Design,Preparation And Performance Study Of Bismuth-based Photocatalytic Composite Materials Heterojunction

In order to cope with the energy crisis and environmental pollution,scientists all over the world have made efforts to explore good solutions to green and sustainable technology.As a technology driven by renewable energy,the photocatalysis process of semiconductor photocatalysts,in which only solar energy is used,can not only generate clean energy,but also solve the problem of pollution.Therefore,it is of great significance to prepare efficient visible light responsive photocatalytic materials and realize the effective utilization of solar energy to split water and degrade pollutants.However,photocatalytic materials generally have some key problems,such as weak absorption of visible light,easy recombination of photogenerated carriers,poor stability and insufficient redox potential,etc.As an important part of high-efficiency photocatalytic materials,bismuth-based composite materials have good photocatalytic performance.As a kind of bismuth-based materials,due to its high oxidation potential of the valence band and good stability,Bi₂O₃ has extensive application prospects in the field of photocatalysts.However,the crucial problems of weak absorption under visble light and easy recombination between photo-generated electrons and holes in Bi₂O₃,which have inevitably blocked their applications in photocatalysis research,need to be solved.Hence,heterojunction construction is proposed to effectively improve the narrow photoresponse range and low photogenerated electron and hole separation efficiency of a single semiconductor photocatalyst.Based on this theory,this work improves the performance of different phases of Bi₂O₃ materials,enhances the capacity of light absorption and separation effect of photogenerated electrons and holes of the bismuth-based composite material,thereby further enhances the photocatalytic effect,and extends its related applications.The main research contents and results are as follows:（1）Combining with the co-catalyst and the heterojunction,we constructed g-C₃N₄/RGO/Bi₂O₃ ternary heterojunction.Under the synergistic drive of the high-efficiency separation of photogenerated electrons and holes by the Z-scheme heterojunction and the high conductivity of RGO to electrons,the overall photocatalytic activity of the sample can be enhanced.The g-C₃N₄/RGO/Bi₂O₃ternary heterojunction composite material shows a good photocatalytic performance,and can degrade 50%of methylene blue（MB）within 40 minutes,which is expected to be used in the catalytic degradation of pollutants under visible light.（2）Combining with surface engineering and heterojunction construction to optimize the photocatalytic activity of Bi₂O₃by the introducing of PCN and Sb₂Mo O₆,this work has realized the construction of a two-dimensional hybrid double Z-scheme heterojunction PCN/Bi₂O₃/Sb₂Mo O₆,which can significantly enhance the separation effect of photogenerated electrons and holes of Bi₂O₃.Affected by the narrow band gap of Sb₂Mo O₆,the visible light absorption capacity of the heterojunction composite is enhanced,and the absorption utilization rate to sunlight of Bi₂O₃ is significantly improved.Based on the synergistic effect of above three improvement,the visible light catalytic ability of the photocatalyst is greatly enhanced.The sample exhibits a strong effect of degrading rhodamine B under visible light,and can degrade 93%of Rh B within 15 minutes.It can also realize the oxygen production process without sacrificial agent under visible light with good stability.Based on experimental data and theoretical calculations of VASP,the band structure of PCN/Bi₂O₃/Sb₂MoO₆ is established.