Hydrogen absorption and desorption by the Li-Al-N-H system

Lithium hexahydridoaluminate Li3AlH6 and lithium amide LiNH2 with 1: 2 molar ratio were mechanically milled, yielding a Li-Al-N-H system. LiNH2 destabilized Li3AlH6 during the dehydrogenation process of Li3AlH6, because the dehydrogenation starting temperature of the Li-Al-N-H system was lower than that of Li3AlH6. Temperature-programmed desorption scans of the Li-Al-N-H system indicated that a large amount of hydrogen (6.9 wt %) can be released between 370 and 773 K. After initial H-2 desorption, the H-2 absorption and the desorption capacities of the Li-Al-N-H system with a nano-Ni catalyst exhibited 3- 4 wt % at 10-0.004 MPa and 473-573 K, while the capacities of the system without the catalyst were 1-2 wt %. The remarkably increased capacity was due to the fact that the kinetics was improved by addition of the nano-Ni catalyst.