A COMPARATIVE-STUDY OF THE IMPEDANCE PROPERTIES OF GLASSY-CARBON ELECTRODES COVERED WITH POLY(STYRENESULPHONATE) AND NAFION(R) FILMS CONTAINING OS(BPY)(3)(3+ 2+) REDOX SITES/

Impedance spectra were recorded for glassy carbon electrodes coated wi th poly(styrenesulphonate) and Nafion(R) films containing Os(2,2'-bipy ridine)(3)(3+/2+) as a function of the concentration of incorporated r edox sites and applied potential. Experimental data were interpreted i n terms of equivalent circuits based on finite transmission lines. Com parisons of the odor capacitances derived from cyclic voltammetry and from impedance spectroscopy showed that only a fraction of the total n umber of redox sites present in Nafion(R) coatings was active during i mpedance measurements. The concentration dependence of the apparent di ffusion coefficient for electron propagation through Nafion(R) films s uggested the presence of charge percolation. (C) 1998 Elsevier Science S.A. All rights reserved.