Dehydrogenation kinetics of as-received and ball-milled LiAlH4

In this paper, we investigate the dehydrogenation kinetics of LiAlH4 into Li3AlH6 (reaction I) and further into LiH (reaction II). We find the apparent activation energies to be similar to 80 and 100 kJ/mol for reactions I and II, respectively. Furthermore, we investigate the effect of ball milling on crystallite size and the dehydrogenation kinetics of both reactions I and It. We find a clear correlation between crystallite size and dehydrogenation kinetics of reaction I. On the other hand, we find the kinetics of reaction II to be independent of the crystallite size. This indicates that reaction I is limited by a mass transfer process, while reaction II is limited by the intrinsic kinetics. (C) 2005 Elsevier Inc. All rights reserved.