Diagnostic Criteria to Identify a Quasireversible Process

1 Diagnostic Criteria to Identify a Quasireversible Process. A quasireversible process is characterized by determining either the thermodynamic parameter E° or the kinetic parameters a and k°. 

The parameter E0 can be calculated to a good approximation as the average value between the forward and the reverse peaks, given that 0.3 a 0.7. In fact, in this case, the shift of the cathodic peak towards more negative potential values and the shift of the reoxidation peak towards more positive values, both caused by the kinetic effects, essentially compensate each other. 

In it the peak-to-peak separation, AEP, is plotted as a function of the above discussed parameter . Thus, if one knows the number of electrons, n, exchanged per molecule of Ox, measuring the peak-to-peak separation (preferably at different scan rates) the corresponding value of is obtained. Then, from the previous relationship  

Generally, the value of a is assumed to be about 0.5 otherwise one must calculate it by comparing theoretical curves for several values of a with the experimental curve (the latter method being very rarely used). On the other hand one can roughly evaluate the value of a taking into account the effect of a on the shape of the voltammogram  

On the basis of the previous discussion, the criteria for defining a process as quasireversible are the following. 

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