INVESTIGATION OF THE ELECTROCHEMICAL REDU CTION OF MOLECULAR-OXYGEN AT GOLD ELECTRODES BY IMPEDANCE SPECTROSCOPY

Oxygen reduction on polycrystalline Au has been studied by the rotatin g disk technique combined with impedance spectroscopy in acid sodium p erchlorate and perchloric acid solutions. A general kinetic model has been proposed which takes into account the diffusion of a reactant to the electrode, the diffusion of the product in the opposite direction and a solution-soluble intermediate. On the basis of the kinetic model an expression has been derived for the ac impedance of the electrode. Characteristic physico-chemical parameters of the system (e.g. diffus ion coefficient of oxygen, heterogeneous rate constant, transfer coeff icient, etc.) have been evaluated from impedance data by CNLS fitting. The values determined on the basis of polarisation curves are in good agreement with the results of impedance spectroscopy.