Photocatalytic decolorization of methylene blue over Zn1−xCoxO under visible light irradiation

Co-doped ZnO photocatalysts were prepared by hydrothermal method. The obtained Co-doped ZnO powders were characterized by X-ray diffraction, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectra. The prepared Co-doped ZnO photocatalysts showed high photocatalytic activities for methylene blue decolorization at pH 10.5 under visible light irradiation. It was found that there were certain relationships between PL spectra and photocatalytic activity, namely, the stronger the PL intensity, the larger the content of oxygen vacancies and defects, the higher the photocatalytic activity. Therefore, in this study 3.0 mol% was the most suitable content of Co2+ in ZnO, at which the recombination of photoinduced electrons and holes could be effectively inhibited and thereby the highest photocatalytic activity was formed.