Electrode Kinetics of the [Fe(CN)6]4−⁄3− Complex Confined in Cationic Perfluoropolymer Films on Electrode Surfaces

Abstract

Abstract A heterogeneous electron-transfer process of the [Fe(CN)6]4−⁄3− complex confined electrostatically 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°/cm s−1 and transfer coefficient; α) of the heterogeneous electron-transfer process and the apparent diffusion coefficient (Dapp/cm2 s−1) of the homogeneous charge-transport process within the films were evaluated at various concentrations (C°) of the complex within the film. The values of Dapp and k° slightly decreased with an increase in C°. The value of α was independent of C° (cathodic transfer coefficient, αc=0.20, anodic transfer coefficient; αc=0.80), The values of k°, α, and Dapp 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°, αc, and Dapp decrease, depending on the polymer film in which the complex is confined, in the following order: for Dapp and k°, PVPH+>PDMA>CPFP and for αc, PVPH+≈PDMA>CPFP.