Hydrogen storage : effect of catalysts on hydrogen desorption/ absorption of Li-N-H and Li-Al-N-H systems

Abstract

This work explored the hydrogen storage capacity of Li-N-H and Li-Al-N-H systems; a mixture of lithium amide (LiNH2) and lithium hydride (LiH) and a mixture of LiNH2 and lithium aluminium hydrides (LiAlH4). The hydrogen desorption/absorption capacity was observed through volumetric analysis. LiNH2 and LiH were mixed by mortar and pestle and ball milling techniques with a small amount of Fe, Ni, ZrCl4, and TiO2 while LiNH2 and LiAlH4 were doped with ZrCl4, TiO2, and VCL3 mixed by ball milling. The hydrogen desorption was performed from room temperature to 200C and hydrogen absorption was at 1500 psig and 180C. The results showed that the transition metals and mixing means seemed to increase the hydrogen desorption capacity from the Li-N-H systems. The mixture of LiNH2 and LiH doped with TiO2 and mixed by agate ball mill gives the best result followed by those mixed with ZrCl4, Ni, and Fe, respectively. The amounts of released hydrogen are between 0.5-1.5 wt% and are not reversible. In the case of the mixture of LiNH2 and LiAIH4, the hydrogen desorptions of the undoped samples are in range 2.5 - 5.0 wt% for the first cycle and they can increase up to 8.0 wt% when doped with catalysts. Moreover, the samples can be reversible about 0.15 - 0.4 wt%.