, wind, tidal, geothermal, hydrogen, and solar energy are receiving great attention. Among them, hydrogen energy can be depleted by obtaining abundant water present on the earth as a raw material and being recycled back to water after combustion. There is almost no endless clean resources. In addition, hydrogen is emerging as the ultimate alternative energy source or energy carrier in the future when anticipating environmental problems and rising or depleting fossil fuel prices.

The hydrogen can be directly burned to obtain energy, and it is also easy to use as a fuel such as a fuel cell. Therefore, almost all fields used in current energy systems such as general fuels, hydrogen vehicles, hydrogen airplanes, and fuel cells can be used. It has functionality that can be used in.

However, to be put into practical use as a future energy source, technology that is classified into three stages of hydrogen production, storage, and application is required. The target amount suggested by the DOE has not been achieved. In 2009, the US DOE revised its technical target for automotive hydrogen storage significantly, with a target of 5.5 wt.% (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 safely and conveniently stored and mounted in a vehicle. It can be said.

Hydrogen storage alloys, liquid hydrogen storage, and gaseous hydrogen storage have been developed so far, but hydrogen storage alloys can be stored safely at pressures of 20 to 40 atm at room temperature. There is a problem that the weight is heavy, the price is expensive, and even in the hydrogen storage capacity is lower than gasoline or diesel. 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.

Recently, the hydrogen storage method using a carbon material has been greatly studied due to the above problems. Attempts to use carbonaceous materials as hydrogen storages began in the 1970s when doping alkali metals into graphite significantly increased hydrogen storage. However, since the amount of storage is very small compared to hydrogen storage alloy, much research has not been conducted since then. Therefore, the search for the development of a new light and safe hydrogen storage has been made steadily, and in particular, studies using carbon materials have been variously conducted.

In recent years, graphite having a layered structure in which each layer is bound by weak van der Waals force as abundant material 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.

Accordingly, graphite powder is a material that is expected to be applied in the fields of electronic information communication, environment, energy, and medicine. In particular, graphite powder as a hydrogen storage medium is safer than the high pressure hydrogen and liquefied hydrogen storage, and the reaction is reversible. It can be used semi-permanently.

Therefore, the present inventors have made diligent efforts to find the optimal functionalization conditions for high efficiency hydrogen storage in order to develop innovative hydrogen storage materials based on the existing graphite powder. As a result, the surface of the graphite powder through chemical impregnation using phosphoric acid solution and The functionalization of the structure was confirmed and the present invention was completed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a graphite powder surface modification method for chemically impregnating a phosphoric acid solution to produce a graphite powder for high efficiency hydrogen storage and a high efficiency hydrogen storage graphite powder containing a large amount of hydrogen affinity points modified by the surface modification method. Is in.

Another object of the present invention is to provide a graphite powder-based adsorbent for hydrogen storage having an improved hydrogen storage amount including the graphite powder.

In order to achieve the above object, the present invention provides a graphite powder surface modification method of chemically impregnated with a phosphate solution and a high-efficiency hydrogen storage suitable graphite powder modified by the surface modification method containing a large amount of hydrogen affinity point. .

The present invention also provides a graphite powder-based adsorbent for improving hydrogen storage amount including the graphite powder prepared according to the above method.

According to the present invention as described above, by functionalizing the surface and structure of the graphite powder through the chemical impregnation process using a phosphoric acid solution, compared to the conventional commercially available graphite powder, by providing a large amount of hydrogen affinity point, the hydrogen storage capacity is greatly improved It is effective to provide graphite powder-based adsorbent for hydrogen storage.

According to the present invention can greatly improve the hydrogen storage capacity of the hydrogen storage medium.

In addition, it can be used in the active material for the electrode material and semiconductor of the electrochemical device including the high-performance graphite powder for hydrogen storage prepared according to the present invention.

1 is an X-ray photoelectron spectroscopy graph of a high efficiency hydrogen storage graphite powder-based adsorbent prepared in the present invention.

Hereinafter, the present invention will be described in detail.

The present invention provides a graphite powder surface modification method for chemically impregnating a structure-modified graphite powder with a phosphoric acid solution using a concentrated acid and an oxidant solution.

Specifically, the present invention comprises the steps of (1) washing the graphite powder; (2) modifying the washed graphite powder by adding an oxidizing agent solution after the concentrated acid treatment at room temperature; And (3) functionalizing the surface of the graphite powder through chemical phosphoric acid deposition on the structure-modified graphite powder; Characterized in that it comprises a.

In the present invention, the graphite powder in step (1) is natural crystal graphite (Natural Crystalline Graphite), artificial graphite (Synthetic Graphite), soil graphite (Amorphous Graphite), activated carbon, activated carbon fibers, pitch-based nanofibers It is preferable to use at least one selected from, and carbon nanotubes (Carbon nanotube).

In addition, the washing process in the step (1) is preferably stirred at least three times for 12 to 24 hours in 200 mL of distilled water and ethanol.

In addition, the concentrated acid treatment in step (2) is preferably impregnated for 1 to 5 hours from one or more selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ) and hydrochloric acid (HCl) solution. .

In addition, in the step (2), the oxidizing agent solution is hydrogen peroxide solution (H ₂ O ₂ ? NH ₂ O), potassium permanganate solution (KMnO ₄ ? NH ₂ O), aqueous potassium thiosulfate solution (K ₂ S ₂ O ₈ ? NH ₂ O), can be a chlorine dioxide _{(Cl 2 O? nH 2 O} ), and hypophosphorous acid aqueous solution of sodium (NaClO (aq), is preferred to add to more than one selected from the group consisting of a), and the graphite powder impregnated in concentrated acid The graphite powder having the structure of graphite is controlled by adding an oxidizing agent aqueous solution.

The surface modification process of the graphite powder using the concentrated acid treatment and the oxidizing agent solution is a pretreatment process for controlling the interlayer spacing. However, excessive surface treatment is not preferable because it disrupts the structure of the graphite powder.

In addition, the modified graphite powder is characterized in that it further comprises a process of washing with distilled water several times until it is neutral and completely dried at 80 ℃ or more for 6 to 24 hours, preferably 12 hours. This washing process is to completely remove the organic volatiles and amorphous carbon and the like present in the graphite powder.

In addition, the step (3) is characterized in that the made in a stirred state at room temperature.

In addition, the concentration of the phosphate solution in the chemical phosphate impregnation treatment of step (3) is preferably 0.01 to 20 M, more preferably 0.1 to 10 M. The extremely low concentration of phosphate solution has too little functional group introduced on the surface of the graphite powder, so the effect of hydrogen-molecule affinity group in the graphite powder-based adsorbent is insignificant. This is undesirable because it inhibits the induction of hydrogen molecules into the adsorbent pores.

The present invention also provides a graphite powder for high efficiency hydrogen storage containing a large amount of hydrogen affinity point modified by the surface modification method.

The present invention also provides a graphite powder-based adsorbent for improving hydrogen storage amount including the graphite powder prepared according to the above method.

The graphite powder-based adsorbent for hydrogen storage, which has greatly improved hydrogen storage amount, is characterized in that the amount of oxygen functional group is introduced in an amount of 15 to 50.0 wt.% Based on the weight ratio of the graphite powder.

In addition, the hydrogen storage graphite powder-based adsorbent significantly improved hydrogen storage is characterized in that it has a hydrogen storage adsorption value of 3 to 10.0 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 1. Measurement of the surface functional group of the surface-modified graphite powder

According to the present invention, the surface functional group change of the graphite powder-based adsorbent for hydrogen storage including the surface-modified graphite powder through chemical impregnation of the phosphoric acid solution was measured by X-ray photoelectron spectroscopy (ESPALAB MK). -II).

Measurement Example 2 Measurement of Hydrogen Storage of Surface-Modified Graphite Powder

In order to measure the hydrogen storage of the prepared graphite powder, each sample was degassed for 6 hours while maintaining the residual pressure at ^{3 -3} K at 10 ^-3 torr or lower, and then subjected to 298 K, 100 atm using BEL-HP (BEL Japan). The hydrogen storage amount was measured at. The hydrogen storage measurement method was a step-by-step method, and the average sample volume was 0.1 g.

Example  One.

After stirring 1 g of graphite powder in distilled water and ethanol solution at room temperature for 12 hours, vacuum drying was carried out at 80 ° C for 12 hours. The same procedure was repeated three times. The washed graphite powder was impregnated with sulfuric acid (H ₃ PO ₄ ) at room temperature for 1 hour, hydrogenated peroxide (H ₂ O ₂ ), and then impregnated for 24 hours, washed and filtered once or twice, and then at 120 ° C. for 24 hours. After drying completely, a graphite powder having a modified structure of graphite was prepared. In addition, the prepared structure-modified graphite powder was impregnated with 1 M phosphoric acid (H ₃ PO ₄ ) solution and stirred for 12 hours. Then, washed 1-2 times in distilled water and completely dried at 120 ℃ for more than 12 hours to prepare a surface functionalized graphite powder introduced oxygen functional group.

The entire process of preparing the graphite powder-based adsorbent for hydrogen storage, in which the hydrogen storage amount introduced with the oxygen functional group was significantly improved by chemically impregnating the phosphoric acid solution by concentration, was performed at room temperature and under stirring.

Example  2.

After stirring 1 g of graphite powder in distilled water and ethanol solution at room temperature for 12 hours, vacuum drying was carried out at 80 ° C for 12 hours. The same procedure was repeated three times. The washed graphite powder was impregnated with sulfuric acid (H ₃ PO ₄ ) at room temperature for 1 hour, hydrogenated peroxide (H ₂ O ₂ ), and then impregnated for 24 hours, washed and filtered once or twice, and then at 120 ° C. for 24 hours. After drying completely, a graphite powder having a modified structure of graphite was prepared. In addition, the prepared structure-modified graphite powder was impregnated with 2M phosphoric acid (H ₃ PO ₄ ) solution and stirred for 12 hours. Then, washed 1-2 times in distilled water and completely dried at 120 ℃ for more than 12 hours to prepare a surface functionalized graphite powder introduced oxygen functional group.

The entire process of preparing the graphite powder-based adsorbent for hydrogen storage, in which the hydrogen storage amount introduced with the oxygen functional group was significantly improved by chemically impregnating the phosphoric acid solution by concentration, was performed at room temperature and under stirring.

Example  3.

After stirring 1 g of graphite powder in distilled water and ethanol solution at room temperature for 12 hours, vacuum drying was carried out at 80 ° C for 12 hours. The same procedure was repeated three times. The washed graphite powder was impregnated with sulfuric acid (H ₃ PO ₄ ) at room temperature for 1 hour, hydrogenated peroxide (H ₂ O ₂ ), and then impregnated for 24 hours, washed and filtered once or twice, and then at 120 ° C. for 24 hours. After drying completely, a graphite powder having a modified structure of graphite was prepared. In addition, the prepared structure-modified graphite powder was impregnated with 5M phosphoric acid (H ₃ PO ₄ ) solution and stirred for 12 hours. Then, washed 1-2 times in distilled water and completely dried at 120 ℃ for more than 12 hours to prepare a surface functionalized graphite powder introduced oxygen functional group.

The entire process of preparing the graphite powder-based adsorbent for hydrogen storage, in which the hydrogen storage amount introduced with the oxygen functional group was significantly improved by chemically impregnating the phosphoric acid solution by concentration, was performed at room temperature and under stirring.

Example  4.

After stirring 1 g of graphite powder in distilled water and ethanol solution at room temperature for 12 hours, vacuum drying was carried out at 80 ° C for 12 hours. The same procedure was repeated three times. The washed graphite powder was impregnated with sulfuric acid (H ₃ PO ₄ ) at room temperature for 1 hour, hydrogenated peroxide (H ₂ O ₂ ), and then impregnated for 24 hours, washed and filtered once or twice, and then at 120 ° C. for 24 hours. After drying completely, a graphite powder having a modified structure of graphite was prepared. In addition, the prepared structure-modified graphite powder was impregnated with 10 M phosphoric acid (H ₃ PO ₄ ) solution and stirred for 12 hours. Then, washed 1-2 times in distilled water and completely dried at 120 ℃ for more than 12 hours to prepare a surface functionalized graphite powder introduced oxygen functional group.

The entire process of preparing the graphite powder-based adsorbent for hydrogen storage, in which the hydrogen storage amount introduced with the oxygen functional group was significantly improved by chemically impregnating the phosphoric acid solution by concentration, was performed at room temperature and under stirring.

Example  5.

The process was performed in the same manner as in Example 3, but the chemical phosphoric acid impregnation treatment was stirred for 2 h to prepare a graphite powder-based adsorbent for hydrogen storage, which greatly improved the hydrogen storage amount into which the oxygen functional group was introduced.

Comparative example  One.

After stirring 1 g of graphite powder in distilled water and ethanol solution at room temperature for 12 hours, vacuum drying was carried out at 120 ° C. for 12 hours. The same procedure was repeated three times.

Comparative example  2.

After the same process as in Comparative Example 1, the washed graphite powder is attached to sulfuric acid (H ₃ PO ₄ ) for 1 hour at room temperature, hydrogen peroxide (H ₂ O ₂ ) is added for 24 hours, 1 ~ After washing twice and filtration, and completely dried at 120 ℃ 24 hours to prepare a structure-modified graphite powder.

Table 1 and Table 2 below are the results showing the amount of oxygen functional group supported and hydrogen adsorption of the hydrogen storage graphite powder-based adsorbent prepared by chemically impregnated with each concentration of phosphoric acid solution according to the present invention.

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 (10)

(1) washing the graphite powder; (2) modifying the washed graphite powder by adding an oxidizing agent solution after the concentrated acid treatment at room temperature; And (3) functionalizing the surface of the graphite powder through chemical phosphoric acid attachment to the structure-modified graphite powder.
The method of claim 1,
In the step (1), the graphite powder is natural crystalline graphite (Natural Crystalline Graphite), artificial graphite (Synthetic Graphite), soil graphite (Amorphous Graphite), activated carbon, activated carbon fibers, pitch-based nanofibers, and carbon nanotubes Graphite powder surface modification method using at least one selected from (Carbon nanotube).
The method of claim 1,
The washing step in the step (1) is a graphite powder surface modification method, characterized in that the stirring three or more times for 12 to 24 hours in distilled water and ethanol.
The method of claim 1,
The concentrated acid treatment in the step (2) is graphite, characterized in that the impregnation for 1 to 5 hours from one or more selected from the group consisting of sulfuric acid (H ₂ SO ₄ ), nitric acid (HNO ₃ ) and hydrochloric acid (HCl) solution. Powder surface modification method.
The method of claim 1,
In step (2), the oxidizing agent solution is hydrogen peroxide solution (H ₂ O ₂ ? NH ₂ O), potassium permanganate solution (KMnO ₄ ? NH ₂ O), aqueous potassium thiosulfate solution (K ₂ S ₂ O ₈ ? NH ₂ O ), the number of chlorine dioxide _{(Cl 2 O? nH 2 O} ), and hypophosphorous acid aqueous solution of sodium (NaClO (aq)) to the graphite, characterized in that to add to the selected one concentrated acid impregnated the treated graphite powder solution equal to or higher than in the group consisting of Powder surface modification method.
The method of claim 1,
Step (3) is a method for surface modification of graphite powder, characterized in that the stirring at room temperature.
The method of claim 1,
The concentration of the phosphate solution in the chemical phosphate impregnation treatment of step (3) is characterized in that the graphite powder surface modification method.
A graphite powder for high efficiency hydrogen storage containing a large amount of hydrogen affinity point modified according to any one method selected from claims 1 to 7.
Graphite powder-based adsorbent for hydrogen storage with improved hydrogen storage amount comprising the graphite powder of claim 8.
The method of claim 9,
The graphite powder-based adsorbent for hydrogen storage according to the treatment conditions, the hydrogen storage amount of the graphite powder-based adsorbent for improved hydrogen storage, characterized in that the amount of oxygen functional group has a 15 to 50.0 wt.% Based on the weight ratio of the graphite powder.

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