石墨相氮化碳纳米片的可控制备及光催化性能

Controllable Preparation and Photocatalytic Performance of Graphitic Carbon Nitride Nanosheets

通过调控前驱体三聚氰胺和尿素比例采用热聚合法得到一系列厚度可控的石墨相氮化碳(g-C_(3)N_(4))纳米片。采用X射线粉末衍射、扫描电镜、原子力显微镜、比表面积测试、紫外可见光谱和荧光光谱等手段对纳米片的结构和性能进行了表征,并探讨了其光催化降解罗丹明B(Rh B)的性能。结果表明:当三聚氰胺和尿素比例为1:8时g-C_(3)N_(4)最薄(1:8-CN),厚度仅为3.518 nm,同时1:8-CN的比表面积是以三聚氰胺为原料制备的g-C_(3)N_(4)(M-CN)的7倍。光电学分析表明,1:8-CN具有更高的光生载流子分离效率。在可见光照射下,1:8-CN对Rh B的光催化降解率可以达到96.2%,是M-CN的1.9倍。1:8-CN光催化降解Rh B的反应机理表现为:光生电子-空穴对分离产生的电子与O2结合生成·O_(2)^(-),·O_(2)^(-)将Rh B氧化生成CO2和H2O,空穴几乎不参与反应。

A series of graphitic carbon nitride(g-C_(3)N_(4))nanosheets with controllable thicknesses were prepared by a thermal polymerization method with different ratios of precursor melamine and urea.The nanosheets were characterized by X-ray diffraction,scanning electron microscopy,atomic force microscopy,specific surface area measurement,ultraviolet–visible spectroscopy and photoluminescence,respectively,which were used for the photocatalytic degradation of Rhodamine B(RhB).The results show that g-C_(3)N_(4) is the thinnest(1:8-CN)with the thickness of 3.5 nm when the ratio of melamine to urea is 1:8.Its specific surface area is 6 times greater than that of g-C_(3)N_(4) prepared using only melamine(assigned as M-CN).The photoelectric analysis indicates that 1:8-CN has a higher separation efficiency of photogenerated carriers.Under the visible-light,the photocatalytic degradation rate of RhB by 1:8-CN can reach 96.2%,which is 1.9 times greater than that of M-CN.Besides,the photocatalytic degradation mechanism of 1:8-CN toward RhB is since the electrons generated by the separation of photogenerated electron-hole pairs combine with O_(2) to generate·O_(2)^(-),and then·O_(2)^(-) oxidizes RhB into CO_(2) and H_(2)O,and the holes do hardly participate in the reaction.