We report the synthesis of nanostructured Co3O4 and their nanocomposites with reduced graphene oxide (GO),using γ-radiolytic approach,for visible light assisted hydrogen generation by water splitting.Steady state γ-irradiation technique was utilized in alcoholic (iso-propanol) cobalt salt solutions,where suspended GO acts as supporting material.γ-ray irradiation of cobalt salt solutions in iso-propanol normally leads to the formation of Co3O4 nanofibres,however the presence of RGO changes it into particulate form with decrease in particle size.