Electrocatalytic Oxygen Reduction at (Tetrasulfonatophthalocyaninato)cobalt Incorporated Polypyrrole Film Electrode

Electrocatalytic activity of oxygen reduction was strikingly improved at a GC(glassy carbon)/PPy(polypyrrole)/CoTSP((tetrasulfonatophthalocyaninato)cobalt) electrode among the other CoTSP doped polymer electrodes. The GC/PPy/CoTSP electrode was formed by electro-oxidized polymerization of pyrrole on a glassy carbon(GC) electrode in methanol solution containing CoTSP. The catalytic oxygen reduction at the GC/PPy/CoTSP electrode was mainly analyzed with RRDE technique. Oxygen reduction reaction at the GC/PPy/CoTSP electrode in 0.05 mol dm−3 H2SO4 showed ca. 0.5 V more anodic onset potential than the value obtained with a GC electrode in 0.05 mol dm−3 H2SO4 containing 10−3 mol dm−3 CoTSP. Kouteckty-Levich plot, i.e., the relation between Ilim−1 and ω−1⁄2 for the GC/PPy/CoTSP electrode gave almost the same slope of theoretical four-electron reduction at the limiting current region. It was indicated that the apparent oxygen reduction is occurred through direct four-electron exchange process. On the other hand, the GC electrode in dissolved CoTSP gave almost the same slope as of theoretical two-electron reduction. A diagnostic criterion for oxygen reduction proposed by Wroblowa et al. indicated that the parallel pathways of two- and four-electron reduction exist for the GC/PPy/CoTSP electrode.