Identification of Visible Photocatalytic and Photoelectrochemical Properties of I-TiO^sub 2^ via Electronic Band Structure

Titanium dioxide is an important metal-oxide semiconductor for photocatalytic applications owing to its unique properties, such as photostability, abundance, low cost, and nontoxicity. However, the photocatalytic activity of TiO2 is limited due to its absorption only in the ultraviolet (UV) region of incident light. In this study, we synthesized iodine-doped TiO2 (I-TiO2) with extended light absorption and exploited its photocatalytic properties for the degradation of methylene-blue (MB) dye. The synthesized I-TiO2 was characterized using X-ray diffraction analysis, transmission electron microscopy, and spectroscopic techniques. UV-visible measurements confirmed that the iodine doping led to a slight increase in the absorbance range of the TiO2 by decreasing its bandgap. X-ray photoelectron spectroscopy revealed new peaks corresponding to Ti3+ and Ti2+, in addition to Ti4+ peaks. Photoluminescence analysis indicated that the I-TiO2 can efficiently separate the charge carriers, yielding high photocatalytic activity. Compared with bare TiO2, the I-TiO2 exhibited increased activity for the photo-degradation of MB.