ELECTRODE-KINETICS OF THE [FE(CN)6]4-/3- COMPLEX CONFINED IN CATIONIC PERFLUOROPOLYMER FILMS ON ELECTRODE SURFACES

A heterogeneous electron-transfer process of the [Fe(CN)6]4-/3- complex confined electrostically in cationic perfluoropolymer (CPFP) films on graphite electrodes and a homogeneous charge-transport process within the films were examined by potential-step methods. The relevant kinetic parameters (i.e., standard rate constant; k-degrees/cm s-1 and transfer coefficient; alpha) of the heterogeneous electron-transfer process and the apparent diffusion coefficient (D(app)/cm2s-1) of the homogeneous charge-transport process within the films were evaluated at various concentrations (C-degrees) of the complex within the film. The values of D(app) and k-degrees slightly decreased with an increase in C-degrees. The value of alpha was independent of C-degrees (cathodic transfer coefficient, alpha-c = 0.20, anodic transfer coefficient; alpha-a = 0.80). The values of k-degrees, alpha, and D(app) were compared with those obtained previously for protonated poly(4-vinylpyridine) (PVPH+)-[Fe(CN)6]4-/3- system and poly(N,N-dimethylaniline) (PDMA)-[Fe(CN)6]4-/3- system. It was found that k-degrees, alpha-c, and D(app) decrease, depending on the polymer film in which the complex is confined, in the following order: for D(app) and k-degrees, PVPH+ > PDMA > CPFP and for alpha-c, PVPH+ almost-equal-to PDMA > CPFP.