A model of cyclic voltammetry for a thin organic layer sandwiched between an electrode and an aqueous solution.: Convolutive modelling in the absence of supporting electrolyte

Abstract

We address experiments in which an electroactive substrate is dissolved in an organic solvent which is then placed on a voltammetric working electrode (WE) and overlain by an aqueous electrolyte solution. Such ‘layered’ systems combine some of the attributes of ITIES experiments with those of more standard voltammetric techniques. In this paper, we use the powerful tool of convolutive modelling to predict how the shapes of cyclic voltammograms from layered systems depend on the experimental parameters for the reaction N−e −→P + occurring reversibly at the electrode ∣ organic interface, electroneutrality being maintained by entry of anions from the aqueous phase. Transport, both diffusive and migratory, occurs partly in a finite domain and partly semiinfinitely. Among the factors that affect the cyclic voltammetry, and whose influence is revealed in this study, are: the concentrations of the substrate and electrolyte, the rest potential, the scan rate, the reversal potential and the thickness of the organic layer. Values of the various diffusion coefficients are also important parameters. Because five distinct polarizations, all of which are time-dependent, are involved, the results are far from simple. Though they hold promise of providing information which is inaccessible conventionally, the analysis of cyclic voltammograms from layered systems will be a major challenge.