Oxygen-induced Restructuring of a Pd/Fe3O4 Model Catalyst
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文摘
We have studied the influence of oxygen on the structure and morphology of a Pd/Fe3O4 model catalyst using molecular beam (MB) methods, IR reflection absorption spectroscopy (IRAS) and scanning tunneling microcopy (STM). The model catalyst was prepared under ultrahigh vacuum (UHV) conditions by physical vapor deposition (PVD) and growth of Pd nanoparticles on an ordered Fe3O4 thin film on Pt(111). It is found that surface oxides are formed on the Pd nanoparticles even under mild oxidation conditions (temperatures of 500 K and effective oxygen partial pressures of around 10−6 mbar). These surface oxides are initially generated at the Pd/Fe3O4 interface and, subsequently, are formed at the Pd/gas interface. The process of formation and reduction of surface and interface oxides on the Pd particles is fully reversible in that all oxides formed can be fully reduced. As a result, the oxide phase acts like a storage medium for oxygen during oxidation reactions, as probed via CO oxidation.
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