Free-Standing Membranes for the Study of Electrochemical Reactions Occurring at Conducting Polymer/Electrolyte Interfaces

A double submerged impinging jet (DSIJ) cell has been built allowing an identical hydrodynamic regime to be established on both faces of a bipolar electrode consisting of either a Pt sheet or a free-standing polypyrrole (PPy) membrane. Both electrode materials have been studied in this cell, in the presence of electrolytes containing redox couples. The experimental current-potential characteristics and impedance diagrams relative to PPy may be analyzed as the result of two parallel paths of charge transport involving (i) convective diffusion of the redox species in solution, electron transfer at the polymer/electrolyte interface, and electron transport within the film and (ii) migration of nonelectroactive ions in solution, ion transfer at the polymer/electrolyte interface, and ion transport within the film. In the most favorable circumstance of a fast redox couple and a low ionic conductivity of the membrane, comparison between Pt and PPy explicitly shows an electrocatalytic effect of the latter.