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Enhanced visible light photocatalytic activity of BiOI/BiOCOOH composites synthesized via ion exchange strategy

The BiOI/BiOCOOH composites were synthesized by a facile ion exchange strategy between BiOCOOH precursor and KI by ultrasonic reaction. The as-prepared BiOI/BiOCOOH composites were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance absorption spectra (DRS), Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectra (PL). Under visible light illumination, the BiOI/BiOCOOH composites exhibited much higher photocatalytic activities than those of single BiOCOOH and BiOI for the degradation of Rhodamine B (RhB). The markedly enhanced photocatalytic activities of BiOI/BiOCOOH composites were attributed to the formation of a p–n heterojunction between p-type BiOI and n-type BiOCOOH, which facilitated the charge separation of photogenerated electron–hole pairs. The photoelectrochemical measurement confirmed that the charge separation efficiency was greatly improved by the formation of the heterojunction structure. Moreover, tests of radical scavengers demonstrated that h+ and ˙O2− were the main active species for the degradation of RhB.