可見光光觸媒粉體及薄膜之製備與特性分析

Abstract

本論文採用溶膠-凝膠法製備BaCo0.5Ta0.5O3粉體。在經過800 oC的鍛燒後，可得到BaCo0.5Ta0.5O3之單相粉體。從紫外光-可見光吸收光譜中可以看出該粉體具有較寬廣的能隙，而從光反應實驗中可知該結構擁有紫外光光觸媒活性。將銀金屬以含浸法負載於此粉體表面後可使其展現出較為優良的光反應性。 另一方面，一種新型的可見光觸媒- BaCo0.5Nb0.5O3粉體以溶膠-凝膠法製備而成。在經過1000oC之熱處理可得該單相粉體。煆燒溫度與此粉體之粒徑大小及結晶性有相當密切的關係。而從紫外光-可見光吸收光譜結果可知該粉體具有比二氧化鈦小之能隙，經由光反應實驗可知該結構具有可見光反應特性，且活性大小會隨著煆燒溫度的不同而有所變化。經過實驗結果可證明經1000oC熱處理後所得粉體具有最佳的反應活性。 而為了使二氧化鈦在可見光下作用，在本論文最後一部份嘗試利用Fe3+離子摻雜於二氧化鈦中，以改變其能階結構。從XRD繞射圖譜中可觀察出摻雜Fe3+離子後會促進rutile相的生成。而從紫外光-可見光吸收光譜中可發現Fe3+離子摻雜後可使二氧化鈦之吸收帶偏移至可見光區域。Fe3+離子之摻雜濃度對光觸媒粉體之活性的影響也從光觸媒活性測試中進行討論。此外，另利用有機金屬沉澱法製備單一銳鈦礦相的光觸媒二氧化鈦薄膜，並將Fe3+離子摻雜其中。結果發現利用新式高壓結晶化製程，可將二氧化鈦的結晶溫度由325oC降至125oC。而薄膜表面形成的粒子會隨著退火溫度上升而變大。由SEM結果顯示出以高壓結晶製備所得薄膜具有較為均勻且緻密的表面形貌，而經由可見光反應測試，高壓結晶製程所製備之薄膜確實具有較佳之光觸媒活性。

BaCo0.5Ta0.5O3 powders were prepared via a sol-gel method. The monophasic perovskite phase was formed after calcining at 800oC. From the UV-vis spectra, this compound revealed a wide band gap and exhibited photocatalytic activity under UV light irriadiation. The photo-activity was improved through loading of silver metal on the surface of BaCo0.5Ta0.5O3 particles. A new type of photocatalyst-BaCo0.5Nb0.5O3 was successfully synthesized by a sol-gel process. After heating at 1000oC, the pure phase of this compound was formed. The particle size and the crystallinity of BaCo0.5Nb0.5O3 powders significantly depended on the calcining temperature. The band gap calculated from the UV-visible spectra was narrower than that of titania. BaCo0.5Nb0.5O3 was demonstrated to have photocatalytic activity under visible light irradiation. The photo-activity of the prepared BaCo0.5Nb0.5O3 powders significantly depended on the synthesis temperature. The 1000oC-calcined powders were found to have the highest photocatalytic activity because of their well-crystallized structure and uniform particle size. In the final part of this thesis, iron-ion doped titania powders were prepared. The XRD result showed that doping iron-ion can promote the phase transformation from anatase to rutile phase. In the UV-vis spectra, the modified Fe3+-doped TiO2 shifted the absorption edge of TiO2 to the visible light region. The relation between the doping content of iron-ion and photocatalytic activity was discussed. Iron-ion doped titania thin films, responding to visible-light irradiation, were successfully synthesized via the high-pressure crystallization (HPC) process. The monophasic anatase of TiO2 was formed at a temperature as low as 125oC under the high-pressure process. The doping content of iron-ion in TiO2 films significantly influenced the photo-activity. The particle sizes of the films were enlarged with a rise in the annealing temperatures. The Fe3+-doped TiO2 thin films prepared via the HPC had uniform surface structure. In comparison with the films prepared via the conventional annealing process, the HPC-derived films have better photo-activity.