Photoelectrochemical and photocatalytic activity of tungsten doped TiO2 nanotube layers in the near visible region

In the present work we study the effect of WO3 doping on the photo-electrochemical behavior of self-organized TiO2 nanotube layers. Mixed oxide nanotubes were grown by anodization of Ti–W alloys containing 0.2 and 9% W, with a thicknesses of the oxide nanotube layers adjusted to about 1.1–1.2 μm. We show that by WO3 doping, the near visible photoresponse and photocatalytic performance can drastically be enhanced. While a content of 9 at% WO3 in photoresponse experiments is most beneficial, in long term experiments a higher efficiency is observed for the 0.2 at% W content. This is due to a gradual leaching of WO3 (dissolution into the electrolyte) for the higher WO3 content. This demonstrates that under optimized WO3 doping conditions a lasting visible light activation of TiO2 nanotubes can be achieved.