摘要
Recently, the g-C3N4-based heterojunctions have been widely investigated for their greatly enhanced photogenerated carrier separation efficiency. However, most studies are based on the study of g-C3N4 powders. In this study, a novel TiN/C3N4/CdS nanotube arrays core/shell structure is designed to improve the photoelectrochemical catalytic performance of the g-C3N4-based heterojunctions. Among them, TiN nanotube arrays do not respond to simulated solar light, and thus only serve as an excellently conductive nanotube arrays backbone for supporting g-C3N4/CdS heterojunctions. g-C3N4 prepared by simple liquid atomic layer deposition, which possesses appropriate energy band position, mainly acts as the electron acceptor to transport and separate electrons. Deposited CdS quantum dots obtained by successive ionic layer adsorption reaction can effectively absorb visible light and thus act as a light absorber. The TiN/C3N4/CdS nanotube arrays core/shell structure could be verified by X-ray diffractions, Raman spectra, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy elemental mappings and X-ray photoelectron spectroscopy. Compared with TiN/C3N4 nanotube arrays, the TiN/C3N4/CdS samples greatly improve the photoelectrochemical performance, which can be evaluated by photoelectrochemical tests and photoelectrochemical catalytic degradation. Especially, the optimized photocurrent density of TiN/C3N4/CdS has almost 120 times improvement on TiN/C3N4 at 0 V bias under simulated sunlight, which can be ascribed to the effective expansion of the light absorption range and separation of electron-hole pairs.
近年来, g-C3N4基异质结由于能极大提高光生载流子的分离效率而得到了广泛的研究.然而,大多数的研究都是基于g-C3N4粉体.为了提高g-C3N4基异质结的光电催化性能,本文设计了一种新颖的具有核/壳结构的TiN/C3N4/CdS纳米管阵列.此结构中Ti N纳米管阵列对模拟太阳光几乎没有响应,因此只是作为支撑g-C3N4/CdS异质结的优良导电纳米管阵列骨架.采用简单液相原子层沉积法制备的g-C3N4由于具有合适的能带位置,在此结构中主要作为电子传输和分离的受体.通过连续离子层吸附反应法制备的Cd S量子点可以有效地吸收可见光,从而在此结构中主要起到增强光吸收的作用.X射线衍射、Raman光谱、扫描电子显微镜、透射电子显微镜、面扫能谱图和X射线光电子能谱等证实了TiN/C3N4/CdS纳米管阵列的核/壳结构;紫外光电子能谱表明, g-C3N4/Cd S形成了Ⅱ型异质结.入射光量子效率和光致发光光谱共同表明这种Ⅱ型异质结不仅极大地提高了光吸收效率,并且电子-空穴对有效地得到了分离.另外,一维TiN纳米管阵列基底具有较大的比表面积和一维的电子传输通道,这有利于增加光照面积和减少电子-空穴对的复合.光电化学性能测试和光电化学催化降解实验结果表明,与TiN/C3N4纳米管阵列相比, TiN/C3N4/CdS样品的光电化学性能有了很大的提升,其中沉积了30个循环周期Cd S的光电化学性能最优,在模拟太阳光照射0 V偏压下,其光电流密度比TiN/C3N4提高了近120倍.这可以归因于光吸收范围变宽以及电子-空穴对的有效分离.本文为其它用于高效的光电化学产氢和有机污染物降解的纳米管核/壳阵列结构异质结的设计提供了一种新的思路.
基金
海南省重点研究开发项目(ZDYF2017166)
国家自然科学基金(51462008,61764003,11574157).
