Synthesis, characterization and application of iodine modified titanium dioxide in phototcatalytical reactions under visible light irradiation

Iodine doped titanium dioxide has been successfully prepared by simple hydrolysis of tetrabutyl titanate in the presence of iodic acid. The adopted method allowed for the production of spherical iodine doped titaniun dioxide nanoparticles with varied amount of iodine content. Analysis by X-ray diffraction, Raman, transmission electron microscopy as well as UV-vis DRS revealed that titanium dioxide nanostructures were doped with iodine which existed in two different valence states I⁵⁺ and I⁻. The iodine in the form of I⁵⁺ is believed to have doped into the lattice whereas I⁻ was well dispersed on the surface of TiO₂ probably as iodine adducts hence rendering it to be highly absorbing in visible light region. The I-TiO₂ exhibited improved photocatalytic activity toward degradation of acid orange 7 (AO7), methyl orange (MO) and 2,4-dichlorophenol (2,4-DCP) under visible light over the pristine TiO₂ prepared by the same method. High catalytic properties are attributed to iodine doping which led to high specific surface area, absorption in visible region as well as alleviation of charge carrier recombination. The most probable route undertaken in the degradation of AO7 is through indirect oxidation by the hydroxyl radicals.