Current step perturbation chronopotentiometry

Assuming, as in Sect. 2.1.2, that the current perturbation is purely faradaic, the surface concentrations given for the mechanisms with only one charge transfer reaction (CE, EC, catalytic) contain two types of function 

Identity of the parameters in eqns. (200), (209) and (211)—(216) for various mechanisms (see also Table 8) 

Under these conditions, the four mechanisms CE, EC, catalytic (a) with total regeneration and catalytic (b) with partial regeneration, can together be described by one general expression for the potential—time relationship 

For each mechanism, the parameters in this equation have their particular meaning, as given in Table 9. 

An expression for the transition time, r, i.e. the electrolysis time at which c0 (0, f) becomes zero, is easily derived by equating the numerator in eqn. (200) to zero and setting t1/2 =r1/2. It is evident that this expression is implicit except for the EC case, where the transition time is not affected by the presence of the chemical reaction. 

---

Chronoamperometry, chronocoulometry, and chronopotentiometry belong to the family of step techniques [1-4]. In chronoamperometry the current, while in chronocoulometry the charge is measured as a function of time after application of a potential step perturbation. In the case of chronopotentiometry, a current step is applied, and the change of the potential with time is detected. 

Chronopotentiometry is a controlled-current technique in which the potential variation with time (0 is measiued following a current step. Other ciurent perturbations such as linear, cyclic, or current reversals are also used [1,3,4,12]. For a reversible electrode reaction following a ciurent step, chronopotentiograms shown in Fig. 7 can be obtained. 

---