KR101146309B1 - Hydrogen storage material and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a hydrogen storage material and a method for producing the same. Hydrogen storage materials include lithium boron hydride (LiBH ₄ ) and yttrium hydride. Yttrium hydride is one or more compounds selected from the group consisting of yttrium dihydride (YH ₂ ) and yttrium trihydride (YH ₃ ).

Yttrium Hydride, Hydrogen Storage Materials, High Energy Ball Milling

Description

Hydrogen storage material and its manufacturing method {HYDROGEN STORAGE MATERIAL AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a hydrogen storage material and a method for manufacturing the same, and more particularly, to a hydrogen storage material and a method for producing the lithium boron hydride and yttrium hydride.

Hydrogen may be stored in a solid material, a liquid material or a gaseous material. In particular, the technique of storing hydrogen in solid materials is superior to liquid and gaseous materials in terms of stability and efficiency.

A study on metal hydrides for hydrogen storage was published in 1997 by Bogdanovic et al. [B. A Bogdanovic & M. Schwickardi, "Ti- doped alkali metal aluminum hydrides as potential novel reversible hydrogen storage materials," Journal of Alloys & Compounds, 253-254 (1997) 1-9] , sodium aluminum hydride (NaAlH ₄₎ by Since the addition of a small amount of titanium-based catalyst is known to lower the dehydrogenation temperature and improve the reversibility, it has been actively progressed. Recently, the focus of research has shifted to metal borohydride (M (BH ₄ ) _n ), which has a larger storage capacity on average than metal aluminum hydride (M (AlH ₄ ) _n ).

SUMMARY To provide a hydrogen storage material including lithium boron hydride and yttrium hydride. It is to provide a method for producing the above-described hydrogen storage material.

Hydrogen storage material according to an embodiment of the present invention includes lithium boron hydride (LiBH ₄ ) and yttrium hydride (yttrium hydride).

Method for producing a hydrogen storage material according to an embodiment of the present invention comprises the steps of i) mixing lithium boron hydride powder and yttrium hydride powder to prepare a mixed powder, ii) the mixed powder and a plurality of balls in the reaction vessel Iii) filling the reaction vessel with an inert gas or hydrogen gas, sealing the reaction vessel, and iv) high energy ball milling the mixed powder to produce a hydrogen storage material. have.

In the step of preparing the mixed powder, there are two kinds of yttrium hydride YH ₂ and YH ₃ , both of which can be used. In the step of preparing the mixed powder, the molar ratio of lithium boron hydride to yttrium hydride may be 2 to 8. The molar ratio of lithium boron hydride powder to yttrium hydride powder can be substantially four.

In the step of introducing the mixed powder and the plurality of balls into the reaction vessel, the reaction vessel may be made of tool steel, stainless steel, cemented carbide (WC-Co), silicon nitride (Si ₃ N ₄ ), alumina or zirconia. Can be. In the step of introducing the mixed powder and the plurality of balls into the reaction vessel, the balls may be made of tool steel, stainless steel, cemented carbide, silicon nitride, alumina or zirconia and the size of the balls may be made from 5 mm to 30 mm. In the step of introducing the mixed powder and the plurality of balls into the reaction vessel, the weight ratio of the plurality of balls to the mixed powder may be 1 to 100.

 In the step of preparing the hydrogen storage material, the mixed powder may be high energy ball milling for 1 to 24 hours. In the step of preparing the hydrogen storage material, the high energy ball mill may be a shaker mill, a vibratory mill, a planetary mill or an attritor mill.

In a hydrogen storage material, the temperature at which two materials react to release hydrogen is lower than the dehydrogenation temperature of pure lithium borohydride. The dehydrogenation product produced by the reaction of two materials undergoes hydrogenation under low temperature and partial pressure of hydrogen compared to the dehydrogenation product of pure lithium borohydride. There is no reduction in hydrogen storage capacity due to the addition of the catalyst since reversible hydrogen storage properties are exhibited even without the addition of catalyst during the production process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

Unless defined otherwise, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. Commonly defined terms used are added to have meanings consistent with the related technical literature and the presently disclosed contents, and are not interpreted in an ideal or very formal sense unless defined.

Figure 1 schematically shows a method for producing a hydrogen storage material according to an embodiment of the present invention in order.

As shown in FIG. 1, in the method of manufacturing a hydrogen storage material, a step of preparing a mixed powder (S10), a step of putting the mixed powder and a plurality of balls into a reaction vessel (S20), an inert gas or hydrogen into the reaction vessel Filling and sealing the gas (S30), and high energy ball milling the mixed powder to produce a hydrogen storage material (S40). Each of the above-described steps will be described in detail as follows.

First, in step S10 to prepare a mixed powder. The mixed powder includes lithium boron hydride powder and yttrium hydride powder. Another powder may be further mixed with the mixed powder. Here, yttrium dihydride (YH ₂ ) or yttrium trihydride (YH ₃ ) may be used as the yttrium hydride powder.

The molar ratio of lithium boron hydride powder to yttrium hydride powder may be 2-8. If the molar ratio of lithium boron hydride powder to yttrium hydride powder is too small, the specific gravity of the heavy yttrium hydride becomes large, thereby reducing the total hydrogen storage capacity. In addition, when the molar ratio of the lithium boride hydride powder to the yttrium hydride powder is too large, the specific gravity of the lithium boride hydride having low reversibility of the hydrogenation reaction becomes large, and the hydrogenation reaction does not occur easily. Preferably, the molar ratio of lithium boron hydride powder to yttrium hydride powder may be substantially four.

Next, in step S20, the prepared mixed powder and a plurality of balls are added to the reaction vessel. The reaction vessel and balls can be made of tool steel, stainless steel, cemented carbide (WC-Co), silicon nitride (Si ₃ N ₄ ), alumina or zirconia. One or more of the balls may have a diameter of 5 mm to 30 mm. If the diameter of the ball is too small, the ball milling strength is so low that no chemical reaction of the above-mentioned powders takes place. In addition, when the diameter of the ball is too large, the ball milling strength is so high that the material of the ball or the container, for example, iron, may be incorporated as impurities in the mixed powder. Therefore, the diameter of the ball is maintained in the above range.

The weight ratio of the plurality of balls to the mixed powder in step S20 may be 1 to 100. If the weight ratio of the plurality of balls to the mixed powder is too small, the ball milling strength is low so that the above-described chemical reaction of the powders does not occur. In addition, when the weight ratio of the plurality of balls to the mixed powder is too large, the ball milling strength is so high that the material of the ball or the material of the container may be incorporated as impurities in the mixed powder.

In step S30, the reaction vessel is filled with inert gas or hydrogen gas and the reaction vessel is sealed. Argon, nitrogen, etc. can be used as an inert gas. Since high energy ball milling the mixed powder in the next step (S40), inert gas is charged to the reaction vessel to prevent explosion due to high energy ball milling.

In step S40, the above-described mixed powder is high-energy ball milled to produce a hydrogen storage material. The mixed powder is uniformly mixed by high energy ball milling. High energy ball milling may be performed using a shaker mill, a vibratory mill, a planetary mill, or an attritor mill.

The mixed powder can be high energy ball milled for 1 to 24 hours. If the high energy ball milling time is too short, the lithium boron hydride powder and the yttrium hydride powder are not uniformly dispersed. Conversely, when the high energy ball milling time is too long, the possibility that the material of the ball or the material of the container is incorporated as impurities in the mixed powder becomes high and the production efficiency is reduced.

When the high energy ball milling is complete, the reaction vessel is opened to remove the gas inside the reaction vessel. And the hydrogen storage material produced by the mechanical mixing reaction mentioned above is taken out.

Hydrogen storage materials prepared through the above-described method include lithium boron hydride and yttrium hydride. Here, yttrium hydride has a chemical formula of YH ₂ or YH ₃ .

The dehydrogenation reaction and the hydrogenation reaction occur according to the following reaction formula (1). As shown in Formula 1, when the hydrogen storage material is heated, lithium boron hydride and yttrium hydride included in the hydrogen storage material react with each other to be converted into lithium hydride (LiH) and yttrium boride (YB ₄ ). Release hydrogen. The theoretical hydrogen storage capacity is 8.4 wt% when the molar ratio of lithium boron hydride and yttrium hydride is 4: 1.

4LiBH ₄ + YH ₃ = 4LiH + YB ₄ + 7.5H ₂

Among the metal borohydrides, lithium borohydride is often used. In theory, lithium borohydride releases 13.9 wt% of hydrogen through a dehydrogenation reaction such as the following Chemical Formula 2.

LiBH ₄ = LiH + B + 1.5H ₂

As mentioned above, lithium borohydride has a theoretically large hydrogen storage capacity. However, the temperature at which the dehydrogenation proceeds is higher than 400 ° C. and the hydrogenation of the dehydrogenation reaction product to obtain lithium borohydride again requires a high temperature of 150 atm and a hydrogen pressure. On the other hand, the hydrogen emission temperature of the hydrogen storage material according to an embodiment of the present invention is low, the temperature and hydrogen pressure required for hydrogen storage is low, and the hydrogen storage rate is also high.

The hydrogen storage material prepared by mixing lithium boron hydride with binary metal hydride and titanium chloride as a catalyst and then high-energy ball milling has better properties than pure lithium borohydride. However, the hydrogen emission temperature of these hydrogen storage materials is still above 400 ° C., and the hydrogen storage rate is still slow for several tens of hours. On the other hand, the hydrogen emission temperature of the hydrogen storage material according to an embodiment of the present invention is low, the hydrogen storage rate is also high.

Hydrogen storage material consisting of lithium borohydride and yttrium hydride according to an embodiment of the present invention has the following properties. First, the temperature at which two materials react to release hydrogen at a high temperature is lower than the dehydrogenation temperature of pure lithium borohydride. Second, the dehydrogenation product produced by the reaction of two materials is hydrogenated under low temperature and hydrogen partial pressure as compared to the dehydrogenated product of pure lithium borohydride. Third, there is no problem of hydrogen storage capacity reduction due to the addition of the catalyst because the reversible hydrogen storage characteristics are shown even without the addition of a catalyst. In one embodiment of the present invention by producing a hydrogen storage material using a method of uniformly dispersed by high energy ball milling after mixing lithium borohydride and yttrium hydride, lower hydrogen emission temperature and improved than conventional hydrogen storage material It may indicate reversibility.

Hereinafter, the present invention will be described through experimental examples. These experimental examples are only for illustrating the present invention, and the present invention is not limited thereto.

Experimental Example

Lithium borohydride powder and yttrium hydride powder were mixed in a molar ratio of 4: 1 to prepare 3 g of mixed powder. Next, the mixed powder was put into a reaction vessel made of tool steel. And 13 balls of diameter 12.7mm and 24 balls of diameter 7.9mm made of chromium steel (Cr steel) were put into the reaction vessel.

After argon was charged to the reaction vessel, hydrogen storage material was prepared by performing high energy ball milling for 12 hours using a planetary mill at a rotational speed of 650 rpm. Next, the reaction vessel was opened to remove the product gas inside the vessel, and the produced hydrogen storage material was taken out of the reaction vessel.

Experiment result

Component Analysis Experiment of Hydrogen Storage Material

Figure 2 shows the results of the X-ray diffraction experiment of the hydrogen storage material prepared according to the experimental example of the present invention.

The X-ray diffraction pattern of FIG. 2 is measured after high energy ball milling the mixed powder. The diffraction pattern showed that the lithium boron hydride and the yttrium hydride exist relatively stably even after high energy ball milling without the incorporation of special impurities. However, some of the yttrium hydride, which was mostly composed of yttrium trihydride (YH ₃ ), was converted into yttrium dihydride (YH ₂ ) through high energy ball milling.

Hydrogen Release Rate Measurement Experiment

Figure 3 shows the hydrogen release curve with time of the hydrogen storage material prepared in a hydrogen atmosphere of 350 ℃, 3 atmospheres.

As shown in FIG. 3, it was confirmed that about 7 wt% of hydrogen was released until 8 hours after about 4 hours of incubation. Considering that the hydrogen release temperature of pure lithium boride hydride is about 470 ° C. in a hydrogen atmosphere of 3 atm, a great reduction in the dehydrogenation reaction temperature of the produced hydrogen storage material was confirmed.

X-ray Diffraction Experiments on Dehydrogenated Hydrogen Storage Materials

Figure 4 shows the X-ray diffraction pattern of the hydrogen storage material dehydrogenated for 24 hours at 350 ℃, 3 atmospheres of hydrogen atmosphere. Although lithium borohydride and yttrium hydride remain in small amounts, it was confirmed that most of the reaction products were composed of yttrium boride (YB ₄ ) and lithium hydride (LiH). That is, it was confirmed that the dehydrogenation reaction of the prepared hydrogen storage material proceeds.

X-ray diffraction experiment of hydrogenated hydrogen storage material

FIG. 5 shows an X-ray diffraction pattern of a material hydrogenated at 350 ° C. and 90 atm for 24 hours after dehydrogenation at 350 ° C. and at 3 atmospheres of hydrogen.

Although a small amount of yttrium boride, a product of the dehydrogenation reaction, was observed, it was confirmed that most of the dehydrogenation reaction was changed to lithium boron hydride and yttrium hydride by the hydrogenation reaction according to the reverse reaction of Chemical Formula 1 described above.

As described above, it was confirmed that the prepared hydrogen storage material reversibly releases and stores hydrogen. In particular, considering that most of the lithium borohydride-based composite hydrogen storage material is difficult to reversible hydrogenation without the aid of a catalyst, it was found that the hydrogen storage material is very reversible.

Although the present invention has been described above, it will be readily understood by those skilled in the art that various modifications and variations are possible without departing from the spirit and scope of the claims set out below.

1 is a flow chart showing a method of manufacturing a hydrogen storage material according to an embodiment of the present invention.

2 is an X-ray diffraction graph of a hydrogen storage material prepared according to an experimental example of the present invention.

3 is a curve showing the amount of hydrogen released over time of the hydrogen storage material.

4 is an X-ray diffraction pattern of the dehydrogenated hydrogen storage material.

5 is an X-ray diffraction pattern of a hydrogen storage material hydrogenated in a hydrogen atmosphere.

Claims (9)

delete delete delete delete Preparing a mixed powder by mixing lithium borohydride powder and yttrium hydride powder without adding a catalyst, Injecting the mixed powder and the plurality of balls into a reaction vessel, Filling the reaction vessel with an inert gas or hydrogen gas, sealing the reaction vessel, and Manufacturing a hydrogen storage material by high energy ball milling the mixed powder Including The yttrium hydride is at least one compound selected from the group consisting of YH ₂ and YH ₃ , the molar ratio of the lithium boron hydride to the yttrium hydride is substantially 4, In the step of preparing the hydrogen storage material, high energy ball milling the mixed powder for 1 to 24 hours, In the step of introducing the mixed powder and the plurality of balls into the reaction vessel, the diameter of one or more of the plurality of balls is 5mm to 30mm, the weight ratio of the plurality of balls to the mixed powder is hydrogen storage of 1 to 100 Method of making the material. delete delete delete delete

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