Poly(3,4-ethylenedioxythiophene) electrodes doped with anionic metalloporphyrins

Conducting poly(3,4-ethylenedioxythiophene) (PEDT) films with metalloporphy rins incorporated as the counter ions were prepared by electropolymerizatio n of the monomer in the presence of metal-tetra(sulfonatophenyl)porphyrin a nions. Cathodic reduction of oxygen on the resulting conducting polymer fil ms was studied. The overpotential for O-2 reduction on electrodes with coba lt-porphyrin complex was significantly smaller in acidic solutions than on gold. In basic solutions, the overpotential at low current densities was cl ose to those on platinum and gold. Polymer electrode with Co-complex yielde d higher limiting currents than with Fe-complex, although the Go-complex po lymer electrode was a poorer electrocatalyst for O-2 reduction in the activ ation range of potential than the Fe counterpart. From the rotating ring-di sk electrode experiments, oxygen reduction was shown to proceed through eit her a 4-electron pathway or a 2-electron pathway. In contrast to the polypy rrole-based electrodes, the PEDT-based metalloporphyrin electrodes were sta ble with wider potential windows, including the oxygen reduction potential. Their electrocatalytic properties were maintained at temperatures up to 80 degrees C in KOH solutions.