Effect of electron-transfer rate and reorganization energy an the cyclic voltammetric response of redox adsorbates

The theory of cyclic voltammetry of redox adsorbates based on the nonadiaba tic kinetic models of Levich and Dogonadze (GMLD kinetics) is re-examined. It is shown that if generalized predictions of cyclic voltammetric behavior are sought, the model is applicable only over a small range of reorganizat ion energies. It is well-known that at high reorganization energies Tafel p lots simulated using both Butler-Volmer and GMLD kinetics give similar resu lts; however, cyclic voltammograms simulated from GMLD kinetics at high reo rganization energies do not reduce to the generalized Butler-Volmer model f or cyclic voltammogram of redox adsorbates derived by Laviron (J. Electroan al. Chen. 1979, 101, 19). Two methods of solution to the cyclic voltammogra m equation are considered: a finite difference numerical solution and an an alytical approximation. The analytical approximation enables a more rapid s imulation of cyclic voltammograms. Methods for applying the model to real s ystems are suggested which include an equation to estimate the reorganizati on energy based on the cyclic voltammogram peak potentials and the standard rate constant for the redox system.