Study by cyclic voltammetry of a reversible surface charge transfer reaction when the reactant diffuses to the electrode

Abstract

A general theoretical equation for the I - E curve of cyclic voltammetry for a reversible surface charge transfer reaction has been established at low scan rates. It is considered that the substrate diffuses to the hanging mercury drop electrode and is adsorbed during the potential sweep. The molecules of both oxidized and reduced species are assumed to be strongly adsorbed on the electrode surface, following a Langmuir isotherm, and to form a non-compact monolayer. From this equation, the theoretical expressions for cathodic and anodic peak currents have been obtained. The equations for the I - E curve, the peak potentials and the peak currents when the film of adsorbed molecules is compact before reduction or oxidation in the negative or positive scan have also been deduced. The validity of the equations obtained has been confirmed by means of an experimental study of the benzo( c)cinnoline—dihydrobenzo( c)cinnoline system in a basic aqueous organic medium at low scan rates and substrate concentrations.