0D/1D碳点修饰硫化镉纳米线异质结增强可见光光催化性能

摘要

Zero-dimensional carbon dots (0D C-dots) and one-dimensional sulfide cadmium nanowires (1D CdS NWs) were prepared by microwave and solvothermal methods, respectively. A series of heter-ogeneous photocatalysts that consisted of 1D CdS NWs that were modified with 0D C-dots (C-dots/CdS NWs) were synthesized using chemical deposition methods. The mass fraction of C-dots to CdS NWs in these photocatalysts was varied. The photocatalysts were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoe-lectron spectroscopy, and ultraviolet-visible spectroscopy. Their photocatalytic performance for the spitting of water and the degradation of rhodamine B (RhB) under visible light irradiation were investigated. The photocatalytic performance of the C-dots/CdS NWs was enhanced when com-pared with that of the pure CdS NWs, with the 0.4% C-dots/CdS NWs exhibiting the highest photo-catalytic activity for the splitting of water and the degradation of RhB. The enhanced photocatalytic activity was attributed to a higher carrier density because of the heterojunction between the C-dots and CdS NWs. This heterojunction improved the electronic transmission capacity and promoted efficient separation of photogenerated electrons and holes.%硫化镉(CdS)作为一种对可见光响应的窄带隙半导体(带隙宽度约为2.4 eV), 具有合适的能带位置, 近年来受到越来越多的重视. 然而在光催化过程中, 光生电子与空穴的快速复合极大地限制了CdS的实际应用, 如何提高光生电子-空穴对的分离效率成为研究重点. 一维CdS纳米棒(1D CdS NWs)具有较大的长径比, 能快速有效地转移光生载流子. 零维碳点(0D C-dots)是一种粒径在10 nm以下的新型纳米碳材料, 其作为助催化剂能够加快光生载流子传递速率, 可提高材料光催化性能. 因此, 通过C-dots对CdS NWs进行修饰并形成异质结, 利用C-dots助催化剂的作用以提升CdS NWs的光催化性能,具有一定的可行性.本文成功构建了一种0D/1D碳点修饰CdS NWs异质结(C-dots/CdS NWs), 并考察其光催化性能. 通过X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)和紫外-可见(UV-Vis)吸收光谱等技术对系列C-dots/CdS NWs样品进行表征. 研究发现, C-dots成功负载在CdS NWs的表面并形成异质结. 通过测试系列样品在可见光照射下光催化降解罗丹明B (RhB)以及光催化产氢性能发现, C-dots的修饰能够有效增强CdS NWs的光催化性能, 其中0.4% C-dots/CdS NWs表现出最佳的光催化降解RhB活性, 其经可见光照射60 min即可实现对RhB的完全降解(相同条件下CdS NWs需要180 min). 同时自由基捕获实验表明, ·O2-是降解罗丹明B过程中的主要活性基团. 在光催化产氢性能测试中, 0.4% C-dots/CdS NWs样品表现出最高的光催化产氢能力, 产氢速率可达1633.9 μmol g-1h-1, 比纯CdS的(196.9 μmol g-1h-1)提高了8.3倍, 并且C-dots/CdS NWs具有良好的稳定性. 研究发现, 在可见光照射下, C-dots/CdS NWs能够产生较强的光生电流, 且形成的0D/1D C-dots/CdS NWs异质结具有良好的电子传输能力, 实现了C-dots/CdS NWs光生电子与空穴的有效分离, 从而增强了光催化性能.