Investigation of localized electrochemical reactivity on a β-PbO2 electrode using scanning electrochemical microscopy

Abstract

Most of the PbO 2 electrode reactivity studies have been mainly focused on the macro level, while the PbO 2 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-PbO 2 electrode. The results show that the β-PbO 2 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 k eff 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-PbO 2 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 PbO 2 electrodes from a micro perspective. • Localized electrochemical reactivity of β-PbO 2 electrodes were imaged using SECM. • Heterogeneous electron transfer kinetics was computed through approach curve. • Macroscopic and microscopic electrochemical reactivity were compared by EIS.