Surface modification on photocatalytic thin films is long considered as an effective strategy to improve the degradation performance, which in turn helps to alleviate the worldwide environmental pollution issue. In this study, a direct Z-scheme photocatalytic system is constructed successfully by integrating black phosphorus quantum dots (BPQDs) on the surface of BiOBr thin film prepared by hydrothermal method. The optimal BPQDs/BiOBr-1 thin film presents remarkable enhanced photocatalytic activity for degrading methyl violet (MV) and tetracycline hydrochloride (TC), which is 3 and 3.65 times higher than that of pure BiOBr counterpart. The active species involved in the reaction are h⁺, •O₂⁻, and •OH, which determined by radical trapping experiments. The formation of direct Z-scheme photocatalytic system makes electrons assembled in the conduction band (CB) of BPQDs and holes gathered in the valence band (VB) of BiOBr, which supports the generation of h⁺ and •O₂⁻ and in turn accelerates the photocatalytic reaction. Besides, the improved efficiency of charge separation, enhanced visible light absorption and enlarged specific surface area also contributed to the enhanced photocatalytic performance of BPQDs/BiOBr. This work provides a feasible strategy for optimizing photocatalytic thin films via detailed analyzing the role of BPQDs in the construction of direct Z-scheme photocatalysts.

长期以来，光催化薄膜的表面改性被认为是提高降解性能的有效策略，这反过来又有助于缓解全球环境污染问题。本研究通过在水热法制备的BiOBr薄膜表面集成黑磷量子点（BPQDs），成功构建了直接Z型光催化体系。最佳的 BPQDs/BiOBr-1 薄膜对降解甲基紫 (MV) 和四环素盐酸盐 (TC) 的光催化活性显着增强，是纯 BiOBr 对应物的 3 倍和 3.65 倍。参与反应的活性物质是 h ⁺ , •O ₂ ^-, 和 •OH，由自由基捕获实验确定。直接Z型光催化体系的形成使电子组装在BPQDs的导带（CB）中，空穴聚集在BiOBr的价带（VB）中，支持h ⁺和•O ₂ ^-的生成，进而加速光催化反应。此外，电荷分离效率的提高、可见光吸收的增强和比表面积的增大也有助于提高BPQDs/BiOBr的光催化性能。这项工作通过详细分析 BPQDs 在构建直接 Z 型光催化剂中的作用，为优化光催化薄膜提供了可行的策略。