Preparation Of Flexible CeO₂/SiO₂ Composite Nanofibers And Their Photocatalytic Performance

The growth of the chemical industry will lead to more and more wastewater discharge.Dye wastewater is one of the main sources of industrial wastewater.Therefore,various new technologies and new composite materials for adsorption and degradation of dye wastewater have been developed.However,with the continuous development of textile,cosmetics and other industries in China,the problem of dye wastewater still needs to be solved.Therefore,exploring new materials for efficient adsorption and catalytic degradation of organic pollutants has become an important development direction.As an n-type semiconductor,CeO₂ can be used as a photocatalyst and can catalyze the degradation of dyes under UV or visible light irradiation.At present,there are many ways to prepare CeO₂ nanomaterials,but most of the CeO₂ nanomaterials are powder by commonly methods.CeO₂ nanofibers can be prepared by electrospinning.This method is simple to operate and the process is adjustable.The polymer/CeO₂ composite fibers are in the form of continuous films,but the CeO₂ nanofibers are brittle and fragile,after removing the polymer components by high temperature calcination.Therefore,how to prepare continuous CeO₂ nanofibers is still a problem to be solved.In this dissertation,firstly,CeO₂ nanofibers were prepared by electrospinning,and then,CeO₂ and SiO₂ solutions were prepared into CeO₂/SiO₂ composite nanofibers by electrospinning.The composite fiber was a flexible continuous film,which can be curved and folded.Finally,the photocatalytic dye degradation performance of CeO₂/SiO₂ composite nanofibers was tested.This will solve the problem of inconvenient recycling by CeO₂powder,and the degradation performance of pure CeO₂ was improved due to the adsorption-photocatalytic synergy in CeO₂/SiO₂ composite nanofibers.（1）CeO₂ nanofibers were prepared by electrospinning.Firstly,the influence of the content of polyvinylpyrrolidone（PVP）and cerium nitrate（Ce（NO₃）₃·6H₂O）in the spinning solution,electrospinning process（voltage and curing distance）and calcination temperature were explored.The optimum spinning solution was determined as 8.56 wt%PVP and 14 wt%Ce（NO₃）₃·6H₂O,the optimum process parameters were the voltage of 20 k V,the curing distance of 19 cm,and the calcination temperature of 800℃.Under these conditions,the CeO₂nanofibers had the best morphology with an average diameter of 401 nm.（2）Secondly,in order to improve the mechanical properties of CeO₂ nanofibers,SiO₂nanofibers were creatively introduced into CeO₂ nanofibers.Flexible CeO₂/SiO₂ composite nanofibers with different Ce/Si ratios could be obtained.The composite nanofibers material was a light yellow film,which could be bent for 10%～50%multiple times without breaking.As a mechanical framework,flexible SiO₂ nanofibers played a role of bonding,which effectively improved the brittleness of CeO₂ nanofibers.The results showed that the calcination temperature of the composite nanofibers should be raised to more than 700℃,after adding SiO₂.（3）Finally,taking methyl orange,methylene blue and rhodamine B dyes as examples,the photocatalytic degradation performance of flexible CeO₂/SiO₂ composite nanofibers with different Ce/Si ratios was tested.Through characterization,CeO₂/SiO₂ composite nanofibers（59.98 m~2/g～89.13 m~2/g）had a larger specific surface area than pure CeO₂ nanofibers（30.75m~2/g）.Combined with the degradation performance of dyes,it was determined that the optimal Ce/Si ratio of 3:2 flexible CeO₂/SiO₂composite nanofibers had the best degradation performance of dyes,which could be improved by 23%～44%compared with pure CeO₂nanofibers.