Reaction Mechanism Study of LiNH2BH3 and (LiH)n (n = 1-5) Clusters Based on Density Functional Theory.

Abstract

Hydrogen energy is an ideal clean energy source for the future. In the promotion and application of hydrogen energy, the safe and effective storage of hydrogen needs to be addressed. LiNH₂BH₃, as an important hydrogen storage material, can reversibly store hydrogen, but it has the problem of a relatively high hydrogen release temperature. (LiH)_n plays a good regulatory role in the metal-N-H system and plays an important role. Using density functional theory, the reaction mechanism of LiNH₂BH₃ and (LiH)_n (n = 1-5) clusters was theoretically calculated and analyzed. The frontier orbitals of LiNH₂BH₃ (LiAB), LiNH₂BH₃-LiH (Li2AB), and LiNH₂-LiH (Li2A) were compared and analyzed, and the dissociation energies of hydrogen atoms at different sites were discussed. The results show that the dehydrogenation of LiNH₂BH₃ with (LiH)_n (n = 1-5) clusters is more likely to occur through the combination of H^δ-(Li)···H^δ+(N), and the minimum reaction energy barrier can reach 113.34 kJ/mol. In the LiNH₂BH₃-LiH system, the presence of -BH₃ and -LiH groups has a significant effect on the hydrogen release performance of the system. The order of hydrogen atom dissociation energies at different positions in LiAB, Li2AB, and Li2A is ΔE_H(N) > ΔE_H(B) > ΔE_H(Li). The dehydrogenation performance of Li2AB is better than that of LiAB and Li2A.