| Titanium dioxide (TiO2) which has the advantages of non-toxic, inexpensive,easy to obtain and so on, is a very promising photocatalytic materials. The forms ofnanoparticles or fibers can improve the specific surface area of the titanium dioxideand enhance their photocatalytic properties. Combined with other materials, themodified TiO2could be fabricated. These materials not only can reduce bandwidthand enhance utilization of spectrum, but also can facilitate separation of electron-holepairs and improve the photocatalytic properties of titanium dioxide.Electrospinning is the only technology that can continuously prepare nanofibersnow. Polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN), and polyvinyl acetate(PVAC) et al. are commonly used in preparing titanium dioxide nanofibers.polyethylene alcohol (PVA) has many advantages such as biocompatibility, electricalconductivity, biodegradability and alcohol groups, which broaden its applications inmany areas. However, some problems such as the poor water-resistant property ofPVA fiber and the uncontrollable hydrolyzed speed of TBT in aqueous solutionrestricted its applications and less studies about the preparation of PVA/TiO2composite fibers are reported. In order to overcome the above problems, in this paper,we used cross-linked PVA nanofibers as a template for preparing titanium dioxidenanofibers, and graphene oxide as a modifier to improve the photocatalytic propertiesof titanium dioxide.Firstly, we introduced the graphene oxide with different amounts into PVAsolution and obtained PVA/GO composite fibers by electrospinning. Glutaraldehydeis used to crosslink the composite nanofibers, and the influences of the amount ofglutaraldehyde and crosslinking time were studied. We found that the nanofibermembrane has a best hydrolysis resistance in the condition: amount of glutaraldehydewas7wt%, the crosslinking time was5h. Field emission scanning electronmicroscopy (FE-SEM), Raman tester, thermal analysis, FT-IR and tensile testingmachine were used to characterizing samples. The results show that GO wasintroduced into PVA nanofibers successfully. GO can not only affect the fibers’ surface morphology, the glass transition temperature, crystallinity and tensile strengthof the nanofibers can be increased because of GO existing. At the same time, thediameter of nanofibers, decomposition temperature and the elongation at breakreduced.After obtaining hydrolysis-resistance PVA/GO composite nano-fiber membrane,we utilized the hydrolysis reaction of tetrabutyl titanate (TBT) to grow titaniumdioxide on the surface of the fibers. We studied the impacts of TBT content, solutionPH value, and the reaction temperature on the coating effect of titanium dioxide. BySEM, we found that GO can induce the uniform growth of TiO2-nanoparticles dioxideon the fibers’ surface. Through the analysis of XRD curve of PVA/GO/TiO2composite nanofibers, we found titanium dioxide is amorphous if TBT hydrolysisdirectly in low temperature.The obtained PVA/TiO2and PVA/GO/TiO2composite nanofibers were sinteredto obtain crystal TiO2. We synthesized hollow TiO2nanofibers in an air atmosphereand obtained porous TiO2-based composite fibers in a nitrogen atmosphere. Aftercharacterizing with XRD, we found all titanium dioxide in the temperature of600℃is anatase type. As the temperature increasing to800℃, the crystal type of hollowTiO2nanofibers changed from anatase type to rutile type, but anatase-type structure isstill existing when composite nanofibers were heated under a nitrogen atmosphere.The results indicated that the reduction graphene oxide can inhibit crystal typetransition. The results of nitrogen adsorption-desorption tests showed that the hollowTiO2nanofibres contain lots of macroporous. We can observe a significant hysteresisloop in the location of P/P0=0.5, which indicates that carbonized compositenanofibers have a lot of mesoporous structure. In the experiment of photocatalyticdegradation of methylene blue, TiO2-based composite nanofibers have the best abilityof photocatalytic degradation in the condition: carbonization temperature was600℃,GO content was12mg. |
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