Experimental Technology and Management

该实验要求学生制备具有良好可见光催化活性的典型铋系材料BiOBr和BiOI，通过材料表征和电化学性能测试，比较并揭示BiOBr和BiOI在结构和特性上的差异；同时，选择环境中毒害作用明显的代表性新污染物双酚A(Bisphenol A BPA)作为降解目标，阐明两种材料结构特性差异与BPA降解性能的关联。结果表明，BiOI降解BPA的效率在120 min内可达88%，明显优于BiOBr(28%)。BiOBr和BiOI的相应导带电位(E_CB)分别为-0.21 eV和-0.39 eV，价带电位(E_VB)分别为2.45 eV和1.32 eV，说明BiOI的带宽相对于BiOBr较窄。BiOI的降解性能优于BiOBr的主要原因是BiOI的带隙宽度更短，在光催化过程中能产生更多的·O₂~-、e^-和h⁺等活性氧化物种。该科研实验的全过程，从实验设计到假设验证形成了一个闭环，包括实验的设计与实施、数据分析以及结果的论证，能够培养学生独立、全过程设计科研实验的能力，激发科研兴趣，提升科研创新能力。

[Objective] The global environmental crisis is intensified by emerging pollutants including Bisphenol A(BPA), which leads to serious threats to the health of ecosystems and humans. To solve the above-mentioned problems, graduate students in environmental engineering must have innovative thinking and technical proficiency. Hence, it is vital to cultivate innovative graduate students through whole-process design of scientific experiments. This study focuses on enabling graduate students to comprehend the structure-performance relationships of bismuth oxyhalides(BiOBr and BiOI) for BPA removal. These practical experiences effectively cultivate critical thinking, technical proficiency and problem-solving skills of graduate students. [Methods] The experiment is structured into three phases: material synthesis, characterization, and performance evaluation. BiOBr and BiOI are synthesized by graduate students using microwave-assisted synthesis. For the preparation of BiOBr, bismuth nitrate pentahydrate is dissolved in a 10% glycol solution, followed by potassium bromide(KBr) was added to the solution and mixed. The mixture was microwave-heated at 160 ℃. By a similar method, potassium iodide(KI) was substituted for potassium bromide to prepare BiOI. After synthesis, materials were washed, dried, and characterized. Crystallinity and chemical composition are confirmed by XRD and FT-IR. Morphological differences revealed by SEM/TEM showed Bi OI nanosheets(～25 nm) and Bi OBr nanosheets(～62 nm). Optical and electrochemical analyses(UV-vis DRS, PL, Mott-Schottky) elucidated the bandgap structures and charge dynamics. Photocatalytic degradation of BPA(10 mg·L^-1) is conducted under a 500 W xenon lamp. Degradation efficiency is monitored via UV-vis spectrophotometry at 278 nm. Reactive species(·O₂~–, h⁺, e^-) are identified using scavengers like tert-butanol. The graduate students conducted systematic correlation analysis to elucidate the relationship between material properties(e.g., band gap, morphology) and degradation performance. [Results] The results showed that BiOI achieved 88% BPA degradation efficiency within 120 min, which was significantly superior to that of BiOBr(28%). The corresponding conduction band potentials(ECB) of BiOBr and BiOI were 0.21 eV and 0.39 eV, respectively, while the valence band potentials(EVB) were 2.45 eV for BiOBr and 1.32 eV for BiOI, indicating that BiOI has a narrower bandgap compared to BiOBr. The superior degradation performance of BiOI over BiOBr was mainly due to the shorter band gap of BiOI, which facilitated the generation of a greater number of reactive oxygen species such as ·O₂~–, e~–, and h⁺ during the photocatalytic process. [Conclusions] Implementing the whole-process design of scientific research experiments demonstrates that this closed-loop system integrates all stages, from design to hypothesis validation. This comprehensive approach includes the development and implementation of experimental plans, precise data collection and analysis, and validation of results through iterative feedback. By participating in this whole process, graduate students are able to develop key skills such as experimental design, problem solving, and technical proficiency. The closed-loop system not only promotes independent thinking and systematic research habits, but also encourages graduate students to critically evaluate their own hypotheses and optimize research methods based on empirical evidence. As a result, the process fosters students' abilities to think critically, innovate, and contribute substantively to their field of study.