Effect of Transition Metal Oxide Doping (Cr, Co, V) in the Photocatalytic Activity of TiO2 for Congo Red Degradation under Visible Light

Comparative study of cr, co or v-doped tio2 was carried out. the photocatalysts were synthesized via sol-gel method. the results indicated that the dopants of cr, co, and v induced anatase to rutile phase transition of tio2 at different dopant amounts of 1, 4, 2 mol%, respectively. besides that, the existence of dopant extended the absorption wavelength of tio2 to visible light region, thus making it a visible-driven photocatalyst. the doped transition metal exhibited different oxidation states on the tio2 surface. the prepared photocatalysts were tested over photodegradation of congo red. amongst all, cr-doped tio2 (3 mol%) was the best photocatalyst attributed to the presence of 45% rutile phase, reduced band gap energy of 2.30 ev and formation of cr^6+, which acted as an electron scavenger to delay the hole-electron recombination.