Shapes of electrochemical impedance of oxygen reduction reaction: A theoretical analysis

Electrochemical impedance spectroscopy (EIS) of many-electron reactions is a high-dimensional response function, exhibiting shapes that vary turbulently with reaction parameters. The elusive link between reaction mechanisms and parameters with EIS shapes hinders mechanistic studies on many-electron reactions using EIS. Herein, we simulate EIS of oxygen reduction reaction, a prototypical many-electron reaction, and present a detailed analysis of EIS shapes with varying electrode potential and electrode material. Despite the complex reaction mechanisms and parameter variations, several robust trends in EIS shapes are obtained and receive semiquantitative experimental support. We reveal that the evolution of EIS shapes is closely associated with transitions in the rate-determining resistive term (RDRT). The implications of EIS shape analysis for enhancing catalytic activity through dynamic modulation are also discussed. Similar theoretical analysis can be used to explore the correlation between impedance shape and electrocatalytic activity across a wide range of reactions.