Yanfang Li, Bin Fang, Li C, Shirui Cui, Chunyang Zhao, Weiwei Hu, Chen Cao, Nianliang Yin, Jing Du, Wenlong Wang, Zelong Li, Chang Li
ABSTRACT The development of efficient and stable electrocatalysts for the oxygen evolution reaction (OER) is crucial for advancing the commercialization of proton exchange membrane water electrolyzers (PEMWEs). Here, we report a ternary oxide catalyst, Ir‐RuSnO x , in which atomically dispersed Ir substitutes surface Ru sites to construct an Ir─O─Ru atomic interface. The catalyst requires an overpotential of only 165 mV to deliver 10 mA cm − 2 and maintains stable operation for over 350 h at 100 mA cm − 2 . When integrated into a PEMWE, Ir‐RuSnO x sustains continuous operation at 1 A cm − 2 for 800 h without observable degradation. Combined electrochemical and theoretical studies reveal that Sn acting as a strong electron donor, enhances electron localization at the bridging oxygen (O bri ) within the Ir─O─Ru motif. This enables O bri as a proton acceptor, facilitating deprotonation of O─H and OO─H species at Ru sites, thereby forming O bri ─H intermediates, lowering the energy barrier of the rate‐determining step (RDS), and accelerating OER kinetics. Simultaneously, Sn incorporation increases the electron density of the Ir─O─Ru structure, strengthening its resistance against oxidative degradation. These findings offer a path to achieving both high activity and long‐term durability in acidic OER electrocatalysts.