Synthesis and Characterization of Co-Doped Brookite Titania Photocatalysts with High Photocatalytic Activity

Abstract

Transition metal-doping could effectively extend the light response range of TiO2 photocatalysts from the ultraviolet (UV) to the visible region. Co-doped brookite titanium dioxide (Co–TiO2) photocatalysts were synthesized via the hydrothermal method with titanium tetrachloride as the raw material and cobalt chloride hexahydrate as the dopant. The prepared Co–TiO2 photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS). The photocatalytic activities of Co–TiO2 photocatalysts were evaluated by photocatalytic degradation of isopropanol alcohol (IPA), a typical volatile organic compound (VOC), under visible light. The influences of different Co doping rates, initial concentrations of IPA gas and the amounts of photocatalyst addition were also studied. At the same time, the enhancement mechanism of cobalt ions as a trap for photogenerated holes was discussed. Thus, we found the optimum doping rate, initial concentration of IPA gas and amount of photocatalyst to add. The results show that the mesoporous Co–TiO2 photocatalysts possess smaller size particles, larger specific surface area, lower forbidden bandgap energy (Eg) and better photocatalytic activity than pure brookite TiO2. When the doping of Co was 7% by mass, the initial concentration of IPA gas was 1.0 × 10−6 mol/L and the addition of Co–TiO2 photocatalysts was 50 mg, the best photocatalytic activity was achieved. Furthermore, the degradation rate of IPA was up to 91%, which shows great potential for waste water treatment.