Hydrogen storage of capped single-walled carbon nanotube via transition-metal doping

We perform density functional theory (DFT) simulations on the capped-CNT for hydrogen storage, focusing on the coating of the capped-CNT with transition metals (Sc, Co, and Ni). It is demonstrated that the metal atom coated on the surface can store up to four, four, and three $\text{H}_2$ molecules, respectively, with significant binding energies in the chemisorption range. At high Sc (Ni) coverage, the hemisphere of the capped-CNT with 30 C atoms is considered to be a promising hydrogen storage device capable of storing 7.08 wt% (5.96 wt%) $\text{H}_2$