POLYPYRROLE DOPED WITH SULFONATE DERIVATIVES OF METALLOPORPHYRIN - USE IN CATHODIC REDUCTION OF OXYGEN IN ACIDIC AND BASIC SOLUTIONS

Incorporation of metalloporphyrins into polypyrrole (PPB) film was ach ieved either by electropolymerization of pyrrole in the presence of me tal-tetra(sulfonatophenyl)porphyrin anion (MTSPP, M=Co, Fe) or by meta lizing hydrogenated tetra(4-sulfonatophenyl)porphyrin anion (H4TSPP) d oped into PPy through ion-exchange. Electrochemical reduction of oxyge n on the PPy doped with metallo porphyrin (PPy-MTSPP) was studied in a cidic and basic solutions. Oxygen reduction on PPy-MTSPP electrodes ap peared to proceed through a 4-electron pathway as well as a 2-electron path. In acidic solutions, the overpotential far O-2 reduction on PPy -CoTSPP electrode was smaller than that on gold by about 0.2 V. In bas ic solutions the overpotential of the PPy-CoTSPP electrode in the acti vation range was close to those of Au and Pt. The limiting current was close to that of Au. However, polypyrrole doped with cobalt-tetra(sul fonatophenyl)porphyrin anion (Py-CoTSPP) or with iron-tetra (sulfonato phenyl) porphyrin anion (PPy-FeTSPP) was found to have limited potent ial windows at high temperatures (above 50 degrees C), and hence the e lectrode could not be held at the oxygen reduction potentials in basic solutions (pH 13) without degradation of the polymer.