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石墨相氮化碳(g-C_3N_4)具有较高的催化活性、良好的生物相容性、廉价易得、低毒性等特点,因而受到了广泛的关注.g-C_3N_4的禁带宽度为2.7 eV,可被可见光激发,相对于二氧化钛和氧化锌,它对可见光具有更高的太阳光利用率.尽管理论上g-C_3N_4是类似于石墨烯结构的二维材料,但通常情况下g-C_3N_4却是层层堆积起来的三维体相结构.从而导致了其比表面积降低,催化反应过程中与反应物接触面积小.同时又使光照下生成的载流子不能迅速传递到材料表面参与反应,大大降低了g-C_3N_4光生载流子的分离和传递效率.另外,作为一种可见光催化剂,g-C_3N_4的禁带宽度比一般的无机半导体光催化剂窄,仅能够吸收部分可见光.本文利用原位煅烧法制备了g-C_3N_4/rGO复合光催化剂,以罗丹明B和2,4-二氯酚为目标探针分子,考察了其可见光催化活性.这对于设计开发其他具有共轭大π键的光催化体系,具有一定的借鉴意义.X射线衍射(XRD),傅里叶变换红外光谱(FTIR),X射线光电子能谱(XPS)和激光共聚焦拉曼光谱(Raman)结果表明,氧化石墨烯成功地被还原为石墨烯,并成功地引入到了g-C_3N_4中去.在三聚氰胺聚合的过程中,石墨烯被夹杂在氮化碳的片层中间,有利于形成π-π共轭作用.复合光催化剂C_3N_4/rGO的带边发生明显的红移,在可见光区域内的吸收强度也有所增加,因而有利于其可见光催化活性的提高.通过外推法算得g-C_3N_4和C_3N_4/rGO-1复合光催化剂的带隙宽度分别为2.70和2.42eV.为了更好地考察复合光催化剂C_3N_4/rGO的能带结构的变化,通过光电化学的手段对其进行进一步的研究.莫特-肖特基结果表明该半导体是n型.计算得出g-C_3N_4和C_3N_4/rGO复合光催化剂的平带电势分别为-1.12和-0.85 V对甘汞标准电极,C_3N_4/rGO复合光催化剂的平带电位发生明显的正移.由此分别确定g-C_3N_4和C_3N_4/rGO复合光催化剂的价带底则位于1.58和1.74 V对甘汞标准电极.相比g-C_3N_4,g-C_3N_4/rGO复合光催化剂的价带位置的降低意味着其具有更强光氧化的能力,且比表面积的增大也有利于光催化反应.结果发现,石墨烯与g-C_3N_4的比例为1%时,复合样品的光催化性能最佳,对罗丹明B和2,4-二氯酚的降解性能均有提高.
Graphite carbonitride (g-C_3N_4) has attracted wide attention because of its high catalytic activity, good biocompatibility, low cost and easy availability.G-C_3N_4 has a band gap of 2.7 eV , Which can be excited by visible light, has higher solar utilization for visible light than titanium dioxide and zinc oxide.Although g-C 3 N 4 is theoretically a two-dimensional material similar to graphene structure, in general g-C 3 N 4 Is a three-dimensional body structure stacked layer by layer, resulting in a decrease of its specific surface area, catalytic reaction with the reactant contact area is small. At the same time so that light generated carriers can not be quickly transmitted to the surface of the material involved in the reaction, As a visible light catalyst, the bandgap of g-C_3N_4 is narrower than that of typical inorganic semiconducting photocatalysts, and it can only absorb part of visible light.In this paper, the in-situ calcination The g-C_3N_4 / rGO composite photocatalyst was prepared by the method of Rhodamine B and 2,4-dichlorophenol as the target probe molecules to investigate its visible photocatalytic activity. This is for the design and development of other conjugated π-bond light Catalytic system has some reference value.X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and laser confocal Raman spectroscopy (Raman) results show that graphene oxide Was successfully reduced to graphene, and successfully introduced into the g-C_3N_4 to go in. During the polymerization of melamine, graphene is intercalated in the middle of the carbon nitride layer, is conducive to the formation of π-π conjugation. The band edge of photocatalyst C_3N_4 / rGO shows obvious red shift, and the absorption intensity in the visible region also increases, which is in favor of the increase of the visible light catalytic activity.G-C_3N_4 and C_3N_4 / rGO-1 complex The bandgap widths of the photocatalysts were 2.70 and 2.42eV, respectively. In order to better investigate the band structure changes of the composite photocatalyst C_3N_4 / rGO, the photocatalyst was further studied by photoelectrochemical method. Indicating that the semiconductor is n type. Calculated that the flat band potential of g-C_3N_4 and C_3N_4 / rGO composite photocatalyst were -1.12 and -0.85 V for the calomel standard electrode, C_3N_4 / rGO composite photocatalyst flat band potential obvious The positive shift The valence band of g-C_3N_4 and C_3N_4 / rGO composite photocatalysts are located at 1.58 and 1.74 V for calomel standard electrode, and the reduction of valence band position of g-C_3N_4 / rGO composite photocatalyst means that And the photocatalytic reaction is also enhanced with the increase of specific surface area.The results show that the photocatalytic activity of the composite sample is the best when the ratio of graphene to g-C 3 N 4 is 1% And 2,4-dichlorophenol degradation performance has improved.