Preparation of core–shell nanostructured black nano-TiO 2 by sol–gel method combined with Mg reduction

Black nano-TiO 2 samples with core–shell nanostructure were successfully prepared by sol–gel method combined with Mg reduction using butyl titanate as titanium source and calcining at 500°C in air atmosphere and at 400–600°C in nitrogen atmosphere. The prepared black TiO 2 samples were characterized by X-ray diffraction, high resolution transmission electron microscopy, Raman spectra, photoluminescence emission spectra, N 2 adsorption–desorption, and ultraviolet–visible spectroscopy. The results show that the black TiO 2 exhibits a crystalline core–disordered shell structure composed of disordered surface and oxygen vacancies, and the thickness of the disordered layer is about 2–3 nm. The optical absorption properties of black nano-TiO 2 samples have been remarkably enhanced in visible light region. Compared with the white TiO 2 , the reduced black TiO 2 samples exhibit enhanced photocatalytic hydrogen production under the full solar wavelength range of light, and the sample prepared with the Mg and TiO 2 ratio of 9:1 calcined at 500 °C has the maximum hydrogen production rate.