Theoretical and experimental study of the surface redox reaction involving interactions between the adsorbed particles under conditions of square-wave voltammetry

A surface redox reaction of a strongly adsorbed redox couple involving interactions between the adsorbed particles was analyzed theoretically under conditions of square-wave voltammetry (SWV). If uniform interactions act between the adsorbed particles, the effect of interaction forces is represented through the product of the relative surface coverage and Frumkin interaction parameter Θa. The kinetics of the redox reaction in the presence of uniform interactions are a function of the apparent rate constant defined as ks,app.=ks exp(−2aΘ), where ks is a real standard rate constant. The apparent reversibility of the redox reaction is determined solely by a dimensionless kinetic parameter defined as the ratio of the apparent rate constant and the signal frequency, ω=ks,app/f. This dimensionless kinetic parameter unifies the effects of both the interaction forces and the charge transfer rate. The height of the dimensionless response depends parabolically on the kinetic parameter ω, as a consequence of the phenomenon known as a ‘quasireversible maximum’. Based on this peculiarity, a method for estimating the real standard rate constant ks and Frumkin interaction parameter a is proposed. The theoretical results are compared qualitatively with the experimental SW voltammograms of probucole.