Cost-effective, highly active water oxidation catalysts are increasingly being demanded in the field of energy conversion and storage. Herein, a simple modified hydrothermally (MHT) synthesized zinc and cobalt based hydroxyl double salt, that is, Zn4-xCoxSO4(OH)6·0.5H2O (ZCS), has been exfoliated for the first time as an efficient electrocatalyst for oxygen evolution reaction (OER) in alkaline medium. Morphology investigation suggests the evolution of unique hexagonal nanoplates of ZCS material. As OER catalyst, it requires only 370 and 450 mV overpotential to achieve 10 and 100 mA cm-2 current density, respectively. More importantly, performance at the overpotential over 400 mV and durability of the designed material have been found to be superior to those of commercial RuO2 catalyst. In the designed ZCS material trace amounts of cobalt species lead to higher mass activity of 146 A g-1, compared to that of the RuO2 catalyst (83 A g-1) at the same overpotential of 370 mV. The outstanding activity and stability of the cost-effective material emerges from the promotional effect of Zn ions, which are present as the principal constituent in the electrocatalyst, and they also protect the cobalt ions in the matrix during its long-term electrochemical test. It is important to note that an appropriate ratio of zinc and cobalt ions synergistically helps to create an economically viable and environmentally suitable electrocatalyst in comparison to other related transition metal based materials.
Keywords: energy conversion and storage; mass activity; overpotential; oxygen evolution reaction; water oxidation.