| Environmental pollution and energy shortage are two of the most challenging problems facing humanity today.Photocatalysis is a technology that uses sunlight to stimulate semiconductors to generate electron-holes and then generates reactive oxygen species through a series of reactions,and organic pollutants and microorganisms are decomposed into CO2 and H2O.Photocatalysis technology becomes one of the ideal method to solve environmental pollution problems.TiO2 is of the most commonly used semiconductor photocatalyst due to its advantages of chemical stability,easy regulation of morphology,low toxicity and low cost.However,pure titanium dioxide itself can only absorb ultraviolet light in the solar spectrum,and the photo-generated carrier recombination rate is fast,which limits its photocatalytic efficiency and application.This thesis focuses on how to improve the solar light utilization efficiency and photocatalytic efficiency of semiconductor nanostructures,the noble metal/titanium dioxide hybrid nanostructure photocatalyst was constructed and the photocatalytic performance and enhancement mechanism were studied.The main contents of the study are as follows:(1)TiO2/Pt-based(TiO2/Pt,TiO2/PtCu,TiO2/PtCuCo)hybrid nanostructured catalysts were prepared by physical mixing under simulated sunlight.The metal loading on TiO2 can be adjusted by changing the dosage of Pt-based metal nanoparticles.Each of Pt based metal NPs connected with TiO2 can resulted in enhanced photocatalytic activities.The results indicated that Pt-based metal/TiO2 hybrid nanostructures at a mass ratio of 2%exhibited the best photocatalyticactivity toward degradation of organic dyes.The order of photocatalytic activity of TiO2/Pt-based catalysts was:TiO2/PtCuCo>TiO2/PtCu>TiO2/Pt>TiO2.Moreover,TiO2/PtCuCo showed good degradation effects on all four azo dyes.In addition,TiO2/PtCuCo hybrid nanostructures superior antibacterial effects against Staphylococcus aureus and Escherichia coli.The generation of reactive oxygen species from photoirradiated photocatalysts was tested by electron paramagnetic resonance spectroscopy.It was found that the Pt-based metal as a cocatalyst could significantly enhance the hydroxyl radicals,superoxides and singlet oxygen generated by photoexcitation of TiO2,and exhibited a composition dependent manner similar to that of photocatalytic activity:PtCuCo>PtCu>Pt.The possible enhancement mechanism is discussed.(2)The plasmonic hybrid nanostructures of Au nanospheres/titanium dioxide(AuNS/TiO2)and Au nanorods/titanium dioxide(AuNRs/TiO2)were synthesized by a simple method by surface modification and assembly.The TiO2 nanosheet particles loaded with gold nanospheres or gold nanorods exhibited strong absorption capacity for long-wavelength light.The results showed that the Au-loaded TiO2 exhibited enhanced activity compared to pure TiO2 for all the conditions.Among them,AuNRs/TiO2 has stronger photocatalytic oxidation and reduction activity under light(λ>700 nm),which may be related to its SPR enhancement effect.Electron spin resonance spectroscopy results showed that the formation of Au/TiO2 hybrid structure can significantly improve the generation of reactive oxygen species and photogenerated electrons.By comparison and analysis,the enhancement under visible light irradiation is mainly due to the SPR effect,while the enhancement under sunlight and ultraviolet light mainly depends on the electron storing effect of Au.These results revealed the contribution of SPR effect to visible light driven photocatalytic activity and the excellent photocatalytic activity of Au/TiO2 nanostructures was related to the enhanced generation of reactive oxygen species and charge carriers. |
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