Milling-Induced Synthesis of BiOCl_1-x Br_x Solid Solution and Their Adsorptive and Photocatalytic Performance

CH₃ COO(BiO) (denoted as BiOAc) is one of the most easily obtained bismuth compounds and was for the first time proposed by our group as an effective UV light photocatalyst. Herein, BiOCl_{1- x} Br_x (x refers to the feeding atomic ratio) were obtained using a facile solid state milling and subsequent water washing. More importantly, all of the as-prepared BiOCl_{1- x} Br_x possessed better visible light photocatalytic activity to the corresponding ones obtained by previously reported solution route. Especially at an optimal x value of 0.5, the solid solution showed the highest photodegradation efficiency (~100%) for rhodamine B (RhB) with a concentration of 30 mg L^-1 , whereas the degradation efficiency was only 63% over that obtained by solution route. Furthermore, the as-prepared BiOCl_0.5 Br_0.5 also exhibited excellent photodegradation activity for malachite green (MG). The superior photocatalytic performance of the as-prepared BiOCl_0.5 Br_0.5 could be attributed to its thinner sheetlike structures and highly exposed (001) facets, which enable effective separation of the photogenerated electrons and holes along the [001] direction. In addition, the as-prepared BiOCl_0.5 Br_0.5 revealed dramatic adsorption capacity for cationic dyes like MG, RhB and methylene violet (MV), as well as anion (Cr₂ O₇ )^2- owing to electrostatic interaction between cationic dyes and negatively charged surface of BiOCl_0.5 Br_0.5 , and positively charged surface in K₂ Cr₂ O₇ solution (pH ≈ 3).