Mechanism, decomposition pathway and new evidence for self-healing of manganese oxides as efficient water oxidizing catalysts: new insights

Abstract

The electrochemical water-oxidation reaction usually requires a catalyst to reduce the overpotential and Earth-abundant catalysts, like MnO₂, are attracting much attention. Here we use chemometric analysis, EPR and UV-Vis spectroscopies to track Mn(II) and MnO₄⁻ byproducts to the reaction of a MnO₂ film in the presence of cerium(IV) ammonium nitrate. Permanganate ion is involved in at least two key reactions: it may oxidize water to O₂ or can combine with Mn(II) to remake MnO₂ solid. We propose mechanisms for water oxidation and present a self-healing process for this reaction.