Preparation,Characterization And Photocatalytic Properties Of TiO₂-Graphene Quantum Dots Composite Nanofibers

Titanium dioxide(TiO₂)has strong oxidizing properties,stable chemical properties,non-toxicity,low cost,easy preparation,etc.It is a very promising photocatalytic material,but has a large forbidden band width and only responds under ultraviolet light.It greatly limits its application in various fields.Doping and compounding other materials in TiO2 to improve the utilization of sunlight,so that TiO₂ can also undergo photocatalytic degradation under natural light is particularly important.Graphene is a new type of carbon material with excellent optical,thermal,electrical and mechanical properties.By utilizing the great gain effect of graphene quantum dots on conductivity,forbidden band width and electron transport speed,the photoresponse range of TiO₂ can be significantly improved and its photocatalytic activity can be improved.In this paper,the preparation,characterization and influencing factors of photocatalytic properties of TiO₂-graphene quantum dot composite nanofibers were studied.Using butyl titanate(Ti(OC₄H₉)₄)as the titanium source and polyvinylpyrrolidone(PVP),polyacrylonitrile(PAN)as the polymer,electrospinning technology was used to prepare TiO₂ nanocrystals with different structures by different processes.The photocatalytic performance characterization results show that the mesoporous hollow structure of TiO₂nanofibers has the highest photodegradation rate and the highest efficiency with its large specific surface area and high anatase phase content,indicating the content of anatase phase.It is the primary factor affecting photocatalytic degradation,and the specific surface area also plays an important role.Using carbon nanofibers as carbon source,small and uniform graphene quantum dots were prepared by chemical stripping method,which was circular,with an average size of6±2 nm,and showed excellent photoluminescence effect;The sheet is a carbon source,and a small and uniform size of graphene quantum dots is prepared by hydrothermal synthesis,which is elliptical with an average size of 4±2 nm.The substitution doping of N can be achieved by using NH₄OH solvent.The TiO₂-graphene quantum dot composite nanofibers were successfully prepared by hydrothermal synthesis.The graphene quantum dots were uniformly decorated on the surface of the nanofibers and exhibited a one-dimensional structure.The results show that the introduction of graphene quantum dots inhibits the recombination of charge carriers and prolongs the existence time of photogenerated holes.The photocatalytic performance characterization results show that 10%mass fraction of TiO₂-graphene quantum dot composite nanofibers have the fastest and most efficient photodegradation rate with its ultrafast electron transport rate and low electron-hole pair recombination rate.The methylene blue dye was degraded by 99%in 50 minutes.