ELECTRODE-KINETICS OF [RU(NH3)6]3+/2+ COUPLE CONFINED IN MONTMORILLONITE CLAY POLY(VINYL ALCOHOL) COMPOSITE FILMS ON GRAPHITE-ELECTRODES AND FILM PERMEATION OF ELECTROACTIVE SOLUTION SPECIES

The electrode kinetics of [Ru(NH3)6]3+/2+ redox couple electrostatically confined in montmorillonite clay/poly(vinyl alcohol) (PVA) composite films on graphite electrodes have been examined by cyclic voltammetry and normal pulse voltammetry. The relevant kinetic parameters [ie standard rate constant (k-degrees) and transfer coefficient (alpha) for the heterogeneous electron-transfer process at electrode-film interfaces and apparent diffusion coefficient (D(app)) for homogeneous charge-transport process within films] were estimated. Permeation of solution-phase neutral and anionic species [hydroquinone, Br-, [Mo(CN)8]4-, [Fe(bphen)3]4- (bphen = bathophenanthroline disulfonato)], which are not incorporated into the films, through clay and clay/PVA films have been also quantitatively examined using hydrodynamic voltammetry based on rotating disk electrodes and the diffusion coefficients (D(s)) of these electroactive species within films have been evaluated. The effect of an introduction of PVA to montmorillonite clay matrix on the charge-transport kinetics and the charge-transport mechanism is discussed on the basis of the data obtained for D(app), k-degrees, alpha and D(s) and the proposed microstructures of clay-PVA matrices.