Study On Preparations And Performances Of Highly Active Bi-based Composite Photocatalysts

Semiconductor photocatalysis technology has a good application prospect in environmental treatment,and the development of semiconductor catalyst materials with high activity is the main task of this technology.Among many photocatalysts,Bi-based semiconductors have attracted wide attentions of researchers because of their special electronic band structures,inherent physical properties,good optical and photoelectric properties,stable physical and chemical properties,and so on.The Bi-based semiconductor materials,such as BiOI,BiVO₄,Bi_xO_yI_z,and Bi₂WO₆,have many advantages,but their efficiencies for visible degradation of pollutants still need to be improved.In this paper,the above Bi-based semiconductor materials were compounded and doped by virtue of solvothermal and ion-doping methods,and the highly active Bi-based composite semiconductor photocatalysts were obtained.The formation and photocatalytic mechanisms of the composites were studied by a series of characterizations.The main research contents of this paper are listed as follows:1.Research on the preparation of Mo-doped BiOI/BiVO₄ two-dimensional heterojunction composite photocatalyst and its visible-light photocatalytic performance.Mo-doped BiOI/BiVO₄ two-dimensional heterojunction composite photocatalyst was prepared by hydrothermal method using the BiOI as the substrate.The composite photocatalysts with different Mo-doping ratios were prepared by changing the amount of added ammonium molybdate.When the ratio of Mo/V is 0.25%,the prepared photocatalyst of V/I8-Mo-0.25%has the highest photocatalytic activity.The results showed that the doping of Mo element and construction of heterojunction structure can synergistically promote the visible-light response of materials and the generation,migration and separation of photogenerated carriers,leading to the significantly improved photocatalytic performance.2.Research on the preparation of Bi₄O₅I₂/Bi₅O₇I heterojunction composite photocatalyst and its visible-light photocatalytic performance.Bi₄O₅I₂/Bi₅O₇I 2D/1D heterojunction composite photocatalysts were prepared by solvothermal method using Bi₅O₇I nanobelts as the substrate.The ratios of two phases in the composites were adjusted by adding different amounts of Biand I sources.When the ratio of Bi₄O₅I₂/Bi₅O₇I was 40%,the composite photocatalyst demonstrated the highest photocatalytic activity.The special 2D/1D morphology of Bi₄O₅I₂/Bi₅O₇I heterojunction composite photocatalyst can provide the more active sites,and the heterojunction between two phases can also promote the generation,migration,and separation of photogenerated carriers.All the above can synergistically improve the photocatalytic performances of the catalysts.3.Research on the preparation of Bi₂WO₆/Ag I heterojunction composite photocatalyst and its visible-light photocatalytic performance.The Bi₂WO₆/Ag I heterojunction composite photocatalysts were synthesized using the BiOI/Bi₂WO₆ composites obtained by hydrothermal method as the substrate materials.By changing the ratio of BiOI content in BiOI/Bi₂WO₆ substrate materials,Bi₂WO₆/Ag I composites with different composition ratios were obtained.When the molar ratio of Bi₂WO₆/Ag I was 0.75,the composite photocatalyst of BA-0.75 had the highest photocatalytic activity.The improvement of the activity of composite catalyst can be attributed to the high dispersion of Ag I nanoparticles and the formation of heterostructure.The heterojunction can promote the migration and separation of photogenerated electrons and holes and improve the utilization of photogenerated carriers.