Theoretical study of the hydrogen release mechanism from a lithium derivative of ammonia borane, LiNH 2BH 3–NH 3BH 3

Abstract

Ammonia borane and lithium amidoborane proved to have potential as efficient hydrogen storage materials. Although a combination of both compounds, LiNH 2BH 3–NH 3BH 3 has been shown to have even better hydrogen release characteristics, the inherent process was not clear. We determined the reaction mechanism of H 2 release from LiNH 2BH 3–NH 3BH 3 using computational quantum chemistry methods (MP2 and CCSD(T) methods and aug-cc-pVnZ basis sets). The energy barrier for H 2 release becomes lower than in pure LiNH 2BH 3 or NH 3BH 3 in agreement with experiment. Relevant transition structures are analyzed in detail and the initial formation of a cyclic adduct is likely responsible for the strong reduction of energy barriers.