奈米光觸媒二氧化鈦粉體與薄膜之製備及特性分析

Abstract

本論文利用新式沉澱-膠溶法製備二氧化鈦溶膠。添加適當的螯合劑可以有效地促進TiO6八面體的排列，並形成具有anatase晶相的二氧化鈦溶膠。而所製備之TiO2溶膠利用亞甲基藍測試其光觸媒活性，發現所製備之TiO2溶膠展現出較商用P25粉體更為優良的光催化活性。 另一方面，具有高比表面積的TiO2薄膜利用上述所得溶膠以含浸法鍍於各式纖維上。發現所得薄膜的特性與纖維的直徑大小都非常密切的關係。由於碳纖維的直徑較其他纖維小，因此可負載較多的TiO2並且薄膜所表現出來的絶熱性和附著性亦較佳。同時在加入適當的結合劑之後，TiO2薄膜與纖維之間的附著性可大幅地提升。 為了使二氧化鈦粉體於可見光之下作用，本論文利用Cr3+離子摻雜於TiO2主體晶格之內，嘗試改變其能階結構。由於所摻雜的Cr3+離子濃度相當低，因此由XRD繞射圖譜中無法觀察出任何具有Cr的雜相。而在DTA/TG結果中顯示，摻雜Cr3+離子之後可以有效地抑制rutile晶相的生成。於UV-visible吸收光譜當中顯示經過摻雜後的TiO2粉體於可見光下有吸收峰。而在XPS的結果中發現，在愈高溫下煆燒有助於Cr3+離子嵌入TiO2主體晶格。同時經過光觸媒活性測試之後，發現經過摻雜後的粉體於可見光之下具有光催化活性。 於本論文的最後一部分中，嘗試利用水熱法製備奈米管狀光觸媒粉體。由XRD的結果中發現所得粉體具有H2Ti3O7的晶相。且經過水熱處理之後的粉體，其比表面積可大幅度地提升。如此可以有效地提升光催化活性。

TiO2 sol has been prepared by a novel precipitation-peptization method. Using appropriate molecule structure for chelation can enhance the rearrangement of TiO6 octahedra to form anatase TiO2. The TiO2 sol has been tested for the photocatalyzed degradation of methylene blue. The TiO2 sol shows a superior catalytic activity, which is greater than Degussa P25. High specific surface TiO2 film coated on fibers was also prepared via dip coating method using the as-prepared TiO2 sol. The properties of TiO2 films strongly depend on the diameter of fibers. The carbon fiber with smaller diameter compared to others can load more TiO2 and this might contribute more to the heat property and photocatalytic activity. The carbon fiber also revealed better adhesion property than the other fibers and the adhesion property was promoted dramatically by the addition of binder. Cr3+-TiO2 photocatalyst responsive to visible light was prepared by chemical coprecipitation-peptization method. Due to very low Cr content, any crystalline phase containing Cr could not be observed by XRD in Cr3+-TiO2. The DTA/TG results show that the doping chromium ions can impede the phase transformation from anatase to rutile phase. The UV-visible diffuse reflectance spectra of all the doped TiO2 samples show that the absorption shifts into visible light region. The XPS results demonstrate that the materials contain Ti, O and Cr. The intensity of chromium decreased with increasing heating temperature and it is proposed that under high annealing temperature, it can enhance the doping of Cr3+ ion into TiO2 lattice. The Cr3+-TiO2 samples revealed photocatalytic activity under visible light illumination and the photocatalytic activity was influenced by the heating temperature. In the final part of this thesis, nanofiber TiO2 was prepared by hydrothermal method. From the XRD results, it can be assigned to trititanate H2Ti3O7 phase. The nanofibers with hydrothermal treatment showed the highest specific surface area of 327.3 m2/g. The photocatalytic activity of nanofibers was found to be better than the raw TiO2 powder.