Investigations on the desorption kinetics of Mm-doped NaAlH4

This paper reports mischmetal (Mm) as an effective catalyst for fast desorption kinetics (3.7wt% in 60min in which 3.3wt% observed in 30min and 5wt% in 180min at the desorption temperature of 150 deg C for the 2mol% Mm-doped material) and rehydrogenation (up to 35 cycles) of the light weight hydrogen storage material NaAlH4. In fact this catalyst Mm has been shown to be better than the presently known catalyst Ti. For Mm, its presence when admixed in NaAlH4 is discernible. Also the higher reversible hydrogen storage capacity (4.77wt% which is 86% of the total reversible storage capacity) of the total is achievable in the 12th cycle. The possible modes of catalyst Mm for fast desorption kinetics has been outlined and the most feasible mechanism in terms of weakening of Na and AlH4 bonding has been put forward.