Ion transfer across polymer gel/liquid boundaries: Electrochemical kinetics by faradaic impedance

Abstract

Cyclic voltammetry and equilibrium faradaic impedance measurements have been used to study the transfer of tetra-alkylammonium, choline, perchlorate and picrate ions across the water/poly-vinylchloride (PVC)+nitrobenzene gel or agar+water gel/nitrobenzene boundaries as a function of the polymer concentration. Ion transport rates reflect the change in the relative fraction of the electrolyte solution phase, which probably occupies sub-micrometer pores dispersed in the bulk or on the surface of the electrochemically inactive polymer matrix. Ion transfer across a polymer gel/liquid boundary is about as fast as that across a liquid/liquid boundary. In particular, when related to the active surface area, the apparent ion transfer rate constants are higher than about 10 −3 m s −1, and those corrected for the ion distribution (double-layer effect) correlate with the corrected Gibbs energy of transfer (Brønsted relationship).