An aromatic Ca2B8 complex for reversible hydrogen storage

Abstract

Ca2B8 cluster which shows high stability is predicted to be a symmetrical 3-dimension complex at coupled-cluster method. Charge analysis shows that the great charge transfers from Ca to B8 ring result in the formation of (Ca)22+(B8)4- complex. The aromaticity of this complex is identified through the negative nucleus-independent chemical shifts (NICS) and delocalized σ and π molecular orbitals. Importantly, the aromatic Ca2B8 is found to be a promising hydrogen storage material with moderate adsorption energy and high gravimetric density (10.6%). The adsorbed H2 molecules on Ca2B8 can be efficiently released at ambient temperature revealed by ab initio molecular dynamics (AIMD) simulation.