Exploring electrocatalysts for oxygen evolution: A comprehensive comparative review in alkaline and acidic medium

Water is electrochemically divided to produce hydrogen in an environmentally friendly manner. Two half-reactions contribute to the process of electrolyzing water, with the oxygen evolution reaction (OER) being the one that loses the most energy. Water electrolysis suffers significantly from poor reaction kinetics in its anodic process, making commercial use challenging. Compared to an acidic approach, the range of materials that remain durable under the specific requirements of alkaline water electrolysis is substantially broader. Therefore, identifying OER catalysts that are active, reliable, and economical in acidic media is crucial. Based on the reported overpotential at a current density of 10 mA cm⁻² (η₁₀), this evaluation systematically examines several material classes. A large number of studies are collected, and the OER catalysts documented in the literature to date are outlined. From this perspective, understanding the reaction mechanism and utilizing advanced anode catalysts are both essential, with the former providing insights for structural engineering of materials to enhance catalytic activity. A critical evaluation is then conducted on several recently reported acidic and basic OER electrocatalysts. Finally, a few recommendations for future research into OER catalysts are proposed.