Eh. Song et Wk. Paik, POLYPYRROLE DOPED WITH SULFONATE DERIVATIVES OF METALLOPORPHYRIN - USE IN CATHODIC REDUCTION OF OXYGEN IN ACIDIC AND BASIC SOLUTIONS, Bulletin of the Korean Chemical Society, 19(2), 1998, pp. 183-188
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.