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.