ROTATING-DISK ELECTRODE FOR VOLTAMMETRY AND ELECTROCHEMICAL IMPEDANCE MEASUREMENTS - APPLICATION TO THE STUDY OF PARTIALLY BLOCKED ELECTRODES

A turbulence-free RDE device has been designed for making accurate measurements with low-amplitude electrical signals. Its mechanical construction as well as the drive mechanism with a Hall-effect motor, and the rotation speed control are described in detail. Electrochemical experiments were effected on platinum electrodes in contact with a solution of ferri- and ferrocyanide in 2 M NaOH from 4 to 256 rps and, under transient conditions, for values of the Laplace parameter up to 105 s-1. Excellent agreement was found between the measured Warburg coefficient and the value calculated using diffusion coefficients derived from steady-state measurements of the limiting currents. The whole theoretical concentration impedance spectrum of the RDE was verified using the pulse technique. It is demonstrated by experiments on partially blocked model electrodes that the approximation neglecting lateral convection, which is valid for the uniformly active RDE, is no longer correct. © 1979 Elsevier Sequoia S.A., Lausanne.