Surface Composition and Catalytic Evolution of AuxPd1−x (x = 0.25, 0.50 and 0.75) Nanoparticles Under CO/O2 Reaction in Torr Pressure Regime and at 200 °C

Au x Pd 1− x ( x  = 0, 0.25, 0.5, 0.75, 1) nanoparticle (NP) catalysts (8–11 nm) were synthesized by a one-pot reaction strategy using colloidal chemistry. XPS depth profiles with variable X-ray energies and scanning transmission electron microscopy (STEM) analyses show that the as-synthesized Au x...

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Veröffentlicht in:Catalysis letters 2011, Vol.141 (5), p.633-640
Hauptverfasser: Alayoglu, Selim, Tao, Franklin, Altoe, Virginia, Specht, Colin, Zhu, Zhongwei, Aksoy, Funda, Butcher, Derek R., Renzas, Russ J., Liu, Zhi, Somorjai, Gabor A.
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Sprache:eng
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Zusammenfassung:Au x Pd 1− x ( x  = 0, 0.25, 0.5, 0.75, 1) nanoparticle (NP) catalysts (8–11 nm) were synthesized by a one-pot reaction strategy using colloidal chemistry. XPS depth profiles with variable X-ray energies and scanning transmission electron microscopy (STEM) analyses show that the as-synthesized Au x Pd 1− x ( x  = 0.25 and 0.5) bimetallic NPs have gradient alloy structures with Au-rich cores and Pd-rich shells. The evolution of composition and structure in the surface region corresponding to a mean free path of 0.6–0.8 nm (i.e., 2–3 layers to the bulk from the particle surface) was studied with ambient pressure X-ray photoelectron spectroscopy (AP-XPS) under CO/O 2 reaction in the Torr pressure regime. Under the reaction conditions of 80 mTorr CO and 200 mTorr O 2 at 200 °C, the surface region of Au 0.75 Pd 0.25 NP is Au-rich (~70% by Au). All Au x Pd 1− x ( x  = 0.25, 0.5, 0.75) NP catalysts have higher turnover rates for the model CO/O 2 reaction than pure Pd and pure Au NPs. The Pd-rich Au 0.25 Pd 0.75 NPs show the highest turnover rates and the Pd-rich Au 0.5 Pd 0.5 NPs the lowest turnover rates at 200 °C. Interestingly, the Au-rich Au 0.75 Pd 0.25 NPs exhibit steady-state turnover rates which are intermediate to those of the Pd-rich bimetallic nanoparticles. Graphical Abstract
ISSN:1011-372X
1572-879X
DOI:10.1007/s10562-011-0565-7