Electroreduction of Oxygen at a Pt/C-Modified Electrode with a Cobaltporphyrin Complex

Cobalt complexes that reversibly bind and release O₂ functioned as O₂ carriers, or O₂-enriching media, at the surface of a cathode to enhance the current for the reduction of O₂. The effect of the cobalt complex to accumulate O₂ was evidenced by the higher open-circuit potential, which reflected the equilibrated concentration of O ₂ at the electrode surface. The combination of the cobalt complex and the conventional Pt/C catalyst resulted in a significant increase in the steady-state current for the four-electron reduction of O₂, particularly at small overpotentials where typical fuel cells operate, based on the facilitated transport of O₂ from the atmosphere to the catalyst at the electrode surface.