DFT Calculations of Pressure Induced Phases of Calcium Borohydride as Hydrogen Storage Material in Fuel Cells

Abstract: Calcium borohydride Ca(BH4)2 is a potential hydrogen storage material due to its outstanding hydrogen capacity, however, its high thermodynamic stability is unfavorable for dehydrogenation processes. Understanding the bonding nature of B and H is essential for improving its dehydrogenation performance. In this work the charge density distribution in Ca(BH4)2 is studied. For this purpose, using calculated NQCCs of hydrogen atoms, the electronic structure of α-Ca(BH4)2 with high pressure forms of Ca(BH4)2 (β- Ca(BH4)2 and γ - Ca(BH4)2 )were compared. The results show that in the high pressure phase, hydrogens have greater NQCC and therefore these hydrogens form stronger bond with B.