Abstract
The density functional theory (DFT) calculations were performed to investigate the structures, electronic properties, and hydrogen-storage capacity of Ni-decorated GeCNT and SnCNT, as well as the effect of Ge, Sn and C vacancies on hydrogen storage capacity. The functionalized Ni is found to be adsorbed on GeCNT, SnCNT, GeCVCNT and SnCVCNT with an adsorption energy of-6.453,-3.780,-5.794 and-4.845 eV. The functionalized GeCNT, SnCNT, GeCVCNT and SnCVCNT bind up to seven, four , five and four hydrogen molecules with the adsorption energy of (-0.236,-0.208,-0.221 and-0.201 eV). The GeCNT, SnCNT, GeCVCNT and SnCVCNT systems exhibit a maximum gravimetric storage capacity of 8.963, 4.083, 6.582 and 4.089 wt%. Our calculations show that nH(2)NiGeCV(Ge) and nH(2)NiSnCV(Sn) system is not a suitable use for hydrogen storage. Therefore, Ni- decorated GeCNT, SnCNT, GeCVCNT and SnCVCNT nanotubes are promising candidate materials for use as hydrogen storage material.