RATIONALIZATION OF TIME-DEPENDENT AND VOLTAGE-DEPENDENT ELECTROACTIVITY IN NAFION(R) OS(BPY)(3)(3+/2+) FILMS IN TERMS OF A MODEL THAT ASSUMES RESTRICTED COUNTERION ACCESS TO NONEQUIVALENT REDOX SITES/

A model for Nafion(R) loaded with Os(bpy)(3)(3+/2+) is presented, whic h rationalises measurable properties such as the discrepancy between e lectroactive amounts measured by cyclic voltammetry and impedance spec troscopy and the inherent peak separation in cyclic voltammetry. The m odel is based on the concept that some sites are freely accessible to counterions whereas sites which reside in aqueous pools with narrow en trances or sites residing in the more or less hydrophobic phase are ac cessible only when a sufficient potential gradient is present to overc ome a potential barrier. The current is modelled by a Butler-Volmer-li ke relationship. The influence of counterion size on the electroactive amount is predicted. An observed constant current in small step chron oamperometry gives further support to the model with non-equivalent si tes. (C) 1998 Elsevier Science S.A. All rights reserved.