A Consideration of the Application of Koutecký-Levich Plots in the Diagnoses of Charge-Transfer Mechanisms at Rotated Disk Electrodes

It has become common practice to estimate the numbers of electrons (n, eq mol−1) transferred in faradaic reactions at rotated disk electrodes (RDEs) from the slope of plots of reciprocal current (1/I) vs. reciprocal square root of rotational velocity (1/ω1/2). This practice is based on the Koutecký-Levich equation derived for a one-step electron-transfer mechanism. Furthermore, the intercept of the Koutecký-Levich plot is assumed to be a reciprocal function of the heterogeneous rate constant (kh, cm s−1) for the electron-transfer process. In this review, we examine the validity of the practice of estimating values of n and kh for various multi-step mechanisms at RDEs.