Modifying redox properties and local bonding of Co₃O₄ by CeO₂ enhances oxygen evolution catalysis in acid

Developing efficient and stable earth-abundant electrocatalysts for acidic oxygen evolution reaction is the bottleneck for water splitting using proton exchange membrane electrolyzers. Here, we show that nanocrystalline CeO₂ in a Co₃O₄/CeO₂ nanocomposite can modify the redox properties of Co₃O₄ and enhances its intrinsic oxygen evolution reaction activity, and combine electrochemical and structural characterizations including kinetic isotope effect, pH- and temperature-dependence, in situ Raman and ex situ X-ray absorption spectroscopy analyses to understand the origin. The local bonding environment of Co₃O₄ can be modified after the introduction of nanocrystalline CeO₂, which allows the Co^III species to be easily oxidized into catalytically active Co^IV species, bypassing the potential-determining surface reconstruction process. Co₃O₄/CeO₂ displays a comparable stability to Co₃O₄ thus breaks the activity/stability tradeoff. This work not only establishes an efficient earth-abundant catalysts for acidic oxygen evolution reaction, but also provides strategies for designing more active catalysts for other reactions.