Asymmetric Bridge-Oxygen Heteronuclear-Bimetallic Sites in Single-Atom Ni-Doped CeO ₂ for Enhanced NO Reduction by CO

The selective catalytic reduction of NO with CO (CO-SCR) faces significant challenges in achieving efficient low-temperature activity. Herein, we report a single-atom Ni-doped CeO 2 catalyst (Ni 0.05 Ce 0.95 O x ) that achieves over 90% conversion of both CO and NO, along with near-complete N 2 selectivity across a broad temperature window of 250–500°C. Through comprehensive characterization, we identify an asymmetric bridge-oxygen heteronuclear-bimetallic moiety (−O−Ni−O−Ce−O V −), as the active site, comprising sub-motifs −O−Ni (2−δ)+ −O− (0 < δ < 2) and −O−Ce (3+λ)+ −O V − (0 ≤ λ < 1). This moiety catalyzes CO-SCR through a directed electron transfer pathway ( Ni ( 2 − δ ) + → e − O α → e − Ce ( 3 + λ ) + ⇒ e − O V ), which modulates the coordination configuration of monodentate carbonates and linear/monodentate nitrites, enhancing their coupling efficiency by 22.1 times relative to pristine CeO 2 and directly correlating with the 22.7-fold rate improvement at 250 °C. This study provides atomic-level insights into active moiety design and structure–activity relationships, advancing CO-SCR for pollutant remediation.