觸媒表面氫氧(OH)官能基已被證實能幫助CO2化學吸附而有助於還原效率的提升，然而OH官能基型態對CO2還原特性卻還不清楚。本研究以鹼性水熱法於P25表面導入不同數量與型態的OH官能基，比較其在氣相與液相系統中光催化還原CO2活性，並透過XPS、DRIFT、與TGA分析，釐清表面結構與還原活性與選擇性的關係。結果顯示，P25以1-2 M NaOH處理後，OH密度由4.86提升至5.94-5.99/nm2，型態以橋接(bridged)為主，而經4M以上 NaOH處理後，OH密度大幅增加至8.10 /nm2，且開始出現末端(terminal) OH。光催化還原CO2的產物以CO與CH4為主，2M NaOH處理後的樣品有最高CO產率(37.90 mol/g水溶液相；30.52 mol/g氣相)及量子效率 (0.04-0.29%)，為P25的2.42-4.00倍(0.01-0.12%)，而1M NaOH處理後的樣品則有相對較高的CH4產率(2.37-3.43 mol/g)，反應活性的提升與增加的bridged OH官能基有關。經3M NaOH處理後，表面元素重組雖生成較厚的無晶相層(4-6 nm)，但高量的表面OH官能基仍使CO2還原活性高於P25。CO2與OH官能基反應後主要生成monodentate/bidentate HCO3-與bidentate CO32-，當生成為monodentate/bidentate HCO3-時，產物主要為CO，而當反應生成為bidentate CO32-時，產物則主要為CH4。

Hydroxyl functional groups (OH) on the surface of the catalyst have been demonstated to help CO2 chemisorption and contribute to the improvement of reduction efficiency. However, the characteristics of the OH functional groups on the reduction of CO2 are still unclear. In this study, different numbers and types of OH functional groups were introduced on the surface of P25 by alkaline hydrothermal method, and their photocatalytic activity for CO2 reduction in gas and liquid systems were examined. In addition, XPS, DRIFT, and TGA analysis were used to clarify the relationship between the surface structure and reducing activity and selectivity. The results showed that the OH density increased from 4.86 to 5.94-5.99/nm2 after treating with 1-2M NaOH and significantly increased to 8.10/nm2 when the NaOH concentration was up to 4M. Bridged OH groups were dominant at 1-2M NaOH treament and terminal OH began to appear above 3M. The products of photocatalytic reduction of CO2 were mainly CO and CH4. The sample treated with 2M NaOH exhibited the highest CO yield (37.90 μmol/g in the aqueous phase; 30.52 mol/g in the gas phase) with a apparent quantum efficiency of 0.04-0.29%, which was 2.42-4.00 times higher than that of P25 (0.01-0.12%). Besides, the sample treated with 1M NaOH had a relatively high CH4 yield (2.37-3.43 mol/g). The improved acivity resulted from increased biedged OH groups. Eventhough surface reconstruction formed a thicker amorphous latyer (4-6 nm) on the surface after treating 3-4M NaOH, high quantity of OH groups still led the treated TiO2 powders to exhibit a higher activity than P25 for CO2 reduction. The bridged OH groups mainly converted CO2 into monodentate/bidentate HCO3- and bidentate CO32- after irradiation. While the monodentate/bidentate HCO3- led to CO formation, bidentate CO32- mainly produced CH4.

摘要 i
Abstract ii
主目錄 iii
表目錄 v
圖目錄 vi
第一章、前言 1
1.1 研究動機與背景 1
1.2 研究目的 3
第二章、文獻回顧 4
2.1 二氧化鈦光觸媒 4
2.2 光催化還原二氧化碳 6
2.2.1 光催化還原二氧化碳特性 6
2.2.2 二氧化鈦光催化還原二氧化碳反應機制 11
2.3 二氧化鈦改性 12
2.3.1 二氧化鈦改性方法 12
2.3.2 二氧化鈦自身缺陷 14
2.4 表面氫氧官能基 15
2.4.1 表面氫氧官能基對CO2光催化還原的效果 15
2.4.2 表面生成氫氧官能基之方法 16
2.4.2 氫氧官能基吸附二氧化碳 18
2.4.3 氫氧官能基對產物的選擇性 19
2.4.4 OH官能基型態 20
第三章、研究方法 23
3.1 實驗架構 23
3.2 實驗藥品 24
3.3 光觸媒材料合成方法 24
3.4 材料鑑定分析 26
3.4.1 紫外光可見光分光光譜儀(UV-Vis Spectrophotometer) 26
3.4.2 等溫氮氣吸脫附分析儀(Nitrogen adsorption-desorption Isothermal analyzer) 27
3.4.3 X光粉末繞射儀(X-ray Powder Diffraction Spectrum , XRD) 27
3.4.4 漫反射紅外線傅立葉轉換即時監測(Diffuse Reflectance Infrared Fourier Transforms, DRIFT) 27
3.4.5 熱重分析儀(Thermogravimetric analysis, TGA) 29
3.4.6 溫度程控脫附儀（Temperature programmed desorption, TPD） 29
3.4.7 化學分析電子儀(Electron Spectroscopy for Chemical Analysis, ESCA) 29
3.4.8 穿透式電子顯微鏡 (Transmission Electron Microscopy, TEM) 30
3.4.9 電子順磁共振儀(Electron paramagnetic resonance, EPR) 31
3.4.10 氣相層析儀(Gas Chromatography, GC) 31
3.5 光催化二氧化碳還原系統 32
3.5.1 液相系統 32
3.5.2 氣相系統 33
第四章、結果與討論 35
4.1 材料基本特性 35
4.2 表面特性 37
4.2.1 氫氧官能基定量 37
4.2.2 氫氧官能基定性 39
4.2.3 化學組成 41
4.3 二氧化碳吸附能力 45
4.4 液相系統中二氧化鈦光催化能力 47
4.5 氣相系統中二氧化鈦光催化能力 49
4.6 反應機制 52
4.6.1 In situ DRIFT 52
4.6.2 OH基隨反應時間的變化 56
4.6.3 表面電荷轉移(EPR) 58
4.7 材料穩定性 60
第五章、結論 63
參考文獻 64
附錄A. 不同NaOH濃度處理下XPS Na1s圖譜 72
附錄B. CO2反應後的ESCA 73
附錄C. 光量子效率比較 77
附錄D. TEM繞射圖 78

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