Hydrazine bisalane is a potential compound for chemical hydrogen storage. A theoretical study

摘要

Electronic structure calculations suggest that hydrazine bisalane (AlH _3NH_2NH_2AlH_3, alhyzal) is a promising compound for chemical hydrogen storage (CHS). Calculations are carried out using the coupled-cluster theory CCSD(T) with the aug-cc-pVTZ basis set. Potential energy surfaces are constructed to probe the formation of, and hydrogen release from, hydrazine bisalane which is initially formed from the reaction of hydrazine with dialane. Molecular and electronic characteristics of both gauche and transalhyzal are determined for the first time. The gauche hydrazine bisalane is formed from starting reactants hydrazine + dialane following a movement of an AlH_3 group from AlH_3AlH _3NH_2NH_2 rather than by a direct attachment of a separate AlH_3 group, generated by predissociation of dialane, to AlH_3NH_2NH_2. The energy barriers for dehydrogenation processes from gauche and transalhyzal are in the range of 21-28 kcal mol~(-1), which are substantially smaller than those of ca. 40 kcal mol~(-1) previously determined for the isovalent hydrazine bisborane (bhyzb) system. H_2 release from hydrazine bisalane is thus more favored over that from hydrazine bisborane, making the Al derivative an alternative candidate for CHS.