Highly visible-light active with Co/Sn co-doping of TiO2 nanoparticles for degradation of methylene blue

We report the changes in the structural and optical property of TiO2 nanoparticles on co-doping Sn and Co ions. Different amounts of Co and Sn co-doped TiO2 (with 1-2-4 mol% Co and 1-5-10 mol% Sn) powders were prepared at temperatures in the range of 475 and 875 degrees C by simple sol-gel synthesis technique and were thoroughly characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope, fourier-transform infrared, Brunauer, Emmett and Teller (BET) surface area, zeta potential and flat band potential measurements. Photocatalytic ability of co-doped TiO2 powders was evaluated by means of methylene blue degradation experiments conducted under the irradiation of simulated solar light. The XRD showed the presence of only anatase TiO2 for the un-doped and Co-doped titania samples. Titania rutile phase formation in nanoparticles was promoted by Sn4+ addition. XRD analysis also pointed out the decrease in the crystal size with the increase in Sn concentration in the samples. The BET analysis reported an increase in the surface area with the increase in the Sn concentration. It was found that the photo-catalytic activity of TiO2 was obviously enhanced by the co-doping. The excellent photo-catalytic activities due to the contribution from the increased visible light absorption, promoted separation of photo-generated electrons and holes as well as enhanced photo-catalytic oxidizing species with the doping of Co and Sn in TiO2.