Ag3PO4/Ag2S/g-C3N4复合光催化剂的制备与性能

通过沉积法和离子交换法成功地制备了Ag_3PO_4/Ag_2S/g-C_3N_4复合型光催化剂。利用X射线多晶粉末衍射仪(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)、N_2吸附-脱附等温线、紫外-可见漫反射光谱、荧光光谱等手段对样品进行了表征。通过降解罗丹明B考察其可见光催化活性及稳定性,研究了硫化钠与磷酸银物质的量的比值(n_(Na_2S)/n_(Ag_3PO_4))、g-C_3N_4添加量对所制备复合光催化材料性能的影响,同时对光催化机理进行了探讨。结果表明,随着n_(Na2S)/n_(Ag3PO4)的增加,所得复合催化材料活性先增加后降低;当n_(Na2S)/n_(Ag_3PO_4)为1.5%、g-C_3N_4与Ag_3PO_4的质量比为3∶7时制备的催化剂ASC1.5的光催化活性最好,在可见光照射下,40 min内可将罗丹明B完全降解,且5次循环使用后仍保持较高的催化活性。和Ag_3PO_4相比,Ag_3PO_4/Ag_2S/g-C_3N_4复合型光催化材料的活性与稳定性都得到明显提高,这主要归因于复合催化剂比表面积和孔结构的增加,载流子分离效率的提高。光催化机理研究表明,空穴(h~+)、超氧阴离子自由基(·O~(2-))和羟基自由基(·OH)都是光催化过程中的主要活性物种。三者作用大小依次为:h~+·O~(2-)·OH。

Preparation and Performance of Ag3PO4/Ag2S/g-C3N4 Composite Photocatalyst

Ag₃PO₄/Ag₂S/g-C₃N₄ composite photocatalysts were successfully prepared by a deposition-ion exchanged combined method. And the obtained samples were characterized by X-ray powder diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), N₂ adsorption and desorption isotherms, UV-visible diffuse reflectance spectroscopy, fluorescence spectrophotometry and so on. The catalytic activity and stability of the catalysts were evaluated by degradation of rhodamine B under visible light. The effect of molar ratio of sodium sulfide to silver phosphate (n_Na2S/n_Ag3PO4) on the photocatalytic performance of the silver phosphate was studied. In addition, the photocatalytic mechanism was also investigated. The results show that, with the increase of n_Na2S/n_Ag3PO4, the activity of the obtained composite catalytic material increased firstly and then decreased. When n_Na2S/n_Ag3PO4 was 1.5%, the obtained ASC1.5 catalyst could completely degrade rhodamine B within 40 min under visible light irradiation, and also maintained high activity after five-cycle use. Compared with single silver phosphate, the activity and stability of Ag₃PO₄/Ag₂S/g-C₃N₄ composite photocatalytic materials were significantly improved, which was mainly attributed to the increase of surface area and the presence of porous structure that enhanced separating efficiency of electron-hole pairs. The study of photocatalytic mechanism over the composite catalyst have shown that h⁺, ·O^2- and ·OH were the main active species in the photocatalytic process. The order of the role of the above three species was:h⁺ > ·O^2- > ·OH.