MASS-TRANSPORT STUDY OF NAFION(R) COATINGS SATURATED WITH [OS(BPY)(3)](2-CRYSTAL MICROBALANCE() BY AN ELECTROCHEMICAL QUARTZ)

Ion transport out of and into the Nafion(R) coating on an electrode du ring the electrochemical processes was studied using an electrochemica l quartz crystal microbalance (EQCM). After saturated loading of [Os(b py)(3)](2+), the first cyclic voltammogram (CV) initiated from the low er limit showed an anodic peak around 0.85 V vs. Ag\AgCl which, accord ing to a previous study by Anson's group, corresponds to ejection of t he [Os(bpy)(3)](3+) complex from the Nafion(R) coating. However, the f requency change-potential (Delta f-E) curve obtained by EQCM showed an increase in the mass on the first positive scan. These contradictory results can be explained by the movement of water molecules in a direc tion opposite to that of [Os(bpy)(3)](3+) complexes. After a number of successive cycles, a steady state voltammogram was obtained. In this case the mass change was attributed mainly to the movement of the hydr ated electroinactive counter-cations of the supporting electrolyte. Th e hydration numbers for two of the supporting electrolyte cations are in good agreement with the published results.