Electrochemical Impedance Analysis of Polyaniline Films on Electrodes

The ac response of polyaniline films on Pt electrodes in was measured at different applied dc potentials, varied in the positive and negative directions. Experimental complex capacitance plots were reproduced using a computer simulation program based upon the equivalent circuit approach. With 150 nm films the complex capacitance plots at +0.55V ( vs. SCE) comprise a single capacitive element, which develops at more negative potentials into a parallel combination of two discrete elements (a capacitor) and (a finite transmission line) in series with a polymer resistance . and are interpreted as double‐layer and faradaic (diffusion‐controlled) components. The hysteresis observed in the voltammetric behavior of polyaniline is evident in the potential‐dependence of , , and , obtained under constant‐potential conditions.