Microwave-Assisted Synthesis of BiOCl/BiOBr Composites with Improved Visible-Light Photocatalytic Activity

BiOCl/BiOBr composite photocatalysts with different Cl-to-Br molar ratios were synthesized by a simple microwave-assisted coprecipitation (MWAC) method. The structures, morphology, and photocatalytic properties of the samples were characterized by X-ray diffraction, scanning electron microscopy, and UV–vis absorption spectrometry. The photocatalytic activities of these BiOCl/BiOBr composites were evaluated by their ability in degradation of Rhodamine B under visible-light irradiation. Results reveal that the MWAC-synthesized 1:5 BiOCl/BiOBr composite is much more active than that synthesized by the hydrothermal method. The former composite obviously maintains high photocatalytic activity after five cycles and thus is the best one among all these photocatalysts. The visible-light photocatalytic activity enhancement of BiOCl/BiOBr composites could be attributed to their strong absorption in the visible region and the low recombination rate of electron–hole pairs. Among different scavengers, the main active species during the photocatalytic process are h+ and •O2–. The possible photocatalytic mechanism was proposed based on the experimental results.