Insights into the Electrochemical Oxygen Evolution Reaction with ab Initio Calculations and Microkinetic Modeling: Beyond the Limiting Potential Volcano

Density functional theory calculations are potentially useful for both understanding the activity of experimentally
tested catalysts and screening for new catalyst materials. For electrochemical oxygen evolution reaction (OER) catalysts, these
analyses are usually performed considering only the thermodynamics of the reaction path, which typically consists of adsorbed
OH*, O*, and OOH*. Scaling relationships between the stability of these intermediates lead to a limiting potential volcano
whose optimum is constrained by the roughly constant offset between the binding energies of OH* and OOH*. In this work,
we evaluate OER kinetics at rutile IrO2, RuO2, RhO2, and PtO2 surfaces by computing reaction barriers with an explicit model
of the electrochemical interface. We conclude that the kinetics of proton transfer between oxygen atoms at the surface and in
the electrolyte is facile and that O−O bond formation is most likely rate-determining in all cases. Combining these results with a
microkinetic model and a scaling relationship for the OOH* formation barrier, we construct a new activity volcano whose
optimum is similar to that of the limiting potential volcano for typical current densities. This kinetic volcano is also shown to
agree reasonably well with experimental observations. Based on this analysis, we propose a more precise requirement for
improving OER catalysts beyond the state of the art: the transition state for OOH* formation must be stabilized as opposed to
the fully formed OOH* final state as has been previously presumed.