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 TiO2 nanocrystallites. I-2 nanoparticles in I-2-hydrosol were used as seeds to initial the nucleation of a precursory TiO2 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 TiO2 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 TiO2 samples have a strong absorption between 400-700 nm. The formation mechanism of (I-2)(n)-C-codoped meso/nanoporous TiO2 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 TiO2 or to the commercial P25 TiO2 nanoparticles. The origin of the enhanced visible light-light driven photocatalytic degradation is attributed to the continuous states in the band gap of TiO2 introduced by I-2 doping. Factors that contribute to the enhanced photocatalytic reaction are also studied, including the enhanced thermostability and conductivity of anatase TiO2 due to C doping, the location of I-2 doping, as well as the morphology of the TiO2 structures.