SOME CONSEQUENCES OF THE SIGNIFICANTLY DIFFERENT MOBILITIES OF HYDROPHILIC AND HYDROPHOBIC METAL-COMPLEXES IN PERFLUOROSULFONATED IONOMER COATINGS AN ELECTRODES

Thin coatings of Nafion on glassy carbon rotating disk electrodes were saturated with hydrophilic [Ru(NH3)(6)(3+), Co(NH3)(6)(3+)] or hydrop hobic [Ru(bpy)(3)(2+)] counterions. With both types of counterions, th e plateau currents obtained when the electrodes were rotated in soluti ons of the cations matched the currents obtained with the uncoated ele ctrodes in the same solutions at all accessible rotation rates. The hi gh rates of cross-coating charge propagation demonstrated by these res ults involved physical diffusion of the hydrophilic complexes and elec tron hopping between adjacent, immobile pairs of the hydrophobic compl exes. The approximate concentration profiles that develop within, and just outside of, Nafion coatings on disk electrodes that are rotated i n solutions of electroactive counterions are depicted.