p-n异质结BiPO_4/Ag_3PO_4的制备及其增强的模拟太阳光活性

采用一步水热合成法制备了BiPO_4、Ag_3PO_4和BiPO_4/Ag_3PO_4复合光催化剂,通过X射线粉末衍射(XRD)、X射线光电子能谱(XPS)、扫描电子显微镜(SEM)、紫外-可见漫反射(UV-Vis DRS)等表征手段对其组成结构、形貌及光吸收性质进行了表征,结果表明Ag_3PO_4呈块状结构,BiPO_4则分布在其表面,形成的BiPO_4/Ag_3PO_4复合光催化剂具有单斜相和立方晶相结构,带边吸收拓宽至571 nm。以甲基橙和加替沙星为目标污染物,考察了BiPO_4/Ag_3PO_4复合光催化剂在模拟太阳光照射下的降解矿化能力,结果表明复合催化剂比单一催化剂的降解矿化能力更强,稳定性更好。此外,自由基捕获实验表明空穴是该光催化过程中的主要活性物种,·O2-次之。p-n异质结的形成使BiPO_4/Ag_3PO_4复合光催化剂具有较强的电子空穴分离能力是光催化活性提高的主要原因,这与光电流和电化学阻抗谱测试结果相一致。基于以上结果,文中对BiPO_4/Ag_3PO_4光催化降解有机污染物的机理进行了推测。

BiPO4/Ag3PO4 p-n Heterojunction with Enhanced Photocatalytic Activity under Simulated Sunlight Irradiation

BiPO₄,Ag₃PO₄ and BiPO₄/Ag₃PO₄ heterostructure photocatalysts were synthesized by one-step hydro-thermal method.X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS),scanning electron microscope (SEM) and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) techniques were used to characterize morphology,crystal structure,and absorption spectrum.The SEM results showed that the BiPO₄/Ag₃PO₄ sample was in blocky structure and BiPO₄ distributed on the surface of Ag₃PO₄.The XRD of BiPO₄/Ag₃PO₄ sample displayed monoclinic and cubic crystal structure.The UV-Vis DRS spectra results indicated that the BiPO₄/Ag₃PO₄ sample displayed obviously red shifts compared to BiPO₄ and the light absorption range broaden to 571 nm.Moreover,the photocatalytic activity was evaluated by photodegradation of methyl orange (MO) and gatifloxacin solution under simulated sunlight irradiation.BiPO₄/Ag₃PO₄ exhibits higher degradation and mineralized activities and the better stability on degradation of methyl orange and gatifloxacin than the single BiPO₄ and Ag₃PO₄.Moreover,the test of active radical showed that the h⁺ was the main active radical in the degradation process,·O₂^- was weaker.The enhanced photocatalytic activity and stability of BiPO₄/Ag₃PO₄ was mainly attributes to the formation of p-n heterojunction interface in BiPO₄/Ag₃PO₄ which facilitated the transfer and separation of photogenerated electron-hole pairs confirmed by the results of transient photocurrent response and electrochemical impedance spectroscopy measurement.Based on the above results,the photocatalytic mechanism for organics degradation over BiPO₄/Ag₃PO₄ was proposed.