An alternating current impedance model including migration and redox-site interactions at polymer-modified electrodes

Electron hopping in redox polymer-modified electrodes requires coincident ion movement to maintain electroneutrality, and transport effects can arise due to either process. In this paper, the equation for diffusion/migration by electron hopping is used with the classical Nernst-Planck equation for mobile ionic species to rigorously model the ac impedance response of a redox-site-containing polymer attached to an electrode and bathed by a binary aqueous electrolyte. The theory also includes the effect of polymer redox-site interactions. Donnan exclusion is assumed, permitting only one mobile ion in the film