An enhanced visible-light-driven photocatalyst: Conduction band control of Bi2WO6 crystallites by Cu ion modification

The Cu-modified Bi2WO6 crystallites have been synthesized by a simple one-step microwave-hydrothermal route. The prepared samples were characterized by an X-ray diffraction technique (XRD), energy-dispersive X-ray analysis, BET surface area analysis, UV-vis diffuse reflectance spectrum (DRS), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). Visible-light-driven photodegradation of rhodamine B (RhB) was carried out to evaluate the photocatalytic activity of the products. The results indicated that the addition of proper Cu ions could evidently improve the activity of pure Bi2WO6. On the basis of experimental result and band structure analysis, an enhanced photocatalytic mechanism is proposed; namely, Cu ions possibly reduce oxygen via a multi-electron transfer mechanism and the formation of oxygen vacancies facilitates the reduction of O2 by the trapped electrons to generate superoxide radicals. These two aspects play key roles in the photodegradation of RhB. This study provides a research foundation to photocatalytic mechanism of metal-modified new composite photocatalyst.