Non-reversible electrochemical reaction

A non-reversible electrochemical reaction that occurs on a planar electrode is considered according to the reaction scheme ... 

As in the case of differential double potential pulse techniques like DDPV, slow electrochemical reactions lead to a decrease in the peak height and a broadening of the response of differential multipulse and square wave voltammetries as compared with the response obtained for a Nemstian process. Moreover, the peak potential depends on the rate constant and is typically shifted toward more negative potentials (when a reduction is considered) as the rate constant or the pulse length decreases. SWV is the most interesting technique for the analysis of non-reversible electrochemical reactions since it presents unique features which allow us to characterize the process (see below). Hereinafter, unless expressly stated, a Butler-Volmer potential dependence is assumed for the rate constants (see Sect. 1.7.1). 

Fig. 7.15 Influence of the dimensionless rate constant Kplane = k° Jr/D on the SWV forward (idashed lines) and reverse (solid lines) currents i//] la"c and i// 3la"e (a) and on the SWV net current (b), corresponding to a non-reversible electrochemical reaction at a planar electrode. sw = 50mV, AEs = 5mV, a = 0.5. The values of Kplane = k°yJr/D appear on the curves...

A discussion of the behavior of an EC mechanism with reversible and non-reversible electrochemical reaction is given in [6]... 

In the case of surface-bound molecules, due to the characteristics of the current obtained when a sequence of potential pulses is applied (see Sect. 6.4.1.2), the use of DSCVC is only recommended for the analysis of non-reversible electrochemical reactions, since for very fast electrochemical reactions (i.e., for values of the dimensionless rate constant which fulfill log( 0r) >0.5), the current becomes negligible, in accordance with Eq. (6.132). The response obtained in DSCVC when non-reversible electrochemical reactions are considered presents two peaks, one maximum positive fV dscvc) an(J one minimum negative (v Sdscvc) which appear for values of the applied potentials EMax and Emin, respectively (with i// >scvc = / >scvc/The cross potential value, at which dscvc = 0,... 

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