Study On Photocatalytic Properties Of 2D/2D Bi₂WO₆/g-C₃N₄ Composites

Two of the great challenges confronting the world today are the increasingly serious global energy crisis and environmental pollution.As an efficient way to address these issues,photocatalytic technology is one of the most prospective and sustainable technologies that utilize solar energy to generate hydrogen and degrade pollutants.Bi-based oxide photocatalysts have some advantages,such as visible light response,low cost,non-toxic and harmless,and have broad application prospects in the photocatalytic field.As a typical representative of visible light responsive photocatalytic materials,Bi₂WO₆has attracted much attention.However,the pure Bi₂WO₆photocatalyst has some problems,such insufficient conduction band position,low solar energy utilization and fast recombination of photogenerated charge carriers,which hinder its practical application.To overcome the weakness of Bi₂WO₆photocatalyst,it is necessary to modify it,including morphology regulation,heterogeneous structure construction and metal deposition.As a carbon-based semiconductor material,g-C₃N₄shows excellent potential in photocatalysis due to its excellent chemical stability,non-toxicity,easy synthesis and appropriate band structure.g-C₃N₄has a suitable band structure,which is particularly suitable for coupling with Bi₂WO₆to construct heterojunctions.Therefore,Bi₂WO₆/g-C₃N₄composite has attracted wide attention.However,how to selectively construct Z-scheme heterojunction and broaden its optical response range remain to be studied.In this paper,Bi₂WO₆/g-C₃N₄Z-scheme heterojunction was first constructed,and the synergy of two-dimensional/two-dimensional（2D/2D）coupling interface was used to preserve the high redox ability of the system and promote the separation efficiency of photogenerated carriers.Then,in order to further improve the absorption ability of the system to visible light and broaden the range of light response,we introduced metal Bi nanoparticles in situ into the system to construct the Bi₂WO₆@Bi/g-C₃N₄ternary composite photocatalyst,and made full use of the surface plasmon resonance（SPR）effect of metal Bi to enhance the photocatalytic performance of the system.The specific research content is as follows:（1）Bi₂WO₆/g-C₃N₄binary composite was prepared by wet chemical method.The 2D Bi₂WO₆nanoparticle is uniformly attached to the 2D g-C₃N₄,forming a 2D/2D coupling interface,which can greatly promote the photogenerated carrier migration.Under simulated sunlight,the hydrogen evolution rate of the composite photocatalyst is 687.6μmol h^-1g^-1,which is 1.29 times that of pure g-C₃N₄.In addition,both Rhodamine B（Rh B）and tetracycline hydrochloride（TC）can be photocatalyzed by the composite under visible light irradiation.In this part of work,we effectively improved the photocatalytic performance of Bi₂WO₆by morphological regulation and the construction of Z-scheme heterojunction.（2）Based on the previous work,we introduce metal Bi nanoparticles in the original site of 2D/2D structure.Metal nanoparticles Bi were grown in situ on the surface of Bi₂WO₆by solvothermal method of ethylene glycol,and then Bi₂WO₆@Bi/g-C₃N₄composite heterojunctions were prepared by wet chemical method.Among the samples with different contents of g-C₃N₄,the optimized Bi₂WO₆@Bi/50g-C₃N₄composite photocatalyst showed the best hydrogen production efficiency of 1219.3μmol h^-1g^-1.Under visible light irradiation,the degradation efficiency of Rh B reached82.4%within 80 min,and the photocatalytic degradation efficiency of TC reached66.7%within 40 min.The composite cooperates with Z-scheme heterojunction and the SPR effect of metal Bi,extends the optical absorption to the full spectrum,and promotes the separation and migration of photogenerated carrier under the premise of retaining high redox power,and the photocatalytic performance of ternary composite was significantly improved.