A comparative study of optical absorption and photocatalytic properties of nanocrystalline single-phase anatase and rutile TiO2 doped with transition metal cations

The effect of nanocrystalline TiO2 doping with transition metal cations (Cu2+, Fe3+, Co2+, Cr3+) on their optical absorption and photocatalytic properties was investigated. The obtained metal-doped TiO2 samples were characterized by X-ray diffraction, scanning electron microscopy, and UV–vis absorption spectroscopy. It is shown that doping effect on anatase (A) and rutile (R) properties is quite different, being much stronger and complicated on A than on R. Contrary to doped R, doped A revealed a significant red shift of the absorption edge along with the band gap narrowing. Photocatalytic activity of anatase increases upon doping in the order: AR/Co>R/Cu>R/Fe>R/Cr, indicating the inhibitory effect of impurity cations. This fact correlates with the decrease in the UV absorption of the doped rutile in the region of the Hg-lamp irradiation at 4.88 eV.

Graphical abstractA red shift of the absorption edge of nanocrystalline single-phase anatase after doping with transition metal cations. Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Single-phase anatase and rutile powders surface-doped with transition metal cations. ► Absorption edge and band gap of rutile do not change with surface doping. ► Band gap of surface-doped anatase reduces being the lowest for A/Fe. ► The surface-doping improves photocatalytic activity of anatase. ► The surface-doping inhibits photocatalytic activity of rutile.