Structural and electronic properties of PtPd and PtNi nanoalloys
Instituto de Física, Universidad Nacional Autónoma de México, Apartado Postal 20-364, 01000 Mexico D. F., Mexico
Corresponding author: a firstname.lastname@example.org
Published online: 18 February 2009
The lowest-energy structures of binary (PtPd)n, (PtNi)m, (PtNi3)s, and (Pt3Ni)s nanoclusters, with n=2–28, m=2–20, and s=4–6, modeled by the many-body Gupta potential, were obtained by using a genetic-symbiotic algorithm. These structures were further relaxed within the density functional theory framework in order to obtain the most stable structures for each composition. Segregation is confirmed in all the (PtPd)n clusters, where the Pt atoms occupy the cluster core and the Pd atoms are situated on the cluster surface. In contrast, for the (PtNi)m nanoalloys, the Ni atoms are mainly found in the cluster core and the Pt atoms are segregated to the cluster surface. Likewise, for the (PtNi3)s nanoalloys, Ni atoms mainly compose the cluster core but there is no clear segregation of the Pt atoms to the surface. Furthermore, for the (Pt3Ni)s bimetallic clusters the Pt atoms concentrate in the cluster core and the Ni atoms are segregated to the surface. On the other hand, it has been experimentally found that the Pt0.75Ni0.25 supported nanoparticles present a higher catalytic activity for the selective oxidation of CO in the presence of hydrogen than the Pt0.5Ni0.5 and Pt0.25Ni0.75 nanoparticles. In order to understand this tendency in the catalytic activity, we also performed density functional calculations of the molecular CO adsorption on bimetallic Pt-Ni nanoclusters with the mentioned compositions.
PACS: 36.40.-c – Atomic and molecular clusters / 36.40.Jn – Reactivity of clusters / 68.43.Bc – Ab initio calculations of adsorbate structure and reactions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2009