A simple method for the synthesis of anatase-rutile mixed phase TiO2 using a convenient precursor and higher visible-light photocatalytic activity of Co–doped TiO2

Abstract

This work reports a novel and simple method for the synthesis of mixed phase TiO2 (Anatase 70% and Rutile 30%). Refluxing aqueous solution of potassium titanyl oxide oxalate lead to direct crystallization of titanium oxalate complex [Ti2O3(H2O)2(C2O4).3H2O] and this complex on calcination at 450 ˚C for one hour yielded TiO2 powder. The powder samples were characterized by XRD, Raman spectroscopy, FESEM-EDX, TEM, XPS, FT-IR, UV–Visible spectroscopy and BET techniques. The XRD, TEM and Raman spectra of TiO2 indicates the coexistence of anatase and rutile phases. The XRD result shows that the primary particle size of anatase crystals is 8.3 nm and that of rutile crystals is 35 nm. From the UV–Visible DRS spectrum, the bandgap of TiO2 was found to be 3.0 eV. Co–doped TiO2 (Co:Ti ratio 1:99) was prepared by adding cobalt nitrate to the precursor solution. On Co–ion doping, anatase:rutile composition was changed to 84:16. The visible light photocatalytic activity of Co–doped TiO2 was found to be better than that of undoped and Degussa TiO2 due to higher visible light absorption caused by Co2+ energy levels due lowered bandgap.