Synthesis And Properties Of New Tri-component Visible-light Driven Photocatalysts

At present,the semiconductor photocatalytic technology has been developed greatly in solving environmental pollution and energy crisis.During the process of semiconductor photocatalysis,the semiconductor materials absorb photons and cause electron transition,producing the photogenerated electron-hole pairs which are involved in redox reaction.In this thesis,the catalytic mechanism and application prospect and recent progress of the semiconductor photocatalysts are briefly reviewed firstly,and then we focus on developing noval tri-component visible-light driven photocatalysts.Three new ternary photocatalysts including g-C₃N₄/Ag/Ag₃VO₄,CdS/RGO/?-Fe₂O₃ and g-C₃N₄/Ag₂CO₃/Ag have been successfully synthesized.The composition,structure,morphology,light absorption of the as-prepared products were investigated by XRD,EDS,TG,TEM,FT-IR,UV-vis and XPS,etc.The photocatalytic activity of the ternary photocatalysts was evaluated by the degradation of organic pollutants of RhB under visible-light irradiation.The photocatalytic degradation mechanisms were systematically explored.The main points of this paper are as follows:1.On the basis of the g-C₃N₄ synthesized by calcination method,the tricomponent g-C₃N₄/Ag/Ag₃VO₄ photocatalyst was prepared through UV irradiation reduction combined with in situ growth method.The content of metal Ag in the composites was regulated by the UV irradiation time.The g-C₃N₄/Ag/Ag₃VO₄ composite exhibited greatly enhanced visible-light photocatalytic activity for RhB degradation as compared with the single-component g-C₃N₄? Ag₃VO₄ and bicomponent g-C₃N₄/Ag₃VO₄ photocatalysts.Meanwhile,the degradation kinetics of the g-C₃N₄/Ag/Ag₃VO₄ photocatalyt is investigated.The possible photocatalytic mechanism was proposed based on the PL characterization and the active species capture experiment.It was found that due to the existence of metal Ag,the gC₃N₄/Ag/Ag₃VO₄ composite is an all-solid-state Z-scheme photocatalyst,which improves the separation of the photogenerated charges and endows strong redox ability of the photogenerated carrier,As a result,the enhanced visible-light catalytic properties was achieved.2.With Prussian blue?PB?as the precursor for ?-Fe₂O₃,the tri-component CdS/RGO/?-Fe₂O₃ photocatalyst was prepared through loading the PB and CdS nanoparticles on graphene oxide?GO?nanosheets,followed by a calcination process in inert atmosphere?N2?.The content of ?-Fe₂O₃ in the CdS/RGO/?-Fe₂O₃ photocatalyst can be adjusted by changing the loading amount of PB,and the morphology of PB was maintained after the calcination.Compared to the bicomponent CdS/RGO photocatalyst,the tri-component CdS/RGO/?-Fe₂O₃ exhibited greatly enhanced photocatalytic activity,demonstating that the ?-Fe₂O₃ played an important role in the photocatalytic process.Moreover,owing to the ferromagnetism of ?-Fe₂O₃,the CdS/RGO/?-Fe₂O₃ photocatalyst could be easily separated from the reaction solution for recycling with the help of external magnetic field.Meanwhile,the degradation kinetics of the CdS/RGO/?-Fe₂O₃ photocatalyst was also studied.A possible mechanism was also proposed based on the PL characterization and the active species capture experiment.3.The tri-component g-C₃N₄/Ag₂CO₃/Ag photocatalyst was successfully synthesized by the UV irradiation of bi-component g-C₃N₄/Ag₂CO₃,which was prepared through a facile in situ method.Compared to the single-component g-C₃N₄,Ag₂CO₃ and bi-component g-C₃N₄/Ag₂CO₃,the tri-component g-C₃N₄/Ag₂CO₃/Ag exhibited enhanced photocatalytic activity for RhB and phenol degradation under visible-light irradiation.It was found that the Ag₂CO₃ content in the tri-component composites had an important influence on the degradation performance.The enhanced photocatalytic activities of tri-component composites could be ascribed to the plasma effect of metal Ag and the synergistic effect between g-C₃N₄ and Ag₂CO₃,which benefit the absorption of visible-light and the separation of photogenerated charge.Meanwhile,the RhB degradation kinetics of the g-C₃N₄/Ag₂CO₃/Ag photocatalyst was studied and a possible mechanism was also proposed.