白金的奈米團簇利用蒸鍍的方法成長在氧化薄膜Al2O3/NiAl(100)上，利用高能電子繞射儀(Reflection High Energy Electron Diffraction)、掃描穿遂式顯微鏡(Scanning Tunneling Microscopy)和歐傑電子能譜儀(Auger Electron Spectroscopy)來研究之。我們發現白金奈米團簇(平均直徑2.25nm、高0.4nm)有很好的排列行為而且它們的結構和相位受到底層氧化物的影響。經由高能電子繞射儀的結構研究，我們發現白金團簇是fcc的結構並且沿著平行NiAl(100)表面的白金團簇的(100)面方向成長。其白金的[0-1-1]方向平行於NiAl(100)的[0-10]方向。這是個理想的成長方式，白金團簇(100)面和表面的氧化物矩形網狀結構互相吻合。白金團簇的晶格常數相對於fcc結構的白金塊材膨脹了約5%，這樣會使白金團簇的(100)面有比較好的晶格去吻合表面的氧化物。 另外白金奈米團簇的電催化性質如甲醇氧化性質(methanol oxidation)和其特性可以用循環伏安法(cyclic voltammetry)、高能電子繞射儀、掃描式電子顯微鏡(SEM)和歐傑電子能譜儀來研究。我們發現白金團簇在CV實驗後會聚成更大的團簇。結果顯示聚集的奈米團簇的直徑約15~30nm，其結構依然為fcc結構但其(111)面有個隨機的方向相對於表面的氧化物。 The Pt nanoclusters grown from vapour deposition on thin film Al2O3/NiAl(100) have been studied by reflection high energy electron diffraction (RHEED), scanning tunnelling microscopy (STM), and Auger electron spectroscopy (AES). The results show that the Pt nanoclusters (with a mean diameter of 2.25 nm and height of 0.4 nm) are highly crystalline and their structures and phases are significantly affected by the oxide substrate. Structural analysis based on the RHEED patterns indicates that Pt clusters, although with different sizes, have an fcc phase and grow with their (001) facets parallel to the NiAl(100) surface, and with [110] axis along the [0-10] direction of the bulk NiAl(100). It is an optimal growth as the Pt fcc (001) facets match better with the rectangular oxygen mesh of the oxide surface. The lattice constant of the Pt clusters is expanded by about 5 % (4.12 Å) relative to that of fcc bulk Pt (3.92Å), as the Pt fcc (001) plane has better lattice match with the oxide surface. The electro-catalytic properties of the Pt/Al2O3/NiAl(100) electrode for methanol oxidation and its kinetic characterization were investigated by cyclic voltammetry (CV), RHEED, AES and scanning electron microscopy (SEM). We observed excellent electro-catalytic activity. The Pt nanoclusters have been sintered under the CV conditions. The result exhibits that the aggregated size of Pt nanoclusters is ca. 15~30nm in diameter. The structures of the aggregated Pt nanoclusters have also an fcc phase but have their (111) plane randomly oriented with respect to the oxide surface.
