Rotating ring-disk study of the oscillating electrochemical reaction of iodide at gold

The ring electrode of a Au-Au rotating ring-disk electrode was used to moni tor the concentrations of I- and I-2 during oscillations in current that oc cur during I- oxidation at the disk electrode. With the ring electrode pois ed at a potential sufficient to oxidize I-, the anodic current at the ring decreased, while the anodic current at the disk increased, as was expected for a typical shielding experiment. However, when the ring was poised at a potential sufficient to reduce I-2 (or I-3(-)) in a collection experiment, the cathodic current also decreased simultaneously with the increase in ano dic current at the disk. These results demonstrate convincingly that the os cillating current involves the periodic formation and dissolution of an I-2 film. (C) 2000 Elsevier Science B.V. All rights reserved.