Effect of counterion type on charge transport at redox polymer-modified electrodes

The effect of counterion type on the ac impedance and linear sweep voltammetry response of a film consisting of Os(bpy) 2 (bpy indicates 2,2'-bipyridal) coordinatively bound in PVP (poly(4-vinylpyridine)) was investigated. Four acids were used at 0.1 M in the aqueous bathing electrolytes: hydrochloric, perchloric, trifluoroacetic, and toluenesulfonic. Analysis of the mobile ion concentrations in the film showed that protons were rejected from the film via Donnan exclusion, mating anions and hopping electrons the only two charge carriers. Ac impedance spectra revealed that, even with the largest counterion studied, ion transport was much faster than electron hopping