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Construction of Z-scheme heterostructure is an effective strategy to enhance the charge carriers' separation. However, successfully achieving this on the defect heterojunction to improve the photocatalytic activity remains challenging. This work successfully obtained sulfur vacancy in the ZnIn 2 S 4 /BiOBr (SZIS/BOB) heterojunction composites with S-O covalent bonding using a hydrothermal method. As a result, they exhibited superior photocatalytic and stability performance. The optimized SZIS/BOB-10 exhibited excellent rhodamine B degradation (95.2%) and chromium (VI) reduction (97.8%) within 100 min under visible light. The enhanced composites with S-vacancies, S-O bond, and internal electric field induced the Z-scheme charge transfer mechanism. We had verified this mechanism based on the surface photovoltage spectra, electron spin response spectra, and density functional theory calculations. This work not only provides valuable insights into designing photocatalysts with a direct Z scheme heterostructure but also delineates a promising strategy for developing efficient photocatalysts to degrade organic pollutants., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

[Display omitted] • Self-regulating S-scheme heterojunction of titanate nanotubes/Bi 2 WO 6 was constructed. • Synergistic effect between hexavalent chromium and tetracycline, with synchronous self-exchange of trivalent chromium. • Trivalent chromium incorporation into titanate nanotubes' interlayer, optimizing the heterojunction. • The degradation pathways of tetracycline were predicted through the Fukui index. The limitation of conventional photocatalysts in simultaneously removing Tetracycline (TC), hexavalent chromium (Cr (VI)) and trivalent chromium (Cr (III)) were addressed in mixed pollution treatment. The S-scheme heterojunction of titanate nanotubes/Bi 2 WO 6 (TNTs/BWO) was successfully constructed to achieve efficient removal of TC, Cr (VI), and Cr (III). The theoretical calculations (DFT) demonstrated that TNTs' ion exchange properties led to the partial replacement of interlayer Na+ by Cr (III), optimizing the S-scheme heterojunction during the photocatalytic reaction. Experimental results revealed that the coexistence of TC, Cr (VI), and Cr (III) had a mutual promotion effect, as evidenced by the apparent rate constant of Cr (VI) reaching 0.7 min−1, which was 87.5 times higher than that of the single pollutant system, while maintaining a high apparent rate constant for TC. The likely intermediate products, degradation pathways, and photocatalytic mechanism were also elucidated using DFT molecular orbitals and Fukui index analysis. This work provides new insights and strategies for simultaneously removing pollutants and contributes to wastewater purification. [ABSTRACT FROM AUTHOR]