Iron Single Clusters Anchored on N-Doped Porous Carbon as Superior Trace-Metal Catalysts toward Oxygen Reduction

A new strategy to in situ immobilize iron (Fe) single clusters on N-doped porous carbon under the confinement effect of N-coordination supplied by porphyrins is demonstrated. During the pyrolysis reaction, the strong chelated interaction between Fe and N atoms serves as the pivotal role for achieving Fe single clusters via inhibiting the superabundant aggregation of Fe atoms. Compared to the Fe-based nanoparticles and commercial Pt-C, the synthesized single Fe cluster catalyst (C/TP-Fe700) owns a superior catalytic performance in alkaline medium, which is confirmed by the more positive half-wave potential (0.865 V, 28 mV higher than Pt-C), high mass activity (0.60 A mg(Fe)(-1), 10 times larger than Pt-C), the excellent durability and remarkable methanol tolerance. Additionally, it likewise presents satisfactory oxygen reduction reaction activity in acidic medium compared with Pt-C. This single metal cluster (metal cluster with subnanometer) catalyst with trace-metal contents displays double advantages from metal and metal-free oxygen reduction catalysts, such as high activity, ultralight mass, and environmental friendliness. Insight into this successful paradigm can provide a novel concept for constructing and understanding oxygen reduction catalysts at an approximate atomic scale.