(667c) Understanding Activation in Mixed Metal Oxides and High Entropy Spinel Oxides for Oxygen Evolution Reaction

Designing electrochemically active, stable, and earth-abundant electrocatalysts for oxygen evolution reaction (OER) remains a challenge for production of sustainable green-hydrogen. Mixed metal oxides and high entropy oxides (HEOs), which consist of five or more metal cations, offer new opportunities for overcoming these challenges. In this work, we combine theoretical and experimental studies to scrutinize the OER activity and stability for spinel-type HEOs and similar mixed metal oxide systems. The high-entropy model developed from our density functional theory calculations reveals a key feature of the HEO system, which is based on equatorial strain of active metal-oxygen bonds under mixing and widening distributions of adsorption energies of the OER intermediates. The electrochemical experiments on Co, Fe, Ni, Cr, and Mn type spinels confirm increased activity and durability of this catalysts. We conclude the work by discussing the future opportunities for a descriptor based optimization of mixed metals and HEO electrocatalysts.