Cyclic voltammetry of electroactive and insulative compounds in solid state: A revisit of AgCl in aqueous solutions assisted by metallic cavity electrode and chemically modified electrode

Abstract

A novel platinum cavity electrode (Pt-CE) was fabricated by drilling a small circular cavity (0.5 mm diameter) through a thin Pt foil ( ca. 0.15 mm thickness, 2.0 mm width). It was used to record cyclic voltammograms (CVs) of the insulative AgCl powder (as a model) in aqueous solutions. The voltammetric response of the electrode was fast (tested to 100 mV/s) and the charge under the reduction peak agreed well with the mass of the AgCl powder. Further, the CVs were featured by not only an “irreversible” reduction peak, but also linear logarithm correlations between the potential scan rate and the reduction peak current or potential. Similar results were also obtained from thin AgCl coating modified Ag disc electrodes (1.0 mm diameter) formed by anodisation in chloride solutions. Based on these common electrode kinetic properties, a general explanation is proposed according to the mixed control of the electro-reduction by charge transfer at the conductor/insulator/electrolyte three phase interlines and mass diffusion through the reduction generated porous metal layer. In addition, some CVs also exhibited a minor reduction peak at less negative potentials and the origin was identified experimentally.