How can we tell from a cyclic voltammogram whether the system is reversible or irreversible?
One advantage of cyclic voltammetry is that it is relatively easy to see from a cyclic voltammogram whether a system is reversible. The peak potential difference for a reversible system is about 60 – 70 mV (the theoretical value is about 58–59 mV, depending on the temperature and the switching potential), and the peak currents are equal. In addition, the peak potential difference does not change with scan rate. If the electron transfer kinetics are slow, the peak potential separation is larger, and increases with increasing scan rate. It should be noted that this behavior is also characteristic of uncompensated solution resistance; the two causes can be distinguished by running cyclic voltammograms at different analyte concentrations. If the redox reaction is coupled to chemical reactions, both the peak currents and peak potentials can be affected. For example, if there is a chemical reaction following the electron transfer reaction, the peak current on the reverse scan is decreased.
