LAUSR

Abstract Most of the PbO2 electrode reactivity studies have been mainly focused on the macro level, while the PbO2 electrode electrochemical reactivity is less studied in the micro range. In this study, scanning electrochemical microscopy (SECM) was employed, and [Fe(CN)6]3−/[Fe(CN)6]4− was used as a redox mediator. Cyclic voltammetry (CV), probe approach curve (PAC), constant-height scanning and electrochemical impedance spectroscopy (EIS) were conducted to study the localized electrochemical reactivity and interfacial reaction kinetics of the β-PbO2 electrode. The results show that the β-PbO2 electrode can support the oxidation reaction of [Fe(CN)6]4− under the open-circuit potential, at microscopically different positions, [Fe(CN)6]4− has different chemical reaction rates, and hence significantly different electrochemical reactivity. The effective heterogeneous charge transfer rate constant keff is computed to be 0.0253 cm/s by fitting the positive feedback curve. The largest [Fe(CN)6]4− oxidation reaction rate on the localized β-PbO2 electrode emerges when the substrate potential is maintained at 0.5 V, achieving the best resolution of the constant-height image; furthermore, the EIS results macroscopically strengthen this conclusion by demonstrating that the charge transfer process of [Fe(CN)6]4− is the easiest. This study provides a novel way to study the electrochemical reactivity of PbO2 electrodes from a micro perspective.