Dioxygen-enhanced CO2 photoreduction on TiO2 supported Cu single-atom sites

Supported Cu single-atom (Cu-SA) catalysts have exhibited unique activity and selectivity in CO2 reduction, but they generally suffer from the easy transformation of active Cuδ+ into inactive Cu0. Herein, porous TiO2 supported Cu single atoms (Cu-SAs/TiO2) photocatalyst was fabricated and dioxygen (O2) enhanced photocatalytic CO2 reduction performance of Cu-SAs/TiO2 was investigated by in-situ characterizations and theoretical calculations. The results showed that both activity and stability of Cu-SAs/TiO2 photocatalyst could be improved by feeding a small amount of O2 (117.6 ppm) in the reaction system. The competitive electron transfer to O2 on Cu-SAs/TiO2 maintained dynamic stability of Cuδ+ active sites, and O2-derived *OOH species lowered the formation energy barrier of key intermediate *COOH as well as delivered *H species for accelerating intermediates protonation process. Total yield rate of CH4 and CO reached 34.64 μmol·gcat·h−1 for CO2 photoreduction over Cu-SAs/TiO2 after introducing 117.6 ppm O2, accompanied by enhanced durability.