The Preparation And Vis-photocatalytic Activity Of TiO₂ Nanowires By Template Assembly Technology

According to the current problems such as low quantum efficiency and limitedavailable visible light energy spectrum range in the titania photocatalytic field, theone-dimension titania nanoarrays were prepared via sol-electrophoretic andsol-dipping method combined with template technology. A wide range of testingtechniques was applied to characterize the influences of technological parameters onthe structure, morphology and photocatalytic performance of titania nanoarrays. Aseries of doped TiO₂ nanowire arrays were prepared by adding different metal ions.Using this method, the self-immobilization of the titania photocatalyst can be easilyachieved and the visible photocatalytic activity can be effectively improved.Titania nanowire arrays with shape of string of candied haws were prepared inporous anodic alumina template (PAA) via sol-electrophoresis template method. Theeffects of electrophoretic voltage, polishing technology, post-treatment method andtime, sintering temperature on the morphology and UV-photocatalytic activity ofnanowires were studied in the experiment. The electrophoretic voltage was the maindriving force of the sol particles to move and form nanowires. The photocatalyticactivity of nanowires reached the best at the voltage of 4V. The study showed thatsodium hydroxide solution was a better post-treatment method than the mixed acidsolution and the most appropriate post-treatment time was 5min. The sinteringtemperature could affect the crystal phase and photocatalytic activity of the titaniananowires. The photocatalytic activity was the best when the content of rutile was10%. Titania nanowire arrays with shape of rod and titania nanotube arrays wereprepared by sol-dipping template method. As for dipping method, the one-dimensionnanoarrays cannot be obtained in normal pressure condition, but the regular titaniananowires and nanotubes could be obtained in a certain negative pressure condition.The photocatalytic activity was characterized by the photocatalytic degradation ofmethyl orange solution under UV-light. The photocatalytic activity of nanowires withshape of string of candied haws was better than that of rod-shaped nanowires.Compared with the TiO₂/glass film, the titania nanowire and nanotube arrays havemuch higher photocatalytic activity.A series of doped TiO₂ nanowire arrays were prepared by adding different metalions (transition-metal ions, rare earth-metal ions). The photocatalytic activity of doped nanowires (M/TiO₂) was measured under the visible light. As for the transition-metalions (Fe³⁺, Zn²⁺, Cr³⁺, Cu²⁺) and rare earth-metal ions (La³⁺, Ce³⁺, Nd³⁺) doped titaniananowires, the best dopping content of each ion was obtained via photocatalyticdegradation of methyl orange solution under visible light. In addition, La³⁺/Fe³⁺co-doped titania nanowires were prepared and the combined action of two types ofmetal ions could further improve the visible photocatalytic activity of titaniananowires. Through comparing the vis-photocatalytic activity of different ion-dopednanowires in the two systems, the metal ion doping mechanisms to achieve thevisible-light photocatalytic activities of the TiO₂ nanowires are discussed fromdifferent views of doping energy level, ion radius, electron configuration and latticedilatation. The UV-vis absorption spectrums of M/TiO₂ film samples showed that theabsorption edge of the UV-Vis spectra shift into visible light region and the band gapvalues were estimated via correlated formulas. In addition, compared with theTiO₂/glass film, the titania nanowire arrays had more than 3 to 8 times higher visiblephotocatalytic activity and showed excellent aging performance. As a result, thetitania nanowire arrays have tremendous application prospect and predominanceunder visible light.