In situ EPR/UV–VIS spectroelectrochemistry of polypyrrole redox cycling

The redox behaviour of polypyrrole layers prepared by the electrochemical oxidation of pyrrole in acetonitrile solutions was studied using insitu EPR/UV–VIS spectroelectrochemistry. Various supporting electrolytes: p-toluene sulfonic acid, tetrabutylammonium perchlorate (TBAP) and tetraethylammonium p-toluene sulfonate (TEATos), were used. Optically transparent indium tin oxide (ITO)-coated glass and gold mesh electrodes were used as electrode materials. Using the calibrated manganese EPR standard, the quantitative time dependences of the three oxidation states in the polymer layer were obtained during redox cycling. The separation of the superimposed UV–VIS spectra was carried out by a least-squares method. The different mechanisms of the polymer oxidation, the polaron/bipolaron route and polaron/dimer route, are compared.