None Catalytic properties of Au nanoclusters supported on Al2O3/NiAl (100) surface

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/7421

Title:	None Catalytic properties of Au nanoclusters supported on Al2O3/NiAl (100) surface
Authors:	許紘瑋;Hung-wei Shiu
Contributors:	物理研究所
Keywords:	氧化鋁;奈米;金;分解;甲醇;觸媒;XPS;Al2O3;Nano;Gold;Decompose;Catalytic;Methanol
Date:	2006-10-13
Issue Date:	2009-09-22 10:57:38 (UTC+8)
Publisher:	國立中央大學圖書館
Abstract:	我們利用同步輻射光源的光激發電子能譜儀(PES)來研究甲醇在良好奈米金觸媒模型上的吸附以及分解反應。利用氣相沈積法，我們在超高真空中於300 K，450 K以及570 K三種溫度下，將金奈米團簇成長在完整有序的氧化鋁薄膜Al2O3/NiAl(100)上；我們超高真空的氣壓小於3 x 10-10 torr。而我們使用PES以及掃描穿隧電子顯微鏡(STM)來研究金奈米團簇。從STM的影像中，我們發現金原子會集結於氧化鋁的結晶條紋上進而形成奈米團簇，且金奈米團簇的平均粒徑大小在樣品表面溫度450 K的時候會有些微的變大。然而，在表面溫度570 K的時候金奈米團簇的平均大小有一個突然的變化，我們認為這可能是因為高擴散係數所造成的。為了研究甲醇分解反應，甲醇在120 K低溫下吸附於Au/Al2O3/NiAl (100)表面上，在這之後並加溫到各種不同的溫度。在加溫的過程中，我們發現甲醇的C1s峰值隨著加溫的溫度往低束縛能的方向偏移，這指出了在甲醇完全分解成一氧化碳之前會有至少一種中間產物的生成。我們也發現甲醇分解反應的活性跟金觸媒的結構有相當大的關係。而在310 K的退火之後，C1s 的峰值忽然產生偏移，或許可以暗示C-O鍵結的斷裂以及碳氫化合物的重新生成。 We have studied the adsorption and decomposition of methanol on well-defined supported Au nanoclusters as a model catalyst by using synchrotron-based high-resolution photoemission spectroscopy (PES). Au nanoclusters are deposited on well-ordered Al2O3 film grown on NiAl (100) through vapor deposition in the ultrahigh vacuum conditions (<3 x 10-10 torr) at 300 K, 450 K, and 570 K. Gold nanoclusters are studied by using both PES and scanning tunneling microscopy (STM). Form STM images, Au atoms nucleated on crystalline Al2O3 films as nanoclusters and the average size of Au nanoclusters is slightly increased at the deposition temperature of 450 K. However, at 570 K deposition temperature sudden change in the average size of Au nanoclusters is observed, which is probably due to higher diffusion coefficient. To study methanol decomposition, methanol was adsorbed on Au/Al2O3/NiAl (100) at 120 K and subsequently annealed to different temperatures. In our annealing experiment we observe that the methanol C1s peak shifts toward lower binding energy with annealing temperature, which indicates more than one intermediate C-species before it decomposes to CO. We also found the activity for methanol decomposition is highly dependent on the structure of supported Au catalyst. After annealing to 310 K, a sudden shift for C1s peaks may imply that C-O scission and reforming to another hydrocarbon species.
Appears in Collections:	[Graduate Institute of Physics] Electronic Thesis & Dissertation

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