A survey of diverse earth abundant oxygen evolution electrocatalysts showing enhanced activity from Ni–Fe oxides containing a third metal†
Mixed metal oxides comprise a diverse class of materials that are appealing as potential water oxidation electrocatalysts. Here we report combinatorial screening of nearly 3500 trimetallic AxByCzOq mixed metal oxide compositions that led to the discovery of electrocatalysts with enhanced activity relative to, inter alia, the well-studied pure oxides, ABO3, and AB2O4 stoichiometries of those metals. Using a fluorescence-based parallel screening method, we directly detect electrolytic oxygen-evolution activity of catalyst arrays under alkaline conditions. From these data, composition–activity relationships amongst mixed oxides composed of earth-abundant elements have been determined. Significant sustained activity is observed only in the presence of Co or Ni, and the data draw attention to synergistic interactions between these redox-active ions and Lewis-acidic cations, such as Fe, Al, Ga, and Cr. The best activities are observed with oxides composed of Ni and Fe, together with another element.