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 |
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Hauptverfasser: | , , , , , , , , , |
Format: | Artikel |
Sprache: | eng |
Schlagworte: | |
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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 |
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ISSN: | 1011-372X 1572-879X |
DOI: | 10.1007/s10562-011-0565-7 |