Electrochemical synthesis of adherent polypyrrole films on zinc electrodes in acidic and neutral organic media

The electrodeposition of polypyrrole on zinc electrodes has been performed by anodic oxidation of pyrrole in acetonitrile, nitrobenzene and propylene carbonate media in the presence of para-toluene sulfonate counter-ions. When the zinc electrode has preferably undergone a chemical treatment by aqueous sodium sulfide solution, homogeneous and adherent PPy films are obtained. While, no PPy film grows (in the case of C6H5NO2 and PC) or a non-homogeneous and poorly adherent PPy-zinc oxide composite forms (in the case of CH3CN) when the zinc surface is simply polished. Among the electrochemical techniques used in these experiments, the galvanostatic mode was proved to be better adapted to perform the electropolymerization of pyrrole on the pretreated zinc electrodes using low applied current densities. The polypyrrole films synthesized by this technique has been characterized by several microscopic and spectroscopic techniques. In particular, SEM, XPS, FTIR and Raman analyses showed that the obtained coatings have the same structure and morphological properties as those electrodeposited on Pt electrodes. (C) 2002 Elsevier Science B.V. All rights reserved.