Stability of Pt10Sn3 Clusters Supported on γ−Al2O3 in Oxidizing Environment : a DFT Comparison of Alloying and Size Effects

International audienceThe understanding of the structure and properties of γ−Al 2 O 3 supported platinum-tin catalysts in oxidizing conditions is of prominent importance for many catalytic reactions. By using density functional theory calculations and ab initio molecular dynamics simulations, we identify the adsorption sites of oxygen atoms on a Pt 10 Sn 3 /γ−Al 2 O 3 (100) cluster model and analyze its reconstruction and electronic charge redistribution. A strengthening of O adsorption is found for the cluster with respect to the Pt 3 Sn(111) surface, due to the key role of Al-Pt interfacial sites at low coverage, the ductility and the metastability of the cluster. Moreover, the ab initio ( [[EQUATION]] , T) thermodynamic phase diagrams show only minor differences between the supported Pt 10 Sn 3 and Pt 13 clusters. Both clusters are much more oxidized than their homologous Pt and Pt 3 Sn(111) surfaces, and their oxygen contents may exceed 1 ML. This suggests a stronger size effect than an alloying effect for the oxidation of the metallic nanoparticles at small size