Abstract
We report that mild oxidation of Ti foils in air results in brookite-rich titanium oxide (TiO2) films with
similar spectral response to that of dye-sensitized TiO2. X-ray powder diffraction and Raman
spectroscopy show that the onset of brookite formation occurs at 500 8C, and the material is
characterized by a strong absorption band in the visible spectral range. The first-principle calculations
show that enhanced visible light absorption correlates with the presence of Ti interstitials. Photocurrent
density measurements of water splitting reveal that the brookite-rich TiO2 exhibits the highest
photocatalytic performance among the different forms of TiO2 produced by oxidation of Ti foils. With
increasing oxidation temperature transformation to the rutile phase accompanied by declining visible
range photoactivity is observed.
