EFFECTS OF HYDRATION ON THE RESISTANCES AND ELECTROCHEMICAL RESPONSESOF NAFION(R) COATINGS ON ELECTRODES

Procedures are described for coating electrodes with films of Nafion(R ) that are saturated with Os(bpy)(3)(2+) and exist in one of two limit ing states: fully hydrated or dehydrated. The anodic electrochemical r esponses from Os(bpy)(3)(2+)-saturated, dehydrated coatings include un usual spiked features that are the result of the initially high ionic resistance of such coatings. Electro-oxidation of such coatings leads to immediate decreases in resistance as one-third of the Os(bpy)(3)(2) counterions are ejected and large quantities of H2O molecules are in corporated by the coatings. On the basis of quartz crystal microgravim etric, a.c. impedance, and voltammetric measurements, a model is propo sed for the internal structures of Nafion(R) coatings which accounts f or their observed behavior.