Catalytic properties of Au nanoclusters supported on Al2O3/NiAl (100) surface

• Main Authors: Hung-wei Shiu, 許紘瑋
• Other Authors: Meng-Fan Luo
• Format: Others
• Language: en_US
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/82083431818454577809

碩士 === 國立中央大學 === 物理研究所 === 95 === 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.