釩/二氧化鈦之合成及其在可見光下的光催化反應

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题名:	釩/二氧化鈦之合成及其在可見光下的光催化反應
作者:	張智盈;Chang,Chih-ying
贡献者:	化學工程與材料工程學系
关键词:	氧化釩/二氧化鈦;溶膠凝膠法;光催化降解;V-doped TiO2;sol gel method;photocatalytic degradation
日期:	2014-06-25
上传时间:	2014-08-11 18:14:14 (UTC+8)
出版者:	國立中央大學
摘要:	二氧化鈦在光觸媒反應中是常見的使用材料，然而，其能隙較大(銳鈦礦為3.2 eV)需要紫外光來活化觸媒，因此在實際的應用上受到了許多限制。本研究以溶膠凝膠法(sol-gel method)製備不同偏釩酸銨/二氧化鈦重量比之中性氧化釩/二氧化鈦溶膠，另外，以浸塗法製備不同比例之氧化釩/二氧化鈦薄膜。本研究目的是研究其在紫外光或可見光下降解有機染料之光催化活性。從研究中發現摻雜釩於二氧化鈦中可減少能隙至2.65 eV，而由HRTEM顯微圖中可發現摻雜釩會使二氧化鈦顆粒由針狀變成不規則立方狀，另外在XRD與XPS分析中可知摻雜之釩離子會以V4+及V5+之離子型態存在，V4+離子取代二氧化鈦晶格中的Ti4+離子，其可增加可見光的吸收，而V5+離子以氧化釩型態存在二氧化鈦表面可分離光誘導電子。光反應活性之鑑定以10 ppm亞甲基藍水溶液為光反應標準物，以20 W 波長為254 nm 的紫外光燈管當作紫外光照射光源，並以27W可見光燈管當作可見光照射光源，光降解樣品取樣利用紫外可見光光譜儀(UV-vis)分析濃度。由光催化降解結果顯示氧化釩/二氧化鈦在紫外光與可見光下皆具有較高的光催化活性。 ;Titanium dioxide has been widely used for the photocatalytic reaction. However, the practical application of TiO2 as a photocatalyst is limited by its large band-gap energy (3.2 eV for anatase), which requires ultraviolet light to activate. In this study, V-doped TiO2 neutral sols with various NH4VO3/TiO2 weight ratios were prepared by sol-gel method. A series of V-doped TiO2 thin films were prepared by dip-coating technique. This study aims to investigate the photocatalytic activity for degradation of organic dye under the UV light and visible light irradiation. It was found that doping vanadium can reduce the band-gap energy value to 2.65 eV. The HRTEM photos showed that doping vanadium in TiO2 cause the particle morphology change from needle shape to irregular cubic shape. XRD patterns, XPS results showed the vanadium ions which in form of V4+ ions and V5+ ions were incorporated in TiO2 lattice. V4+ ions present in the substitutional site of Ti4+ in TiO2 lattice are responsible for increasing visible light absorption while V5+ ions present in the form of V2O5 islands on the surface of TiO2 particles are responsible for separation the photo-induced electrons. The photoreaction was carried out in a 10 ppm methylene blue solution with 20 W 254 nm UV light as the UV light source or 27 W visible light as the visible light source. The concentration of MB in the degradation samples were measured by UV-vis spectrometer (UV-vis). The V-doped TiO2 showed the higher photocatalytic activity than pure titania under UV light and visible light irradiation due to the significantly reduction of band gap energy, which may improve the photoactivity.
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