Preparation Of BiOI-based Binary Composite And Its Photocatalytic Performance

Water pollution has become more and more serious due to the rapid industrialization.Compared with traditional physical and chemical methods,semiconductor photocatalysis has been deemed as a technology with application potential to eliminate kinds of pollutants in aquatic environments.The development of catalysts with high catalytic activity,physicochemical stability and visible-light response is the key to treating pollutants by photocatalysis because of its low-cost and high efficiency.Among various photocatalysts,Bi OI has attracted great attention due to its unique layered structure,suitable valence-band position and narrow band gap（1.7～1.9 e V）that can response to visible light.However,Bi OI structures in nanoscale suffer from serious agglomeration and recombination of carriers,resulting in unsatisfactory photocatalytic performance,which greatly limits its practical application.To this end,Bi OI-based binary composites with excellent photocatalytic performance were designed in our works by combining Bi OI with other semiconductors.The main research contents are as follows:（1）Preparation of BiOI/KTaO₃hybrid material and its photocatalytic performance.Firstly,KTa O₃ nanocubes were synthesized via hydrothermal method,then a series of Bi OI/KTa O₃ composites were prepared by growing Bi OI nanosheets on the surface of KTa O₃ cubes during a precipitation process.The photocatalytic performance of Bi OI/KTa O₃ composites was evaluated by degradation of Rh B and phenol under visible light irradiation.Compared with pure Bi OI and KTa O₃,Bi OI/KTa O₃ composites exhibited enhanced photocatalytic performance.Among them,54 wt%Bi OI/KTa O₃composite displayed the highest photocatalytic activity,its reaction rate constant（k）reached to 0.115 min^-1,which ws about 2.56 and 11.5 times higher than that of pure Bi OI and KTa O₃,respectively.The analysis results of microstructure characterization,photoluminescence spectroscopy（PL）,photocurrent and electrochemical impedance spectroscopy（EIS）indicated that the heterojunction structure formed between Bi OI and KTa O₃ can effectively promote the separation and transfer of photogenerated carriers,thereby the photocatalytic performance of Bi OI/KTa O₃ was improved.Free-radical capture experiment illustrated that h⁺and·O₂^-were the key factors in the process of photodegradation of Rh B.（2）Construction of WO₃/BiOI composite and its photocatalytic performance.WO₃/Bi OI composites were prepared by hydrothermal and co-precipitation methods.The phase structure,morphology and optical properties of WO₃/Bi OI were characterized by X-ray diffractometry（XRD）,field emission scanning electron microscopy（SEM）and ultraviolet-visible diffuse reflectance spectroscopy（UV-vis DRS）.The photocatalytic performance of WO₃/Bi OI composites was evaluated by degradation of Rh B and MB under visible light irradiation.Compared to WO₃ and Bi OI,WO₃/Bi OI composites exhibited enhanced photocatalytic performance.When the mass percentage of WO₃was 10%,WO₃/Bi OI showed the highest photocatalytic activity,and its k value was 3.3 and 33.6 times higher than that of Bi OI and WO₃,respectively.The enhanced photocatalytic performance of WO₃/Bi OI can be attributed to two reasons.（i）The formation of hierarchical structure enabled the WO₃/Bi OI to expose a much larger catalytic surface area.（ii）The heterojunction formed between WO₃ and Bi OI promoted the separation and transfer of photogenerated carriers.Trapping experiments implied that h⁺and·O₂^-were the dominant active species for organic pollutants decomposition by WO₃/Bi OI composites.（3）Construction of CoTiO₃/BiOI heterojunction photocatalyst and its photocatalytic performance.Co Ti O₃/Bi OI composites were constructed by using a two-step co-precipitation method,and characterized by SEM,XRD,XPS and UV-vis DRS.The photocatalytic performance of the as-prepared Co Ti O₃/Bi OI composites was explored by degradation of various organic dyes under visible light irradiation.Compared to Co Ti O₃ and Bi OI,Co Ti O₃/Bi OI showed much higher photocatalytic performance for Rh B,MO and TC degradation.The improved photocatalytic performance can be attributed to the increased specific surface area,enhanced light absorption ability and improved separation efficiency of photogenerated carriers.Trapping experiments indicated h⁺and·O₂^-played a significant role in the removal of RhB by CoTiO₃/BiOI composites.