TiO2 nanotubes:: H+ insertion and strong electrochromic effects

The present work studies H+ intercalation and electrochromic effects on anodic TiO2 nanotube layers. The nanotube layers were fabricated by anodization of titanium in 1 M (H3PO4) + 1 M (NaOH) + 0.5 wt% HF electrolyte at 20 V, this results in nanotubular layers with a thickness of 1 +/- 10.1 mu m with individual tube diameter of 100 +/- 10 nm and a tube wall thickness of 10 +/- 2 nm. The cathodic behavior of the nanotube layers in the "as formed" (amorphous) structure as well as in the annealed (anatase) structure were studied in 0.1 M (HClO4) solution. Cyclic voltammograms and potential step experiments combined with reflectance measurements show a high storage capacity for H+ for the nanotubes structures and a very high specific optical contrast when switching the layers from the H-loaded to the H-unloaded state. (c) 2006 Elsevier B.V. All rights reserved.