Dual single-atom catalyst design to build robust oxygen reduction electrode via free radical scavenging

Abstract

Metal-nitrogen-carbon materials are the most promising platinum replacement catalysts for oxygen reduction reaction. However, lacking an efficient approach to improve durability—i.e., to cope with the attack by in situ formed radicals, leaching of central ions, etc.—has limited these catalysts from widespread application. Herein we present a novel, dual-metal, single-atom catalyst design (Fe,Ce-N-C) to confront the formidable deactivation issue of the best-performing yet unstable Fe-N-C catalysts. Cerium single sites are revealed as efficient chemical catalysts to catalyze the H2O2 disproportionation into O2, leading to increased 4e selectivity. Moreover, rather than Fe single sites that catalyze the formation of reactive ·OH and ·OOH species, these cerium single sites act proactively to eliminate in situ-generated radicals. The final Fe,Ce-N-C catalyst represents excellent durability exceeding that of Fe-N-C. This work opens a new path to alleviate the degradation of Fe-N-C catalysts in an acidic medium.