| Abstract
| - We report an extensive first-principles investigation of a both exohedral and endohedral Ti decorated BC4N nanotube for hydrogen storage. The results reveal that an endohedral capping of Ti is energetically favorable compared to exohedral capping, albeit marginally by ∼0.1−0.4 eV/Ti atom. However, this endohedral insertion process is difficult since it requires overcoming of a rather high energy barrier of ∼4 eV/Ti atom, as obtained from our nudge elastic band calculation of the minimum energy path. We observe that the exohedral Ti@BC4N can bind up to four hydrogen molecules with successive energies of adsorption lying in the range of ∼0.4−0.7 eV. We further predict that, at high Ti coverage, the system can absorb up to 5.6 wt % of hydrogen. After establishing the adsorption of hydrogen molecules on the Ti@BC4N nanotube, we have performed molecular dynamics simulation to understand the desorption behavior. It is observed that at 300 K the system remain stable with all four H2 attached with Ti, while at 500 K hydrogen gets released in molecular form from the Ti@BC4N nanotube without breaking the cage. This investigation underscores the potential of Ti-decorated BC4N nanotube as a promising candidate material for hydrogen storage.
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