Visible-light-driven composite La2O3/TiO2 nanotube arrays: Synthesis and improved photocatalytic activity

In this work, using a lanthanum nitrate solution as lanthanum source, a visible-light responsive La2O3/TiO2 nanotube arrays (TNTs) composite was synthesized by a facile impregnation-calcinations technique. The as-synthesized samples were characterized by field emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy and photocurrent tests. The photocatalytic activity of the La2O3/TNTs composite under visible-light irradiation (λ>420 nm) was evaluated by the degradation of Rhodamine B (RhB). The results revealed one part of La was doped, and the other part was dispersed on the TNTs surface in the form of La2O3. La-doping narrowed the band gap and La2O3 modification accelerated the separation of photo-induced electron-hole pairs. Consequently, the as-prepared La2O3/TNTs composite exhibited much higher photocatalytic activity than pure TNTs. The photocatalytic activity of the composite was related to impregnation time of lanthanum nitrate solution, and an optimal time was 2 h. The activity of 2-La2O3/TNTs displayed 3.7 times as high as that of pure TNTs. A possible mechanism on the La2O3/TNTs photocatalytic activities is suggested. The composite, as promising materials, could be used to degrade dye wastewater or other organic pollutants.