Fabrication of ZnIn2S4/CeO2 S-scheme heterojuntion for the enhanced removal of tetracycline under visible light irradiation

A series of S-scheme ZnInS/-CeO heterojunction were designed and fabricated through precipitation and hydrothermal method. XRD, SEM, TEM, EDX, XPS, UV–vis DRS and adsorption-photocatalytic techniques were employed to investigate its crystal phase structure, morphology, size, elemental composition, photo-response property and elimination ability for tetracycline. XRD analysis revealed CeO and ZnInS in ZnInS/-CeO sample presented cubic and hexagonal phase structure, respectively. SEM and TEM images indicated that CeO particles with irregular-shaped of around 20 nm were attached on the smooth surface of ZnInS microparticles with 4 μm. All the as-synthesized ZnInS/-CeO samples could harvest more visible-light and the absorption edges were red-shifted in comparison with pure CeO. ZnInS/0.3-CeO sample exhibited remarkably enhanced photocatalytic performance and its removal efficiency for tetracycline reached 87.29 % within 100 min. The detailed experimental and DFT calculation indicated that the enhanced photocatalytic property was mainly ascribed to the synergistic effect of wide light-response range, suitable band position and successful fabrication of S-scheme heterostructure, which was in favor of rapid transfer and available separation of photo-generated e/h pairs. The scavenger experiments and the ESR data revealed that the •O and h active species played the dominant role in tetracycline removal over ZnInS/0.3-CeO system. In addition, the as-synthesized ZnInS/0.3-CeO samples had excellent stability and the removal efficiency still reached 70.73 % after being repeatedly used for 4 times. Furthermore, the possible enhanced photocatalytic mechanism over ZnInS/-CeO was proposed to get a better understanding of photocatalytic process. This work provided the guidance to fabricate CeO-based heterojunction with promising prospect for the efficient elimination of antibiotic residues from wastewater.