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

Abstract

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>420nm) 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 2h. 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.