Black TiO2 attracts enormous attention due to its large solar absorption and excellent photocatalytic activity. An approach assisted by hot filament hydrogen plasma to synthesize the black TiO2 nanostructure is presented in our work. The black TiO2 possesses a larger solar absorption, especially in the visible and near infrared region. The measurement results show that the oxygen vacancy and Ti-H are the major impacts to form disorder layer and the coloration of black. High absorption of light and numerous active sites ensure the excellent photocatalytic activity for the black TiO2 in the photo-oxidation of organic molecules in water. Considered that Cr has important effect on the electronic structure of TiO2 reported by some researchers, Cr ions were introduced into the structure of TiO2, but Cr ions play the opposite role for its photocatalytic activity because it plays a role in the recombination of photo-generated carriers. (C) 2013 Elsevier B.V. All rights reserved.