Sol-gel derived cobalt doped nano-titania photocatalytic system for solar light induced degradation of crystal violet

Cobalt-doped nano-titania synthesized by a sol-gel method was evaluated for its photocatalytic efficiency under solar irradiation towards degrading the chosen target organic compound, crystal violet. A calcination temperature of 500 °C was found suitable to produce pure cobalt doped titania. XRD and TEM results showed the average crystallite size of cobalt-doped titania to be 19-24 nm. Cobalt was found to be uniformly dispersed on titania in its divalent state. Agglomeration of the spherical titania particles due to cobalt doping increased the average crystallite size and caused a decrease in the surface area compared to undoped titania. The viability of using cobalt doped titania as a photocatalyst under solar irradiation was demonstrated by the complete degradation of crystal violet in 120 min in its presence, compared to partial degradation of the dye using Degussa P25 and undoped nano-titania, with the same duration. Despite the considerable increase in the average particle size and decrease in the surface area, the synthesized cobalt doped titania samples exhibited significant photocatalytic activity for the degradation of crystal violet under solar irradiation. This can be attributed to the extension of absorption band of titania to visible region by the divalent cobalt dopant.