title: Cobalt phenanthroline-indole macrocycles as highly active electrocatalysts for oxygen reduction.
abstract: The replacement of scarce and expensive platinum species poses a challenge in fuel-cell development. The design and synthesis of a novel type of Co(II) -N4 macrocyclic complex, [CoN4 ], based on the phenanthroline-indole macrocyclic ligand (PIM) is reported. This unique ligand allows the formation of mono- and dinuclear complexes with defined active sites that facilitate the direct four-electron reduction of oxygen. Electrochemical measurements revealed that the [CoN4 ]/C (20 wt %) catalysts have a high activity and long-term stability for the oxygen-reduction reaction (ORR) under alkaline conditions, similar to the Pt/C catalyst. These structurally well-defined complexes represent a nonprecious alternative to platinum species for future fuel-cell applications.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany), Fax: (+49) 6131-379-350.
authors.forename: Martin
authors.initials: M
authors.lastname: Quernheim
authors.forename: Haiwei
authors.initials: H
authors.lastname: Liang
authors.forename: Qi
authors.initials: Q
authors.lastname: Su
authors.forename: Martin
authors.initials: M
authors.lastname: Baumgarten
authors.forename: Nobuyoshi
authors.initials: N
authors.lastname: Koshino
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Higashimura
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
keywords: N ligands; cobalt complexes; electrocatalysts; macrocyclic ligands; oxygen reduction reaction