Cyclic voltammetric characteristics mechanism

Simulation of the Cyclic Voltammetric Characteristics of a Second Order EC Catalytic Mechanism... 

TABLE 2.1. Characteristics of the Irreversible Cyclic Voltammetric Responses (Pure Kinetic Conditions) for the Main Mechanisms That Involve the Coupling of a Fast Electron Transfer and a Homogeneous Rate-Determining Follow-up Reaction... 

A comparison of experimental and simulated cyclic voltammograms obtained from oxidation of cis-Mn microparticles mechanically adhered to a GC electrode in [C2mim][N(T 2] and simulated data is shown in Fig. 14.12. Once again, aside from the larger magnitudes of the measured currents in the ionic liquid medium, the voltammetric characteristics obtained under dissolved or solid-state conditions are almost identical. The formal potentials ( j j and 2)7 and the ratio of equilibrium constants KJK ) Ki = kflk, K2 = kfi/k yi, kf and kfi are the rate constants of the forward reactions described in Fig. 14.13. k and bi are the rate constants of the backward reactions) derived from the voltammetric data were identical under dissolved and adhered solid-state conditions, as shown in Table 14.2. 

Table 8.2 lists some characteristic electrode reactions. The linear sweep and cyclic voltammetric diagnostic features of these are described below. They have been selected as examples of the chemical systems most likely to be incorporated in chemical sensors. Further discussion of a wider range of mechanisms can be found in (21). Cyclic voltammetry of surface-confined species is discussed in Chapter 5. 

Further increasing the scan rate in the case of the initial ErevCrev mechanism yields cyclic voltammograms with identical characteristics to those shown in Fig. II. 1.21 a for the ErevCinev mechanism. Indeed, the operational rather than the absolute definition of the terms reversible and irreversible is revealed in this example as clearly an ErevCrev process as defined at slow scan rate becomes an Er evCirrev or Erev (or even Emev) process as the voltammetric timescale becomes progressively decreased. There is abundant experimental evidence [95] to testify to the importance of the ErevCrev mechanistic chemical process. A related and recently extensively studied mechanism has been denoted ErevCdim [96] (Eq. II. 1.23) (or more correctly ErevCdim.irrev)-... 

Voltammetric methods produce current-voltage curves with features characteristic of the reaction mechanism and kinetic conditions. Combining this with the ease of changing the waveform parameters, cyclic voltammetry is nearly always the first technique used to study a new systan. It is particularly usefril for assessing reaction mechanisms, even when there are additional complications such as coupled homogeneous reactions, or surface adsorption. These techniques also provide quantitative information as will be shown below with a selection of theoretical expressions. 

Linear sweep voltammetry (LSV), with the corresponding reversal technique, cyclic voltammetry (CV), are definitely the most frequently used voltammetric techniques. This is true when a qualitative approach to the study of the redox characteristics of a solution is pursued, as well as when a quantitative study of the electrode mechanism and even the evaluation of the relevant thermodynamic and kinetic parameters are faced, and also when electroanalytical quantitative information are sought. The potential waveforms for LSV and for CV, with the relevant equations expressing the time dependence of E, are shown in Fig. 10.12. 

---