Recent advances in CO-tolerant catalysts for PEMFC anodes: Mechanisms, materials design, and system-level integration

Proton exchange membrane fuel cells (PEMFCs) are a leading technology for efficient hydrogen-to-power conversion, yet their large-scale deployment remains constrained by high noble-metal cost and severe susceptibility of Pt-based anode catalysts to carbon monoxide (CO) poisoning. Although the hydrogen oxidation reaction (HOR) is intrinsically rapid on Pt, its practical performance is governed by complex interfacial phenomena. This review discusses fundamentals and key catalyst challenges in anode PEMFCs and provides a mechanistically integrated perspective on CO-tolerant HOR catalysis. Guided by these perspectives, recent advances in Pt-based, alloyed, single-atom, and other Pt-group HOR catalysts are evaluated, with emphasis on their activity, stability, and impurity resistance. This work explicitly integrates interfacial kinetics with system-level constraints governing practical PEMFC operation. Furthermore, the gap between model electrochemical measurements and membrane electrode assembly performance is discussed. Finally, key design principles for developing low-Pt, impurity-tolerant catalysts under realistic operating conditions are outlined.