Electrode kinetics of [Ru(NH 3) 6] 3+/2+ couple confined in montmorillonite clay/poly(vinyl alcohol) composite films on graphite electrodes and film permeation of electroactive solution species

Abstract

The electrode kinetics of [Ru(NH 3) 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°) and transfer coefficient (α) 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 quantatively 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°, α and D s and the proposed microstructures of clay-PVA matrices.