Effect of substrate on polyaniline film properties - A cyclic voltammetry and impedance study

The electrochemical properties of polyaniline (PANI) films, grown using mul ticycling methods, but using two different upper limits, have been examined in detail at three different substrates [Au, Pr, and glassy carbon (GC)]. Overall, type I films are only weakly dependent on the substrate employed. Even so, impedance measurements have shown that type I PANT films (grown by cycling between 0 and ca. 1 V in 0.1 M aniline + 1 M H2SO4), formed on Pt and Au, exhibit the most rapid growth rate, while the highest film pseudoca pacitance per unit charge is seen for Pt substrates. Type I PANT has a poro sity of 45-50% when formed on Pt and Au, but the porosity is much higher te n. 77%) on GC, inversely correlated with film growth rate. The substrate ha s a more pronounced effect on the electrochemical properties of type II PAN I films (grown by cycling between 0 and 1.7 V in 0.02 M aniline + 1 M H2SO4 solution). This is because type I films are Formed at potentials at which PANT is conducting, while type II are formed primarily when PANI is insulat ing. Therefore, type I film growth occurs predominantly at the conducting P ANI/solution interface, while growth of type II films occurs primarily at t he underlying metal/solution interface, causing the substrate properties to become more significant. The growth rate of type II PANI is most rapid on GC, due to the absence of a barrier oxide film, vs, on Pt and Au. (C) 2000 The Electrochemical Society. S0013-4651(99)11-096-6. All rights reserved.