Embed Oxygen-Tolerant Active Site for Enhanced Photocatalytic CO ₂ Reduction in Oxygenated Atmosphere

Photocatalytic conversion of CO 2 in realistic oxygen-containing gas streams remains extremely challenging because O 2 strongly competes for photogenerated electrons and initiates thermodynamically favored ORR, thereby suppressing CO 2 RR. Here, we report an oxygen-tolerant photocatalyst constructed by embedding Au atoms into Ni-based alloy nanoclusters supported on TiO 2, followed by controlled etching to expose unsaturated Au sites while maintaining Ni–Au cooperative centers. The optimized E 1.5 -Ni 5 Au 1 –TiO 2 catalyst exhibits substantially enhanced CO 2 RR performance under 5% O 2, and it sustains CO formation with nearly 100% selectivity and a rate of 375.5 μmol g –1 h –1 . The pronounced shift in product selectivity from CH 4 to CO is directly linked to the evolution of these specific atomic sites and O 2 accessible microenvironment. Time-resolved in situ DRIFTS and DFT calculations further demonstrate that Au incorporation significantly weakens O 2 adsorption, reduces charge transfer to O 2, and suppresses ORR, while expanded Au exposure amplifies this effect. These findings establish that engineering specific atomic coordination environments via etching to expose oxygen-tolerant active sites provides an effective strategy for enabling aerobic photocatalytic CO 2 reduction, offering mechanistic insights and a pathway toward practical CO 2 utilization in oxygenated industrial gas streams.