Preparation Of Bi₂WO₆-based Composite Photocatalysts And Their Degradation Performance Of Organic Pollutants

With the development of science and technology and the progress of society,the demand and use of resources are increasing day by day,which brings serious environmental pollution problems,especially the organic pollutants in wastewater are difficult to decompose,which seriously threaten human life and health.Photocatalytic semiconductor materials can use solar energy to achieve high-efficiency degradation of organic pollutants,so they have received extensive attention and research from academia and industry.Bismuth tungstate（Bi₂WO₆）can effectively absorb visible light and exhibit good photocatalytic performance due to its narrow band gap（～2.8 e V）.Some important breakthroughs and progress have been made in the research fields of pollutant degradation,catalytic conversion of energy,and photodynamic therapy.However,the Bi₂WO₆ photocatalyst itself has relatively serious photo-generated electron-hole recombination,which limits the further improvement of its performance.In this thesis,through the construction of heterostructures and the use of surface plasmon resonance enhancement effects,the separation efficiency of photogenerated electrons and holes and the utilization rate of photons of Bi₂WO₆ photocatalyst are improved,and phenol and methylene blue are used to simulate organic pollutants in water.The prepared composite photocatalyst exhibited more efficient photocatalytic degradation activity than single Bi₂WO₆.The specific research content is as follows:（1）Firstly,the flower cluster-like Bi₂WO₆ is prepared by low-temperature hydrothermal method,and then with the aid of ultrasonic dispersion and stirring,graphite phase carbon nitride（g-C₃N₄）and ascorbic acid modified g-C₃N₄（COCN）were introduced to construct g-C₃N₄/Bi₂WO₆ and COCN/Bi₂WO₆ composite photocatalysts.Combining XRD,SEM,FT-IR,UV and PL and other characterization methods,the photocatalyst’s morphology,structure,photon absorption,photo-generated charge separation and other properties have been studied in detail.Through the degradation experiment of phenol,the photocatalytic degradation efficiency of g-C₃N₄/Bi₂WO₆ and COCN/Bi₂WO₆ were increased by 50%and80%,respectively,compared with that of single Bi₂WO₆.（2）Based on the prepared flower cluster-like Bi₂WO₆,the Ag NPs/Bi₂WO₆ composite photocatalyst was obtained by uniformly depositing silver nanoparticles（Ag NPs）on its surface by in-situ reduction method.The introduction of Ag NPs not only enhanced the absorption of photons by the composite photocatalyst through the surface plasmon resonance effect,but also improved the separation efficiency of photogenerated electrons and holes through the heterostructure formed with Bi₂WO₆.By optimizing the loading of Ag NPs,5%Ag NPs/Bi₂WO₆ achieves rapid and efficient photocatalytic degradation of methylene blue.The degradation efficiency exceeds 90%in only 40 minutes,which is much higher than that of single Bi₂WO₆（<50%）.