Molten salt-assisted synthesis of Ce4O7/Bi4MoO9 heterojunction photocatalysts for Photo-Fenton degradation of tetracycline: Enhanced mechanism, degradation pathway and products toxicity assessment

Photo-Fenton as an advanced oxidation technology has been proved as a multifunctional strategy for environmental remediation. In this study, a novel Ce4O7 modified Bi4MoO9 (C-BMO) Photo-Fenton heterojunction catalyst with the in-built dual redox centers (Ce4+/Ce3+ and Mo6+/Mo5+) was successfully constructed via a facile molten salt-assisted synthesis route. Systematic studies showed that 0.4C-BMO (0.4 meant the molar ratio of Ce and Bi was 0.4) heterojunction exhibited the optimal degradation rate of 2.16032 h−1 in the Photo-Fenton degradation of tetracycline (TC), being nearly 12.28 and 7.69 times higher than that of pristine Bi4MoO9 and Ce4O7. Such remarkably enhanced Photo-Fenton performance was mainly ascribed to the formation of intimate contacted interface favoring the highly effective transfer and spatial separation of photoexcited carriers, and the Ce4+/Ce3+ and Mo6+/Mo5+ cycling redox couples accelerating the activation of H2O2 to generate massive reaction radicals. Additionally, the possible Photo-Fenton degradation pathways of TC were proposed and the toxicity changes during TC degradation were detailed investigated. This present study broadens the application of Ce4O7 and highlights its promise in environmental remediation.