HYDROGEN STORAGE MATERIAL AND MANUFACTURING METHOD THEREOF

Abstract

A hydrogen storage material includes Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2. A manufacturing method of a hydrogen storage material includes steps of manufacturing a mixture by mixing Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2, and pulverizing the mixture.

Claims

1. A hydrogen storage material, comprising: Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2.

2. The hydrogen storage material of claim 1, wherein the hydrogen storage material comprises Mg(NH.sub.2).sub.2 at about 30 to 45 mol %, LiH at about 40 to 60 mol %, and MgH.sub.2 at about 5 to 15 mol %.

3. The hydrogen storage material of claim 1, wherein the hydrogen storage material further comprises a metal borohydride at about 1 to 10 mol represented by Chemical Formula 1 with respect to the total amount of 100 mol of Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2:
M(BH.sub.4).sub.n[Chemical Formula 1] where M includes one or more selected from the group consisting of Li, K, Mg, Ca, Sr, Ba, Y, La, and Ce, and n indicates an oxidation number of M.

4. The hydrogen storage material of claim 3, wherein M includes one or more selected from the group consisting of Li and K, and n indicates 1.

5. A manufacturing method of a hydrogen storage material, comprising steps of: manufacturing a mixture by mixing Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2; and pulverizing the mixture.

6. The manufacturing method of the hydrogen storage material of claim 5, wherein the step of manufacturing the mixture includes mixing Mg(NH.sub.2).sub.2 at about 30 to 45 mol %, LiH at about 40 to 60 mol %, and MgH.sub.2 at about 5 to 15 mol %.

7. The manufacturing method of the hydrogen storage material of claim 5, wherein the step of manufacturing the mixture further includes adding a metal borohydride represented by Chemical Equation 1 at about 1 to 10 mol with respect to the total amount of 100 mol of Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2:
M(BH.sub.4).sub.n[Chemical Formula 1] where M includes one or more selected from the group consisting of Li, K, Mg, Ca, Sr, Ba, Y, La, and Ce, and n indicates an oxidation number of M.

8. The manufacturing method of the hydrogen storage material of claim 7, wherein M includes one or more selected from the group consisting of Li and K, and n indicates 1.

9. The manufacturing method of the hydrogen storage material of claim 5, wherein the step of manufacturing the mixture by mixing Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2 includes mixing Li(NH.sub.2) and MgH.sub.2, and then heat-treating the mixed Li(NH.sub.2) and MgH.sub.2 at a temperature of about 120 to 170 C. and a hydrogen pressure of about 50 to 200 atm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 illustrates an analysis result of thermogravimetric analysis (TGA) after the synthesis of a hydrogen storage material manufactured by Exemplary Embodiment 1 and one cycle are properly conducted.

[0026] FIG. 2 illustrates an analysis result by an X-ray diffraction (XRD) analysis after the synthesis of the hydrogen storage material manufactured by Exemplary Embodiment 1, hydrogen release, and one cycle are properly conducted.

[0027] FIG. 3 illustrates an analysis result of thermogravimetric analysis (TGA) after the synthesis of hydrogen storage materials respectively manufactured by Exemplary Embodiment 1 and Comparative Example 1 is properly conducted.

[0028] FIG. 4 illustrates an analysis result by the thermogravimetric analysis (TGA) after hydrogen is released from the hydrogen storage materials respectively manufactured by Exemplary Embodiment 1 and Comparative Example 1.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0029] The advantages and features of the present inventive concept and the methods for accomplishing the same will be apparent from the exemplary embodiments described hereinafter with reference to the accompanying drawings. However, the present inventive concept is not limited to the exemplary embodiments described hereinafter, but may be embodied in many different forms. The following exemplary embodiments are provided to make the disclosure of the present inventive concept complete and to allow those skilled in the art to clearly understand the scope of the present inventive concept, and the present inventive concept is defined only by the scope of the appended claims. Throughout the specification, the same reference numerals denote the same elements.

[0030] In some exemplary embodiments, detailed description of well-known technologies will be omitted to prevent the disclosure of the present inventive concept from being interpreted ambiguously. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, throughout the specification, unless explicitly described to the contrary, the word comprise and variations such as comprises or comprising will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Further, as used herein, the singular forms a, an, and the are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0031] A hydrogen storage material according to an exemplary embodiment of the present inventive concept includes Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2.

[0032] In an exemplary embodiment of the present inventive concept, the hydrogen storage material includes LiH and MgH.sub.2, thereby decreasing the equilibrium temperature of hydrogen release and increasing reversible capacity.

[0033] For example, when only LiH is added without adding MgH.sub.2, a reversible endothermic chemical reaction occurs as in Chemical Equation 1.

4Mg(NH.sub.2).sub.2+6LiH2Li.sub.2Mg.sub.2(NH).sub.3+2LiNH.sub.2+6H.sub.2[Chemical Equation 1]

[0034] In this case, the reversible capacity is approximately 4.43 wt % and the equilibrium temperature of the hydrogen release reaches approximately 100 C.

[0035] Alternatively, in the exemplary embodiment of the present inventive concept, when both LiH and MgH.sub.2 are included in the hydrogen storage material, Chemical Equation 2 proceeds simultaneously with Chemical Equation 1 due to the addition of MgH.sub.2.

4Mg(NH.sub.2).sub.2+6LiH2Li.sub.2Mg.sub.2(NH).sub.3+2LiNH.sub.2+6H.sub.2[Chemical Equation 1]

2LiNH.sub.2+MgH.sub.2.fwdarw.Mg(NH.sub.2).sub.2+2LiH[Chemical Equation 2]

[0036] Therefore, Chemical Equation (3) is finally represented by combining both Chemical Equations (1) and (2).

3Mg(NH.sub.2).sub.2+4LiH+MgH.sub.22Li.sub.2Mg.sub.2(NH).sub.3+6H.sub.2[Chemical Equation 3]

[0037] Since Chemical Equation 2 described above represents an exothermic reaction, the equilibrium temperature of the hydrogen release of Chemical Equation 3 is lower than that of Chemical Equation 1.

[0038] Further, while an amide containing a high hydrogen content exists as a final product in Chemical Equation 1, all of the contents exist as the form of an imide in Chemical Equation 3. As a result, the reversible capacity of Chemical Equation 3 is higher than that of Chemical Equation 1.

[0039] Each component will be now described in detail.

[Mg(NH.sub.2).sub.2]

[0040] Mg(NH.sub.2).sub.2 may be included from about 35 to 45 mol % with respect to 100 mol % of the hydrogen storage material.

[0041] When the added amount of Mg(NH.sub.2).sub.2 is too small, hydrogen release capacity may deteriorate.

[0042] When the added amount of Mg(NH.sub.2).sub.2 is too large, the hydrogen release temperature may increase, and side products such as NH.sub.3 may be generated.

[0043] Accordingly, the added amount of Mg(NH.sub.2).sub.2 may be properly controlled in the above-mentioned range.

[LiH]

[0044] The hydrogen included in Mg(NH.sub.2).sub.2 is released by reacting with MgH.sub.2 and LiH.

[0045] LiH may be included from about 40 to 60 mol % with respect to 100 mol % of the hydrogen storage material.

[0046] When the added amount of LiH is too small, the hydrogen included in Mg(NH.sub.2).sub.2 may not be completely released, thus some hydrogen may remain.

[0047] When the added amount of LiH is too large, hydrogen storage capacity may deteriorate.

[0048] Accordingly, the added amount of LiH may be properly controlled in the above-mentioned range.

[MgH.SUB.2.]

[0049] The hydrogen included in Mg(NH.sub.2).sub.2 is released by reacting with MgH.sub.2 and LiH.

[0050] MgH.sub.2 may be included from about 5 to 15 mol % with respect to 100 mol % of the hydrogen storage material.

[0051] When the added amount of MgH.sub.2 is too small, the exothermic reaction of Chemical Equation 2 may not properly occur, and thus the equilibrium temperature of the hydrogen release may not drop.

[0052] When the added amount of MgH.sub.2 is too large, the reaction represented by Chemical Equation 4 is induced, and thus reversible capacity may deteriorate.

[0053] As a result, the added amount of MgH.sub.2 may be properly controlled in the above-mentioned range.

Mg(NH.sub.2).sub.2+MgH.sub.22MgNH+2H.sub.2[Chemical Equation 4]

[Metal Borohydride]

[0054] A hydrogen storage material according to an exemplary embodiment of the present inventive concept may further include a metal borohydride described in the following Chemical Formula 1.

[0055] The metal borohydride serves to accelerate the above-mentioned Chemical Equations 1 to 3.

M(BH.sub.4).sub.n[Chemical Formula 1]

[0056] In Chemical Formula 1, M includes one or more kinds of Li, K, Mg, Ca, Sr, Ba, Y, La, and Ce, and n indicates an oxidation number of M.

[0057] When M is two or more in Chemical Formula 1, it means that two or more kinds of the metal borohydride are included in the hydrogen storage material.

[0058] For example, when the M is K and Li, it means that both KBH.sub.4 and LiBH.sub.4 are included in the hydrogen storage material.

[0059] In Chemical Formula 1, n indicates the oxidation number of M.

[0060] For example, when M is Li, n is 1.

[0061] The metal borohydride at about 1 to 10 mol with respect to the total amount 100 mol of the Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2 may be further added.

[0062] When the added amount of the metal borohydride is too small, the improvement effect of the reaction rate may be insignificant.

[0063] When the added amount of metal borohydride is too large, hydrogen storage capacity may deteriorate.

[0064] Therefore, the added amount of the metal borohydride may be properly controlled in the above-mentioned range.

[0065] A manufacturing method of a hydrogen storage material according to an exemplary embodiment of the present inventive concept includes manufacturing a mixture by mixing Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2 (S10), and pulverizing the mixture (S20).

[0066] First, the mixture is manufactured by mixing Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2 at step S10.

[0067] A description with respect to each component of the mixture is the same as the above-mentioned description, so a description thereof will be omitted.

[0068] Step S10 may include mixing Li(NH.sub.2) and MgH.sub.2, and heat-treating the mixture at a temperature of about 120 to 170 C. and a hydrogen pressure of about 50 to 200 atm.

[0069] Mg(NH.sub.2).sub.2 and LiH may be prepared through step S10.

[0070] Next, the mixture is pulverized at step S20.

[0071] The hydrogen storage capacity may be enhanced by pulverizing the mixture.

[0072] Hereinafter, the present inventive concept will be described in detail on the basis of exemplary embodiments.

[0073] However, the following exemplary embodiments are only examples of the present inventive concept, and the present inventive concept is not limited to the exemplary embodiments.

Exemplary Embodiment 1

[0074] Heat-treatment was conducted at a temperature of about 150 C. and a hydrogen partial pressure of about 100 atm after Li(NH.sub.2) at about 0.81 g and MgH.sub.2 at about 0.46 g, and metal borohydrides such as LiBH.sub.4 at about 0.038 g and KBH.sub.4 at about 0.036 g, were properly mixed.

[0075] MgH.sub.2 at about 0.15 g was additionally mixed into the mixture described above after Mg(NH.sub.2).sub.2 and LiH generated from the starting materials was confirmed.

[0076] FIG. 1 illustrates the analysis result by a thermogravimetric analysis (TGA) after the synthesis of a hydrogen storage material manufactured by Exemplary Embodiment 1 and one cycle are properly conducted.

[0077] In this case, one cycle conducted the release and absorption of hydrogen at a temperature of about 170 C.

[0078] As shown in FIG. 1, it can be seen that since the hydrogen storage capacity is similar after the synthesis and the one cycle are properly conducted, the hydrogen storage material manufactured by Exemplary Embodiment 1 is reversible.

[0079] In addition, FIG. 2 illustrates the analysis result of X-ray diffraction (XRD) after the synthesis of the hydrogen storage material manufactured by Exemplary Embodiment 1, hydrogen release, and one cycle are properly conducted.

[0080] As shown in FIG. 2, it can be seen that since the starting materials such as Mg(NH.sub.2).sub.2, LiH, and MgH.sub.2 are apparently formed after the hydrogen release and the one cycle are properly conducted, the hydrogen storage material manufactured by Exemplary Embodiment 1 is reversible.

Comparative Example 1

[0081] In Comparative Example 1, a hydrogen storage material that is the same as in Exemplary Embodiment 1 was manufactured, except that MgH.sub.2 was not added.

[0082] FIG. 3 illustrates the analysis result of thermogravimetric analysis (TGA) after the synthesis of hydrogen storage materials respectively manufactured by Exemplary Embodiment 1 and Comparative Example 1 is properly conducted.

[0083] As shown in FIG. 3, it can be seen that the weight of the hydrogen storage material manufactured by Exemplary Embodiment 1 is reduced at a lower temperature.

[0084] In the thermogravimetric analysis (TGA), because the weight loss represents hydrogen release, it can be seen that the hydrogen storage material manufactured by Exemplary Embodiment 1 released hydrogen at a lower temperature.

[0085] FIG. 4 illustrates the analysis result by the thermogravimetric analysis (TGA) after the hydrogen storage materials respectively manufactured by Exemplary Embodiment 1 and Comparative Example 1 release hydrogen.

[0086] In this case, the hydrogen release was conducted at a temperature of about 170 C. for about 2 h.

[0087] As shown in FIG. 4, it can be seen that the amount of residual hydrogen of the hydrogen storage material manufactured by Exemplary Embodiment 1 is reduced, and this indicates that the hydrogen storage material manufactured by Exemplary Embodiment 1 has a fast chemical reaction.

[0088] The present inventive concept may be embodied in many different forms, and should not be construed as being limited to the disclosed embodiments. In addition, it will be understood by those skilled in the art that various changes in form and details may be made thereto without departing from the technical spirit and essential features of the present inventive concept. Therefore, it is to be understood that the above-described exemplary embodiments are for illustrative purposes only and the scope of the present inventive concept is not limited thereto.

[0089] While this inventive concept has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the inventive concept is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.