One-step hydrothermal synthesis of iron and nitrogen co-doped TiO2 nanotubes with enhanced visible-light photocatalytic activity

TiO2 nanotubes co-doped with iron and nitrogen were successfully synthesized with commercial TiO2 powders (CTPs) using a one-step hydrothermal method. The morphology, structure and composition of the as-prepared nanotubes were characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis), photoluminescence (PL) spectroscopy and Raman spectroscopy. The photocatalytic activities of the samples are evaluated for the degradation of tannic acid (TA, 25 mg L-1) in aqueous solutions under visible light (lambda > 420 nm). The results of TEM suggest that all the samples present a diameter of approximately 9 nm and a length of approximately 200-600 nm. The results of XRD suggest that the predominant phase of all the as-prepared samples was the anatase crystal. The XPS results indicate that Fe and N were successfully introduced into the TiO2 nanotubes (TNTs). Compared with the CTPs and pure TNTs, the Fe and N co-doped TiO2 nanotubes (Fe/N-TNTs) exhibit a stronger visible-light absorption capability, and an enhanced photocatalytic activity toward the photo-degradation of TA aqueous solution under visible-light irradiation. Notably, the xFe/N-TNT catalysts can be easily recycled due to their one-dimensional nanostructural properties.