IS CYCLIC VOLTAMMETRY ABOVE A FEW HUNDRED KILOVOLTS PER SECOND STILL CYCLIC VOLTAMMETRY

The development of ultramicrolectrodes and fast potentiostats in very recent years has allowed the investigation of electrochemical kinetics in the submicrosecond time scale by means of cyclic voltammetry at scan rates in the megavolt per second time scale. Extraction of kinetic data from such cyclic voltammograms, after their correction for distortions arising from effects due to instrumental bandpass, ohmic drop and capacitive charging currents, has been performed using classical theories for cyclic voltammetry. However, application of these classical theories supposes that the diffusion layer and the double layer can be separated theoretically. It is shown here that this classical assumption is no longer valid when scan rates in the megavolt per second range are considered, since the two layers, being then of similar sizes, are no longer physically separable. The ensuing distortions of cyclic voltammograms, with respect to the classical theories, are examined for a single electron transfer mechanism. It is shown that the cyclic voltammograms should normally be extremely dependent on their location with respect to the point of zero charge.