Ternary TiO2/WO3/CQDs nanocomposites for enhanced photocatalytic mineralization of aqueous cephalexin: Degradation mechanism and toxicity evaluation

Abstract

A highly solar active nanocomposite with sheet-like WO3 skeleton and evenly loaded TiO2 and carbon quantum dots (CQDs) was synthesized by facile hydrothermal-calcining process, which showed 3.1- and 46.6- times activity on antibiotic (cephalexin) degradation than TiO2 and WO3, respectively. The construction of TiO2/WO3 heterojunction narrowed the band gap and facilitated the electrons-holes separation. The π conjugated CQDs was found to further improve the charge separation and extend the visible light response by photosensitization. However, the promoted charge separation predominantly contributed to the improved photocatalytic activity. The contributions of detected reactive species follows the order of: O2–>1O2>OH>h+. The cephalexin degradation mechanism and pathway were proposed based on DFT (density functional theory) calculation and experimental analysis. The photocatalytic mineralization efficiency can reach 92.4% in 4 h, indicating the efficient reduction of ecotoxicity of cephalexin and its intermediates. This new composite proved to have great potentials for emerging contaminants degradation in water.