A New Concept of Hydrogen Storage Using Lithium Hydride and Ammonia
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1042-S06-01
A New Concept of Hydrogen Storage Using Lithium Hydride and Ammonia Yoshitsugu Kojima1, Satoshi Hino2, Kyoichi Tange2, and Takayuki Ichikawa1 1 Institute for Advanced Materials Research, Hiroshima University, 1-3-1, Kagamiyama, Higashi-Hiroshima, 739-8530, Japan 2 Department of Quantum Matter, ADSM, Hiroshima University, 1-3-1, Kagamiyama, Higashi-Hiroshima, 739-8530, Japan ABSTRACT Lithium hydride LiH reacted with NH3 at room temperature by the exothermic reaction (∆H:-43.1 kJ/molH2), generating H2 and lithium amide LiNH2. X-ray diffraction and gas chromatography indicated that LiNH2 and H2 were formed by the reaction of LiH in the NH3 atmosphere of 0.5 MPa at room temperature. After H2 generation, LiNH2 was able to store H2 at 573 K to form LiH and NH3 under 0.5 MPa H2 flow. In contrast, LiNH2 could not store H2 in a closed vessel at the pressure and the temperature, because the low NH3 partial pressure prevents the decomposition of LiNH2. Thus, we found that the H2 storage and the generation of the LiH-NH3 system took the following reaction path, LiH + NH3 ↔LiNH2 + H2. H2 of 8.1 mass% [H2/LiH+NH3] can be reversibly stored in this reaction. INTRODUCTION Fuel cell is a battery, which is actuated with hydrogen (H2) and oxygen. Energy obtained upon a reaction of hydrogen and oxygen is directly converted into electric energy. Since such a fuel cell has efficiency much higher than that of conventional combustion engines, FCV (Fuel Cell Vehicle) is expected as a car having high efficiency [1]. One of the most widely envisioned sources of fuel for the FCV is H2. Therefore, it is necessary to have a storage tank of H2 to start the system on demand. H2 can be reversibly stored in tanks as compressed [1], liquefied H2 [1] or by adsorption on carbon materials [1, 2]. It can also be stored in hydrogen absorbing alloys [3, 4] or as a chemical hydride, such as NaBH4 [5, 6], NaAlH4 [7], Li-N-H [8], Li-Mg-N-H [9-12], Li-Mg-B-H [13] or MgH2 [14, 15] as well as in an organic hydride, such as methylcyclohexane [16]. A high-pressure MH tank with a heat-exchanger module containing Ti1.1CrMn (300kg) has been developed [3, 4]. The measured H2 capacity at 35 MPa was 7.3 kgH2/180L (outer volume), which was 2.5 times of the high pressure tank (35MPa). But, the high-pressure MH tank was heavy (420 kg) compared with the high pressure tank (
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