Tuning the physicochemical property of BiOBr via pH adjustment: Towards an efficient photocatalyst for degradation of bisphenol A

• Photocatalysis of BiOBr was optimized by raising the pH of hydrothermal reaction.
• The increasing pH facilitated the nucleation of BiOBr to form smaller nanosheets.
• As pH increased, nanosheets rotated to reduce the total surface energy of crystal.
• The pH-driven morphological evolution was the major contributor to the activity.

The initial pH value of hydrothermal reaction has a significant impact on the photocatalytic activity of BiOBr photocatalyst; however, the influence mechanism is still unclear. In this work, a series of BiOBr photocatalysts were prepared via a hydrothermal route at different initial pH values. Various methods were performed to investigate the effects of pH on the structure, composition, morphology, optical and electronic properties of the as-prepared samples. The results indicated that the increasing pH facilitated the nucleation of BiOBr, leading to the decrease of crystallite size. Moreover, due to the change of {001} facets exposure, the BiOBr nanosheets rotated to reduce the total surface energy of crystal and formed looser structure, even assembled into flower-like structure at pH 7. The photocatalytic activity evaluated by the degradation of bisphenol A (BPA) was positively correlated with the initial pH value. The BiOBr obtained at pH 7 exhibited the highest photocatalytic activity, whose rate constant was about 2.9, 1.9 and 1.5 times than that of BiOBr samples prepared at pH 1, 3 and 5, respectively. The enhanced photocatalytic activity of BiOBr was mainly attributed to the smaller crystallite size and looser structure.

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