First-principles study of interaction of molecular hydrogen with Li-doped carbon nanotube peapod structures

Using first-principles density functional theory based on gradient corrected approach, we have studied interaction of H(2) molecule with Li-doped carbon nanotube and nanotube based peapod structures. We find that H(2) physisorbs on pure carbon nanotube, which is in agreement with earlier studies, and this binding increases when H(2) binds to Li-decorated on carbon nanotube surfaces: the binding is further enhanced with Li atoms deposited on C(60) doped nanotube peapod structures. The increase in binding in the latter structures arises due to charge transfer between the nanotube and C(60), which further facilitates charge transfer from Li to the nanotube. Encapsulating fullerene molecule inside the nanotube provides a different way of increasing charge concentration on Li atom adsorbed outside the nanotube. The increase in H(2) binding energy due to C(60) encapsulation, compared to recently engineered metal doped nanotube structures, may lead to different carbon based materials for hydrogen storage at room temperature.