Preparation Of Silver-based Composite Photocatalyst And Study Of Its Photocatalytic Properties

Photocatalytic technology can directly convert solar energy into chemical energy,which attracts widespread attention in the field of environmental purification and energy development.However,the low utilization of solar energy and recombination of photoexcited electrons and holes lead to a decrease of photocatalytic activity.In order to solve these problems,several silver-based photocatalyst including Ag₃PO₄,Ag₂ S and AgVO₃ have been studied,and the strategies by constructing heterojunction and core-shell structure were proposed to prepare composite photocatalysts.These results may provide some useful experimental and theoretical evidences to fabricate photocatalysts with highly efficient activity and broad spectral response region.The main contents are as follows:1 ? Ag₃PO₄/In₂S₃ composite photocatalysts with ultra–low loading of Ag₃PO₄?0.017?4.89 wt%?were prepared by a facile precipitate method.The high dispersionof Ag₃PO₄ in composite might be due to the space–confined effect of In₂S₃ hierarchical pores.The Ag₃PO₄/In₂S₃ composites were employed to degrade different kinds of organic pollutants in aqueous solution under visible light irradiation,and exhibited excellent adsorption capacity and photocatalytic activity.The optimal composite with 0.086 wt% Ag₃PO₄ content exhibited the highest photocatalytic activity,which is six times than pure In₂S₃.The photocatalytic activity enhancement of Ag₃PO₄/In₂S₃ composites could be mainly attributed to the efficient separation of photogenerated charge carriers through a Z-scheme system composed of Ag₃PO₄,Ag and In₂S₃.The high photocatalytic stability was ascribed to the successful inhibition of the photocorrsion of both In₂S₃ and Ag₃PO₄ by transferring the photogenerated holes and electrons from them to Ag,respectively.This study firstly indicated the application of Ag–Ag₃PO₄ as cocatalyst to enhance the photocatalytic efficiency of semiconductor photocatalyst.2?A series of Ag₂S/Ag₃PO₄ composites with well-defined core/shell structures were synthesized via an in-situ anion-exchange reaction between Ag₃PO₄ dodecahedrons and Na2 S solutions.Ag₂S-5%/Ag₃PO₄ sample show that a few of Ag₂ S nanoparticles with size below 5 nm are deposited on the surface of Ag₃PO₄ dodecahedrons.The degradation of MO reached nearly 100 % after 120 min light irradiation.For Ag₂S-50%/Ag₃PO₄ sample,it could be observed that Ag₂ S nanoparticles with increasing amounts and large sizes ranging from approximately 20 to 50 nm were uniformly distributed on the Ag₃PO₄ dodecahedrons.The photocatalytic activity was highly dependent on the Ag₂ S content and the well-defined core/shell structure.The in-situ formed Ag nanoparticles at surfaces of Ag₃PO₄ and Ag₂ S during photocatalytic process acted as charge transmission bridges and electron trapping centers,respectively,resulting in the stable Ag₂S/Ag/Ag₃PO₄ Z-scheme heterostructure system and Ag/Ag₂S/Ag₃PO₄ ternary system.The introduction of Ag₂ S extended the light response range of Ag₃PO₄ and thus increased the solar utilization.3?Ternary Ag₂S/AgVO₃/Ag photocatalysts were synthesized through a one-pot hydrothermal process.The more S2-added in the hydrothermal system promoted the in situ formation of metallic Ag and the phase transition from b-AgVO₃ to ?-AgVO₃.Ag₂S/AgVO₃/Ag exhibited much higher photocatalytic activity than binary Ag/AgVO₃ and Ag/Ag₂ S under visible light irradiation.The improved activity could be attributed to the sensitization effect of Ag₂ S,the phase transformation from b-to ?-AgVO₃,and the facilitated charge transfer in Ag₂S/?-AgVO₃/Ag.