Preparation Of Some Metal Oxides Based Composite Photocatalysts And Their Applications In Visible-Light Driven Photocatalysis

Tungsten oxide?WO₃?is a kind of traditional n type semiconductor material with the advantages of high oxidizing power,no secondary pollution,low energy consumption and recycling.It has broad application prospects in the field of photocatalytic degradation.However,WO₃ is hindered by its high recombination rate of photogener-ated electron-hole pairs and low quantum efficiency.Layered perovskite oxides have attracted considerable attention owing to their structural simplicity and flexibility,good stability and efficient photocatalytic performance.However,the practical application of the layered perovskite nanosheets is sill restricted by its main disadvantages,such as the wide bandgap,response only for UV-light and low availability of solar energy.In order to enhance the solar efficiency of the metal oxides and develope efficient,low-cost and stable photocatalysts,which can work under visible light,it is requisite to modify the metal oxides facilitate visible light absorption.In this academic dissertation,the metal oxides were coupled with other materials.The obtained nanocomposites were characterized by various analytical instrument.Research content were listed as following:1.Novel redox-mediator-free direct Z-scheme AgI/WO₃ nanocomposites were prepared by a facile precipitation method.The nanocomposites were characterized by XRD,XPS and TEM.The results showed that the redox-mediator-free direct Z-scheme AgI/WO₃ nanocomposites improved the separation efficiency of photogenerated electron and hole pairs.The photocatalytic activity of the nanocomposites was evaluated by using colorless antibiotic agent tetracycline hydrochloride?TC?.The 20% AgI/WO₃ held an excellent performance in TC degradation.The drgradation rate was reaching 75% after 60 min under visible light irradiation.And the 20% AgI/WO₃ shows an excellent stability during the photodegradation process.The possible mechanism analysis showed that the main active species are determined to be the photogenerated holes and superoxide free radical in this system.2.The 2D-2D heterojunction photocatalysts were constructed based on g-C₃N₄ nanosheets and exfoliated K⁺CNb₃O₁₀^-ultrathin nanosheets,which is derived from Dion-Jacobson phase layered perovskites.The photocatalysts were characterized by XRD,FT-IR,XPS,BET and TEM.The results showed that there is a strong interfacial effect between g-C₃N₄ nanosheets and K⁺CNb₃O₁₀^-ultrathin nanosheets.Comparedwith bare K⁺Ca₂Nb₃O₁₀^-and g-C₃N₄,the heterojunctions exhibited obviously improved photocatalytic efficiency.The 20% g-C₃N₄/K⁺CNb₃O₁₀^-could decompose 81% of TC during 90 min and showed high stability in the reaction system.The intermediates in TC drgradation process and the reaction mechanism were investigated.3.The GO/K⁺CNb₃O₁₀^-nanocomposites were fabricated by a facile one-step hydrothermal approach.The as-preoared nanocomposites were characterized by XRD,Raman,XPS,AFM and TEM.The results showed a strong synergistic effect existed in the that GO/K⁺CNb₃O₁₀^-nanocomposites between GO nanosheets and K⁺CNb₃O₁₀^-nanosheets.The 2% GO/K⁺CNb₃O₁₀^-exhibited optimal performance in TC degradation.The drgradation rate was 81.6% after 150 min under visible light irradiation.The reaction mechanism in the drgradation process were analysied to be the sensitization of GO nanosheets.