A survey of diverse earth abundant oxygen evolution electrocatalysts showing enhanced activity from Ni–Fe oxides containing a third metal

Abstract

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 A_xB_yC_zO_q 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.