BiOBr/g-C3N4 S型异质结无H2O2光-自芬顿高效催化降解RhB

通过焙烧-超声混合法成功地制备了BiOBr/g-C₃N₄ S型异质结复合光催化剂。采用多种表征手段对样品物理属性进行了表征，包括X射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、紫外可见漫反射光谱(UV-VisDRS)。研究了所制备样品有/无Fe³⁺的光-自芬顿催化/光催化降解罗丹明B (RhB)性能。通过捕获实验确定了光催化反应中的主要活性物种，提出了光-自芬顿反应的降解机理。研究结果表明，BiOBr/g-C₃N₄ S型异质结能原位生成H₂O₂，添加Fe³⁺后，H₂O₂被原位活化成活性物种且光生电流和载流子分离效率获得显著提高。该光-自芬顿过程能高效降解RhB，其反应速率常数为0.208 min^-1，约为无Fe³⁺光催化反应速率常数的5.3倍，在光-自芬顿循环使用过程中表现出良好的稳定性。Fe³⁺的加入促进了光生电荷的分离和H₂O₂的活化，超氧阴离子自由基(·O₂^-)、空穴和羟基是光-自芬顿催化过程中的主要活性物种，且·O₂^-作用更大。

Efficient degradation of RhB over BiOBr/g-C3N4 S-scheme heterojunction by a H2O2-free photo-self-Fenton catalysis

The fabrication of the BiOBr/g-C₃N₄ S-scheme heterojunction is an effective way to improve photocatalytic activity. Yet, its photocatalytic activity is expected to further improve, and its photo-Fenton catalytic activity for pollutant degradation in the absence of H₂O₂ has not been investigated up to now. In this work, a BiOBr/g-C₃N₄ S-scheme heterojunction photocatalyst was successfully prepared by a calcination-ultrasonic mixing method. Herein, its photo-self-Fenton catalytic activity was investigated for the first time in the absence of H₂O₂. The physical properties of the samples were characterized by X-ray polycrystalline powder diffractometer (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). Photocatalytic and photo-self-Fenton catalytic degradation of rhodamine B (RhB) were studied over BiOBr/g-C₃N₄ S-scheme heterojunction without/with Fe³⁺ in the absence of H₂O₂, respectively. The main active species in the photo-self-Fenton catalytic reaction were determined by capturing experiments, and the degradation mechanism of the photo-self-Fenton catalysis was proposed. The results showed that H₂O₂ could be formed in situ over the BiOBr/g-C₃N₄ S-scheme heterojunction under visible-light irradiation. The photogenerated current and the separation efficiency of photo-generated carriers can be greatly improved in the presence of Fe³⁺ over BiOBr/g-C₃N₄ S-scheme heterojunction, resulting in the enhancement of photocatalytic efficiency for RhB degradation in the photo-self-Fenton process than in the photocatalytic reaction without Fe³⁺. The reaction rate constant of photo-self-Fenton over BiOBr/g-C₃N₄ S-scheme heterojunction with Fe³⁺ was 0.208 min^-1, which was about 5.3 times that of photocatalysis without Fe³⁺. It also showed good stability in the recycling experiment. The addition of Fe³⁺ promotes the separation of photogenerated charges and the activation of generated H₂O₂ by the Fe²⁺/Fe³⁺ redox cycle. The results of capturing experiments show that superoxide anion radicals (·O₂^-) and holes (h⁺) are found the main active species, and ·O₂^- plays a more important role in photo-self-Fenton catalysis.