Raman Spectroscopy of Titania (TiO\u3csub\u3e2\u3c/sub\u3e) Nanotubular Water-Splitting Catalysts

The phase composition of nanotubular TiO2 films was correlated with photoelectrochemical activity as a function of O2-annealing temperature. TiO2 nanotubes have been shown to be more efficient than polycrystalline TiO2 for the photocatalytic splitting of water. Raman spectroscopy was used to identify and quantify the amorphous and crystalline TiO2 phases. The amorphous TiO2 nanotubular array was found to consist of TiO6 8- octahedra having the same average structure as those present in the anatase and rutile phases of TiO2. Results show that the anatase-to-rutile transformation on Ti metal initiates at much lower temperatures compared to polycrystalline TiO2 and this is attributed to oxygen vacancies located at the metal/oxide interface and is likely responsible for increasing the photocurrent density