Preparation Of WO₃-based Composite Photocatalysts And Their Photocatalytic Performance

With the rapid development of industrialization and urbanization,problems such as energy shortages and environmental pollution have become increasingly serious.It is particularly important to realize sustainable development of society.Visible light photocatalysis technology is an ideal way to generate clean energy and deal with environmental purification problems.WO₃nanomaterials,as a photocatalyst that can respond to visible light,have the advantages of non-toxicity,resistance to photocorrosion,and excellent performance,and are a nanomaterial with promising photocatalytic applications.However,the insufficient reduction ability due to the low electron potential of the conduction band of WO₃and the excessively high recombination ratio of photogenerated electrons and holes limit its further development and application.In view of the above problems of WO₃,this paper modified WO₃to construct a direct Z-scheme heterostructure,thereby improving its photocatalytic activity.1.Using the terminal amino group of g-C₃N₄ to control the morphology of tungsten oxide,a novel Z-scheme W₁₈O₄₉nanowire-g-C₃N₄nanosheet composite photocatalyst was prepared by solvothermal method.The introduction of g-C₃N₄improves the absorption of visible light and promotes charge transfer at the interface of the composite.The composites exhibited higher photocatalytic activity than pure W₁₈O₄₉and g-C₃N₄.When the content of g-C₃N₄was 50 mg,WCN50 showed the best photocatalytic activity.The corresponding hydrogen production rate was 1.700mmol?g^-1?h^-1and the conversion of cyclohexane was 7.35%.The improvement of photocatalytic activity is mainly due to the enhancement of visible light absorption capacity,and the Z-scheme charge transfer mechanism promotes interface charge transfer and prolongs the lifetime of photo-generated electrons.2.Z-scheme WO₃ nanosheet-carbon quantum dot composites were prepared by loading carbon quantum dots with different terminal amine groups and carboxyl groups on the surface of WO₃nanosheets.And compare their micromorphology,structural composition,optical and electrochemical performance.NCDs-loaded composites have lower fluorescence intensity and interface resistance,which means efficient electron transfer.WO₃-NCDs composite with a mass content of 9.3%of NCDs showed photocatalytic hydrogen production activity and significantly improved the catalytic activity of cyclohexane oxidation.The highest cyclohexane conversion rate was 7.88%and the selectivity to KA oil was 98.9%.This performance is 1.2times that of WO₃-CCDs and 1.5 times that of pure WO₃nanosheets.The improvement of the catalytic performance is attributed to the effective Z-scheme charge transfer mechanism and the photo-thermal synergistic catalysis to accelerate chain initiation of cyclohexane oxidation.3.WO₃-MoS₂-NCDs composites were prepared by solvothermal method.The introduction of MoS₂and NCDs makes composites have enhanced visible light absorption capacity,higher photoelectric conversion efficiency and interface charge transfer efficiency.The average hydrogen production rate of WMC composites is16.02μmol?g^-1?h^-1,which is 87%of the catalytic performance of WC composites using Pt as a cocatalyst,indicating that MoS₂has the potential to replace the noble metal Pt as a cocatalyst.WMC composites have both a type II heterostructure and a Z-type heterostructure.The type II heterostructure maximizes the effective use of photogenerated electrons and holes,while the Z-scheme heterostructure maximizes the photo-generated electron’s reducing capacity.The ternary heterostructure enables efficient transfer of photogenerated electrons and holes,thereby significantly improving the photocatalytic hydrogen production capacity.