Optimization of carbon-supported polypyrrole complex as cathode catalyst for fuel cells

Carbon particles coated with metal complexes were prepared as cathode catalyst for fuel cells. The metal complex composed of metal ions such as cobalt(II), iron(II), and nickel(II) ions, and nitrogen-containing conductive polymers such as polypyrrole as polymeric ligands. The catalysts were prepared by electropolymerization of corresponding monomers onto the surface of carbon particles such as carbon black which was dispersed in the electrolyte solution containing the monomers, followed by complexation using metal acetates and related salts. Rotating ring-disk voltammetry experiments revealed that the complex composed of a mixture of cobalt and palladium ions as central ions and polypyrrole as the ligand served as a highly efficient electrocatalyst for the selective four-electron reduction of oxygen at E_1/2 ≈ 0.5 V vs SCE, without the formation of partially reduced oxygen species such as H ₂O₂.