CONDUCTING POLYMER ELECTRODES MODIFIED BY METAL TETRASULFONATED PHTHALOCYANINES - PREPARATION AND ELECTROCATALYTIC BEHAVIOR TOWARDS DIOXYGEN REDUCTION IN ACID-MEDIUM

Polypyrrole (Au/PPy) and polyaniline (Au/PAni) electrodes were prepared and their activities towards oxygen reduction in acid medium were examined. The insertion of iron or cobalt phthalocyanines into the conducting polymer during the electropolymerisation process was carried out and the modified electrodes were characterised by esr and uv-visible differential reflectance spectroscopies. The electrocatalytic behaviour of such electrodes towards oxygen reduction was examined. The influence of the central metal of the macrocycle and of the kind of polymer was investigated. It appears that the modified electrodes containing iron tetrasulfonated phthalocyanine are the most active ones but they are less stable than electrodes containing cobalt tetrasulfonated phthalocyanine. The comparison of the electrocatalytic behaviour of the Au/polymer-FeTsPc electrode with that of a bare platinum electrode towards oxygen reduction indicates that the reduction process is the same for both electrodes. The Au/polymer-FeTsPc electrode allows then to reduce the oxygen molecule mainly via the ii-electron process-into water as main product. In the case of the Au/polymer-CoTsPc electrode, the role of the conducting polymer in the whole reduction process is demonstrated. The Au/PAni-CoTsPc electrode allows to reduce the oxygen molecule mainly via the 2-electron reaction into hydrogen peroxide, whereas the Au/PPy-CoTsPc electrode allows it to reduce into water via the hydrogen peroxide formation for potentials lower than 0.4 V the.