Preparation, Characterization And Photocatalytic Properties Of TiO₂/NiO Nanofibers

In these semiconductor materials, titanium dioxide (Ti02) as photocatalyst is widely used to photodegradate many organic pollutants for its relatively high catalytic reactivity, physical and chemical stability, avirulence and cheapness and so on. Even so, only under irradiation of ultraviolet light (λ< 387 nm) Ti02 catalyst can effectively destroy the organic pollutants in wastewaters because of its broad band-gap (Eg=3.2～4.5 eV). In general, the sunlight only contains 3%～5% ultraviolet light, so it is impossible to utilize sunlight directly for activating Ti02 photocatalyst effectively. Hence, the photocatalytic degradation method treating wastewaters needs costly equipments and large numbers of energies as light source. Aiming at the actuality of disadvantages of Ti02, difficult to separate, low using rate of light and easy to deposit and agglomerate,which hold back the transformation of photocatalytic technology into utility, TiO2/NiO nanofibers were prepared from poly vinyl pyrrolidone (PVP)/ Ti(OiPr)4/ Ni(CH3COO)2composite were formed as a result of combining the sol–gel process with electrospinning technique. These nanofibers could be subsequently converted into TiO2/NiO without changing their morphology via calcination in air.The morphology of fibers was discussed by adjusting conditions such as the concentration of PVP, the capillary screen distance, the voltage, and the velocity of calcination. As a result, with increasing the concentration of PVP, the diameter of electrospun fibers increased and the morphology changed from beads to regular and then unregular. Increasing the concentration of ethanol decreased the surface tension and increased the viscosity of solution. Increasing the concentration of inorgnic salts made the diameter of fibers increased and increasing the electrospinning voltage decreased the diameter of the fibers. The fibers ruptured when the temperature raised quickly, then the velocity should be controled below 50oC/h.The structures and physicochemical properties of the composites were characterized by powder X-ray diffraction (XRD), Raman scattering studies(Raman),UV diffuse reflectance spectroscopy (UV/DRS), field emission scanning electron microscopy(SEM). All the results show that five kinds of favorite nanofibers with smooth surface, homogeneous diameters of 50-150nm and uniform morphology were obtained. The photocatalytic efficiencies of the products were assessed by monitoring the photodegradation of rhodamine B(RB). The photocatalytic reactions confirmed that the presence of the second metal oxide in the titania framework resulted in enhanced photocatalytic activity relative to the pure titania framework, and the reasons were discussed.