- 學位論文
FTIR觀察有機分子在二氧化鈦上的光反應行為
FT-IR Study of Photoreaction of Organic Molecules on TiO2
摘要
本篇論文主要分為兩個部分，第一部份是甲基碘與金紅石和銳鈦礦相二氧化鈦的氣相光催化反應，甲基碘與金紅石相二氧化鈦的氣相光催化反應發現主要產生二氧化碳(2349 cm-1)、一氧化碳(2163 cm-1)、甲醛(1713 cm-1) 、乙醚(1160 cm-1) ，直至第8小時甲基碘幾乎已降解完全，與之前實驗室歷屆的數據(300 W)相比，可明顯觀察到500 W光源的汞燈照射下，甲基碘降解的時間減少很多，其可能的原因為500 W的燈源提供較高的光通量，使得我們的光催化的時間縮短。 甲基碘與銳鈦礦相二氧化鈦光催化反應約2小時降解，反應過程中間產物訊號不強，表示其存在時間短暫而快速轉化成二氧化碳。此組反應會比金紅石相二氧化鈦的光催化時間快速的原因為銳鈦礦相二氧化鈦的比表面積比金紅石相大，所以光催化的效率也較佳。 第二部份為FTIR觀察N3染料和異菸酸在二氧化鈦上的光穩定度行為。自從1991年Grätzel 等人發展第一個以N3為染料的高光電轉換效率的染料敏化太陽能電池(DSSC)，染料敏化太陽能電池即成為綠色能源發展的重點項目。通常N3分子吸附二氧化鈦的工作電極是透過carboxylate來鍵結。本論文研究目的希望用FTIR觀察N3分子在二氧化鈦的光穩定行為，藉以幫助了解照光使電池降解的可能性。為了簡化系統，我們還使用異烟酸來模仿N3官能基吸附二氧化鈦的行為，進行平行式的控制實驗。N3吸附二氧化鈦和異烟酸吸附二氧化鈦藉著汞燈照光下，N3經過了16小時始主要的兩根訊號1750 cm-1 (COOH) 和1390 cm-1 (COO-s) 完全降解，異烟酸則在15分鐘即降解完成，表示吸附分子光分解完全。主要的產物為二氧化碳。 二氧化鈦吸附N3分子的熱氧化實驗，在423K以上二氧化鈦吸附N3會開始降解，而在溫度473 K時幾乎完全降解，此時二氧化碳訊號強度約是溫度423 K時二氧化碳訊號的二倍。
並列摘要
The thesis is mainly divided into two parts. The first part is the study of photooxidation of methyl iodie (CH3I) on TiO2, including rutile phase and anatase phase. On the TiO2 rutile phase, the major products are CO2(g), CO(g), CH2O(g), and (C2H5)2O. The CH3I decomposed completely after ~ 8 hours mercury lamp radiation for rutile TiO2. The decomposition rate increased with higher irradiation power due to the higher photon flux. Photooxidation of CH3I on anatase TiO2 took about 2 hours to degrade completely. No obvious intermediates can be identified during the photooxidation process due to the fast reaction rate. The reaction intermediates existed for a short period of time and only CO2 was observed as the final product. The reason for the faster decomposition rate of CH3I on anatase TiO2 compared to rutile TiO2 is due to the larger surface area based on the BET measurement. The second part of this thesis is the study of photostability of N3 dye (Ru(dcbpyH2)2(NCS)2) and isonicotinic acid (IA) on TiO2. Since 1991, Grätzel et al. have developed the first dye-sensitized solar cells (DSSC) using Ru-complex based dye, (N3), with high photo to electron conversion efficiency, DSSCs has been proposed as a future alternative energy sources. In general, the N3 molecules adsorbed on TiO2 working electrode through carboxylate bonds. The purpose of this study is to perform FT-IR study in the photostability of N3 molecules on TiO2 which may help in understanding the irradiation induced cell degradation. The controlled experiments were also carried out using the IA to mimic the adsorption functionality of N3. It was found that upon irradiation of N3/TiO2 and IA/TiO2 by Hg lamp, the absorption peak at 1750 cm-1 (COOH) and 1390 cm-1 (COO-s) completely disappeared within 16 hours for N3 and 15 minutes for IA, indicating the decomposition of both adsorbed molecules. The major product is CO2 (2345 cm-1). The thermal-oxidation reaction of N3 molecules adsorbed on TiO2 was also studied. The signals of N3 molecules adsorbed on TiO2 are reduced as the temperature rised to above 423 K and completely disappeared at 473 K. Simultaneously, the intensity of CO2 peak increased to twice as strong as the that at 423 K.