Introducing oxygen vacancies in TiO2 lattice through trivalent iron to enhance the photocatalytic removal of indoor NO

The synthesis of oxygen vacancies (OVs)-modified TiO2 under mild conditions is attractive. In this work, OVs were easily introduced in TiO2 lattice during the hydrothermal doping process of trivalent iron ions. Theoretical calculations based on a novel charge-compensation structure model were employed with experimental methods to reveal the intrinsic photocatalytic mechanism of Fe-doped TiO2 (Fe-TiO2). The OVs formation energy in Fe-TiO2 (1.12 eV) was only 23.6％ of that in TiO2 (4.74 eV), explaining why Fe3+ doping could introduce OVs in the TiO2 lattice. The calculation results also indicated that impurity states introduced by Fe3+ and OVs enhanced the light absorption activity of TiO2. Additionally, charge carrier transport was investigated through the carrier lifetime and relative mass. The carrier lifetime of Fe-TiO2 (4.00, 4.10, and 3.34 ns for 1at％, 2at％, and 3at％ doping contents, respectively) was longer than that of undoped TiO2 (3.22 ns), indicating that Fe3+ and OVs could promote charge carrier separation, which can be attributed to the larger relative effective mass of electrons and holes. Herein, Fe-TiO2 has higher photocatalytic indoor NO removal activity compared with other photocatalysts because it has strong light absorption activity and high carrier separation efficiency.