Visible light-active hybrid film photocatalyst of polyethersulfone–reduced TiO₂: photocatalytic response and radical trapping investigation

The present work emphasizes the facile synthesis and characterization of reduced TiO₂–polyethersulfone and evaluation of its visible light photocatalytic response. Reduced TiO₂ (rTiO₂) was prepared by a simple thermal reduction of NaBH₄ at 300 °C for 50 min before immobilized into polyethersulfone polymer film via phase inversion. X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray characterization showed the photoactive rTiO₂ was still intact onto the PES with homogeneous dispersion after the preparation process. The incorporation of rTiO₂ was observed to improve the hydrophilicity and film’s surface roughness up to 7.03 nm. X-ray photoelectron spectroscopy confirmed the formation of interstitial site of rTiO₂ at lower binding energies of 456.1 and 461.8 eV, which extends visible light absorption by either the existence of Ti³⁺ species or oxygen vacancies. The low band gap (2.85 eV) of the film photocatalyst synergistically envisages the best degradation performance at 13 wt% of rTiO₂ loading by degrading 100% methyl orange in acidic conditions. Based on pseudo-first-order kinetic model, the highest degradation rate constant of 1.41 × 10⁻³ min⁻¹ was obtained with ·O₂⁻ acted as the main active species during the process. The reusability studies revealed that the film photocatalyst could be repeatedly used for up to five times without severe deactivation.