Dehydrogenation kinetics of as-received and ball-milled LiAlH4LiAlH4

In this paper, we investigate the dehydrogenation kinetics of LiAlH4LiAlH4 into Li3AlH6Li3AlH6 (reaction I) and further into LiH (reaction II). We find the apparent activation energies to be ∼80∼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 II. 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.

Effect of ball milling on kinetics. Rate constants for the dehydrogenation of lithium tetrahydroaluminate into trilithium hexahydroaluminate as a function of crystallite size obtained from XRPD line broadening.Figure optionsDownload full-size imageDownload as PowerPoint slide