Effects of calcining temperature on photocatalytic activity of Fe-doped sulfated titania.

Using industrial titanyl sulfate as a raw material, Fe-doped sulfated titania (FST) photocatalysts were prepared by using the one-step thermal hydrolysis method and characterized using XRD, SEM, TGA-DSC, FTIR, UV-Vis DRS and N(2) adsorption-desorption techniques. The effects of calcining temperature on the structure of the titania were investigated. The photocatalytic activity of the FST was evaluated using the photodegradation of methylene blue and photooxidation of phenol in aqueous solutions under UV and visible light irradiation, respectively. The results evinced that Ti(4+) is substituted by Fe(3+) in titania lattice and forms impurity level within the band gap of titania, which consequently induces the visible light absorption and visible-light-driven photocatalytic activity. The synergistic effects of Fe-doping and sulfation are beneficial to the efficient separation of the photogenerated carriers and also improve the quantum efficiency of photocatalysis. In addition, Brönsted acidity arisen from the strong inductive effect of sulfate is also conducive to enhancing the photocatalytic performance of FST. However, when the calcining temperature is higher than 800°C, sulfur species and surface hydroxyl groups decompose and desorb from FST and the specific surface area decreases sharply. Moreover, severe sintering and rutile phase formation occur simultaneously. All these are detrimental to photocatalytic activity of FST.