Photoelectrochemical responses of doped and coated titanium dioxide composite nanotube anodes

Nanostructured photoelectrochemical anodes were made from titanium dioxide nanotubes doped with various metals including Fe, Cu, Ni, Ag, and added with polyaniline to enhance the photosensitivity. The TiO2 nanotubes were obtained through electrochemical oxidation of Ti foil in a glycerol aqueous solution. Electroplating followed by high temperature treatment induced element substitution approach was used to achieve doping effect. Transmission electron microscopy and energy dispersive X-ray diffraction analysis were performed to reveal the structure and obtain the composition information. To examine the photoelectrochemical response, the anode was polarized at the constant bias voltages of 0.5, 1.0, 1.5, 2.0 V and under the exposure of both ultraviolet and visible light. Linear scan was also performed in the potential range of 0-2 V. It is found that Fe, Ni, and Cu doped and polyaniline covered nanotubes show obvious photoelectrochemical activities. Polyaniline covered nanotube anode has better performance than others. Cu-doped anode shows the highest current density in the linear scan voltage range.