Abstract
Various synthesis and rehydrogenation processes of lithium hydride (LiH) and magnesium amide (Mg(NH2)2) system with 8:3 molar ratio are investigated to understand the kinetic factors and effectively utilize the essential hydrogen desorption properties. For the hydrogen desorption with a solid-solid reaction, it is expected that the kinetic properties become worse by the sintering and phase separation. In fact, it is experimentally found that the low crystalline size and the close contact of LiH and Mg(NH2)2 lead to the fast hydrogen desorption. To preserve the potential hydrogen desorption properties, thermochemical and mechanochemical rehydrogenation processes are investigated. Although the only thermochemical process results in slowing the reaction rate due to the crystallization, the ball-milling can recover the original hydrogen desorption properties. Furthermore, the mechanochemical process at 150 °C is useful as the rehydrogenation technique to preserve the suitable crystalline size and mixing state of the reactants. As a result, it is demonstrated that the 8LiH and 3Mg(NH2)2 system is recognized as the potential hydrogen storage material to desorb more than 5.5 mass% of H2 at 150 °C.
Highlights
Hydrogen (H2) is an attractive energy carrier to effectively utilize natural energy resources such as solar, hydro, and wind energy
The kinetic control would be main issue to utilize the essential hydrogen storage properties because hydrogen is desorbed by the solid-solid reaction and the hydrogen absorption proceeds with the phase separation
The diffraction peaks observed in the case of pristine lithium hydride (LiH) were high intensity and sharp
Summary
Hydrogen (H2) is an attractive energy carrier to effectively utilize natural energy resources such as solar, hydro, and wind energy. In this policy, more than 5.5 mass% of the reversible hydrogen capacity and less than 150 °C for the operating temperature are required, where these values are based on material. Li2NH and Mg3N2 under higher temperature condition [17] This system is recognized as a potential hydrogen storage material to achieve the above practical properties. The cyclic hydrogen absorption and desorption properties were investigated by Ikeda et al [24] They reported that the initial hydrogen desorption capacity was 4.6 mass%. The kinetic control would be main issue to utilize the essential hydrogen storage properties because hydrogen is desorbed by the solid-solid reaction and the hydrogen absorption proceeds with the phase separation. From the obtained experimental results, the feasibility of achieving 5.5 mass% H2 desorption at 150 °C is discussed
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