In Situ Formation of Au–Pd Bimetallic Active Sites Promoting the Physically Mixed Monometallic Catalysts in the Liquid-Phase Oxidation of Alcohols

Authors

  • Di Wang Dr.,

    1. Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Institute, Faradayweg 4–6, 14195 Berlin (Germany), Fax: (+49) 7247-82-8976, Fax: (+49) 30-8413-4405
    2. Current address: Institut für Nanotechnologie, Karlsruher Institut für Technologie, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany)
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  • Alberto Villa Dr.,

    1. Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Institute, Faradayweg 4–6, 14195 Berlin (Germany), Fax: (+49) 7247-82-8976, Fax: (+49) 30-8413-4405
    2. Current address: Dipartimento CIMA L.Malatesta, Università di Milano via Venezian 21, 20133 Milano (Italy)
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  • Paolo Spontoni,

    1. Dipartimento CIMA L.Malatesta, Università di Milano via Venezian 21, 20133 Milano (Italy)
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  • Dang Sheng Su Dr.,

    1. Department of Inorganic Chemistry, Fritz Haber Institute of the Max Planck Institute, Faradayweg 4–6, 14195 Berlin (Germany), Fax: (+49) 7247-82-8976, Fax: (+49) 30-8413-4405
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  • Laura Prati Prof.

    1. Dipartimento CIMA L.Malatesta, Università di Milano via Venezian 21, 20133 Milano (Italy)
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Abstract

The catalytic oxidation of alcohols with molecular oxygen on supported nanometallic catalysts represents one of the green methods in a crucial process for the synthesis of fine chemicals. We have designed an experiment using physically mixed Au/AC and Pd/AC (AC=activated carbon) as the catalyst in the liquid-phase oxidation of benzyl alcohol by aerobic oxygen. The evolution of the physically mixed catalyst structures at different stages in the catalytic reaction was investigated by aberration-corrected high-resolution transmission electron microscopy and spatially resolved element mapping techniques at the nanometre scale, and they were also compared with the structure of the bimetallic alloy. For the first time we show the formation of surface Au–Pd bimetallic sites by reprecipitation of Pd onto Au nanoparticles. Negligible Au leaching was observed. The in situ structural evolution can be directly correlated to the great enhancement of the catalyst activity. Moreover, we distinguish the different behaviours of Au and Pd, thus suggesting an oxygen differentiating mechanism for Au and Pd sites. The findings are of great importance to both the understanding of the structure–activity correlation and the design of highly active catalysts in green chemistry.

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