Z型Ag_(2)CO_(3)/BiOCl异质结光催化剂的制备及其可见光催化机理分析

通过溶剂热法制备BiOCl纳米片,共沉淀法制备Ag_(2)CO_(3)和复合催化剂Ag_(2)CO_(3)/BiOCl,研究各材料可见光催化降解罗丹明B的效果,确定Ag_(2)CO_(3)与BiOCl的最佳配比,并通过表征分析复合材料的结构和异质结光催化降解机理。结果表明,当Ag_(2)CO_(3)与BiOCl的质量比为50%时,Ag_(2)CO_(3)/BiOCl异质结催化剂的可见光催化效率最高,其一级动力学反应速率常数是BiOCl和Ag_(2)CO_(3)的6.79和12.58倍。紫外可见漫反射分析证明,Ag_(2)CO_(3)的加入使Ag_(2)CO_(3)/BiOCl对可见光的吸收增加,拓宽了光响应范围。XPS价带谱证明,调控后的BiOCl纳米片能带位置上移。通过自由基捕获实验和电子顺磁共振(ESR)证明,其主要活性物种是·O^(-)_(2)、h^(+)和·OH,从而推断Ag_(2)CO_(3)与BiOCl构成Z型异质结,相比Ⅱ型异质结拥有较高的氧化还原能力,可充分利用水中的溶解氧(O_(2))和OH^(-),大大提升了光催化效率。

Z-scheme Ag2CO3/BiOCl heterojunction photocatalyst:preparation and visible-light photocatalytic mechanism analysis

BiOCl nano-sheets was prepared by solvent thermal method,Ag₂CO₃ and novel Ag₂CO₃/BiOCl heterojunction photocatalysts were prepared in situ precipitation.The visible-light catalytic degradation of Rhodamine B over the prepared catalysts was studied and the optimal ratio of Ag₂CO₃/BiOCl was determined.The structure and the photocatalytic degradation mechanism of heterojunction photocatalysts were analyzed by characterization.The results showed that when the mass ratio of Ag₂CO₃ to BiOCl comes to 50%,the heterojunction catalyst shows the highest visible-light catalytic efficiency,which was 6.79 and 12.58 times higher than that of pure BiOCl and Ag₂CO₃.Uv-visible diffuse reflectance spectra proves that the addition of Ag₂CO₃ increases the absorption of visible light,and widens the optical response range of the Ag₂CO₃/BiOCl composite.The XPS valence band spectrum proves that the energy band position of the regulated BiOCl nanocrystals moves up.Active species trapping experiments and ESR spectra prove that its main active species are ·$O_{2}^{-}$, h⁺ and ·OH, and the Z-scheme heterostructure of Ag₂CO₃/BiOCl.Compared with the type-II heterojunction,it possesses high redox capacity,makes full use of O₂ and OH^- in water and greatly improves the photocatalytic efficiency.