| Summary: | 碩士 === 國立中央大學 === 物理研究所 === 99 === We have studied the adsorbate-induced restructuring of Au-Pt bimetallic nanoclusters on the well-defined θ-Al2O3/NiAl(100) by using synchrotron-based high-resolution photoemission spectroscopy (PES). The Au-Pt bimetallic clusters were vapor deposited on ordered thin film Al2O3 at 300 K. Upon adsorption of adsorbates, such as methanol, ethanol and cyclohexene, the Au atoms aggregate at the surface of clusters. However, we find that the CO from methanol (and/or ethanol) decomposition remains on the surface and block the aggregation of Au atoms.
After annealing to 650 - 800 K, the metallic Pt become oxidized Pt and the surface of clusters is coated with alumina materials; some Au are exposed at the surface. Adsorbing the hydroxyl group (-OH) such as CH3OH and C2H5OH, the annealed Au-Pt bimetallic undergo dramatic changes in chemical state—oxidized Pt is reduced to metallic Pt, and thus Pt alloys with Au again. In contrast, no substantial alternation was found in the oxidized bimetallic clusters exposed to C6H10 which had only (CHn-) group.
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