Triangular Trinuclear Metal-N4 Complexes with High Electrocatalytic Activity for Oxygen Reduction

A new class of macrocyclic metal-N-4 complexes [MN4](n) (M = Co and Fe) were designed and synthesized based on a triangular ligand. Their unique triangular trinuclear structure provides a high density of active sites and facilitates the reduction of dioxygen via a four-electron pathway. Among them, a [CoN4](3)/C catalyst (20 wt %) exhibits high catalytic activity and long-time stability for the oxygen reduction reaction (ORR) in alkaline conditions, superior to the commercial Pt/C catalyst. Such structurally well-defined [MN4](n) complexes provide a platform for a new generation of non-precious metal catalysts (NPMCs) for fuel cell applications.