臺灣博碩士論文加值系統

本研究利用溶膠-凝膠法製備以二氧化鈦(TiO2)為基材的光觸媒,仿照綠色植物 進行人工光合作用還原 CO2 產生 CH4,並釐清材料表面性質(如、氫氧官能基密度與鐵 修飾濃度)與環境因子(如、分散方式以及光強度)對於還原活性之影響。研究結果指 出 Thiele modulus 於本系統中介於 0.012 - 0.019,顯示速率限制步驟為化學反應,而可 忽略掉質傳上的影響。負載方式以直接分散法,具有最佳 CH4 產生量(1.52 μmol g-1), 而對於TiO2經過含水的氧氣前處理後,表面氫氧官能基密度由3.7提升至7.2 #OH nm-2, 初始反應速率則由 0.39 μmol g-1 h-1 提升至 1.19 μmol g-1 h-1,還原活性提升 3.1 倍,來自 於 TiO2 表面經光誘導後變為超親水性質與去除表面積碳所致。另種改善表面性質的方 式,是利用 0.1 at.%鐵表面修飾的 Fe-TiO2 光觸媒,在表面氫氧官能基密度為 11.6 #OH nm-2 時,初始反應速率達到 1.72 μmol g-1 h-1,其量子效率為 6.8%,相較單純 TiO2 光催 化還原活性提升 1.5 倍(1.13 μmol g-1 h-1)。而表面鐵摻雜量達 40 at.%時,最高甲烷產 量(3.35 μmol g-1)相較於 0.1 at.%狀況,提升了 1.9 倍的 CO2 還原活性。而對於釐清電 荷利用率與再結合速率,將光觸媒於不同光強度測試中,得到最佳光強度操作闕值位於 147μW cm-2。

In this study, the photocatalytic behavior of pure and Fe-surface-doped TiO2 photocatalsts for CO2 reduction is carried out under different loading types of the catalysts, humidity, and light intensity to clarify the contributions of doped Fe ions and density of hydroxyl groups to the photocatalytic activity. Direct dispersion of the photocatalysts in the reactor showed the highest CH4 yield for the gaseous system. The Thiele modulus in the range of 0.012-0.019 indicates the surface reaction, rather than mass diffusion, determines the kinetics. Pre-treatment of the catalysts with UV irradiation in the presence of O2 and H2O vapor increased surface density of hydroxyl groups, thus raising the reductive activity by 3.1 times. Incorporation of Fe ion in the surface lattice further improved the reductive activity in the humified CO2 atmosphere by 1.5 times due to enhanced surface acidity, though it reduced the activity a bit in the absence of H2O vapor. The optimal light intensity for the most efficient reduction is 147 μW cm-2. The highest quantum efficiency of 6.8 % was achieved when 0.1 at.% Fe-doped TiO2 was irradiated with UV light under the optimal light intensity and in the presence of water vapor. The highest accumulated CH4 yield of 3.35 μmol g-1 was produced by 40.0 at.% Fe-doped TiO2 after 4-hour irradiation. The lower reduction potential of the holes resulting from the segregated iron oxide clusters retard the oxidation of the products.

摘要...............................................I
Abstract...............................................II
致謝...............................................III
目錄...............................................IV
表目錄...............................................VI
圖目錄...............................................VII
第一章、前言...............................................1
1.1 研究動機...............................................1
1.2 研究目的...............................................2
第二章、文獻回顧...............................................3
2.1 光觸媒簡介...............................................3
2.1.1 二氧化鈦光觸媒...............................................3
2.1.2 光催化反應原理...............................................6
2.1.3 光觸媒表面金屬修飾...............................................7
2.2 光觸媒還原二氧化碳...............................................10
2.2.1 二氧化碳特性...............................................10
2.2.2 光催化還原二氧化碳反應機制...............................................14
2.3 光觸媒反應環境影響因素...............................................15
2.3.1 光觸媒分散方式...............................................16
2.3.2 光強度...............................................18
2.3.3 水氣濃度...............................................19
第三章、研究方法...............................................22
3.1 藥品...............................................23
3.2 光觸媒材料合成方法...............................................24
3.3 材料鑑定分析...............................................26
3.3.1 紫外光-可見光光譜儀（UV-Visible Spectrophotometer）...............................................26
3.3.2 等溫氮氣吸脫附分析（Nitrogen Adsorption-Desorption Isotherm Measrurment）...............................................27
3.3.3 X光粉末繞射儀（X-ray Powder Diffraction Spectrum, XRD）...............................................27
3.3.4 化學分析電子儀（Electron Spectroscopy for Chemical Analysis, ESCA）...............................................28
3.3.5 感應耦合電漿質譜儀（Inductively Coupled Plasma Mass Spectrometry, ICP-MS）...............................................28
3.3.6 飛行時間二次離子質譜儀（Time-of-Flight Secondary Ion Mass Spectrometer, TOF-SIMS）...............................................29
3.3.7 電子式掃描顯微鏡（Scanning Electron Microscopy, SEM）...............................................29
3.3.8 穿透式電子顯微鏡（Transmission Electron Microscopy, TEM）...............................................30
3.3.9 熱重分析儀（Thermogravimetric Analysis, TGA）...............................................30
3.4 二氧化碳還原系統...............................................31
3.4.1 人工光合作用系統實驗設備...............................................31
3.4.2 氣相層析儀器之參數設定...............................................33
3.4.3 光催化還原實驗操作步驟...............................................33
第四章、結果與討論...............................................36
4.1 材料特性鑑定...............................................36
4.2 光觸媒分散方式...............................................43
4.3 前處理步驟...............................................48
4.4 水氣存在與否對於光催化還原系統影響...............................................50
4.4.1 單純TiO2系統在有無水氣存在下的還原催化活性...............................................50
4.4.2 Fe-TiO2系統在有無水氣存在下的還原催化活性...............................................53
4.5 光強度對於光催化還原系統影響...............................................56
4.5.1 光強度對單純TiO2系統CH4產生量的影響...............................................57
4.5.2 光強度對Fe-TiO2系統CH4產生量的影響...............................................59
4.6 鐵離子修飾濃度對於光催化還原活性影響...............................................62
第五章、結論...............................................66
未來建議...............................................67
參考文獻...............................................68
附錄A...............................................73
附錄B...............................................74

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