Studies of the limiting currents associated with several oxidation reactions mediated by tris(2,2′-bipyridyl)iron(III) incorporated in nafion® films on carbon electrodes

The kinetics of the oxidation of ferrocyanide, catechol and tiron at carbon electrodes covered with Nafion films containing tris(2,2′-bipyridyl)iron(III) were studied by rotating-disc methods. Under conditions in which these reactions were confined to the film-solution interface, limiting currents were observed that were independent of both the substrate concentration and the electrode rotation rate. This saturated behaviour was interpreted in terms of the rate of electron transfer within the precursor complex formed between the dissolved substrate and the limited number of active mediator sites accessible on the coating surface.