One-pot synthesis of twist-like helix tungsten–nitrogen-codoped titania photocatalysts with highly improved visible light activity in the abatement of phenol

The twist-like helix W,N-codoped TiO2 photocatalysts were prepared by a simple one-pot synthesis route to hydrolysis of titania tetrachloride using ammonium tungstate as tungsten and nitrogen sources. The morphology and microstructure characteristics of W,N-codoped titania photocatalysts with different amount of tungsten doping were characterized by means of BET, TEM, SEM, XPS, UV–vis DRS, PLS and XRD. The probable mechanism of codoping effect is proposed. It is presumed that cooperation of nitrogen and tungsten ions leads to produce new states and narrow the band gap between the valence band and conduction band effectively, which will greatly improve the photocatalytic activity in the visible light region. On the other hand, the tungsten ions with changing valences in the W,N-TiO2 samples are considered to act as trapping sites, which will effectively decrease the recombination rate of photo-induced electrons and holes and then increase the photo-oxidation efficiency of the catalysts. The metal and nonmetal codoped 1%-W,N-TiO2 sample shows the best photocatalytic activity, which is much superior to P25 under both visible and ultraviolet light irradiation. The superior activity of W,N-TiO2 photocatalysts can also be ascribed to the special twist-like helix structure with regular holes on the wall, high surface area, large pore volume and well-crystallized anatase phase.