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Article

Effect of Particle Size on the Oxidizability of Platinum Clusters

Ye Xu,^† William A. Shelton,^† and William F. Schneider*^‡

Computer Science and Mathematics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, and Department of Chemical and Biomolecular Engineering, and Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, Indiana 46556

J. Phys. Chem. A, 2006, 110 (17), pp 5839–5846

DOI: 10.1021/jp0547111

Publication Date (Web): April 6, 2006

†

Oak Ridge National Laboratory.

To whom correspondence should be addressed. William F. Schneider, 182 Fitzpatrick Hall, University of Notre Dame, Notre Dame, IN 46556. E-mail: wschneider@nd.edu.

‡

University of Notre Dame.

Abstract

The catalytic properties of transition metal particles often depend crucially on their chemical environment, but so far, little is known about how the effects of the environment vary with particle size, especially for clusters consisting of only a few atoms. To gain insight into this topic, we have studied the oxygen affinity of free Pt_x clusters as a function of cluster size (x = 1, 2, 3, 4, 5, and 10) using density functional theory (DFT) calculations (GGA-PW91). DFT-based Nosé−Hoover molecular dynamics has been used to explore the configuration space of the Pt_xO_x and Pt_xO₂_x clusters, leading to the discovery of several novel Pt−oxide structures. The formation of small Pt−oxide clusters by oxidizing the corresponding Pt_x clusters is found to be significantly more exothermic than the formation of bulk Pt−oxides from Pt metal. The exothermicity generally increases as cluster size decreases but exhibits strongly nonlinear dependence on the cluster size. The nanoclusters are also structurally distinct from the bulk oxides and prefer one- and two-dimensional chain and ringlike shapes. These findings help elucidate the oxidation behavior of Pt nanoclusters and lay the foundation for understanding the reactivity of Pt nanoclusters in oxidizing chemical environments.

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