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.
Abstract
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+.
关键词
Bi5O7I/g-C3N4 /
Z型异质结 /
常温沉淀法 /
可见光催化性能
Key words
Bi5O7 I/g-C3N4 /
precipitation method at room temperature /
visible-light photocatalytic property /
Z-scheme heterojunction
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基金
国家自然科学基金（51378129，51108094）；广东省自然科学基金（2017A030313321，2015AS030313494）；广东省高教厅-普通高校特色创新类项目（2016KTSCX035）
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