Templatesynthesis Of Fe³⁺,Zn²⁺,Sn⁴⁺-doped TiO₂ Hollow Fibers And Their Photocatalytic Properties

The application of titanium dioxide as a heterogeneous photocatalyst is attractingconsiderable attention for water and air purification and remediation. Unfortunately,because of its large band gap of 3.2 eV, it can be activated only under UV lightirradiation of wavelength < 380 nm, which constitutes only a small fraction (about3-5 %) of the solar spectrum. Simultaneously, the nano-TiO₂ powder as aphotocatalyst exists as the questions for recycles difficultly and difficult to use suchissues as secondary. So it will be very important to develop a TiO₂ photocatalyst withhigher activity by shifting its optical response to the visible light and increasing theseparation efficiency of photogenerated e--h+ pairs. In our study, a series of metalion-doped TiO₂ semiconductor photocatalytic nanomaterials with hollow fiberstructure were successfully prepared using cotton fiber as the template. This thesismainly consists of three major aspects.1. A series of Fe³⁺-doped TiO₂ photocatalytic materials (Fe³⁺/TiO₂) with hollowfiber structure were successfully prepared using cotton fiber as the template. Usingthe degradation of methylene blue (MB) solution as the model reaction, the effect ofthe amounts of Fe³⁺-doped, calcining temperature and time and the catalyst amounton the photocatalytic activity of the Fe³⁺/TiO₂ nanofiber material was investigated.The results showed that a large number of nanosized particles existed on the surfaceof the fiber material with hollow structure, indicating that the material had a largerspecific surface area. Fe³⁺ ions were possibly well-distributed in the lattice structureof anatase TiO₂ and partially replaced Ti⁴⁺, causing the broadening of the spectralresponse of TiO₂ and the defects of the crystal structure. The fiber structure materialshowed better photocatalytic property for the degradation of methylene blue (MB)than the pure TiO₂ under the solar light and the amount of Fe³⁺-doped significantlyaffected the catalytic property. On the surface of the fiber material with 0.15 %Fe³⁺-doped, the decolorizing efficiency of MB solution reached 93 % when radiation time was 2 h and remained above 90 % when it was repeatedly used for 5 times andthe material was easily removed by centrifugal separation. Therefore, using thetemplate method and doping Fe³⁺, TiO₂ is hopeful to become a non-energyconsumption, high activity, green environment-friendly catalytic material.2. A series of Zn²⁺-doped TiO₂ photocatalytic materials (Zn²⁺/TiO₂) with hollowfiber structure were successfully prepared using cotton fiber as the template. Usingthe degradation of methylene blue (MB) solution as the model reaction, the effect ofthe amounts of Zn²⁺-doped, calcining temperature, calcining time, catalyst amountand the concentration on the photocatalytic activity of the Zn²⁺/TiO₂ nanofibermaterial was investigated. The results showed that the low amount of Zn²⁺-doped canobviously inhibit TiO₂ transformation from anatase to rutile. The size of Zetapotential value is not the main reason for affecting the sample photocatalytic activity.The optimal catalytic reaction condition is, the amounts of Zn²⁺-doped is 0.7 %,calcination temperature is 600 oC, calcination time is 2 h, catalyst amount is 40 mgand the concentration is m(Zn²⁺:TiO₂) = 0.0055 g:0.2348 g. Under the optimalcatalytic reaction condition, the decolorizing efficiency of MB solution reached 100% when radiation time was 5 h under the solar light.3. A series of Sn⁴⁺-doped TiO₂ photocatalytic materials (Sn⁴⁺/TiO₂) with hollowfiber structure were successfully prepared using cotton fiber as the template. Usingthe degradation of methylene blue (MB) solution as the model reaction, the effect ofthe amounts of Sn⁴⁺-doped, calcining temperature, calcining time, and the catalystamount on the photocatalytic activity of the Sn⁴⁺/TiO₂ nanofiber material wasinvestigated. XRD showed that the low amount of Sn⁴⁺-doped did not obviouslyaffect for the TiO₂ phase transition temperature. UV-Vis spectra showed thatSn⁴⁺/TiO₂ hollow nanofiber had a stronger absorption in the 200⁸00 nm UV-visiblelight scope than pure TiO₂ hollow nanofiber, and its initial absorption band edge had acertain red shift. The optimal catalytic reaction condition is, the amounts ofSn⁴⁺-doped is 0.3 %, calcination temperature is 600 oC, calcination time is 2 h, and the catalyst amount is 40 mg. Under the optimal catalytic reaction condition, thedecolorizing efficiency of MB solution reached 100 % when radiation time was 3 hunder the solar light.