Abstract: Based on the theories of conventional electrodes, as well as the properties of microdisk electrode, the i-Eequations for chronoamperometry at disk microelectrode for reversible, quasi-reversible and irreversible systems are derived. Steady-state voltammograms for the oxidation of [Fe(CN)₆]^4-, Fe²⁺ and ascorbic acid were measured at a series of microdisk electrodes with different radii. The conventional log-plot shows that oxidations of [Fe(CN)₆]^4- and ascorbic acid are reversible and totally irreversible, respectively, but the oxidation of Fe²⁺ is reversible at larger radius microdisk electrodes and quasi-reversible at smaller radius microdisk electrodes. The application of the log-plot to the voltammograms yielded a straight line, its slope allows us to evaluate the charge transfer coefficient and the intercept gives values of the electron transfer rate constant.

Key words: i-E equation, Microdisk electrode, Steady-state votammograms