Synthesis Of Bi₂WO₆-based Nanomaterials And Their Application In Environmental Catalysis

Compound photocatalyst has been widely utilized in the environmental catalysis owing to its unique advantage in photocatalytic environmental treatment and energy resources regeneration.Bi₂WO₆ has the highest visible-light photocatalytic activity among the Aurivillius compounds,but its narrow visible-light response range and highly efficiency of photogenerated electron-hole recombination limit its photocatalytic applications.In this thesis,Bi₂WO₆-based compound photocatalysts have been synthesized by quantum dots modified or surface modification.Through the analysis of component,morphology and structure,as well as the investigation of photogenerated carrier dynamics and photocatalytic activities,the mechanisms of enhanced photocatalytic activities were discussed.According to the above research purpose and content,this thesis has carried out the following works:1.Co₃O₄ quantum dots with high optical absorption and activity were utilized to construct Co₃O₄/Bi₂WO₆ heterojunction compound photocatalyst.The scanning electron microscope?SEM?and transmission electron microscope?TEM?images demonstrated that the as-prepared sample was flower-like,and Co₃O₄ QDs distributed on the surface of Bi₂WO₆ uniformly.The photocatalytic degradation of gaseous benzene,a VOCs simulant,displayed that Co₃O₄/Bi₂WO₆ exhibited significantly enhanced photocatalytic ability,compared with pure Bi₂WO₆.Through the analysis of optical properties,it is conclued that Co₃O₄ quantum dots not only improve the optical response ability,but also promote the photogenerated carriers seperation in the p-n heterojunction due to the staggerd band structures.2.CuInS₂ quantum dots-Bi₂WO₆ p-n heterojunction compound photocatalyst?CIS-BWO?were successfully synthesized through low-temperature thermal treatment method.The photocatalysis results exhibited that the CIS-BWO sample possesses superior photocatalytic toluene conversion and Cr?VI?reduction efficiencies,compared with pure Bi₂WO₆ and the mechanical mixture of CuInS₂ quantum dots-Bi₂WO₆ photocatalyst?CIS-BWO-Mix?.The in-situ Fourier transform infrared spectrometer?FTIR?illustrated that the photocatalytic conversion of toluene over CIS-BWO was an oxidation process followed by mineralization.In additon,CIS-BWO remained good photostability in the recycling Cr?VI?photoreduction.Bi-S bonds were verified via X-ray photoelectron spectroscopy?XPS?analysis,and could be utilized as carriers transfer highway between CuInS₂ quantum dots and Bi₂WO₆,and accelerate the migration of photogenerated electrons and holes,thus promoting the photocatalytic activity of heterojunction compound photocatalyst,which were proved by carrier dynamics investigation and band structure analysis.3.Sn-surface modified Bi₂WO₆ nanoplates compound photocatalysts were synthesizedthroughsimplehydrothermalmethod.Structureandmorphology characterization were performed,which illustrated that Sn⁴⁺ions were grafted onto the?WO₄?^2-layer at?001?facets of Bi₂WO₆ nanoplates via W-O-Sn linkage.The Sn⁴⁺/Sn²⁺redox couple could accelerate the surface reaction rate,thus transferring photogenerated electrons on the surface of Bi₂WO₆ nanoplates to adsorbed O₂ to produce O₂·^-or H⁺to generate H₂ effectively.Meanwhile,the efficient outflow of photogenerated electrons promoted the photogenerated carrier seperation,and the photocatalytic RhB degradation and H₂ evolution effiencies were enhanced.