Hydrogen storage in a Li-Al-N ternary system

摘要

Hydrogen-storage properties and mechanisms of a novel Li-Al-N ternary system were systematically investigated by a series of performance evaluation and structural examinations. It is found that ca. 5.2 wt% of hydrogen is reversibly stored in a Li_3N-AlN (1:1) system, and the hydrogenated product is composed of LiNH_2, LiH, and AlN. A stepwise reaction is ascertained for the dehydrogenation of the hydrogenated Li_3N-AlN sample, and AlN is found reacting only in the second step to form the final product Li_3AlN_2. The calculation of the reaction enthalpy change indicates that the two-step dehydrogenation reaction is more thermodynamically favorable than any one-step reaction. Further investigations exhibit that the presence of AlN in the LiNH_2-2LiH system enhances the kinetics of its first-step dehydrogenation with a 10% reduction in the activation energy due likely to the higher diffusivity of lithium and hydrogen within AlN.