Electrocatalytic activities for the reduction of oxygen of carbon particles modified with polypyrrole including various metal ions as electrocatalytic sites

We reported that carbon black modified with cobalt and various transition metal ions (M) incorporated in a polypyrrole film (Co+MPPy/C) were good electrocatalysts for the reduction of oxygen (O₂). After heat treatment of the catalysts at 600 to 650°C under argon atmosphere, which were prepared using with iron and iridium ions as M, the resulted catalysts gave rise to the reduction of O₂ at a remarkably positive potential (E_p > 0.40 V vs SCE). Rotating ring disk voltammetry (RRDV) revealed that Co+IrPPy/C reduced O₂ completely with four electrons (n_av = 4.0). X-ray photoelectron spectroscopy and X-ray diffraction indicated that the cobalt and M ions were coordinated with nitrogen as the donor atoms and the active sites were maintained even after the heat treatment under argon atmosphere without aggregation of metals and formation of alloys.