Photoinduced terminal fluorine and Ti³⁺ in TiOF₂/TiO₂ heterostructure for enhanced charge transfer

As an effective way to enhance the photo/electro-catalytic performance of titanium dioxide (TiO₂) is to explore the positive roles of doped fluorine sites in the fluorinated TiO₂ systems, which, currently still lacks the direct experimental evidence due to the complexity of the species involved. Herein, we have fabricated TiOF₂/TiO₂ with interfacial bridging fluorine (Ti₂–F) via a coherent phase transition through hydrothermal synthesis. Nuclear magnetic resonance and electron paramagnetic resonance characterization have provided strong evidence of the transformation of the doped fluorine from Ti₂–F to Ti₁–F and the subsequent generation of Ti³⁺ at the interface of the TiOF₂ and TiO₂ under UV–visible (UV–vis) light irradiation. Density functional theory (DFT) calculations and photo/electrochemical measurements further confirmed the electron donor behavior of the Ti³⁺. The benefit is a significantly enhanced charge transfer efficiency in TiOF₂/TiO₂, which not only resulted in improved performances for the photodegradation of acetone being 5.5 times higher than the commercial TiO₂ but also supported high capacity for sodium-ion storage. Thus, the TiOF₂/TiO₂ with

Ti₂–F provided a perfect structure to investigate the roles of fluorine sites in fluorinated TiO₂ systems and their interaction with material properties.