Bi5O7I/g-C3N4Z型异质结的常温沉淀制备及其光催化性能研究

以Bi（NO₃）₃·5H₂O、KI和g-C₃N₄为前驱体，采用常温沉淀法制备Bi₅O₇I/g-C₃N₄Z型异质结复合光催化剂，表征其光吸收性能、微观形貌、光生电子-空穴的分离效率等特性，研究新型光催化剂对RhB的可见光催化降解性能，探讨其可见光催化过程活性基团种类以及作用机理.结果表明：利用沉淀法合成Bi₅O₇I/g-C₃N₄的条件为：Bi（NO₃）₃·5H₂O、KI和g-C₃N₄的投加量分别为4.85g、1.66g和1.61g，乙二醇的用量为50mL，反应液的pH值为12，反应搅拌速度为200r/min，反应温度为25℃.Bi₅O₇I/g-C₃N₄异质结无杂相生成且纯度高，异质结复合发生在g-C₃N₄的（002）晶面和Bi₅O₇I的（203）晶面，但g-C₃N₄和Bi₅O₇I的化学结构未受影响.Bi₅O₇I/g-C₃N₄呈三维纳米花瓣形貌结构，为光生电子-空穴的迁移提供了大量的接触位点.Bi₅O₇I的g-C₃N₄掺杂改性使其光催化活性显著增强，其光吸收边缘由425nm红移至462nm，Bi₅O₇I/g-C₃N₄的能带排列结构与Z型异质结匹配，促进了光生电子-空穴的分离.其光电流密度（11.5mA/cm）约为g-C₃N₄和Bi₅O₇I对应值的2.66倍和1.47倍.Bi₅O₇I/g-C₃N₄对罗丹明B的可见光催化降解率为93.9%，显著高于g-C₃N₄（58%）和Bi₅O₇I（49.7%）的降解效果，其光催化氧化活性主要来自羟基基团、超氧基团和光生空穴等中间态自由基.

Room-temperature precipitation synthesis and photocatalysis of Bi5O7I/g-C3N4 Z-scheme heterojunction

In this work, by using Bi₅O₇ I、KI and g-C₃N₄ as precursors, a novel Bi₅O₇ I/g-C₃N₄ Z-scheme heterojunction has been synthesized successfully by precipitation method at room temperature, its property of light absorption、morphologic structure、efficiency of photogenerated electron-hole were characterized. The visible-light degradation performance on Rhodamine B(RhB)by new type composite photocatalyst、the kinds of radicals and the mechanism in photocatalytic reaction system were studied. The results revealed that:The synthesis conditions of Bi₅O₇ I/g-C₃N₄ by precipitation were shown as follow:4.85g Bi(NO₃)₃·5H₂O, 1.66g KI, 1.61g g-C₃N₄, 50mL glycol, 12 of reaction pH, 200r/min of reaction stirring rate and ambient reaction temperature(25℃).There's no impurity and influence on chemical structure of g-C₃N₄ and Bi₅O₇ I during the synthesis process, the recombination of Bi₅O₇I/g-C₃N₄ crystallographic plane occured on the {002} crystal plane of g-C₃N₄ and the {312} crystal plane of Bi₅O₇ I.The morphologic structure of Bi₅O₇ I/g-C₃N₄ was 3D nano petal-like, which furnished a large number of contacting site for the transfer of photogenerated electron-hole. The doping of g-C₃N₄ on Bi₅O₇ I can significantly enhance photocatalytic activity, its wavelength edge of light absorption shifted to 462nm from 425nm.The band arrangement structure of Bi₅O₇ I/g-C₃N₄ was matched with the Z-scheme heterojunction, which promoted the separation of photogenerated electron-hole, its photocurrent density (11.5mA/cm) is 2.66 and 1.47times than that of g-C₃N₄ (4.32mA/cm) and Bi₅O₇ I(7.8mA/cm) respectively. The photocatalytic degradation rate for RhB by Bi₅O₇I/g-C₃N₄ under visble light irradiation is 93.9%, which is 1.89 and 1.62times than that of Bi₅O₇ I and g-C₃N₄ respectively, the activity of photocatalytic oxidation was attributed to the intermediate radicals including ·OH、·O₂^- and h⁺.