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 ${\mathrm{H}}_{2}$ molecule with Li-doped carbon nanotube and nanotube based peapod structures. We find that ${\mathrm{H}}_{2}$ physisorbs on pure carbon nanotube, which is in agreement with earlier studies, and this binding increases when ${\mathrm{H}}_{2}$ binds to Li-decorated on carbon nanotube surfaces: the binding is further enhanced with Li atoms deposited on ${\mathrm{C}}_{60}$ doped nanotube peapod structures. The increase in binding in the latter structures arises due to charge transfer between the nanotube and ${\mathrm{C}}_{60}$, 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 ${\mathrm{H}}_{2}$ binding energy due to ${\mathrm{C}}_{60}$ encapsulation, compared to recently engineered metal doped nanotube structures, may lead to different carbon based materials for hydrogen storage at room temperature.