Effect of Cobalt Precursor on Microstructures and Visible Light Photoactivity of Doped TiO2 Powders

In order to develop photoactive cobalt-doped TiO2 for the degradation of organic pollutants using visible light irradiation, the effects of cobalt precursor on TiO2 microstructure were investigated. Three cobalt-precursors, i.e. CoCl2, Co(NO3)2 and CoSO4 with two doping levels (nominally 1% and 10%), and two annealing temperatures (400 and 800 C) were adopted to prepare the doped titania through the sol-gel method. The powder samples were characterized with XRD, SEM, BET surface area analysis and UV-Vis absorption spectroscopy, and their photocatalytic activities were evaluated by the degradation of aniline under visible light irradiation. The results showed that the distribution of titania phases, particle size, morphology, surface area and the optical absorption of the catalysts were greatly dependent on the cobalt precursors. Samples prepared from Co(NO3)2, especially for those doped at 1% and calcined at 400 C, showed the highest photocatalytic activity towards the degradation of aniline, and the possible reasons are discussed briefly.