Synthesis And Visible-Light Photoactivity Of BiOI Photocatalysts

Aging behaviors are frequently observed in many kinds of materials,indicating the gradual changes of certain properties of materials with time elapsing.The research and development of new visible photocatalyst is the key of photocatalytic technology.In recent years,BiOX?X=Cl,Br,I?has attracted wide attention due to its unique layered structure,suitable band structure and effective carrier separation.Among them,BiOCl and BiOBr can only absorbs ultraviolet and a small part of visible light,which limits their practical application.As the material with the narrowest band gap in Bi OX,BiOI has a wider visible light absorption range,and it can utilize solar light more effectively.However,the fast recombination of photogenerated carriers would result in the lower activity of BiOI.In this study,the photocatalytic activity of BiOI under the visible light irradiation was improved by coupling with other semiconductor materials.The mechanism of photocatalysis was further explored through the various characterizations.The specific research contents in this study are listed as follows:1.The study on the preparation of AgI/Bi2MoO6/AgBi?MoO4?2 heterojunction by low-temperature calcination method and its visible light photocatalytic activity.BiOI nanosheets were synthesized at room temperature.AgI/Bi₂MoO₆/AgBi?MoO₄?₂multi-heterostructure was prepared by low-temperature calcination of the mixture of as-prepared BiOI,AgVO₃,and?NH₄?₆Mo₇O₂₄·4H₂O.The composite materials were characterized by a series of techniques?such as XRD,SEM,TEM,UV-Vis,XPS,EIS,PL,etc.?to analyze the phase composition,microstructure,charge separation,and photocatalytic mechanism.When the added Ag⁺ions reached 1.6 mmol,the prepared sample had the highest photocatalytic activity.The results showed that the generated multi-heterostructure can effectively cause the separation of photogenerated electrons and holes,leading to the improved photocatalytic performance.2.The study on the preparation of BiOI/Bi2O2CO3 two-dimensional composite photocatalyst and its visible light photocatalystic activity.BiOI/Bi₂O₂CO₃ two-dimensional heterostures were prepared through the ion exchange by adding NaCO₃ into the BiOI solution.The proportion of the two phases in the heterostructure is controlled by changing the amount of added C source.Compared with the pure BiOI and Bi2O2CO3,the composite samples have demonstrated the improved visible light photocatalytic performance.When the molar ratio of C/I was 40%,the composite sample showed the highest photocatalytic performance.The heterojunction structure in the two-dimensional composite photocatalyst greatly improves the effective separation of photogenerated electrons and holes,resulting in a significant increase in its catalytic activity.3.The study on the preparation of AgI/Bi₂WO₆/BiOI heterojunction by low-temperature calcination method and its visible light photocatalytic activity.BiOI nanosheets were synthesized at room temperature.AgI/Bi₂WO₆/BiOI multi-heterostructure was prepared by low-temperature calcination of the mixture of as-prepared BiOI,Ag,and W sources.When the added Ag⁺ions reached 0.35 mmol,the prepared sample showed the highest activity.The results showed that the enhanced photocatalytic performances of composite catalysts were mainly due to the constructions of multi-heterostructures,which could promote the efficient separation of photogenerated carriers and effectively inhibit the recombination of photogenerated carriers.