Defective Black TiO2 Synthesized via Anodization for Visible-Light Photocatalysis

Defective TiO2-x was synthesized via a facile anodization technique. Electron paramagnetic resonance spectra confirmed the presence of oxygen vacancy, which extended the photon-absorbance deeply into the visible-light region. By stripping off the nanotubes on top, a hexagonally dimpled layer of black TiO2-x was exposed and exhibited remarkable photocatalytic activity.