Asymmetries in elliptic cyclic voltammograms of strongly-adsorbed redox couples: kinetics or thermodynamics?

Abstract

The accurate description of electrochemical responses of strongly-adsorbed redox couples is a fundamental aspect of physical electrochemistry. The description of such redox properties has been developed over the past 50 years to cover multiple electrochemical techniques, such as cyclic voltammetry, square wave voltammetry and alternating current voltammetry, for the cases of (i) reversible and quasireversible kinetics, (ii) ideal non-interacting species and (iii) the cases where lateral interactions are taken into account. Recently, the development of new non-triangular voltammetric techniques has attracted attention due to their potential to offer more sensitive electroanalytical determinations, along with a new tool for the understanding of the physical chemistry behind electron transfer reactions. This work presents, for the first time, a theoretical approach to the elliptic cyclic voltammetry of strongly-adsorbed redox couples when lateral interactions are taken into account, under diverse kinetic regimes. This work also examines the role of lateral interactions (of thermodynamic origin) and electron transfer rates (of kinetic origin) in the non-ideal asymmetries of the elliptic cyclic voltammograms; other features such as the application of the theory to multilayer redox systems are also discussed. This work therefore offers a more complete description of an emerging electrochemical technique with the potential to provide new tools for investigations in fundamental electrochemistry.