Facile one-pot preparation of Ti3+, N co-doping TiO2 nanotube arrays and enhanced photodegradation activities by tuning tube lengths and diameters

Abstract

Abstract Well aligned Ti3+, N co-doping TiO2 nanotube array (NTA) film on Ti foil substrate has been successfully prepared by anodic oxidation method using fluoride-based electrolyte in ethylene glycol solution with 3 vol.% H2O, followed by calcination at 400 °C for 2 h. The TiO2 NTA exhibits high UV and visible light absorption capability with a narrow band gap of 2.74 eV, which is attributed to Ti3+ self-doping, probably induced by N doping. The Ti3+ site was found to be 0.46 eV below the conduction band and the N 2p surface state is 1.04 eV above the valence band. Effects of the preparation parameters on tube lengths and diameters of the TiO2 NTAs were investigated based on series of control experiments. The photocatalytic activities of two series of Ti3+, N co-doping TiO2 NTAs with different tube lengths (similar diameter) and different diameters (similar tube length) were assessed by means of photodegradations of rhodamine B (RhB) solutions under simulated sunlight irradiation. The results show that the photocatalytic activity of the Ti3+, N co-doping TiO2 NTA can be enhanced by simply tuning the tube length and diameter in an appropriate range. The photocatalytic reaction mechanism was proposed, based on series of radical-trapping experiments. The results show that ⋅OH is the major active species for photodegradation of RhB.