Cyclic multipulse voltammetric techniques. Part II: EC mechanism

• The cyclic multipulse voltammograms which reflect EC mechanism were simulated for three different techniques.
• Simple diagnostic criteria for recognition of EC reactions are given.
• The estimation of the rate constant of follow-up chemical reaction is presented.

A theoretical analysis of electrode processes controlled by kinetics of follow-up homogeneous chemical reaction under conditions of (simple) cyclic multi pulse voltammetry (CMPV), cyclic differential multi pulse voltammetry (CDMPV) and cyclic square-wave voltammetry (CSWV) is presented. The study was performed under linear diffusion conditions and for equal diffusion coefficients of all participants of the electrode process. Chemical reaction changes the shape and position of CMPV response, compared to a simple reversible electrode reaction. As the chemical process becomes faster, forward/reduction wave decreases whereas a pronounced maximum appears on it. On the other hand, the influence of following chemical reaction on the shape of CDMPV and CSWV reduction signal is not significant, while their voltammograms shifted towards more positive potentials as well. Experimentally, the rate constant of follow-up chemical reaction (kf) can be estimated from the linear dependence of limiting to maximum reduction currents ratio (il,c/imax,c) on log(tp) in CMPV, as well as of anodic to cathodic net peak currents ratio (Δip,a/Δip,c) on log (tp) in CDMPV and on log (f) in CSWV. Combination of two or more cyclic multipulse voltammetric techniques gives more information about kinetics i.e. more precise determination/estimation of the rate constant of follow-up chemical reaction, compared with application of only one technique.