Abstract
Extremely short-lived anodic currents were observed in the early parts of the transient response following the application of a cathodic potential step to a mercury working electrode. It is proposed that this phenomenon is due to the existence of a brief precapacitive period, which precedes full development of the double-layer charging current, and which allows momentary reaction (reduction) of species present at the electrode surface. The observed anodic currents are explained in terms of a re-oxidation of such “resident” species that were reduced during this precapacitive period. The subsequent capacitive surge produced by the charging of the electrical double layer leads to an anodic shift of the electrode potential that can be sufficient for the re-oxidation of the precapacitive amalgam. The anodic peak is linearly related to depolarizer concentration and varies with supporting electrolyte concentration, ion mobility and potential step size. Cathodic preconcentration of the depolarizer enhances the effect.
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