Issue 39, 2008
From the journal:

Physical Chemistry Chemical Physics

A first-principles investigation of the effect of Ptcluster size on CO and NOoxidation intermediates and energetics†

Ye Xu,a   Rachel B. Getman,b   William A. Sheltonc  and  William F. Schneider*bd  

* Corresponding authors

a Center for Nanophase Materials Sciences and Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge

b Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame

c Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge

d Department of Chemistry and Biochemistry, 182 Fitzpatrick Hall,, University of Notre Dame, Notre Dame
E-mail: wschneider@nd.edu

Abstract

As catalysis research strives toward designing structurally and functionally well-defined catalytic centers containing as few active metal atoms as possible, the importance of understanding the reactivity of small metal clusters, and in particular of systematic comparisons of reaction types and cluster sizes, has grown concomitantly. Here we report density functional theory calculations (GGA-PW91) that probe the relationship between particle size, intermediate structures, and energetics of CO and NO oxidation by molecular and atomic oxygen on Ptx clusters (x = 1–5 and 10). The preferred structures, charge distributions, vibrational spectra, and energetics are systematically examined for oxygen (O2, 2O, and O), CO, CO2, NO, and NO2, for CO/NO co-adsorbed with O2, 2O, and O, and for CO2/NO2 co-adsorbed with O. The binding energies of oxygen, CO, NO, and of the oxidation products CO2 and NO2 are all markedly enhanced on Ptx compared to Pt(111), and they trend toward the Pt(111) levels as cluster size increases. Because of the strong interaction of both the reactants and products with the Ptx clusters, deep energy sinks develop on the potential energy surfaces of the respective oxidation processes, indicating worse reaction energetics than on Pt(111). Thus the smallest Pt clusters are less effective for catalyzing CO and NO oxidation in their original state than bulk Pt. Our results further suggests that oxidation by molecular O2 is thermodynamically more favourable than by atomic O on Ptx. Conditions and applications in which the Ptx clusters may be effective catalysts are discussed.

Graphical abstract: A first-principles investigation of the effect of Pt cluster size on CO and NO oxidation intermediates and energetics

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Article information

DOI
https://doi.org/10.1039/B805179H
Article type
Paper
Submitted
28 Mar 2008
Accepted
20 Jun 2008
First published
11 Aug 2008

Phys. Chem. Chem. Phys., 2008,10, 6009-6018

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A first-principles investigation of the effect of Pt cluster size on CO and NO oxidation intermediates and energetics

Y. Xu, R. B. Getman, W. A. Shelton and W. F. Schneider, Phys. Chem. Chem. Phys., 2008, 10, 6009 DOI: 10.1039/B805179H

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