Synthesis And Photocatalytic Properties Of Bismuth Silicate Based Composite Materials

The energy shortage and environmental pollution caused by industrialization have attracted global attention.As the world’s largest energy consumption country,China is even more urgent to solve the above two major problems.Since semiconductor photocatalysis technology was created in the 1970s,through the unremitting efforts of scientific researchers from all over the world,the improvement and treatment of energy shortage and environmental pollution problems have achieved initial results.However,because traditional photocatalysts led by TiO₂ and ZnO have a wide band gap,the utilization efficiency of the visible and infrared wavelengths of sunlight is low,which greatly restricts its development and application.Therefore,the exploration of new semiconductor catalysts is inevitable.In recent years,bismuth-based semiconductors have gradually entered people’s field of vision because of their narrower band gap and stronger ability to degrade pollutants.Bismuth silicate,as a very important functional material,is widely used in the fields of chemicals,materials and national defense with its excellent photoelectric,acousto-optic,and dielectric properties.However,it has less research on photocatalysis,which is worthy of further investigation.In this paper,flower-like particles of cubic bismuth silicate(Bi₁₂SiO₂₀)were prepared by the oil bath method.Bi and Bi₂O₂CO₃ were grown in situ on the surface of Bi₁₂SiO₂₀ by two-step light irradiation method,and finally a Bi/Bi₂O₂CO₃/Bi₁₂SiO₂₀（Bi/BOC/BSO）three-component material was synthesized.Compared with the pure Bi₁₂SiO₂₀ sample,the heterojunction structure of the Bi/BOC/BSO composite exhibits better photocatalytic activity.Under simulated sunlight,the photocatalytic degradation rate of rhodamine B（Rh B）and tetracycline hydrochloride（TC）increased by 12 times and 3.3 times,respectively.At the same time,the recycling tests of the composite sample showed its good stability in the photocatalytic reaction.Further experiments of the trapping tests show that·O₂^-and h⁺play a major role in the degradation of organic pollutants.Combined with the conclusions of related experiments,we attribute the enhancement of Bi/BOC/BSO photocatalytic activity to the formation of heterojunction structure and surface plasmon resonance（SPR）effect.In addition,this simple surface modification method can provide a new way to improve the photocatalytic performance of Bi-based systems.In order to explore a variety of modification methods for different photocatalysts,we prepared orthogonal phase nanosheets bismuth silicate（Bi₂SiO₅）by hydrothermal method,and prepared Ag/AgBr/Bi₂SiO₅ three-component material by in-situ deposition and photoreduction methods.The morphology of the composite was observed by SEM that the presence of Bi₂SiO₅ effectively prevented the agglomeration of AgBr.The composite exhibits more excellent photocatalytic activity in degrading pollutants under simulated sunlight.The degradation rate of the composite sample with the best photocatalytic activity in the degradation of Rh B and TC is 5.4 times and 4.6 times that of the pure phase Bi₂SiO₅ sample,and the corresponding mineralization rate is also increased by 2.4 times and 2.1 times,respectively.In addition,the charge transfer between heterojunctions enhances the stability of the composite during the photocatalytic process.Finally,we proposed a possible photocatalytic enhancement mechanism,and attributed improved activity to the synergistic effect of both the heterojunction structure and the SPR effect.