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Issue 10, 2014
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Volcano-shape glycerol oxidation activity of palladium-decorated gold nanoparticles

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Abstract

Bimetallic PdAu catalysts are more active than monometallic ones for the selective oxidation of alcohols, but the reasons for improvement remain insufficiently detailed. A metal-on-metal material can probe the structure–catalysis relationship more clearly than conventionally prepared bimetallics. In this study, Pd-on-Au nanoparticles with variable Pd surface coverages (sc%) ranging from 10 to 300 sc% were synthesized and immobilized onto carbon (Pd-on-Au/C). Tested for glycerol oxidation at 60 °C, pH 13.5, and 1 atm under flowing oxygen, the series of Pd-on-Au/C materials showed volcano-shape catalytic activity dependence on Pd surface coverage. Increasing surface coverage led to higher catalytic activity, such that initial turnover frequency (TOF) reached a maximum of ∼6000 h−1 at 80 sc%. Activity decreased above 80 sc% mostly due to catalyst deactivation. Pd-on-Au/C at 80 sc% was >10 times more active than monometallic Au/C and Pd/C, with both exhibiting TOF values less than ∼500 h−1. Glyceric acid was the dominant primary reaction product for all compositions, with its zero-conversion selectivity varying monotonically as a function of Pd surface coverage. Glyceric acid yield from Pd-on-Au/C (80 sc%) was 42%, almost double the yields from Au/C and Pd/C (16% and 22%, respectively). Ex situ X-ray absorption near edge structure analysis of two Pd-on-Au/C materials with comparable activities (60 sc% and 150 sc%) showed that the former had less oxidized Pd ensembles than the latter, and that both catalysts were less oxidized compared to Pd/C. That Au stabilizes the metallic state of surface Pd atoms may be responsible for activity enhancement observed in other PdAu-catalyzed oxidation reactions. Decorating a Au surface with Pd generates a catalyst that has the deactivation resistance of Au, the higher glyceric acid selectivity of Pd, and the synergistically higher activities that neither metal has.

Graphical abstract: Volcano-shape glycerol oxidation activity of palladium-decorated gold nanoparticles

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Publication details

The article was received on 05 Apr 2014, accepted on 02 Jun 2014 and first published on 02 Jun 2014


Article type: Edge Article
DOI: 10.1039/C4SC01001A
Citation: Chem. Sci., 2014,5, 3715-3728
  • Open access: Creative Commons BY-NC license
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    Volcano-shape glycerol oxidation activity of palladium-decorated gold nanoparticles

    Z. Zhao, J. Arentz, L. A. Pretzer, P. Limpornpipat, J. M. Clomburg, R. Gonzalez, N. M. Schweitzer, T. Wu, J. T. Miller and M. S. Wong, Chem. Sci., 2014, 5, 3715
    DOI: 10.1039/C4SC01001A

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