Hydrogenation of LiH/Al catalyzed with TiN, TiMn2 and LaNi5

In order to investigate the catalytic effect of TiN, TiMn2 and LaNi5 on the hydrogen storage capacity of LiAlH4, 2 mol% of the catalyst was milled with LiH/Al and then hydrogenated in Me2O. Doping with TiN, TiMn2 or LaNi5 led to substantial hydrogenation of LiH/Al in accordance with the formation of LiAlH4. In each case the amount of hydrogen absorbed was dependent on the catalyst and the ball-to-powder ratio used during milling. A high ball-to-powder ratio results in an improvement in the hydrogen storage capacity of LiAlH4. For each ball-to-powder ratio the highest hydrogen storage capacity was recorded for the TiN-catalyzed sample; hydrogen storage capacity increased from 3.2 to 4.8 to 6.0 wt.% H as the ball to-powder ratio increased from 10:1 to 20:1 to 40:1. The high levels of hydrogenation of LiH/Al catalyzed with TiN, TiMn2 and LaNi5 are remarkable because for the LiAlH4 system only a TiCl3 catalyst has previously been shown to result in rehydrogenation of the dehydrogenated products to LiAlH4.

► Reversible hydrogen storage by LiAlH4.
► First example using a catalyst other than TiCl3.
► Rare example of other hydrogen storage materials (AB5/AB2) acting as transfer catalysts.