Beyond thermodynamic-based material-screening concepts: Kinetic scaling relations exemplified by the chlorine evolution reaction over transition-metal oxides

Abstract

State-of-the-art material screening in the field of electrocatalysis mainly uses the concept of linear scaling relationships in order to express the (free) adsorption energies of different reaction intermediates, adsorbed on the surface of a solid-state electrocatalyst, as function of a descriptor. This thermodynamic analysis, based on the application of the computational hydrogen electrode approach (CHE), ultimately results in the construction of a Volcano plot, which facilitates identifying promising catalysts within a class of materials. The conventional ab initio Volcano concept, however, lacks of two critical aspects: on the one hand the applied overpotential, which constitutes the driving force of an electrocatalytic reaction, is not included in the underlying approach, since the thermodynamic analysis refers to the standard equilibrium potential of the electrocatalytic process; on the other hand, the kinetics is not accounted for. Herein, an alternate material-screening concept is presented, which promotes a discussion of the catalytic performance within a class of materials by explicitly including both the kinetic description and applied overpotential: kinetic scaling relations enable resolving the rate-determining reaction step in a homologous series of single-crystalline electrocatalysts in the overpotential regime of interest for practical applications. The proposed methodology is exemplified by the chlorine evolution reaction over transition-metal oxides, which corresponds to the anode reaction in the industrially relevant chlor-alkali process for the production of gaseous chlorine as basic chemical.