Engineering atomically dispersed Fe sites into TiO2 for largely enhanced photocatalytic CO2 reduction to CH4

Photocatalytic CO2 reduction to produce high value-added hydrocarbons has attracted significant attention, yet its overall efficiency remains unsatisfactory. In this work, a micro-liquid film reactor featuring enhanced mixing efficiency was utilized to realize the doping of single Fe atoms into the lattice of TiO2, enabling the generation of abundant atomically dispersed Feδ+ -Ov-Ti structures (Ov: oxygen vacancy). The results showed that compared to pristine TiO2, the optimized Fe-TiO2 photocatalyst bearing a 4 wt.% Fe content exhibited 15.2 times higher activity, with a significant shift in the predominant product from CO to CH4, as well as an impressively high CH4 formation rate of 29.2 μmol•g-1•h-1 , surpassing those over most of the state-of-the-art TiO2-based photocatalysts previously reported. It was revealed that the incorporation of single-atom Fe could reduce the bandgap of TiO2 matrix and surface atomically dispersed Feδ+ -Ov structures could improve the separation efficiency of photogenerated charge carriers and facilitated the adsorption and activation of CO2 and the formation and stabilization of key *CO reaction intermediate, thereby accelerating photocatalytic CO2 reduction to produce CH4. The present work affords a simple and efficient strategy for designing single-atom Fe-regulated TiO2-based photocatalysts for a synergistic enhancement of CO2 photoreduction activity and CH4 selectivity.