Research On The Preparation And Performance Of Z-scheme Heterojunction Photocatalyst Based On Bismuth Ferrite

Energy crisis and environmental pollution are two major problems that cannot be avoided in the development of human society.In order to solve these two problems,people have invested a lot of research and semiconductor photocatalysis technology is one of the promising methods.Semiconductor photocatalysts,which can collect huge and inexhaustible solar energy and convert it into clean chemical energy（for example,H₂）or treat pollutants,has become a research hotspot.However,because many semiconductor photocatalyst materials are still limited with high photogenerated electron-hole recombination rate,low carrier migration rate and low visible light absorption,the efficiency of semiconductor photocatalysis is low and it will be a long time before its practical application.Therefore,it is urgent to develop new high-efficiency semiconductor photocatalysts.Bismuth ferrite materials have a narrow band,strong visible light absorption,good stability and unique magnetoelectric properties,so their photocatalytic application has attracted people’s attention.At present,bismuth ferrite materials have been used for photocatalytic oxygen production,degradation of pollutants and reduction of carbon dioxide.However,the single bismuth ferrite materials also have the disadvantages of high photogenerated electron-hole recombination rate and low carrier migration rate.Studies have shown that,in order to improve the photocatalytic performance of bismuth ferrite materials,it is feasible to construct Z-scheme heterojunction photocatalyst based on bismuth ferrite materials.This paper is mainly focused on the research background of Z-scheme heterojunction photocatalysts and bismuth ferrite materials,the controllable preparation of bismuth ferrite materials and the construction,performance as well as mechanism of Z-scheme heterojunction photocatalysts based on bismuth ferrites.（1）Bi₂Fe₄O₉ is prepared by hydrothermal method.By changing the temperature and time of hydrothermal reaction,the thickness of Bi₂Fe₄O₉ nanosheets is controlled and the exposure of photocatalytic active crystal face is increased,improving its photocatalytic activity.BiFeO₃ is also fabricated by hydrothermal method.Through changing the surfactant used in the hydrothermal reaction,the size and morphology of BiFeO₃ particles are adjusted and the exposure of the photocatalytic active crystal face is increased to improve its photocatalytic performance.（2）By the in-situ growth method under the action of electrostatic force,with Bi₂Fe₄O₉nanosheets as the substrate,zinc chloride as the zinc source,2.5 hydrated cadmium chloride as the cadmium source and sodium sulfide nonahydrate as the sulfur source,Cd_0.5Zn_0.5S quantum dots are grown on the surface of Bi₂Fe₄O₉ nanosheets.The Cd_0.5Zn_0.5S@Bi₂Fe₄O₉ heterojunction photocatalyst with intimate contact interface,enhanced photocatalytic activity and Z-scheme charge transfer mechanism is obtained（3）Using BiFeO₃ nanoparticles as the core,the core-shell photocatalyst coated with Zn In₂S₄nanosheets is successfully prepared by a simple oil bath method.The S-Bi bonds are formed between the interface of Zn In₂S₄ and BiFeO₃,which play an important role in the formation of core-shell structure and carriers migration.Finally,the Zn In₂S₄@BiFeO₃ heterojunction photocatalyst with enhanced photocatalytic activity and Z-scheme charge transfer mechanism is obtained.