Synergistic effects of sulfation and co-doping on the visible light photocatalysis of TiO2

Sol–gel synthesis and sulfation process has been carried out to prepare Fe3+/Zn2+ co-doped and SO42− impregnated TiO2 photocatalysts. The aim of the present investigation is to improve the visible light photocatalytic activity of TiO2 using (i) co-doping with transition metal species, Fe3+/Zn2+ and (ii) sulfur impregnation procedures. Structural (XRD) characteristics of SO42− impregnated TiO2 reveals the presence of anatase nanoparticles with average grain sizes of 9.8 and 14.8 nm. This sulfation process inhibits, the anatase to rutile phase transformation of TiO2 at higher calcination temperatures (e.g. 600 °C) and increases the number and strength of surface acid sites. The UV–vis photocatalytic activity between the sulfated and non-sulfated Fe3+/Zn2+ co-doped TiO2 catalysts have been found roughly the same. However, there is an enhancement in the visible light photoactivity, which is clearly discernable from the degradation of phenol in aqueous medium.