CO-Tolerant PEMFC Anodes Enabled by Synergistic Catalysis between Iridium Single-Atom Sites and Nanoparticles

Proton-exchange membrane fuel cells (PEMFCs) are limited by their extreme sensitivity to trace-level CO impurities, thus setting a strict requirement for H₂ purity and excluding the possibility to directly use cheap crude hydrogen as fuel. Herein, we report a proof-of-concept study, in which a novel catalyst comprising both Ir particles and Ir single-atom sites (Ir_NP @Ir_SA -N-C) addresses the CO poisoning issue. The Ir single-atom sites are found not only to be good CO oxidizing sites, but also excel in scavenging the CO molecules adsorbed on Ir particles in close proximity, thereby enabling the Ir particles to reserve partial active sites towards H₂ oxidation. The interplay between Ir nanoparticles and Ir single-atom centers confers the catalyst with both excellent H₂ oxidation activity (1.19 W cm^-2 ) and excellent CO electro-oxidation activity (85 mW cm^-2 ) in PEMFCs; the catalyst also tolerates CO in H₂ /CO mixture gas at a level that is two times better than that of the current best PtRu/C catalyst.