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研究生:夏于耀
研究生(外文):Yu-Yao Hsia
論文名稱(外文):Oxidative Reforming of Ethanol on Rh(111): effect of co-adsorbed oxygen and hydroxyl
指導教授:羅夢凡
學位類別:碩士
校院名稱:國立中央大學
系所名稱:物理學系
學門:自然科學學門
學類:物理學類
論文種類:學術論文
論文出版年:2018
畢業學年度:106
語文別:英文
論文頁數:79
中文關鍵詞:氧化蒸氣改造乙醇
外文關鍵詞:Oxidative reformingEthanolRh(111)OxygenWater
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藉由改變乙醇(C2H5OH)、水(H2O)和氧氣(O2)的比例,我們利用了熱脫附質譜儀術(TPD)和以同步輻射作為光源的光電子能譜(PES),研究在銠單晶111晶面上的乙醇氧化蒸氣重組(oxidative reforming of ethanol)。
  為了闡明反應過程,我們首先進行在氧氣的共同吸附下,乙醇分解的實驗。共同吸附的氧原子,會促進乙醇分解,進而導致了氫氣(H2)、一氧化碳(CO)、以及甲烷(CH4)等產物的增加;而相反的,當氧原子的覆蓋量增加至0.5 ML時,氫氣和一氧化碳的生成被抑制了,但是水分子和二氧化碳的生成量卻增加了。因此我們可以發現氧原子有傾向和表面的氫原子和一氧化碳鍵結。
  當表面的氧原子的覆蓋率在0.15 ML以下時,吸附的水分子會部分分解成氫原子和氫氧根團。只有一層的水覆蓋在表面上時,乙醇的反應機率幾乎會倍增,這顯示了氫氧根團可以使得表面變得更加氧化,而促進乙醇分解。然而,氫氣和甲烷的產量卻只有些微的增加,雖然由水分解來的表面氫原子多少可以幫助氫的產量增加,但是水的脫附使得大量氫原子無法留在表面上,去增加氫氣的產量。而當有大量的水先覆蓋在表面上時,乙醇仍然可以鑽進水層,與單晶表面進行蒸氣重組的反應。
We investigated the oxidative steam reforming of ethanol on Rh(111) single crystal controlled by the ethanol/water/oxygen molecular ratio with temperature programmed desorption (TPD) and synchrotron-based photoemission spectroscopy (PES). To shed light on the reaction, we first carried out the decomposition of ethanol co-adsorbed with atomic oxygen on Rh(111) single crystal. The co-adsorbed atomic oxygen promoted decomposition of ethanol and resulted in an enhanced production of hydrogen, carbon monoxide and methane; a high coverage of co-adsorbed atomic oxygen (0.5 ML), in contrast, suppressed the production of hydrogen and carbon monoxide but promoted the formation of water and carbon dioxide. The atomic oxygen atoms presents the tendencies to binding to surface hydrogen atoms and surface carbon monoxide.
Adsorbed water molecules were partially dissociated into hydroxyl groups and hydrogen atoms when they were co-adsorbed with atomic oxygen less than 0.15 ML. With one monolayer adsorbed water, the reaction probability of ethanol almost doubled, showing that hydroxyl groups provided a more oxidative environment for ethanol to decompose. Whereas, the production of hydrogen and methane slightly increased. Hydrogen-rich surface somehow improved the production but the diffusion of ethanol into water layers pressed out the position of monolayer water, leading to the contribution of hydroxyl and water reduced.
Contents
摘 要 i
Abstract ii
List of Figure .. iv
Chapter 1 Introduction 1
Chapter 1 reference 3
Chapter 2 Literature Survey 4
2.1 Oxygen adsorption on Rh(111) single crystal surface 4
2.2 H2O dissociation on oxygen-covered Rh(111) 7
2.3 Ethanol reforming on Rh catalyst 10
Chapter 2 reference 20
Chapter 3 Experimental Method & Apparatus 21
3.1 Experimental methods 21
3.2 Photoemission Spectroscopy (PES) 32
Chapter 3 reference 36
Chapter 4 Results and Discussion 37
4.1 Water dissociation on oxygen-covered Rh(111) surface 37
4.2 Decomposition of ethanol on clean Rh(111) surface 42
4.3 Oxidative reforming of ethanol on Rh(111) surface 46
4.4 Diffusion of ethanol into water layer 59
Chapter 4 reference 64
Chapter 5 Conclusion 65
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