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 H-2 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 H-2 the desorption temperature is below the room temperature. These systems are to be fine tuned to have a higher binding energy per H-2, so that they would qualify as a viable hydrogen storage medium.