(335ak) Hydrogen Storage Property of New Li-Al-N-H System

Although there have been numerous materials systems studied as potential candidates for hydrogen storage applications, none of the materials known to date has demonstrated enough hydrogen capacity or efficiency at required operating temperature ranges. There are still considerable opportunities for discovery of new materials or material systems that could lead to advances in science as well as commercial technologies in this area. LiAlH4 is one of the most promising materials owing to its high hydrogen content. In the present work, we investigated dehydrogenation properties of combined systems of alanate and amide under atmospheric argon. Thermogravimetric analysis (TGA) of 2LiAlH4/LiNH2 mixtures without any catalysts indicated that a large amount of hydrogen (~ 8.1 wt%) can be released between 85 and 320 C in three dehydrogenation reaction steps. Thermogravimetric analysis (TGA) of Li3AlH6/3LiNH2/4 wt% TiCl3-⅓AlCl3 mixtures indicated that a large amount of hydrogen (~ 7.1 wt%) can be released between 150 and 300 C in two dehydrogenation reaction steps. The results also show that the dehydrogenation reaction of this material system is nearly 100% reversible under 2000 psi pressure of hydrogen at 300 C. It is found that LiNH2 effectively destabilizes alanates (LiAlH4 and Li3AlH6) by reacting with LiH during the dehydrogenation process of alanates. Further, a short-cycle experiment on the mixture of Li3AlH6/3LiNH2 has demonstrated that this combined material system can maintain its hydrogen storage capacity upon cycling of the dehydrogenation/re-hydrogenation reactions.