Design Criteria for Oxygen Evolution Electrocatalysts from First Principles: Introduction of a Unifying Material-Screening Approach

The oxygen evolution reaction (OER) is the bottleneck in proton-exchange membrane (PEM) electrolyzers as substantial overpotentials are required for the formation of gaseous oxygen at anode side to reach a satisfying current density. In the past years, substantial research investigations were dedicated to search for electrode materials with an ameliorated OER activity. Therein, different frameworks are proposed in the literature. The conventional method based on the computational hydrogen electrode approach relies on an assessment of simple binding energies by deriving linear scaling relationships that translate to a volcano plot at zero overpotential. Recently, the traditional volcano concept was extended, in that the applied overpotential and kinetics were accounted for by deducing overpotential-dependent volcano curves or kinetic scaling relations, respectively. An alternative framework corresponds to the electrochemical-step symmetry index (ESSI), which was suggested as an improved measure within the search of potential OER electrocatalysts. Hitherto, there is no connection between these diverse methods, and it remains elusive which of these approaches is most suitable for material-screening purposes. On the example of the OER over transition-metal oxides, porphyrins, perovskites, metal oxides, and functionalized graphitic materials, a powerful combination of linear scaling relationships, kinetic scaling relations, overpotential-dependent Volcano plots, and ESSI is presented. While the computational costs for this unifying approach are the same as for the traditional volcano analysis, the inclusion of a single experimental input parameter in the underlying framework enables gaining unprecedented insights into catalyst design, thereby considering various aspects, such as binding energies, applied overpotential, decisive reaction intermediate, rate-determining reaction step, and catalytic symmetry. It is suggested to employ the concept of activity maps, as introduced in this contribution, for material-screening studies of multielectron processes in energy and environmental science.