Oxygen evolution reaction (OER) is known as bottleneck problem during the water splitting process due to high energy barrier and non-availability of efficient nonprecious electrocatalysts. The cobalt oxide (Co3O4) in the spinel phase has limited OER activity and stability in the alkaline media. For this purpose, we have carried out the synthesis of Co3O4–MgO (CM) composite by wet chemical method and it offers abundant oxygen vacancies and Co2+ concentration for the efficient OER reaction. The effect of different amounts of MgO on the OER activity of Co3O4 was also studied. Despite inactivity of MgO towards OER, it creates high density of oxygen vacancies and favored the formation Co2+ ions at the surface, thus accelerated the OER kinetics. The physical studies were performed to investigate the morphology, crystalline structure, surface information and chemical composition using several analytical …