Facile synthesis of Fe-doped TiO2 hollow fibers for photocatalytic degradation of methylene blue under white light-emitting diode irradiation

Abstract

Bandgap and morphology engineering are effective strategies for enhancing the photocatalytic activity of TiO₂-based photocatalysts. In this study, Fe-doped TiO₂ hollow fibers (Fe-THFs) were synthesized via a template replication method, using natural kapok fiber as a biotemplate. With increasing Fe³⁺ doping concentration, Fe-THF could retain the hollow fiber morphology with an increase in specific surface area (47–93 m² g⁻¹). X-ray diffraction and Raman spectroscopy analyses confirmed that all samples exhibited a pure anatase phase, with slight lattice distortions attributed to Fe³⁺ incorporation into the TiO₂ lattice. Fe³⁺ doping narrowed the bandgap from 3.18 to 2.90 eV by creating localized energy states, which extended light absorption from the ultraviolet to the visible region. The photocatalytic activity was evaluated by methylene blue degradation under white light-emitting diode (LED) irradiation. After irradiation for 8 h, Fe-THF (0.38 atom%) achieved a degradation efficiency of 64%, outperforming undoped THF (46%). This enhanced photocatalytic activity of Fe-THF is attributed to the combined effects of increased surface area, bandgap narrowing, effective electron/hole trapping at localized energy states, and suppressed recombination. Additionally, the macroscopic hollow fiber structure of Fe-THF facilitated easy recovery and recycling, with 9% activity loss after four cycles, demonstrating excellent stability and reusability.