C2H2M (M = Ti, Li) complex: A possible hydrogen storage material

The hydrogen storage capacity of Ti-acetylene (C2H2Ti) and Li-acetylene (C2H2Li) complex has been tested using second order Mّller Plesset method with different basis sets. Single Ti(Li) decorated acetylene complex can adsorb maximum of five(four) hydrogen molecules, which corresponds to the gravimetric hydrogen storage capacity of 12(19.65) wt % and it meets the target of 9 wt % by 2015 specified by US Department of Energy. The hydrogen adsorption energies with zero point energy and Gibbs free energy correction show that hydrogen adsorption on C2H2Ti is energetically favourable for a wide range of temperature and that is unfavourable on C2H2Li complex even at a very low temperature. Atom centered density matrix propagation molecular dynamics simulations reveal that four H2 molecules remain adsorbed on C2H2Ti complex at 300 K. Though H2 uptake capacity of C2H2Li complex is higher than that of C2H2Ti complex, the thermochemistry results favour to C2H2Ti complex over C2H2Li complex as a possible hydrogen storage media.