Hydrogen storage properties of Li-Ca-N-H system with different molar ratios of LiNH2/CaH2

In this work, dehydrogenation and rehydrogenation of three LiNH2/CaH2 samples with LiNH2/CaH2 molar ratio of 2/1, 3/1 and 4/1 were systematically investigated. Remarkable differences were observed in the temperature dependence of hydrogen desorption and subsequent absorption. LiNH2/CaH2 in a molar ratio of 2/1 transforms to ternary imide Li2Ca(NH)(2) after desorbing about 4.5 wt.% H-2 at 350 degrees C. And it has a reversible hydrogen storage capacity of 2.7 wt.% at 200 degrees C. As for the LiNH2/CaH2 mixture in a molar ratio of 4/1, it transforms to a new compound with a composition of Li4CaN4H6 after being dehydrogenated at 350 degrees C. The rehydrogenation of both LiCa(NH)(2) and Li4CaN4H6 gives LiNH2, LiH and the solid solution of 2CaNH-Ca(NH2)(2). (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.