Improvement of visible light photocatalytic activity over flower-like BiOCl/BiOBr microspheres synthesized by reactable ionic liquids

BiOCl/BiOBr uniform flower-like composite photocatalysts had been successfully synthesized through a one-pot ethylene glycol (EG)-assisted solvothermal process in the presence of 1-hexadecyl-3-methylimidazolium chloride ([C16mim]Cl) and 1-hexadecyl-3-methylimidazolium bromide ([C16mim]Br) reactable ionic liquids. Their structures, morphology, and optical properties were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and UV–vis diffuse reflectance spectroscopy (DRS). The DRS analysis and high photocurrent suggested that BiOCl/BiOBr possessed absorption under visible light and was a benefit for the efficient generation and separation of the electron–hole pairs. Photocatalytic activity experiment proved that BiOCl/BiOBr composites exhibited higher photocatalytic activity than single BiOCl and BiOBr for the degradation of rhodamine B (RhB) under visible light (λ > 400 nm). A possible photocatalytic mechanism based on the relative band positions of BiOCl and BiOBr had been proposed.