Construction of efficient S-scheme TiO2/Bi3.84W0.16O6.24 heterojunction with abundant O vacancies: Kinetics, performance and mechanism insight

The photocatalytic oxidation of Tetracycline hydrochloride (TC) under visible light irradiation is an economically viable solution to address energy and pollution concerns. Herein, an oxygen vacancies (Ovs) defecting-TiO₂/Bi_3.84W_0.16O_6.24 S-scheme heterostructure with strong redox ability was constructed, exhibiting superior catalytic capability for TC destruction. 30 % Ov-TiO₂/Bi_3.84W_0.16O_6.24 (Ov-TBW30) composite demonstrated the highest activity, with the constant (0.872 min⁻¹). The results indicated that Ov is conducive to the reduced bandgap and promoting effective charge transfer. In the ligand-metal charge transfer (LMCT) effect, charge transferred from the Highest Occupied Molecular Orbital (HOMO) of the TC to the conduction band (CB) of the heterojunction, which enables the heterogeneous structure to be much more light-responsive. Furthermore, the variable cycling of Ti⁴⁺/Ti³⁺ facilitated charge balance and quickened the charge transport rate on the heterojunction surface. Noteworthy, the work function calculation, differential charge density, and XPS results jointly confirmed that electrons flowed from Bi_3.84W_0.16O_6.24 to the TiO₂ side. O₂-TPD and NH₃-TPD demonstrate that Ov-TBW30 has a strong catalytic oxidation ability for pollutants. Additionally, the calculated AQE value for COD removal is 0.08 %. 3DEEMs results confirmed that the Ov-TBW photocatalysis system has a strong mineralization capacity for TC. This work provides new perspectives on the design of S-scheme photocatalysis with efficient photocatalytic performance.