First-principles study of LiBH4 nanoclusters interaction with models of porous carbon and silica scaffolds

Density functional theory calculations of an interaction of LiBH4 represented by n = 2−6 and 12 formula units nanoclusters with models of activated carbon and porous silica show that on both non-defective substrates only physisorption is observed for all cluster sizes. The binding energies are low, reaching up to −43 kJ/mol for smallest clusters. The charge transfer between LiBH4 and the support is not observed. On defective graphene (LiBH4)2 may adsorbed dissociatively. Hydrogens detached from BH4 groups saturates under-coordinated C atoms while the binding between BH3 moiety and underlying C atoms restores sp3-hybridization in the BH4 group. The dissociative adsorption of LiBH4 clusters leads to the retrieval of the three-fold coordination of the C atoms, the subsequent (LiBH4)2 physisorps with the differential heat of adsorption not exceeding −46 kJ/mol. The present calculations indicate that chemical interaction between matrix and lithium borohydride, leading to a destabilization of LiBH4, takes place until substrate's defects remain unsaturated.