It is demonstrated that physisorption of CO molecules on a MgO (100) surface, supporting epitaxially grown Pd particles, acts as a precursor state for CO chemisorption on the particles. The adsorption rate of CO on the Pd particles is measured, at zero coverage by a molecular beam technique, as a function of the substrate temperature and for different particle sizes. A kinetic model describing the adsorption, desorption, diffusion, and capture by the clusters of CO molecules is given. Comparison with the experimental data gives the adsorption probability: 0.5±0.05 and the saddle energy for surface diffusion: 0.25±0.05 eV of CO molecules on MgO.

No abstract

No abstract

No abstract

Homogeneous collections of Pd-Ni core-shell nanoparticles have been prepared by decomposition of metal-organic compounds and studied by several electron microscopy techniques: transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), energy-filtered microscopy (EFTEM), and by X-ray photoelectron spectroscopy (XPS). The physical and chemical properties of the Pd shell are supposed to depend on its electronic properties, which are influenced by the presence of the Ni core and by the deformation in the Pd lattice. Here, the interfacial structure of Pd/Ni and the lattice deformations in the core and the shell are studied in detail. The catalytic properties of the pure metal and the bimetallic particles, toward CO oxidation, have been investigated.