铋修饰BiOBr/g-C3N4异质结光催化剂合成及其可见光催化性能研究

以尿素为氮化碳（g-C₃N₄）合成的前驱体，柠檬酸（CA）作为还原剂，以一步溶剂热法制备铋修饰BiOBr/g-C₃N₄异质结型复合光催化剂（简称Bi/BiOBr/g-C₃N₄）.通过调控CA的投加量，实现了对Bi/BiOBr/g-C₃N₄可见光催化的可控制备，并以RhB为目标污染物研究其光催化活性.结果表明：1被还原在BiOBr表面上的Bi金属含量随还原剂CA投加量增加而增加，CA最佳投加量为2 mmol，Bi/BiOBr/g-C₃N₄的光生载流子的分离效率最高、禁带宽度最窄（2.43 eV）.而未采用CA改性的BiOBr/g-C₃N₄，其禁带宽度为2.8 eV.2投加CA能调控BiOBr形貌（如结晶度、尺寸大小以及晶粒平均厚度），进而调控其光催化活性.当CA投加量为2 mmol时，BiOBr纳米微球大小适中，结晶度最高，晶粒平均厚度最小.3Bi修饰BiOBr/g-C₃N₄光催化剂对RhB的可见光降解率高达99.8%，其光催化降解速率达到0.097 k·min^-1，是BiOBr/g-C₃N₄光催化速率（0.026 k·min^-1）的3.73倍.4Bi/BiOBr/g-C₃N₄异质结光降解机理是：在Bi金属等离子体效应、BiOBr表面氧空缺与异质结的协同作用下，提高了Bi/BiOBr/g-C₃N₄异质结对可见光吸收能力和光生载流子的分离效率，从而实现对RhB的高效降解.

Synthesis of Bi-decorated BiOBr/g-C3N4 heterojunction photocatalyst and its visible light-driven photocatalytic performance

Taking urea as a precursor for the preparation of carbon nitride (g-C₃N₄) and citric acid (CA) as a reducing agent, the composite photocatalyst Bi-amended BiOBr/g-C₃N₄ heterojunction (Bi/BiOBr/g-C₃N₄) was synthesized by taking one-step solvothermal method. By adjusting the dosage of CA, the visible light responsive activity of the Bi/BiOBr/g-C₃N₄ was optimized and verified in the process of degrading the dying pollutant RhB. The results were shown below:with the addition of the dosage of the reducing agent CA, the content of the metal Bi being reduced on the surface of BiOBr increased. When the dosage of CA was up to the optimum (2 mmol), the separation efficiency of the photoinduced electron-hole pairs of Bi/BiOBr/g-C₃N₄ reached the highest and the band gap (2.43 eV) was the narrowest, while the BiOBr/g-C₃N₄ band gap was 2.8 eV. 2The reducing agent CA affected the crystallinity, size and average thickness of BiOBr. When the dosage of CA was 2mmol, the size of BiOBr nanospheres was moderate, its crystallinity was the highest, and its average thickness was the smallest. 3 under the optimum dosage of CA, the Bi/BiOBr/g-C₃N₄ demonstrated the highest visible light degradation efficiency of RhB (99.8%), and its photocatalytic degradation rate reached 0.097 k·min^-1, which was 3.73 times of that of BiOBr/g-C₃N₄ (0.026 k·min^-1).4The photodegradation mechanism of Bi/BiOBr/g-C₃N₄ heterojunction was that the synergistic effect between Bi metal plasma, surface oxygen vacancy of BiOBr and heterojunction. The synergistic effect promoted the separation rate of the photoinduced electron-hole pairs markedly, thereby Bi/BiOBr/g-C₃N₄ achieved high degradation efficiency of RhB.