Fe-Co heteronuclear atom pairs as catalytic sites for efficient oxygen electroreduction.

Single-site Fe-N-C catalysts are the most promising Pt-group catalyst alternatives for the oxygen reduction reaction, but their application is impeded by their relatively low activity and unsatisfactory stability as well as production costs. Here, cobalt atoms are introduced into an Fe-N-C catalyst to enhance its catalytic activity by utilizing the synergistic effect between Fe and Co atoms. Meanwhile, phenanthroline is employed as the ligand, which favours stable pyridinic N-coordinated Fe-Co sites. The obtained catalysts exhibit excellent ORR performance with a half-wave potential of 0.892 V and good stability under alkaline conditions. In addition, the excellent ORR activity and durability of FeCo-N-C enabled the constructed zinc-air battery to exhibit a high power density of 247.93 mW cm -2 and a high capacity of 768.59 mA h g Zn -1 . Moreover, the AEMFC based on FeCo-N-C also achieved a high open circuit voltage (0.95 V) and rated power density (444.7 mW cm -2 ), surpassing those of many currently reported transition metal-based cathodes. This work emphasizes the feasibility of this non-precious metal catalyst preparation strategy and its practical applicability in fuel cells and metal-air batteries.