- 學位論文
二氧化鈦的改質及可見光光催化反應與染料敏化太陽能電池的應用
Preparation of Modified TiO2 and its Application for Visible Photocatalysis and Dye-Sensitized Solar Cells
摘要
本論文研究方向有二，一為將自製的未含氮(Undoped)及含氮可見光二氧化鈦奈米粒(TiOxNy)進行可見光光催化反應並探討其效果。另一為將自製的三氧化鎢/二氧化鈦漿料製作成染料敏化太陽能電池的工作電極，探討其光電轉換效果。 第一部分，以正四丁基氧化鈦(Ti[n(C4H9O)]4)為前驅物，利用硝酸水溶液催化產生乳白色混合膠體，再緩緩加入以胍氯化物(CH5N3•HCl)為氮源的溶液，進行水熱及鍛燒處理來合成奈米級含氮可見光二氧化鈦，藉由反射式UV、XRD、TEM、BET及ESCA來分析及鑑定其性質；由反射式UV的觀察來看，加入的氮源濃度愈高，波長會偏移到可見光區較多，波長偏移範圍從411到427 nm；由XRD分析結晶相，其結果顯示加入的氮源愈多，金紅石相也增加愈多；TEM觀察其形態，氮摻雜量愈多其粒徑有增大趨勢；ESCA結果可證明N是以取代的方式和Ti鍵結；以BET量測粉體的比表面積大小；最後以總比表面為基準取樣，利用偶氮染料酸橙(Acid Orange 7, AO7)的降解反應來探討不同濃度的奈米級含氮二氧化鈦之可見光光催化活性，由結果可得知含氮濃度4 M的可見光二氧化鈦奈米粒的催化活性較好。 第二部分，以正四丁基氧化鈦(Ti[n(C4H9O)]4)為前驅物，再加入三氧化鎢及三氧化鎢前驅物粉末，經水熱後所生成的三氧化鎢(三氧化鎢前驅物)/二氧化鈦溶膠溶液再分別製成三氧化鎢(三氧化鎢前驅物)/二氧化鈦奈米粒及漿料；三氧化鎢(三氧化鎢前驅物)/二氧化鈦奈米粒，藉由反射式UV、XRD、TEM、BET、XRF、ESCA及SEM來分析及鑑定其性質；三氧化鎢/二氧化鈦漿料製作成工作電極，將工作電極浸泡於染料(N719)中，使染料吸附在電極上，相對電極為鉑(Pt)電極，加入電解液(I-/I3-)後，進行封裝，以模擬太陽光AM 1.5，光強度為100 mW/cm2的光源照射，進行光電轉換效率測試。經實驗結果顯示，0.5 %三氧化鎢/二氧化鈦及0.5 %三氧化鎢前驅物/二氧化鈦漿料所製成的工作電極會比銳鈦礦相二氧化鈦漿料所製成的工作電極效率還高，分別可達5.996 %及6.773 %。
並列摘要
This thesis was divided to two parts. In the first part, I will discuss the visible photocatalytic activity of undoped and visible-light active N-doped TiO2 nanoparticles (TiOxNy). In the second part, I will discuss the preparation of WO3 (WO3 precursor)/TiO2 paste for application in dye-sensitized solar cells (DSSCs). Part I, the visible-light active N-doped TiO2 nanoparticles were prepared by mixing Ti precursor (titanium (IV) n-butoxide) and nitric acid. The above sol solution was mechanically stirred until a white translucent sol was obtained, then added guanidine hydrochloride solution, followed by hydrothermal treatment. The visible-light active N-doped TiO2 nanoparticles was characterized using UV-VIS, XRD, TEM, BET, and ESCA. Based on UV-VIS and XRD, we found a red-shift of absorption wavelength (from 411 to 427 nm) and rutile phase percentage of TiOxNy upon increase the amount of doped nitrogen (2 M to 8 M). TEM allowed us to determine particles size and morphology and it was found that upon increasing the N content, the particle size increased as well. ESCA observations suggested that N atom substituted O atom in TiOxNy. The specific surface area of as-prepared TiOxNy was measured by BET. The visible photocatalytic activity of undoped and visible-light active N-doped TiO2 nanoparticles were tested by photodegradation of Acid orange 7 in aqueous solution. The TiOxNy sample containing 4 M guanidine hydrochloride showed the best photocatalytic activity under visible-light irradiation. Part II, the WO3 (WO3 precursor)/TiO2 sol was synthesized by hydrolysis of mixed Ti precursor (titanium (IV) n-butoxide) and WO3 (WO3 precursor) powder in acetic acid, followed by hydrothermal treatment at 200 °C for 5 h. The WO3 (WO3 precursor)/TiO2 nanoparticles were characterized by using UV-VIS, XRD, TEM, BET, XRF, ESCA, and SEM. The WO3 (WO3 precursor)/TiO2 paste was used for fabricating the working electrodes for DSSC application. The TiO2 electrodes were immersed in N719 dye solution. Platnium was sputterd on the FTO glass as a counter electrode. Electrolyte (I-/I3-) was injected into the cell and the device was sealed. Solar energy conversion efficiency of device was measured by simulated AM 1.5 sunlight (100 mW/cm2). It was found that conversion efficiency of 0.5 wt % WO3/TiO2 and 0.5 wt % WO3 precursor/TiO2 paste-based DSSCs can achieve 5.996 % and 6.773 %, respectively.