Preparation Of Bismuth-based Nanocomposites And Their Applications In Photocatalysis

Due towidely appications of photocatalytic technology in environmental remediation and clean energy production,improving visible light harvesting efficiency and developing high photocatalytic performance and good stability photocatalyst havebecome a hot topic of the photocatalytic research.Considering that most of bismuth-containing photocatalysts could be excited under visible light,and the construction of heterojunction could enhance photocatalytic activity,a series of bismuth-containing composites with specials junction were synthesized by facile methods in this work.By studying the relationship between structures and catalytic performance,appropriate methods toward improving the photogeneration carriers separation efficiency were investigated,which could enhance the photocatalytic ability.The main works are as following:?1?The Bi₂S₃/Bi₂WO₆ heterostructures weresynthesized at room temperature by using Bi₂WO₆hollowsphereandlowconcentrationNa₂S.X-raypowder diffraction?XRD?scanning electron microscopy?SEM?and high resolution transmission electron microscopy?HRTEM?dates for as-prepared products revealed that the Bi₂S₃ was generated at room temperature for amorphous state containing a lot of defects.Enhancement of photocatalytic activity of the nanocomposites was observed for the RhB and TC photodegradation.The amorphous/crystalline contact in Bi₂S₃/Bi₂WO₆heterostructures played a crucial role in the enhancement of photocatalytic efficiency.Based on DRS,photoluminescence spectra,photocurrent intensity,electrochemical impedance spectroscopy and OCVD measurements,it was proposed thatthe enhanced performance could be ascribed to increased visible light utilization,promoted separation efficiency and prolonged life time of photogenerated electron-hole pairs by the introduction of amorphous Bi₂S₃.?2?Bi₂WO₆ nanoplate with average thickness of 4.2 nm was prepared by a hydrothermal route in sodium oleate solution,which was verified by atomic force microscopic?AFM?characterization.Then photoreduction method was applied for Ag loading and photocatalytic degradation of RhB was used to evaluate the photocatalytic activity of Ag loaded catalysts.Enhancement photocatalytic activity was observed in all incorporated products,among which the highest activity is Ag loading amount at 3%.The results could be owing to the enhancement of visible light absorption ability by plasma resonance of Ag on the surface.Moreover,the schottky junction between metal Ag and Bi₂WO₆ could promote charge separation.?3?Hollow tube–like Bi₂S₃ was synthesized by using Bi₂WO₆ hollow sphere and high concentration Na₂S via a hydrothermal method.According to XRD,SEM and HRTEM characterizations,it was found that the Bi₂S₃ with high purity,uniform morphology,and the special rectangular cross section shape growing along the[001]direction.The formation process of the unique Bi₂S₃ tube was followed by examining the phase and morphology of the products obtained at different intervals of reaction time,which couldbe concluded that the morphology of Bi₂S₃ tube was determined by the structure confined effect of Bi₂WO₆ hollow sphere and Bi₂S₃ with intrinsic highly one dimensional anisotropic.Meanwhile,the rectangular shape reflect the intrinsic symmetry of the corresponding lattice.Then Ag/Bi₂S₃ composite was prepared by simple photo-reduction method and the photocatalytic Cr?VI?reduction ability was investigated.Moreover,the rapid recombination of the photoinduced carriers in single component Bi₂S₃ led to its low activity,and the Ag/Bi₂S₃ composite showed higher activity than that of Bi₂S₃.The electrons excited to the conduction band of Bi₂S₃ were trapped by Ag nanoparticels due to the construction of schottky junction,and thus improving the separation efficiency of carriers,which was confirm by the EIS plots.The large number of electrons gathered in Ag could react with Cr?VI?and improve the photocatalytic activity.