Sol-gel preparation and characterization of Co/TiO2 nanoparticles: Application to the degradation of methyl orange

Cobalt doped titania nanoparticles were synthesized by sol-gel method using titanium(IV) isopropoxide and cobalt nitrate as precursors. X-Ray diffraction (XRD) results showed that titania and Co/TiO₂ nanoparticles only include anatase phase. The framework substitution of Co in TiO₂ nanoparticles was established by XRD, scanning electron microscopy equipped with energy dispersive X-ray microanalysis (SEM-EDX) and Fourier transform infrared (FT-IR) techniques. Transmission electron microscopy (TEM) images confirmed the nanocrystalline nature of Co/TiO₂. The increase of cobalt doping enhanced “red-shift” in the UV-Vis absorption spectra. The dopant suppresses the growth of TiO₂ grains, agglomerates them and shifts the band absorption of TiO₂ from ultraviolet (UV) to visible region. The photocatalytic activity of samples was tested for degradation of methyl orange (MO) solutions. Although the photocatalytic activity of undoped TiO₂ was found to be higher than that of Co/TiO₂ under UV irradiation, the presence of 0.5% Co dopant in TiO₂ resulted in a catalyst with the highest activity under visible irradiation.