Rapid and morphology controlled synthesis of anionic S-doped TiO2 photocatalysts for the visible-light-driven photodegradation of organic pollutants

In recent years, growing concerned has been raised to the global problem of the drainage of organic pollutants into water steams. Therefore, a great demand has been raised for the development of efficient technologies for the treatment of wastewater pollution. The photocatalytic oxidation of organic pollutants under visible-light irradiation has several advantages for the remediation of wastewater compared to other conventional adsorption techniques. This study reports a rapid and morphology controlled synthesis of anionic 1D S-doped TiO2 photocatalysts by a facile and efficient oxidant peroxide route (OPM), followed by crystallization through a hydrothermal method. In particular, S-doping into the TiO2 crystal lattice and the formation of S-Ti-O bonds were confirmed by structural characterization of the as-prepared samples with the help of X-ray photoelectron spectroscopy, X-ray diffraction, UV-vis diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The as-prepared S-doped TiO2 photocatalysts showed enhanced photocatalytic activity for the liquid phase degradation of an organic compound (methyl orange) under visible-light irradiation (>420 nm) compared to the undoped TiO2. To extend the viability for the photocatalytic activity of the as-prepared S-doped TiO2 nanorods, other organic compounds (RhB and phenol) were also tested in photodegradation experiments. The promising effects of OPM treatment for S-doping and the enhanced photocatalytic performance were observed to be due to the large porous channels of nanorods, pure anatase phase crystallization, the high surface area, excellent stability from photocorrosion, enhanced absorbance shifts toward the visible-light region, improved effective interfacial charge transfer, and enhanced efficiency for the separation of photoinduced electron-hole pairs. The optimum photocatalytic activity was achieved for the ATO-3 sample for the degradation of the organic compounds under visible-light irradiation and was similar to 8.12 times higher for MO compared to undoped TiO2. The synergistic effect and role of the active species, i.e., superoxide radical anions (O-center dot(2)-) and holes (h(+)), on the photocatalysis mechanism for the degradation of organic pollutants are discussed in detail.