Oligomerization of Vanadium-acetylene systems and its effect on hydrogen storage

Abstract

A systematic computational study of oligomers and hydrogen storage properties of Vanadium-acetylene complexes has been performed by using the density-functional B3LYP method with 6-311++G (3df, 3pd) basis sets. C2H2V monomers can trap up to five hydrogen molecules with a binding energy of 0.13–0.46 eV/H2, reaching gravimetric uptake capacity as high as 11.57%. In condensed phase, oligomers are possible. Because the maximum number of H2 molecules that can be stored by (C2H2)nVm (n = 1–4; m = 1, 2) complexes not only depends on the coordination number of a single metal atom but also on the steric condition, the corresponding gravimetric uptake capacity reduce from 11.57% (C2H2V) to 2.85% ((C2H2)4V2). Both monomers and oligomers of Vanadium-acetylene complexes can coordinate multiple hydrogen molecules by the Kubas-typed orbital interaction, and back donation is the only determinant of the hydrogen adsorption state.