Design of N-Coordinated Dual-Metal Sites: A Stable and Active Pt-Free Catalyst for Acidic Oxygen Reduction Reaction.

We develop a host-guest strategy to construct an electrocatalyst with Fe-Co dual sites embedded on N-doped porous carbon and demonstrate its activity for oxygen reduction reaction in acidic electrolyte. Our catalyst exhibits superior oxygen reduction reaction performance, with comparable onset potential (Eonset, 1.06 vs 1.03 V) and half-wave potential (E1/2, 0.863 vs 0.858 V) than commercial Pt/C. The fuel cell test reveals (Fe,Co)/N-C outperforms most reported Pt-free catalysts in H2/O2 and H2/air. In addition, this cathode catalyst with dual metal sites is stable in a long-term operation with 50 000 cycles for electrode measurement and 100 h for H2/air single cell operation. Density functional theory calculations reveal the dual sites is favored for activation of O-O, crucial for four-electron oxygen reduction.