Preparation And Properties Of Several Photocatalysts With Heterojunction Structures

With the development of modern industry,the environmental problems arose more and more attention.The development of heterogeneous semiconductor photocatalysts for degrading organic pollutant under solar-light has been an indispensable and challenging topic for decades.TiO2 is a traditional material that is widely used due to its low cost and high stability.However,its wide band gap,which can only be excited by UV light,limited its wide application under visible light irradiation.Consequently,to utilize the solar-light effectively,developing photocatalysis has become one of the significant issues.The preparation,properties and photocatalytic activities of several novel photocatalysts with heterojunction structure were studied in this paper.The morphologies,phase structures and optical properties of the obtained products were investigated by a variety of characterization equipments.The photocatalytic activities of photocatalysts were estimated by photocatadegrading rhodamine B solution.Specific work is as follows:In this study,the novel AgI/AgIO3 heterojunction was prepared through a mild ion-exchange method at room temperature.The AgI/AgIO3 composites performed better photocatalytic activities than pure AgI and AgIO3 with 15%AgI/AgIO3 heterojunction showing the highest photocatalytic efficiency,which can decompose RhB completely in 50 min.Moreover,the 15%AgI/AgIO3 hybrid photocatalyst also showed excellent repeatability and stability during photocatalytic reaction.The improvement of photocatalytic performance can be attributed to effective separation of photo-excited electrons and holes at the interface of AgI/AgIO3 composites.Radical trap experiments determined that the O2·-radical was the main reactive species for the photodegradation of RhB.In this study,the novel heterojunction AgIO3/WO3 was fabricated through hydrothermal and chemical precipitation methods.Compared with pure AgIO3 and WO3,50%AgIO3/WO3 heterojunction was recorded to have the optimum rate constant,and can decompose RhB completely in 140 min.The enhancement of the photocatalytic activity could be attributed chiefly to the effective separation and migration of photogenerated electron-hole pairs at the interface of AgIO3 and WO3.In addition,radical trap experiments confirmed that the ·OH was the primary reactive species during the photodecomposition RhB process.In this study,the efficient visible-light-driven AgIO3/AgBr photocatalyst was successfully synthesized by an in-situ anion-exchange method at room temperature.Compared with pure AgBr and AgIO3,the AgIO3/AgBr compounds showed drastically improved visible-light photocatalytic activity.Besides,the results also reveled that 20%AgIO3/AgBr exhibited the best photocatalytic activity,which could decomposed the RhB completely in 24 min.The enhanced photocatalytic activity of the composites could be ascribed to the high separation rate of the photoinduced electron-hole groups in the heterojunction structure.Moreover,the radical trap experiments were also carried out and confirmed that h+ played the major role in the RhB photodegradation process.In this study,Bi2WxM1-xO6-BiOCl(x=0,0.2,0.4,0.6,0.8 and 1.0)heterojunctions were successfully synthesized through a solvothermal crystallization method.And the band structure is regulated by adjusting the relative content of W and Mo in compounds.The photocatalytic activities of Bi2WxMO1-xO6-BiOCl composites were estimated by the degradation of Rhodamine B(RhB)under the visible light irradiation.And Bi2W0.6Mo0.4O6-BiOCl(1:14)composite was proved to be the best photocatalyst among the as-prepared samples,and it can photodegrade RhB completely in 7.5 min.It was found that the separation efficiency of photogenerated charge carriers will be affected by the different band structures of heterojunction photocatalysts,thus affecting the production of active species during photocatalysis.