利用硫化铋纳米颗粒增强类石墨相氮化碳的光生载流子分离效率和光催化活性（英文）

二氧化钛,氧化锌,磷酸铋等传统的紫外光响应光催化剂虽然具有良好的光催化性能,但是对太阳能利用率很低(紫外光只占太阳光能量的4%左右).近年来,类石墨相氮化碳(g-C3N4)受到了广泛的关注.g-C3N4的带隙约2.7 eV,它只能吸收460nm以下的光,对太阳能的利用率依然比较低.构筑异质结是一种有效的提高光催化活性的方法.BiOCl/g-C3N4,TiO2/g-C3N4, Bi2MoO6/g-C3N4, Al2O3/g-C3N4, Ag3PO4/g-C3N4等异质结光催化剂曾被广泛的报道.硫化铋是属于正交晶系的窄带隙半导体,它的带隙约1.3–1.7 e V.由于其独特的电子结构和光学特性,硫化铋在光催化,光检测器和医药成像等领域有着广泛的应用.另外,硫化铋还具有优异的光热转换性能,在光热癌症治疗领域有显著的效果.微波辅助法,水热法,惰性气体下高温煅烧法等都曾被用来合成g-C3N4/Bi2S3异质结光催化剂.不同的文献也提出了不同的催化机理.如何使用更简单环保的方法来合成g-C3N4/Bi2S3异质结光催化剂?电子和空穴的转移路径是怎样的?本文利用简单的低温方法合成了硫化铋,利用超声法得到了g-C3N4/Bi2S3异质结光催化剂,分析了其微观形貌,结构,并探讨了光催化的反应机理和提高光催化性能的因素.X射线衍射,傅里叶变换红外光谱, X射线光电子能谱和透射电子显微镜的结果表明,硫化铋纳米颗粒被成功地引入到g-C3N4中.使用亚甲基蓝为分子探针研究了所制材料在模拟太阳光下的光催化活性.结果发现, CN-BiS-2表现出最佳的光催化活性,是g-C3N4的2.05倍,是Bi2S3的4.42倍.利用液相色谱二级质谱联用分析了亚甲基蓝的降解路径.硫化铋的引入拓展了复合材料的吸收边,使其向可见光区红移,且在整个可见光区的光吸收能力都有明显的增强.光电流的增强和交流阻抗谱圆弧半径的减小,表明光生载流子的迁移与分离速率得到了增强.自由基捕获试验表明,最主要的活性物种是光生空穴,次之是羟基自由基和超氧自由基.在CN-Bi S-2样品中羟基自由基和超氧自由基的电子顺磁共振信号都比g-C3N4有明显的增强,表明复合样品中能够产生更多的羟基自由基和超氧自由基.基于光电流,交流阻抗,荧光光谱,自由基捕获和电子顺磁共振的结果,我们提出了高能电子由硫化铋转移到g-C3N4,同时空穴由g-C3N4转移到硫化铋的电子空穴转移机制.此外,红外热成像的结果表明, g-C3N4/Bi2S3异质结材料具有更强的光热转换能力,从而有利于加速光生载流子分离.

Accelerated separation of photogenerated charge carriers and enhanced photocatalytic performance of g-C3N4 by Bi2S3 nanoparticles

Employing photothermal conversion to improve the photocatalytic activity of g-C3N4 is rarely reported previously. Herein, different ratios of g-C3N4/Bi2S3 heterojunction materials are synthesized by a facile ultrasonic method. Advanced characterizations such as X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy are employed to analyze the morphology and structure of the prepared materials. Compared with sole counterparts, the heterojunction materials CN-Bi S-2 exhibit significantly enhanced photocatalytic performance, which is 2.05-fold as g-C3N4 and 4.42-fold as Bi2S3. A possible degradation pathway of methylene blue(MB) was proposed. Based on the photoproduced high-energy electrons and photothermal effect of Bi2S3, the transfer and separation of electron-hole pairs are greatly enhanced and more active species are produced. In addition, the relatively high utilization efficiency of solar energy has synergistic effect for the better photocatalytic performance.