Photoelectrochemical activities of W-doped titania nanotube arrays fabricated by anodization

Titania nanotube arrays and W-doped (containing 3-wt% W) titania nanotube arrays were obtained using a direct anodization method in ethylene glycol electrolyte containing 0.5-wt% HF at 60 V. Anneal was conducted to get anatase crystals. The microstructure and crystal structure of the nanotubes were characterized by scanning electron microscopy and X-ray diffraction. The ultraviolet-visible diffuse reflectance spectra of the annealed samples show that the addition of W led to the red shift of absorbance edge and a decrease of bandgap energy for about 0.14 ev. The photoelectrochemical behavior of these samples has been also studied. Results show that photocurrent densities of W-doped titania nanotube arrays were much larger than that of the undoped sample.