Electron-enriched Ir centers at Ir-O-W interfaces enable O₂-tolerant CO-assisted NO reduction

The selective catalytic reduction of NO_x with CO (CO-SCR) offers an attractive route for simultaneous multi-pollutant removal, yet achieving high activity under O₂-rich atmospheres remains a formidable challenge. Herein, we report a supported Ir nanocluster catalyst constructed on a high-surface-area mesoporous SiO₂ spherical framework, in which highly dispersed WO₃ and Ir nanoclusters are simultaneously achieved, thereby strengthening the Ir-O-W interfacial interaction. The strengthened interaction generates abundant Ir-O-W interfacial sites at the Ir nanocluster/WO₃ interface, where interfacial Ir atoms acquire increased electron density through electron transfer from W to Ir, as evidenced by HRTEM, XPS, EXAFS, and DFT calculations. The resulting electron-rich Ir favors π*-orbital back-donation to NO, the cleavage of the N-O bond, which is the rate-limiting step in the CO-SCR reaction, and enables the catalyst to achieve > 90% NO_x conversion at 250 ℃ under 5% O₂, with excellent stability. Also, the Ir and W act as adsorption sites for the dissociated N and O, further react with adsorbed CO and another N atom to form CO₂ and N₂. This work establishes a rational strategy for boosting CO-SCR performance through interfacial-site-mediated electron modulation, offering new insights into the design of noble-metal catalysts for emission control under oxygen-rich conditions.