Unique S-scheme TiO2/BaTiO3 heterojunctions promote stable photocatalytic mineralization of toluene in air

Exploring stable and efficient photocatalysts to promote the photo-oxidation of volatile organic compounds (VOCs) to CO2 and H2O is crucial for air pollution control. In this research, the S-type TiO2/BaTiO3 heterojunctions synthesized by simple physical milling were developed. Compared to the pristine TiO2, it possesses the capability to suppress the production of refractory intermediates and efficiently mineralize the toluene under a wide range of humidity. Density functional theory calculations combined with experimental studies demonstrate that the directional electron transfer from BaTiO3 to TiO2 via Ti-O link bridge (Ti belongs to BaTiO3 and O belongs to TiO2) in TiO2/BaTiO3 heterojunctions can form an internal electric field (IEF). The carriers migration of TiO2/BaTiO3 under illumination is induced in an S-type trajectory by IEF, which effectively improves the carriers separation efficiency, and retains the holes and electrons with high redox potential. And the photogenerated holes and electrons react with H2O and O2 adsorbed at different locations, respectively, generating numerous reactive oxygen radicals and promoting the photocatalytic oxidation of toluene. This work could provide new insights into the development of efficient and stable photocatalysts for air purification.