Electrocatalytic Oxygen Evolution Over Co3 − xMnxO4: Correlating Structure with Reactivity
摘要
Water electrolysis, driven by renewable energy, offers a sustainable route for alternate energy. The oxygen evolution reaction, the key anodic reaction of water electrolysis is a complex reaction due to its four-electron process involving multiple oxygen intermediates. Mixed-valence spinel oxides, such as Co3O4 and Mn3O4 have attracted significant attention as anodic catalyst owing to the low cost, earth abundance, low toxicity, and multiple oxidation states. Despite extensive studies on activity descriptors and the mechanistic aspects of the oxygen evolution reaction over these spinel oxides, a comprehensive understanding of the structure–reactivity correlation remains underexplored. While Co3O4 adopts a cubic structure, Mn3O4 crystallizes in a tetragonal form due to Jahn–Teller distortion, making intermediate Co3 − xMnxO4 solid solutions ideal for studying structure–reactivity correlations. Phase-pure Co2MnO4 (cubic) and CoMn2O4 (tetragonal) were synthesized via combustion synthesis. Despite similar porosity and surface area, CoMn2O4 showed higher electrochemical surface area, better charge transfer, and more oxygen vacancies. Mn-rich CoMn2O4 exhibited superior OER activity, requiring just 260 mV overpotential at 10 mA cm− 2, alongside a low Tafel slope of 55 mV dec− 1 and activation energy of 10 kJ mol− 1. Surface analysis confirmed the formation of