Design,Synthesis And Application Of Bi-based Photocatalysis

Photocatalytic technology can continuously utilize solar energy,directly convert solar energy into other energy sources,and achieve high efficiency and no secondary pollution of green chemistry requirements.It has the advantages of low cost,stability and multifunction.It has been widely studied and applied in water pollution control and new energy production,and is considered to be an ideal way to solve future energy and environmental problems.The traditional anatase TiO₂ photocatalyst cannot meet the requirements for ideal photocatalyst due to its low utilization of sunlight due to its wide band gap（-3.2 e V）.Therefore,the development of efficient and stable visible light catalysts has become one of the research hotspots in the field of photocatalysis in recent years.In addition to TiO₂,metal oxides and their composite oxides,due to their relatively low synthesis cost and high chemical stability,have gradually become more popular visible light catalytic materials.Among them,bismuth-based oxides and their composite oxides have narrow band gap and high visible light photocatalytic activity.They can effectively degrade organic pollutants and photolysis water under visible light,and become a kind of visible light catalytic materials with potential development.In this paper,aiming at the problem of low photocatalytic efficiency of traditional bismuth-based semiconductor materials,a new type of Bi-based photocatalyst was constructed by semiconductor recombination,morphology control,non-metallic doping and other technical means,so as to achieve effective separation of photogenerated electron-hole pairs and enhance photogenerated carriers,thereby improving the photocatalytic performance of the catalyst.At the same time,various characterization techniques were used to systematically study the composition,morphology and catalytic performance of the prepared catalysts for photocatalytic degradation of pollutants,and the photocatalytic mechanism was discussed according to the experimental data and results.The main research contents and results of this paper are as follows:（1）The controlled synthesis of BiOCl/In₂S₃ composite photocatalyst and its photocatalytic performance were studied.Pure phase BiOCl and In₂S₃ were synthesized by hydrothermal method,and then the novel heterojunction composite photocatalyst BiOCl/In₂S₃ was constructed by simple mechanical grinding.The photocatalytic properties of different grinding ratios for the degradation of tetracycline hydrochloride（TC）under visible light（λ≥420 nm）were studied.The results showed that when the molar ratio of BiOCl to In₂S₃ was 1:1,the photocatalytic performance was the best.The degradation efficiency of TC was 91.40%after illumination for 90 min,and the reaction rate constant was 0.02637 min^-1,which was about 7 times that of pure BiOCl.In addition,the composite catalyst has high photocatalytic stability,and its photocatalytic activity did not decrease significantly after three cycles.The reasonable photocatalytic degradation mechanism was obtained by active species capture experiment.This study fully demonstrated the advantages of physical composite method in the construction of BiOCl-based visible light catalytic system,and provided an effective reference for the design and synthesis of simple and efficient composite photocatalyst and the treatment of antibiotic environment.（2）Bi-based photocatalysts were prepared by controllable calcination of MOFs materials.Hexagonal prism CAU-17 was synthesized by solvothermal method with bismuth nitrate as bismuth source and trimellitic acid as ligand.CAU-17 was directly calcined in argon atmosphere using the self-sacrificing template method.The microstructure of Bi-based photocatalyst derived from CAU-17 was finely adjusted by systematically controlling the calcination temperature and time to construct porous nanostructures with uniform pore size,high porosity and controllable morphology.After the removal of CAU-17 organic ligand by calcination,a series ofβ-Bi₂O₃catalysts with highly dispersed active sites were prepared.The catalyst CAU-17-450-℃-2 h with uniform spherical bismuth oxide nanoparticles in the hexagonal prism showed the best photocatalytic activity,which could efficiently degrade amino black10B and tetracycline hydrochloride（TC）.Under visible light irradiation for 150 min,the degradation efficiency of amino black 10B was 93.0%,and TC was 90.0%under visible light irradiation for 7 h.After four photocatalytic cycles,the degradation efficiency of CAU-17-450-℃-2 h for amino black 10B remained at 90.6%,indicating that the photocatalyst had good photocatalytic stability.（3）the structure and properties of Bi-based photocatalysts are further regulated by changing the morphology of MOFs materials.In the case of keeping the Binode unchanged,the organic ligand was changed to 4,4′-biphenyldicarboxylic acid,and the Bi-bpdc with hexahedral morphology was prepared first.Bi-bpdc was used as the precursor/sacrificial template for direct calcination in air.The microstructure of Bi-based photocatalyst derived from MOF was regulated by systematically regulating the calcination conditions（350～450℃,holding for 1～3 h）,and the uniform distribution of the active componentβ-Bi₂O₃ of the catalyst was realized.When the temperature was400℃for 2 h,the catalyst Bi-bpdc-400℃-2 h with uniform distribution of nanosheets had the highest photocatalytic activity.The material could efficiently degrade amino black 10B,and the degradation efficiency could reach 97.8%under visible light irradiation for 60 min.（4）the composition and properties of Bi-based photocatalysts were further controlled by changing the composition of MOFs materials.Bi-tdc microspheres were synthesized by solvothermal method using sulfur-containing organic ligand（2,5-thiophenedicarboxylic acid）and Bi³⁺to control the growth time.Then,using Bi-MOF as the precursor/sacrificial template,sulfur-doped Bi-based photocatalyst with uniform pore size,high porosity and controllable morphology was prepared by adjusting the calcination temperature（300℃,400℃,500℃）and holding time（2 h,3 h,4 h）.The effect of S doping on the morphology and photocatalytic activity of Bi₂O₃.The sulfur-doped Bi-based photocatalyst Bi-tdc-400℃-3 h obtained by calcination at 400℃for3 h had the best photocatalytic activity,and the degradation efficiency of TC was 93.3%under visible light irradiation for 6 h.