Using dispersion corrected density functional theory (DFT+D), the interaction of Vanadium adatom and cluster with divacancy (555-777) defective graphene sheet has been studied elaborately. We explore the prospect of hydrogen storage on V 4 cluster adsorbed divacancy graphene system. It has been observed that V 4 cluster (acting as a catalyst) can dissociate the H 2 molecule into H atoms with very low barrier energy. We introduce the spillover of the atomic hydrogen throughout the surface via external mediator gallane (GaH 3 ) to form a hydrogenated system.