I-doped titanium dioxide nanospheres （I-TNSs） were synthesized via a two-step hydrothermal synthesis route, their potential for the efficient utilization of visible light was evaluated. The prepared anatase-phase I-TNSs had a bimodal porous size distribution with a Brunauer-Emmett-Teller surface area of 76 m2/g, a crystallite size of approximately 14 nm calculated from X-ray diffraction data, and a remarkable absorption in the visible light region at wavelengths 〉 400 nm. The photocatalytic activity of the samples was evaluated by decoloration of Methyl Orange in aqueous solution under visible light irradiation in comparison to the iodine-doped TiO2 （I-TiO2）. The I-TNSs showed higher photocatalytic efficiency compared with I-TiO2 after irradiation for 180 rain even though the latter had a much greater surface area （115 m2/g）. It was concluded that the surface area was not the predominant factor determining photocatalytic activity, and that the good crystallization and bimodal porous nanosphere structure were favourable for photocatalysis.
Zhiqiao HeLiyong ZhanFangyue HongShuang SongZhengying LinJianmeng ChenMantong Jin
A series of TiO2 with different crystal phases and morphologies was synthesized via a facile hydrothermal process using titanium nbutoxide and concentrated hydrochloric acid as raw materials. The photocatalytic activity of the samples was evaluated by degradation of Methyl Orange in aqueous solution under UV-Visible light irradiation. On the basis of detailed analysis of the characterizing results of high-resolution transmission electron microscopy, X-ray powder diffraction measurements, X-ray photoelectron spectroscopy and Brunauer-Emmett-Teller measurement, it was concluded that the photo-activity of the catalyst is related directly to the 3D morphology and the crystal phase composition. An excellent catalyst should have both a futile 3D flower-like structure and anatase granulous particles. The 3D flower-like structure could enhance light harvesting, as well as the transfer of reactant molecules from bulk solution to the reactive sites on TiO2. In addition, the optimum anatase/rutile phase ratio was found to be 80：20, which is beneficial to the effective separation of the photogenerated electron-hole pairs.
