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

Abstract The hydrogen storage capacities of a sandwich-type ethylene dimetallocene complex (Cp 2 Ti 2 C 2 H 4 ) are studied using first-principles calculations. It is found that the TiC 2 H 4 Ti 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 H 2 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 Cp 2 Ti 2 C 2 H 4 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/H 2 .