“Influence of point defects on the hydrogen storage in nickel decorated GeC and SnC nanotubes’’

•Ni-decorated GeCNT and SnCNT without a vacancy, and with single Ge, Sn, and C vacancies are investigated.•Seven, and four, H2 molecules can be absorbed per Ni atom for defect-free GeCNT and SnCNT.•Five and four, H2 molecules can be absorbed per Ni atom for (C vacancy VC) GeCVCNT and SnCVCTN.•The hydrogen gravimetric densities are estimated to be 8.963, 4.083, 6.582 and 4.089 wt%.•nH2NiGeCVGe and nH2NiSnCVSn system is not a suitable use for hydrogen storage.