(256d) Novel Light Weight Complex Hydrides for Hydrogen Storage

The development of light weight hydrogen storage systems with high volumetric and gravimetric hydrogen densities is indeed essential for realizing the pollution free vehicular transportation [1]. Though, conventional metal hydrides possess the highest volumetric efficiencies, their gravimetric capacities are rather low (< 2wt.%). On the other hand, complex chemical hydrides bearing light weight elements such as Li, Na, Mg, B, Al etc. show promising hydrogen storage behavior at moderate temperatures. Some of the complex hydrides are having high theoretical capacity of 10.0-18.0 wt.% (e.g. NaBH₄, LiBH₄ etc). However, the reversibility of these hydrides require the following individual or combined effects, (i) catalyst doping, (ii) lattice substitution and (iii) high temperature and pressure conditions. The breakthrough discovery of Ti- catalyzed NaAlH₄ exhibits an enhancement in the dehydrogenation and rehydrogenation behavior at moderate temperatures [2]. The available hydrogen storage capacity in Ti- doped NaAlH₄ is 5.6 wt.%, which is well below the DOE technical targets [3]. In the present investigation, we have developed the novel light weight complex hydrides and demonstrated their hydrogenation characteristics. A new class of hydrogen storage system Zn(BH₄)₂ with theoretical hydrogen capacity of 8.4 wt.% has been synthesized by an inexpensive mechanochemical process. The enthalpy of decomposition and the gravimetric capacity of these hydrides are measured using high pressure DSC and TGA techniques. The structure-property correlations of the as-prepared material have been analyzed via various metrological tools. References: [1] L. Schlapbach, A. Zuttel, Nature, 414, 2001, 353; [2] B. Bogdanovic, M Schwikardi, J. Alloys Compd., 253-254, 1997, 1-9; [3]http://www.eere.energy.gov/hydrogenandfuelcells/posture_plan04.html