MIXED-MODE OSCILLATIONS IN THE PEROXODISULFATE REDUCTION ON PLATINUM AND GOLD ROTATING-DISK ELECTRODES

It is shown experimentally that mixed-mode oscillations may be observe d in the peroxodisulfate reduction on platinum and gold rotating disk electrodes, in addition to previously reported monoperiodic (relaxatio n) oscillations. If account is made for the internal drift of the syst em, the typical features of the mixed-mode oscillations are in good ag reement with the predictions of a model which combines the negative fa radaic impedance characteristics with a treatment of the mass transpor t that goes beyond the stationary diffusion layer approximation. Altho ugh the actual observation of mixed-mode oscillations requires a pretr eatment procedure the precise effect of which is poorly understood, th ese results may be interpreted as evidence for the importance of slow mass transport in the explanation of multiperiodic and chaotic electro chemical oscillations.