ZIF-8 derived ZnS decorated electrospun TiO2 nanofibers for highly efficient photocatalytic reduction of Cr(VI)

The design and construction of diverse heterojunction structures have emerged as an effective strategy for enhancing the photocatalytic performance of semiconductors. In this study, ZIF-8/TiO₂ composite nanofibers were successfully fabricated by combining electrospinning technology with a facile in-situ solvothermal method, followed by ZIF-8 sulfurization to form ZnS/TiO₂ nanofiber heterostructures. Comprehensive characterization confirmed that ZIF-8 on the surface of TiO₂ nanofibers was completely converted into ZnS, establishing a robust and intimate interface with TiO₂. The resulting ZnS/TiO₂ heterostructures exhibited remarkable photocatalytic reduction activity for Cr(VI), achieving 100% removal efficiency within 20 min under visible light irradiation. The photocatalytic reaction rate constant of the ZnS@TiO₂ was approximately 10 and 319.5 times higher than those of ZnS and TiO₂ nanofibers, respectively. This enhanced photocatalytic performance is attributed to the formation of the heterojunction, which effectively narrows the bandgap of the composite, optimizes photogenerated charge transfer pathways and significantly improves electron-hole pairs separation. Furthermore, mechanistic studies identified photogenerated electrons (e⁻) and superoxide radicals (O₂⁻) as the dominant active species involved in the photocatalytic reduction process. This work provides both fundamental understanding and practical methodology for developing high-performance TiO₂-based photocatalytic systems, highlighting their potential for advanced water purification technologies.