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.