Photocatalytic Properties of Sb-doped TiO2 for Water Purification

The need for clean water is a critical problem since this resource is limited. Typical wastewater management (filtration, chlorination, etc.) suffers from severe limitations because of ineffective decontamination and/or elevated costs. In the last few years, among the possibilities for an economic path to clean water, solar-driven photocatalytic materials based on oxide semiconductor nanostructures proved to be promising. The photocatalytic degradation efficiency of pollutants in water depends on the separation of the photogenerated electrons and holes, so as to minimize the simple recombination. In this context, TiO2-based photocatalysts have attracted great attention because of their low cost, excellent stability, and photoactivity.[1] The main disadvantage of TiO2 is the wide bandgap that makes it promising for ultraviolet detection but less efficient for sun-driven applications.[2] This limitation can be overcome by doping TiO2 with different dopants, for example N, B, C, V, Fe, Sn, etc. With the above perspective, in the present study, some Sb-doped TiO2 polycrystalline materials were synthesized and characterized. In particular, we observed that calcined Sb-doped TiO2 adopts the rutile structure and Sb doping in TiO2 produces new occupied states above the VB maximum, thus reducing the effective band gap and increasing the absorption in the visible range. Therefore, the photocatalytic properties of 1.5% Sb-doped TiO2 and laser-irradiated Sb-doped TiOx versus undoped TiO2 were evaluated by decomposition of a standard methylene blue solution (MB) under sunlight irradiation. Indeed, photocatalytic tests for Sb-doped TiO2 showed an increased MB degradation photoactivity of more than 1 order of magnitude with respect to the undoped sample, under both ultraviolet and visible irradiation. This increased photocatalytic activity was ascribed to both enhanced visible region absorption, associated with Sb-induced lone pair surface electronic states and trapping of the holes at the lone pair surface sites, thus inhibiting the recombination of the electrons and holes generated in the initial photoexcitation step. A further increase in the absorption was observed after laser irradiation in water because of the realization of a continuum of states in the bandgap. Therefore, Sb-TiO2 is a promising, efficient and sensitive photocatalyst for water purification..