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

Abstract

Electronic structure calculations suggest that hydrazine bisalane (AlH₃NH₂NH₂AlH₃, 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 AlH₃ group from AlH₃AlH₃NH₂NH₂ rather than by a direct attachment of a separate AlH₃ group, generated by predissociation of dialane, to AlH₃NH₂NH₂. 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. H₂ release from hydrazine bisalane is thus more favored over that from hydrazine bisborane, making the Al derivative an alternative candidate for CHS.