Synthesis of Cr,N-codoped titania nanotubes and their visible-light-driven photocatalytic properties

Cr and N-codoped TiO2 nanotubes with larger specific surface area and smaller band gap energy compared with pure TiO2 nanotubes were prepared via a two-step process of hydrothermal and post-impregnation method. The obtained catalysts were characterized by TEM, XRD, XPS, BET, FT-IR and UV-Vis DRS measurements for investigating nanostructure, crystal phase, specific surface area, bonding state and light-harvesting properties of these samples, respectively. Additionally, the effects of doping amount of Cr ions on the morphology, crystal structure, optical adsorption and photocatalytic activity of codoped TiO2 nanotubes were investigated. The photocatalytic activity was evaluated by degradation of methyl orange (MO) under visible light for 100 min. It was found that the highest photocatalytic activity could be realized when the concentration of Cr was 1.06%, and the degradation rate was up to 97.16%, far higher than that of undoped TiO2 nanotubes (10.56%). In addition, photocatalytic degradation of MO on codoped TiO2 nanotubes surface was proven to be in accordance with the first-order kinetics. (C) 2014 Elsevier B.V. All rights reserved.