I₂-Hydrosol-Seeded Growth of (I₂)_n-C-Codoped Meso/Nanoporous TiO₂ for Visible Light-Driven Photocatalysis

We report a template-free process to fabricate (I 2 ) n -C-codoped meso/nanoporous TiO 2 nanocrystallites. I 2 nanoparticles in I 2 -hydrosol were used as seeds to initial the nucleation of a precursory TiO 2 shell formed by the hydrolysis of organotitanium molecules. The hybridized jumbles were further calcinated at different temperatures. The resulting (I 2 ) n -C-codoped meso/nanoporous TiO 2 structure was confirmed by transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer−Emmett−Teller (BET) isotherm adsorption of N 2 . UV−visible diffuse reflectance spectroscopy (DRS) showed that (I 2 ) n -C-codoped porous TiO 2 samples have a strong absorption between 400−700 nm. The formation mechanism of (I 2 ) n -C-codoped meso/nanoporous TiO 2 spheres is discussed. Under visible light radiation, our samples exhibit superior ability in the photocatalytic degradation of methylene blue to that of the only C-doped TiO 2 or to the commercial P25 TiO 2 nanoparticles. The origin of the enhanced visible light−light driven photocatalytic degradation is attributed to the continuous states in the band gap of TiO 2 introduced by I 2 doping. Factors that contribute to the enhanced photocatalytic reaction are also studied, including the enhanced thermostability and conductivity of anatase TiO 2 due to C doping, the location of I 2 doping, as well as the morphology of the TiO 2 structures.