Z-Scheme CuWO4/BiOCl photocatalysts with oxygen vacancy as electron mediator for boosted photocatalytic degradation of norfloxacin

An oxygen-vacancy-rich CuWO4/BiOCl composite (CuWO4/Vo-BiOCl) was constructed using a simple precipitation-hydrothermal method, which exhibited excellent photocatalytic degradation performance of norfloxacin compared with pure Vo-BiOCl and CuWO4. Under 300 W xenon lamp, the degradation rate constants of the 6CuWO4/4Vo-BiOCl composite were 4.92 and 3.05 times that of CuWO4 and Vo-BiOCl, respectively. The remarkable enhancement of photocatalytic activity of the composites was attributed to the successful combination of CuWO4 and Vo-BiOCl to form a Z-scheme structure. CuWO4 increased the absorption of the catalyst in the visible light region. Through various characterization, experimental results and the density functional theory (DFT) calculations, a possible Z-scheme photocatalytic degradation mechanism was put forward. The Z-scheme structure had excellent carrier separation efficiency and higher redox ability, in which the oxygen vacancies acted as electron mediators to quench the electrons from the conduction band of Vo-BiOCl with the h+ from the valence band of CuWO4. Furthermore, a possible degradation pathway for NOR was also proposed based on ultrahigh performance liquid chromatography–mass spectrometry (HPLC-MS) data. In this degradation process, the piperazine ring was completely opened, and it formed a simple aliphatic compound. This research may provide new ideas for the development and design of oxygen-rich Z-scheme structure in the field of photocatalysis.