Studies On Electrospinning Preparation And Properties Of Semiconductor Nanofibers For Photocatalysis

Environmental pollution and energy shortage are two of the most important issues facing mordern society.As a result,photocatalyst based on semiconductor materials,which convert solar light into chemical energy,have attracted much attention as a promising candidate for clean energy,contaminants elimination and so on.In this dissertation,electrospinning was employed to prepare semiconductor photocatalyst nanofibers like TiO₂,BiVO₄,?ZnO?_x?GaN?_1-x,and so on.By the modification of heterostructure,phase junction,doping and defect engineering,high photocatalytic activity was obtained under visible light irradiation.The results may be beneficial to the future study of exploring the highly efficient visible light driven photocatalysis materals.Hybrid carbon and TiO₂ core-shell nanofibers were prepared.The effect of the structure of the carbon layer on the photocatalytic property was investigated.Enhanced photocatalytic efficiency was obtained with the carbon shell.The nanofibers with the carbon thickness of 2 nm showed the best photocatalytic activity.Carbon induced surface defect was the main reason for the adsorption of visible light.In addition,the up conversion property of the carbon quantum dots enabled the nanofiber to utilize more solar energy.Moreover,efficient seperation of the electrons and holes can be obtained due to the heterostructure of carbon and TiO₂,resulting in enhanced photocatalytic activity.BiVO₄ nanofibers were successfully prepared by electrospinning and precisely controlled heat treatment.The nanofibers showed a phase junction structure of tetragonal sheelite and monoclinic sheelite phases.When the phase junction was formed in the nanofibers,an enhanced photocatalytic activity was obtained.Structure analysis showed that efficient seperation of the electrons and holes in the phase junction structure was the reason for the enhanced photocatalytic activity.In addition,the tetragonal sheelite phase can help the nanofiber to get more energy in the range of longer wavelength to increase the photocatalytic activity.Heterostructured Ag/BiVO₄ nanofibers were prepared.In the heterojunction structure,Ag loading trapped the photoexcited electrons and enhanced the life time of the photogenerated electron and hole pairs.As a result,enhanced photocatalytic activity was obtained.?ZnO?_x?GaN?_1-x solid solution nanofibers enriched with surface defects were prepared.The surface defects were tuned by varying the ammonification temperature carefully,resulting in controlled zinc doping content as well as tunable surface defects in the nanofiber.The effect of the surface defects on the photocatalytic activity was studied.Surface oxygen vacancy,which serves as intermediate steps for the photocatalytic process and delays the recombination of the photogenerated electron-hole pairs,is found to be the critical factor for controlling the photocatalytic efficiency of the nanofiber.