Core-shell bimetallic particles, prepared by sequential impregnations

Bimetallic particles (10-20 nm), with a Cu or Ag core and a Pd shell were elaborated by sequential impregnations on various oxides. Their shapes are limited by (100) and (111) faces which correspond to the planes of lowest surface energy for pure fcc metal particles of the same size. The Pd shells are epitaxially oriented on the core and locally accommodated to the metal lattice. In the case of Pd/Cu particles, annealing at 400 degreesC induces the structural transition to the ordered structure with shapes limited by (111), (001) and (110) faces. The adhesion energy of the annealed particles does not seem to depend on the substrate.