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 nonadiabatic 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 reorganization energies. It is well-known that at high reorganization energies Tafel plots simulated using both Butler-Volmer and GMLD kinetics give similar results; however, cyclic voltammograms simulated from GMLD kinetics at high reorganization energies do not reduce to the generalized Butler-Volmer model for cyclic voltammogram of redox adsorbates derived by Laviron (J. Electroanal. Chen. 1979, 101, 19). Two methods of solution to the cyclic voltammogram equation are considered: a finite difference numerical solution and an analytical approximation. The analytical approximation enables a more rapid simulation of cyclic voltammograms. Methods for applying the model to real systems are suggested which include an equation to estimate the reorganization energy based on the cyclic voltammogram peak potentials and the standard rate constant for the redox system.