Interfacial Engineering of a Z-Scheme Bi₂O₂S/NiTiO₃ Heterojunction Photoanode for the Degradation of Sulfamethoxazole in Water

To develop a semiconductor interface with enhanced spatial separation of carriers under visible light irradiation for the photoelectrochemical (PEC) oxidation process, we explored the fabrication of a Bi₂O₂S/NiTiO₃ heterojunction photoanode for the removal of sulfamethoxazole in water. The Bi₂O₂S/NiTiO₃ photoanode was synthesized via an in situ hydrothermal process, and it exhibited better light absorption and charge separation, as well as a reduced rate of recombination of photoexcited charge species compared to pristine Bi₂O₂S and NiTiO_3. The improved photoelectrocatalytic performance was attributed to the synergistic interaction between Bi₂O₂S and NiTiO₃ and the presence of an S-O bond at the heterojunction interface, thus resulting in Z-scheme heterojunction formation. Various characterization methods such as XPS, UV-DRS, electrochemical impedance spectroscopy, photoluminescence, FESEM, TEM, and photocurrent response measurements were explored to explain the optical and electrochemical properties of the semiconductor heterojunction. The PEC degradation process was optimized, demonstrating a degradation efficiency removal of 80% for 5 mg/L sulfamethoxazole in water, with a TOC removal of 45.5%. A Z-scheme heterojunction formation mechanism was proposed to explain the enhanced photoelectrocatalytic activity of the photoanode. This work generally contributes to the development of efficient and sustainable photoanodes for environmental remediation.