First-principles study on hydrogen storage in single walled carbon nanotube functionalized with ammonia

We report the hydrogen storage capacity of single walled carbon nanotube (5, 5) functionalized with ammonia exohedrally. This hydrogen rich, neutral molecule exhibits hydrogen binding to a good extent. The study is performed for half and full coverage of NH₃ molecules on SWCNT. The adsorption of H₂ by the CNT+NH₃ complex is molecular. Weak clustering of NH₃ molecules is observed in full coverage case which has no effect on the storage capacity. The calculated value of storage capacities are 8.1 wt% in half coverage case and 13.2 wt% in full coverage case. Even though these systems have considerable storage capacities, because of the weak binding of H₂ the desorption temperature is below the room temperature. These systems are to be fine tuned to have a higher binding energy per H₂, so that they would qualify as a viable hydrogen storage medium.