Hierarchical nanostructure of WO3nanorods on TiO2 nanofibers and the enhanced visible light photocatalytic activity for degradation of organic pollutants

Abstract

A hierarchically nanostructured TiO₂/WO₃ photocatalyst was synthesized via the subsequent hydrothermal treatment of electrospun TiO₂ nanofibers in the presence of tungstic acid. With a uniform WO₃ seed layer providing growth sites, the nucleation on the nanofibers was uniform, thus uniform WO₃ nanorods could be grown. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photoluminescence spectra (PL), and Brunauer–Emmett–Teller (BET) method. The results indicated that the WO₃ nanorods with a diameter of about 40 nm and an average length of about 150 nm grew perpendicularly on the TiO₂ nanofibers. The crystallite size and specific surface area of the bare TiO₂ nanofibers were about 30 nm and 46.5 m² g⁻¹. The bare nanofibers are anatase phase with the average diameter of about 350 nm. The TiO₂/WO₃ heterostructures provide more accessible sites for both catalysis and adsorption, and the WO₃ nanorods possess a single crystal structure, which facilitates the migration of the photogenerated electrons. Photocatalytic tests show that the TiO₂/WO₃ heterostructures exhibit a remarkably higher degradation rate of organic pollutants than that of the bare TiO₂ nanofibers under visible light irradiation. The enhanced photocatalytic activity is attributed to the extended absorption in the visible light region and the effective charge separation derived from the coupling effect of TiO₂ and WO₃ nanocomposites.