Highly Efficient Bifunctional Electrocatalyst Using Structurally Architectured N‐doped Cobalt Oxide

Abstract In this work, N‐doped cobalt oxide (Co 3 O 4 ) is prepared in the forms of cubes and spheres using dopamine as a nitrogen source and its application as a bifunctional electrocatalyst for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) associated with alkaline water electrolysis is demonstrated. Initially dopamine incorporated two dimensional Co 3 O 4 aggregates are prepared using wet chemical method and subsequently annealed at two different temperatures namely 200°C and 400°C. Depending upon the annealing temperature, resultant materials showed varied structural morphology which influences their electrocatalytic behaviour. Electrocatalytic activities of two important reactions associated with water splitting reaction namely OER and HER are systematically investigated by grafting such materials onto Ni foam. Among the two, CoDA‐400 sample exhibited higher bifunctional activity for OER and HER applications when compared to CoDA‐200. Interestingly, CoDA‐400 displays a lower overpotential of 378 mV for obtaining 100 mA/cm 2 current density towards OER and shows a lower overpotential of 147 mV for obtaining 10 mA/cm 2 current density towards HER enabling its potential use as a promising bifunctional electrocatalyst. Moreover, this particular material exhibits appreciable long‐term stability for both these electrocatalytic processes. The difference in catalytic activity is assigned to the presence of oxygen vacancies, doped graphene like structures and Co−N bonds present in the resultant product.