Direct synthesis and hydrogen storage behaviors of nanocrystalline Na LiAlH

Nanocrystalline NaLiAlH was directly synthesized by mechanical milling 2NaH/LiH/Al mixture with TiF catalyst under hydrogen pressure of 3.0 MPa. The synthesized NaLiAlH exhibits a dehydriding capacity of 3.09 wt% in the first cycle, which is higher than that of NaAlH. Because of the complexity of mass transfer, the rehydrogenation process of the dehydrided NaLiAlH is more intricate than that of the dehydrided sodium alanate, causing the formation of NaAlH and the reduction of rehydriding capacity in the following cycles. As temperature increases from 70 to 120 °C, hydrogen absorption kinetics is extremely enhanced. The dehydrided material can reabsorb 80% of the reversible hydrogen capacity within 5 min when the temperature is above 100 °C with an initial hydrogen pressure of 4 MPa. The scanning electron microscopy and energy dispersive X-ray spectroscopy show that the as-synthesized NaLiAlH along with the catalyst form a much homogeneous composite with a spherical particle size of 200 nm-2 μm. © 2011 Springer Science+Business Media, LLC.