Electrochromic properties of anodically grown mixed V2O5–TiO2 nanotubes

Mixed V₂O₅–TiO₂ nanotube arrays were fabricated by self-organizing anodization of different Ti–V alloys. The mixed oxide nanotubes show switchable V-oxidation states and strong cathodic coloration. Already a low V content of ≈ 0.2 at.% significantly increases the electrochromic switching properties. Using a sample with 3 at.% V, very high electrochromic contrast can be established and a significantly lower switching onset voltage than for pure TiO₂ nanotubes is observed. At high V contents, although charge storage is increased, the improvement of contrast is diminished due to the strong background color of the sample.