The effect of the counter ion concentration on the electrochemistry of tetracyanoquinodimethane polymer film electrodes

Abstract

The effect of the counter in concentration on the cyclic voltammetric behavior of TCNQ polymer film electrodes has been studied in different aqueous electrolytes. The variation of the peak currents and peak potentials as a function of the counter ion concentration is explained in terms of salt or ion pair formation between the reduced redox sites in the film and the counter ions, as well as the polyelectrolyte behavior of the surface layer. The voltammetric behavior is simulated by an empirical model that takes into account ionic shielding of fixed-site charges by electrolyte ions. With increasing concentration of the supporting electrolyte, the reduced polymer film adopts a more compact structure and the diffusion of the counter ions and/or the segmental motion of the polymer chain becomes hindered. No dissolution of the film occurs at negative potentials in simple salt electrolytes or in buffers up to pH 10 at high enough electrolyte concentration.