KR100973305B1 - Pore controlling method for activated carbons and hydrogen storage device employing the activated carbons by the the method - Google Patents

Abstract

 Provided are a method for controlling porosity of activated carbon and a hydrogen storage device including activated carbon treated by the same.

Pore control method of activated carbon according to the present invention comprises the steps of placing the activated carbon in the reaction chamber equipped with an electrode; Supplying a fluorine-based gas and applying a voltage to form a plasma; And treating the surface of the activated carbon with the plasma to increase the fraction of micropores and reduce the average micropore diameter. According to the present invention, the fraction of commercially available carbon can be increased through a simple process. The average micropore diameter can be reduced, and the hydrogen storage device including the activated carbon surface-treated according to the present invention increases the hydrogen storage capacity by up to 50% or more compared with the conventional commercial activated carbon.

Description

Pore controlling method for activated carbons and hydrogen storage device employing the activated carbons by the the method}

The present invention relates to a method for controlling porosity of activated carbon, and more particularly, a method for controlling pore of activated carbon capable of increasing the fraction of micropores of activated carbon and decreasing the average micropore diameter, and hydrogen comprising the activated carbon treated thereby. Relates to a storage device.

Hydrogen is emerging as the ultimate future alternative energy source or energy carrier when anticipating environmental problems and rising or depleting fossil fuel prices. This is because fossil fuels are the main culprit of air pollutants, and in recent years, the increased concentration of carbon dioxide emitted into the atmosphere raises the concern about global warming, while hydrogen does not emit pollutants, and it is environmentally friendly, fuel, and hydrogen vehicles. This is because it can be used in almost all fields used in current energy systems such as hydrogen airplanes and fuel cells.

However, since hydrogen exists as a gas at room temperature and atmospheric pressure, energy density per volume is low and transport and storage are inconvenient. In particular, for mass production of hydrogen vehicles, hydrogen should be able to be stored at a high storage rate at low pressure. The annual target for hydrogen storage from the US Department of Energy (DOE) is 6% by 2010 and 9% by 2015.

The storage technology of hydrogen has been proposed to be stored in gas, liquid and solid state, and the method of storing hydrogen in gas state is to store and store high pressure hydrogen in cylinder to increase storage density. As a method used, it is easy to store and does not require a special auxiliary device, but has a disadvantage of low storage density and danger because it is ultra-high pressure of 500 atmospheres or more.

Meanwhile, as a method of storing hydrogen in a solid state, a method of storing hydrogen by using a hydrogen storage alloy made of rare earth metal and forming a metal hydride by reversibly reacting with hydrogen is known. Titanium-iron alloys, lanthanum-nickel alloys and magnesium-nickel alloys are in the practical stage of practical use and have the advantage of storing hydrogen at a pressure of 20 to 40 atm at room temperature, but they are heavy, expensive, and have performance due to poisoning and micronization. There is a problem of deterioration.

In addition, research on the use of a porous material such as a carbon-based material such as carbon nanotubes or a metal-organic framework (MOF) as a large surface area hydrogen adsorbent for inducing hydrogen adsorption, In the case of the metal-organic skeleton structure, the metal cluster occupies most of the weight, so that the weight is relatively heavy and the manufacturing cost is expensive.

On the contrary, although the carbon material is composed of a single element, there are various forms of bonding, and the carbon material is an excellent material having excellent properties such as chemical stability, electrical and thermal conductivity, high strength, high elastic modulus, and biocompatibility. In addition, it has the advantages of being safer and lighter than the conventional hydrogen storage method, and having a low storage cost. Since hydrogen storage is reversible, it can be used semi-permanently as well as being environmentally friendly.

However, the commercially available activated carbon was not suitable for storing hydrogen because its fraction of micropores was too low and the average micropore diameter was about 2 nm, which is considerably larger than the average diameter of hydrogen molecules. That is, a space suitable for storing hydrogen requires pores of about 1 to 1.5 nm in size and smaller micropores that can fix hydrogen molecules by physical bonds. To this end, a new method for pore provision or a technique for reducing the pore size of existing commercially available activated carbon should be provided.

Accordingly, the first problem to be solved by the present invention is to provide a pore control method of activated carbon that can increase the micropore fraction of activated carbon and reduce the average micropore diameter.

In addition, a second problem to be solved by the present invention is to provide a hydrogen storage device using the activated carbon treated by the method.

The present invention to achieve the first object,

Placing activated carbon in a reaction chamber equipped with an electrode; Supplying a fluorine-based gas and applying a voltage to form a plasma; And treating the surface of the activated carbon with the plasma to increase the fraction of the fine pores and to reduce the average fine pore diameter.

According to an embodiment of the present invention, the plasma is formed at atmospheric pressure, and the fluorine-based gas may be fluoro alkanes having 1 to 3 carbon atoms substituted with one or more fluorine atoms, and the concentration of the fluorine-based gas is 10 to 500 ppm. Can be.

In addition, the fluorine-based gas is CHF ₃ , CH ₂ F ₂ Or CH ₃ F.

According to another embodiment of the invention, the voltage is preferably 5 to 100W.

According to another embodiment of the present invention, the distance between the electrode and the activated carbon may be 0.1 to 10mm.

In addition, the time for treating the surface of the activated carbon with the plasma may be 30 to 600 seconds.

According to a preferred embodiment of the present invention, the micropore fraction of the plasma-treated activated carbon is 87 to 97%, the average micropore diameter may be 1.2 to 1.9 nm.

The present invention to solve the second problem,

It provides a hydrogen storage device comprising the activated carbon treated by the pore control method.

According to the present invention, while increasing the micropore fraction of the commercially available activated carbon through a simple process, it is possible to reduce the average micropore diameter, in the case of a hydrogen storage device containing the surface-treated activated carbon according to the present invention conventional commercial activity Compared with carbon, hydrogen storage capacity is increased by up to 50% or more.

Hereinafter, the present invention will be described in more detail.

The pore control method of activated carbon according to the present invention can increase the micropore fraction of the commercially available activated carbon by the fluorine-based plasma treatment process, reduce the average micropore diameter, the hydrogen storage device using the activated carbon treated according to the present invention Is characterized in that it can increase the hydrogen storage capacity up to 50% or more than when using a conventional commercial activated carbon.

The reason why the micropore fraction of the activated carbon is increased and the average micropore diameter is decreased by the fluorine-based plasma treatment is that there are atmospheric, medium and micropores in the activated carbon. This is because a large number of micropores are newly generated by fine etching. On the other hand, although the etching is performed in the case of atmospheric or mesopores, micropores are an important factor in hydrogen storage, and in the case of newly formed micropores, the pore size is very small, so the overall micropore fraction is very small. And the average micropore diameter decreases. Among the various plasmas, fluorine-based plasma is most preferable because it can form micropores while minimizing pore destruction by proper interaction with carbon.

As the activated carbon used in the present invention, commercially available activated carbon or activated carbon fibers may be used.

Gas, which is used when the fluorine-based plasma treatment in using an alkane as a fluorine-based gas, fluoroalkyl having 1-3 carbon atoms or the like inert gas He, to the fluoro-alkane is not particularly limited as long as that present in a gas at normal temperature and normal pressure, CHF _3, Preference is given to CH ₂ F ₂ or CH ₃ F. The use of small molecular weight gas has the advantage of making more micropores.

Preferably, the fluorine-based gas is contained in an amount of about 10 ppm to about 500 ppm, because the plasma treatment effect is too weak at less than 10 ppm, and negatively affects plasma generation when exceeding 500 ppm.

In the present invention, it is preferable that the voltage of the plasma is in the range of 5W to 100W. This is because the plasma treatment time is long in the low region and it is not easy to control by the sudden reaction in the high region.

In the present invention, the injection amount of gas during the plasma treatment is preferably 3 to 5 l / min, more preferably 5 l / min. In the present invention, the frequency for plasma generation is preferably 12 to 14 MHz, more preferably 13.56 MHz.

On the other hand, the distance between the plasma source and the activated carbon is preferably 0.1 to 10 mm, more preferably 1 to 5 mm. If the distance is less than 0.1 mm, the distance is too close, there is a risk of explosion, and if it is more than 10 mm, the treatment effect is weak, which is not preferable.

In the present invention, the plasma treatment time is preferably 30 seconds to 600 seconds. More preferably, between 60 and 300 seconds is preferable because strong energy must be used to introduce sufficient fluorine groups in too little time, and if the plasma treatment is performed for too long, pore structure destruction of activated carbon can be caused.

The hydrogen storage device according to the present invention includes a hydrogen storage container, a hydrogen injection tube and a discharge tube, and is characterized in that the activated carbon value treated according to the present invention is filled in the hydrogen storage container. The injection tube and the discharge tube may be integrally formed.

In the present invention, the hydrogen storage container is not particularly limited as long as it is a material capable of withstanding high vacuum and high pressure of 100 to 200 bar. For example, the hydrogen storage container is manufactured by using a high strength aluminum material as a lining and overlaying an ultra-lightweight, high elastic carbon fiber composite material. Can be. The vacuum degree is a vacuum degree required before hydrogen injection, and the hydrogen injection pressure during hydrogen storage is generally about 100 bar, so it is designed to withstand a pressure of about 200 bar as an upper limit to withstand such a high pressure. In addition, the shape of the hydrogen storage container is not particularly limited, but it is preferable that the pressure distribution is cylindrical so that the pressure distribution is uniform and the pressure can be sustained.

Hereinafter, with reference to the accompanying drawings will be described in more detail the present invention.

1 is a schematic cross-sectional view of a hydrogen storage device according to an embodiment of the present invention, which is intended to explain the structure of the hydrogen storage device according to the present invention, but the present invention is not limited thereto.

Referring to FIG. 1, the hydrogen storage device 1 according to the present invention is filled with an activated carbon 20 treated according to the present invention inside a cylindrical hydrogen storage container 10 and of the hydrogen storage container 10. One side is provided with an injection tube 30 for injecting hydrogen gas at a predetermined pressure, and the other side is provided with a discharge tube 40 for discharging the hydrogen gas, the injection tube 30 and the discharge tube 40 is opened and closed Valve (not shown) that can be adjusted is installed. As already mentioned, the injection tube and the discharge tube may be integrally formed.

Finally, when the hydrogen injection is completed, the injection pipe 30 may be closed and the discharge pipe 40 may be connected to an automobile or other apparatus using hydrogen as a raw material to release hydrogen to use as an energy source.

Although not shown in the drawing, the hydrogen storage device 1 according to the present invention may further include one or more hydrogen pipes along the axial direction of the hydrogen storage container 10 to facilitate the injection / discharge of hydrogen. Of course, other additional devices known in the art may be further provided.

Figure 2 shows an example of the use of a plurality of hydrogen storage device is connected according to the present invention. Referring to FIG. 2, a group of hydrogen storage devices including a plurality of hydrogen storage devices 1 according to the first embodiment is illustrated, and the group of hydrogen storage devices is generated through an external hydrogen generator 2. The hydrogen gas is introduced through the injection pipe 30 along the supply pipe 15 through a pressurizing feeder 3 for supplying it at a constant pressure, and each hydrogen storage device 1 in parallel to the supply pipe 15. Is placed. In addition, the discharge pipe 16 is installed so that the discharge pipe 40 of each hydrogen storage device 1 is connected in parallel, and is supplied to the external hydrogen gas consumption device 4 through this.

Hereinafter, the present invention will be described in more detail with reference to preferred examples, but the present invention is not limited thereto.

Example 1

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 1 mm. CHF ₃ gas was supplied at 10 ppm, and the voltage was treated at 10 W for 60 seconds.

Example 2

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 3 mm. CHF ₃ gas was supplied at 10 ppm, and the voltage was treated at 10 W for 60 seconds.

Example 3

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 5 mm. CHF ₃ gas was supplied at 10 ppm, and the voltage was treated at 10 W for 60 seconds.

Example 4

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 5 mm. CHF ₃ gas was supplied at 10 ppm, and the voltage was treated with 10 W for 120 seconds.

Example 5

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 5 mm. CHF ₃ gas was supplied at 10 ppm, and the voltage was treated with 10 W for 300 seconds.

Example 6

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 5 mm. CHF ₃ gas was supplied at 100 ppm, and the voltage was treated with 10 W for 300 seconds.

Example 7

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 5 mm. CHF ₃ gas was supplied at 500 ppm, and the voltage was treated with 10 W for 300 seconds.

Example 8

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 5 mm. CHF ₃ gas was supplied at 500 ppm, and the voltage was treated at 50 W for 300 seconds.

Example 9

5 g of activated carbon was placed in the gown of a 300 mm × 400 mm reaction chamber fed with He at a flow rate of 5 l / min, and then the position with the plasma electrode was set to 5 mm. CHF ₃ gas was supplied at 500 ppm, and the voltage was treated with 100 W for 300 seconds.

Test Example 1

The specific surface area, micropore fraction and average micropore diameter of the activated carbon treated by Examples 1 to 9 were measured 10 times, respectively, and the average values thereof are shown in Table 1 below, and the activities treated by Examples 1 to 9 were measured. Hydrogen storage using carbon is shown in FIG. 3.

The measurement was carried out by the following method.

(1) Activated carbon pore structure measurement

The pore structure of the surface-treated activated carbon was measured by taking about 0.1 g of a sample under a 77 K liquid nitrogen atmosphere and adsorbing nitrogen gas as an adsorbate. Pretreatment of the sample was degassed for about 9-12 hours at 573 K until the residual pressure in the sample was 10 ^-3 torr or less. After N ₂ isothermal adsorption test, P / P _o (P is the partial pressure, _Po is the saturated vapor pressure), the slope of the straight line with respect to the adsorption amount from about 0.05 to 0.3, from which the BET specific surface area, micropore fraction, average micropore diameter, etc. were determined.

(2) Determination of hydrogen storage amount (wt.%)

In order to measure the hydrogen storage amount of functional graphite, each sample was degassed for 6 hours while maintaining the residual pressure at 10 ^-3 torr or lower at 573K, and then subjected to conditions of 298K and 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 amount of samples was 1.0 g.

Sample name Specific surface area (m ² / g) Micropore fraction (%) Average micropore diameter (nm) Untreated 1550 85 2.0 Example 1 1525 88 1.73 Example 2 1530 87.5 1.8 Example 3 1540 87 1.9 Example 4 1525 88 1.75 Example 5 1510 90 1.7 Example 6 1470 94 1.5 Example 7 1450 95.5 1.35 Example 8 1435 96 1.3 Example 9 1420 97 1.2

Referring to Table 1 and the accompanying Figure 3, the activated carbon surface-treated by the pore control method according to the present invention was found to have a high micropore fraction and a low average micropore diameter compared to conventional commercially available activated carbon, As a result, although the specific surface area was reduced, the hydrogen storage capacity was increased.

1 is a schematic cross-sectional view of a hydrogen storage device according to an embodiment of the present invention.

2 is an embodiment in which a plurality of hydrogen storage devices according to the present invention are connected.

3 is a view of the hydrogen storage results using the activated carbon treated in Examples 1 to 9.

<Description of the symbols for the main parts of the drawings>

10: hydrogen storage container 20: organic-inorganic composite material

30: injection tube 40: discharge tube

50: organometallic precursor supply pipe 60: vacuum gas pipe

Claims (9)

Placing activated carbon in a reaction chamber equipped with an electrode; Supplying a fluorine-based gas at a concentration of 10 to 500 ppm and applying a voltage to form a plasma; And treating the surface of the activated carbon with the plasma to increase the fraction of micropores and to reduce the average micropore diameter. The method of claim 1, Formation of the plasma proceeds at atmospheric pressure, the fluorine-based gas is pore control method of activated carbon, characterized in that fluoro alkanes having 1 to 3 carbon atoms substituted with one or more fluorine atoms. 3. The method of claim 2, The fluorine-based gas is CHF ₃ , CH ₂ F ₂ Or CH ₃ F pore control method of the activated carbon. delete The method of claim 1, The voltage is pore control method of the activated carbon, characterized in that 5 to 100 W. The method of claim 1, Pore control method of the activated carbon, characterized in that the distance of the electrode and the activated carbon is 0.1 to 10mm. The method of claim 1, The time for treating the surface of the activated carbon with the plasma is 30 to 600 seconds, characterized in that pore control method of activated carbon. The method of claim 1, The fine pore fraction of the plasma-treated activated carbon is 87 to 97%, the average fine pore diameter of 1.2 to 1.9 nm characterized in that the pore control method of activated carbon. A hydrogen storage device comprising activated carbon treated by the pore control method according to any one of claims 1 to 3 or 5 to 8.

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