Construction of floating photothermal-assisted S-scheme heterojunction with enhanced photocatalytic degradation of tetracycline: Insights into mechanisms, degradation pathways and toxicity assessment

Abstract

Inspired by ecological floating beds to treat water pollution through photosynthesis, we employed a combination of calcination and hydrothermal methods to construct a photothermal-assisted photocatalysis system based on a floating monolithic porous mesh of g-C3N4 (MPMCN) loaded with the excellent photothermal material Bi2MoO6 (BMO), forming a BMO/MPMCN S-scheme heterojunction. This approach improved the utilization efficiency of solar light by BMO/MPMCN, minimized heat loss, and enhanced the overall temperature of the material during the reaction process, thereby accelerating interfacial electron transfer. The unique floating structure confers a larger specific surface area to BMO/MPMCN, providing more reaction sites for TC pollutants and efficiently removing TC contamination from water. BMO/MPMCN degradated 99.3% of TC after 90 min of photothermal reaction, and exhibited good recyclability and reusability. Structural and performance characterizations of the material were carried out using techniques such as XRD, TEM, electrochemical testing, and ESR. Furthermore, the corresponding band structure and S-scheme electron transfer mechanism of the BMO/MPMCN heterojunction were deduced through the combination of in-situ XPS and UPS. The possible degradation pathways of TC and the ecological toxicity changes of intermediate products were analyzed. Finally, a mechanistic model for the photothermal-assisted photocatalytic degradation of TC in water by the BMO/MPMCN S-scheme heterojunction was established, providing a novel approach for the practical application of photocatalysis technology.