Preparation And Application In Environmental Catalysis Of Bi₂MoO₆-Based Nanocomposites

Recently,more and more concerns have been concentrated on the application of solar conversion,which not only can help people overcome the energy crisis,but also shows a promising prospects about the environment remediation.Therefore,it has become a difficult problem to seek efficient photocatalysts and how to improve the overall efficiency of the photcatalytic reaction.Many works focused on the modification of a matrix to obtain an ideal photocatalyst with good performance.Furthermore,modified photocatalysts were also investigated to maximize the overall efficiency,which could provide a new way for their practical application.In this paper,multi-modified Bi₂MoO₆-based photocatalysts were synthesized through a facial hydrothermal method.And the photocatalytic activity of obtained photocatalysts was evaluated by the photodegradation of organic pollutants or toxins.Moreover,the structure,photochemical properties and photocatalytic activity of the photocatalysts were also analyzed in detail,which deeply investigate the mechanism of the enhancement.The main works are summarized as follows:1.Hierarchical Bi_3.64Mo_0.36O_6.55/Bi₂MoO₆ isotype heterostructures were successfully prepared via a one-pot hydrothermal route by using Bi₂O₃ porous nanospheres as a sacrificial template.By tuning the reaction time,the formation process of Bi_3.64Mo_0.36O_6.55/Bi₂MoO₆ heterostructure involving Mo etching,phase transition and anisotropic growth were clearly clarified.More importantly,Bi_3.64Mo_0.36O_6.55/Bi₂MoO₆ heterostructure displayed remarkably enhanced photocatalytic activity for dye photodegradation than pure phase bismuth molybdate due to the efficient electron-holes separation and the interfacial photogenerated hole migration from inside Bi_3.64Mo_0.36O_6.55 layer to outside Bi₂MoO₆ layer.The hypothesis that the migration direction of the hole is significant for the photocatalytic efficiency was also examined by another heterostructure?Bi₂O₃/Bi2WO6?.The opposite hole migration from outer layer to inner layer in Bi₂O₃/Bi2WO6 heterostructures resulted in the decrease of photocatalytic activity,further verifying the importance of hole migration direction.This work provides a novel route to fabricate heterostructured photocatalyst,as well as gives a strategy for mediating thecharge migration to improve photocatalytic performance2.Crystal defects have been extensively proved to have great influence on semiconductor photocatalysis.Thus,crystal defect engineering makes the improvement of the photocatalytic efficiency possible and has initiated a considerable interest in real catalysts.Herein,we develop a general strategy to manufacture and mediate crystal defects in the host Bi₂MoO₆ lattice by varying the cerium dopant content,resulting in the greatly improved visible-light-driven photocatalytic performance for the degradation of highly toxic nerve agent simulants?NAS?and organic dyes,as well as bacterial photoinactivation.After careful examination of crystal defects structure and charge carrier dynamics,it was evidently proved that the Ce-doping mediated crystal defect is crucial for controlling the photocatalytic efficiency of Aurivillius Bi₂MoO₆.More importantly,the well-engineered crystal defects not only exert a beneficial influence on the electron dynamics and band structure,but also facilitate the one-electron and two-electron reactions by introducing the Ce3+/Ce4+ and Mo4+/Mo6+ redox couples,which results in a significant enhancement in ROS photogeneration.3.Se-loaded Bi₂MoO₆ photocatalysts with different Se loading content were successfully synthesized by solvethermal method.Systermatical structure and morphology characterization was performed,which verified that all the loading agent added was loaded onto Bi₂MoO₆ matrix.In addition,structural analysis results have shown that the strong interaction between selenium and oxygen influenced the chemical environment of other elements.The structure variation caused by Se loading has resulted in great enhancement in the light absorption,electron migration and electron-hole separation.After exmined by both cationic and anionic dyes photodegradation experiments,the 5% Se-BMO sample exhibits the best photocalytic performance.