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Issue 37, 2011
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Adsorption energetics of CO on supported Pd nanoparticles as a function of particle size by single crystal microcalorimetry

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Abstract

The heat of adsorption and sticking probability of CO on well-defined Pd nanoparticles were measured as a function of particle size using single crystal adsorption microcalorimetry. Pd particles of different average sizes ranging from 120 to 4900 atoms per particle (or from 1.8 to 8 nm) and Pd(111) were used that were supported on a model in situ grown Fe3O4/Pt(111) oxide film. To precisely quantify the adsorption energies, the reflectivities of the investigated model surfaces were measured as a function of the thickness of the Fe3O4 oxide layer and the amount of deposited Pd. A substantial decrease of the binding energy of CO was found with decreasing particle size. Initial heat of adsorption obtained on the virtually adsorbate-free surface was observed to be reduced by about 20–40 kJ mol−1 on the smallest 1.8 nm sized Pd particles as compared to the larger Pd clusters and the extended Pd(111) single crystal surface. This effect is discussed in terms of the size-dependent properties of the Pd nanoparticles. The CO adsorption kinetics indicates a strong enhancement of the adsorbate flux onto the metal particles due to a capture zone effect, which involves trapping of adsorbates on the support and diffusion to metal clusters. The CO adsorption rate was found to be enhanced by a factor of ∼8 for the smallest 1.8 nm sized particles and by ∼1.4 for the particles of 7–8 nm size.

Graphical abstract: Adsorption energetics of CO on supported Pd nanoparticles as a function of particle size by single crystal microcalorimetry

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Article information


Submitted
24 May 2011
Accepted
05 Aug 2011
First published
22 Aug 2011

Phys. Chem. Chem. Phys., 2011,13, 16800-16810
Article type
Paper

Adsorption energetics of CO on supported Pd nanoparticles as a function of particle size by single crystal microcalorimetry

J. M. Flores-Camacho, J.-H. Fischer-Wolfarth, M. Peter, C. T. Campbell, S. Schauermann and H.-J. Freund, Phys. Chem. Chem. Phys., 2011, 13, 16800
DOI: 10.1039/C1CP21677E

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