Research On Preparation Of TiO₂Nanofibers By Electrospinning And Photocatalysis For Water Splitting Into Hydrogen

Photocatalysts can be used for water splitting into hydrogen, and this is a goodway to produce new energy resources. TiO₂nanofibers with high photocatalyticactivity were synthesized by electrospinning method, and the effects of thehydrogenation process on TiO₂nanofibers were investigated. The characterizationmethods such as SEM/EDX, TEM, XRD, Raman and XPS, were used to analyze themorphology, structure and composition of the obtained TiO₂samples. Finally thephotocatalytic performance of the TiO₂nanofibers after hydrogenation treatment forwater splitting into hydrogen had been studied.To obtain spinable solutions, tetrabutyl titanate as and polyvinylpyrrolidon（PVP） were adopted as titanium source and thickening agent, respectively, andethanol and glacial acetic acid mixture was used as the solvent. Throughelectrospinning processing, TiO₂products with different morphology were produced,including TiO₂nanofibers with diameters ranging20-800nm, TiO₂nanotubers with adiameter of about100nm, TiO₂microspheres with a diameter of about5μm andcuplike TiO₂particles with different size. The relationship between the morphologyof TiO₂pruoducts and the electrospinning parameters was discussed. The influenceof the calcination temperature on the TiO₂products was also probed into. From theresults of XRD and Raman, it can be deduced that anatase TiO₂can be preparedusing treatment temperature below600oC, and rutile TiO₂appear when temperaturereaching about600oC, while when treatment temperature reaching800oC theobtained product is wholly rutile TiO₂.Subqequrently, we investigated the effects of the hydrogenation process on theTiO₂nanofibers. The use of different hydrogenation temperature resulted in the TiO₂nanofibers with different colors. XRD and Raman results showed that during thehydrogenation at600oC the crystal type of the TiO₂nanofibers has little change, andthe anatase crystal type would be maintained. When the hydrogenation temperatureexceeding600oC, rutile TiO₂begined to form companying with the formation of asmall amount of Ti₂O₃component. The color of the TiO₂nanofibers prepared byhydrogenation at600oC changed from white to gray brown. The sample faterhydrogenation treatment at850oC becomed purple black and the component wasTi₂O₃. The XPS results indicated that the binding energy of Ti2p and O1s changedafter hydrogenation treatment, and these change related to the band gap of the TiO₂would extert some effects on photocatalytic aivity for splitting water into hydrogenofhe TiO₂samples.The photocatalytic activities of different TiO₂products were tested, and the thereason that different TiO₂samples showed different photocatalytic activity was discussed. It can be concluded that the hydrogenation process had importantinfluence on the photocatalytic activity of TiO₂nanofibers. The UV-Vis resultsshowed that the higher the hydrogenation temperature, the better the absorption ofvisible light of TiO₂nanofiber products in the investigated conditions, and from theUV-Vis result the energy gap can be proved out, the narrower energy gap isE_g600H=2.95eV. And the TiO₂nanofibers hydrogenerated at600oC exhibited thehighest photocatalytic performance for water splitting into hydrogen in this work,and the produced amount of hydrogen reached about3.3μmolg^-1h^-1.