Reversible Hydrogen Storage in the Lithium Borohydride -- Calcium Hydride Coupled System

We report large reversible hydrogen storage in a new coupled system, LiBH$_{4}$/CaH$_{2}$, via the reaction 6 LiBH$_{4}$ + CaH$_{2}$ $\leftrightarrow $ 6 LiH + CaB$_{6}$ + 10 H$_{2}$ having a theoretical hydrogen capacity of 11.7 wt{\%} and an estimated reaction enthalpy of $\Delta $H = 59 kJ/mole H$_{2}$. Samples that include 0.25 mole (18.2 wt{\%}) TiCl$_{3}$ reproducibly store 9.1 wt{\%} hydrogen, corresponding to 95{\%} of the available hydrogen. H$_{2}$ is the only evolved gas detected by mass spectrometry. X-ray diffraction confirms that the sample cycles between LiBH$_{4}$ and CaH$_{2}$ in the hydrogenated state and LiH and CaB$_{6}$ in the dehydrogenated state.