First-principles predictions of potential hydrogen storage materials: Novel sandwich-type ethylene dimetallocene complexes

The hydrogen storage capacities of a sandwich-type ethylene dimetallocene complex (Cp2Ti2C2H4) are studied using first-principles calculations. It is found that the TiC2H4Ti molecule can intercalate into the two cyclopentadienyl (Cp) rings and form a stable sandwich-type complex. Each Ti atom can adsorb a maximum of three H2 molecules, which corresponds to a gravimetric storage capacity of 4.73 wt%. This hydrogen storage capacity is close to the 2015 target of 5.5% set by the US Department of Energy (DOE) in 2009. Furthermore, the Cp2Ti2C2H4 molecule proposed in this paper is favorable for both adsorption and desorption of hydrogen molecules at room temperature and ambient pressure because its average binding energy of 0.34 eV/H2.