Fabrication Of One-dimensional Ag/AgBr Composite Nanofibers Via Electrospinning And Their Photocatalytic Applications

Photocatalysis, in which photogenerated electrons and holes are used to drive redox reactions, is a perfect technique for environmental cleanup and green energy production. Therefore, the technique has received enormous attention from the scientists and engineers. Moreover, tianium dioxide（TiO₂）, is the most representative semiconductor photocatalyst for its distinctive properties. However,the practical application of TiO₂ has been greatly hampered by the low quantum efficiency and photocatalytic activity. Hence, we make efforts to enhance the visible-light absorption and improve the charge separation of the nanomaterials in order to construct more effective photocatalysts. On one hand, Ag/AgBr possesses strong visible-light absorption for the surface plasmon resonance（SPR） of Ag nanoparticles and the narrow-band of AgBr, so Ag/AgBr system is an excellent photocalytic candidate; on the other hand, one-dimensional nanomaterials own excellent electron capture and transport properties, large specific surface area, and excellent reusability. Among the synthetic methods of one-dimensional nanomaterials, electrospinning is the most convenient and direct technique.Consequently, we combine the electrospinning technique with Ag/AgBr nanoparticles in our work and successfully fabricate more effective one-dimensional composite photocatalysts. The details are listed as follows:（1） Fabrication, characterization and photocatalytic application of one-dimensional Ag/AgBr/PVP nanofibers: one-dimensional Ag/AgBr/PVP nanofibers were successfully prepared by electrospinning. Then the surface morphology, crystal structure and of the as-prepared photocatalysts were examined.The results show that Ag/AgBr nanoparticles are well-dispersed within the PVP nanofibers and the composite nanofibers exhibit enhanced absorption in the visible-light region. Moreover, Photocatalytic performances of the samples were evaluated by the visible light photocatalytic degradation of methylene blue（MB） and rhodamine B（Rh B）. The experimental results depict that one-dimensional Ag/AgBr/PVP nanofibers show strong absorption towards MB and the removal efficiency of MB reaches 84% after 30 min of visible-light irradiation. But there still exist some drawbacks, for example, the composite nanofibers are not stable inalkaline solution, so we need to make further efforts to improve the performance of the photocatalysts.（2） Fabrication, characterization and photocatalytic application of one-dimensional porous Ag/AgBr/TiO₂ nanofibers: one-dimensional porous Ag/AgBr/TiO₂/PVP nanofibers were successfully prepared by one-pot electrospinning technique. Subsequently, the as-prepared nanofibers were calcined at450°C for 3h to get porous Ag/AgBr/TiO₂ nanofibers. Then we conducted experiments to investigate the surface morphology, crystal structure and photoelectrochemical properties of the composite nanofibers. The results show that one-dimensional Ag/AgBr/TiO₂ nanofibers display excellent photoelectrochemical properties. Besides, the photocatalytic properties were investigated by photodegradation of MB. The results clearly reveal that composite nanofibers possess large absorption capacity towards MB and the decomposition efficiency of MB achieves almost 100% in 20 min. The removal efficiency analyzed by TOC for MB on Ag/AgBr/TiO₂ NFs is as high as 84.6% which further verifies the excellent photocatalytic activity of the composite nanofibers. In addition, the longevities of the photocatalysts were also investigated by recycling Ag/AgBr/TiO₂ nanofibers for MB photocatalytic degradation under visible-light irradiation. The results uncover that the photocatalytic removal efficiency of MB maintains over 90% in the third cycle. Accordingly, the combination of Ag/AgBr nanoparticles and TiO₂ nanofibers significantly improves the stability of the photocatalysts.