Abstract
The Pd 70 Ag 30 alloy nanoparticles were heated in air at 250-450 °C. During heating, segregation of Ag to the surface driven by its lower surface energy competes with the oxidation of Pd. At 250 °C, selective oxidation of Pd occurred preferentially, and the formation of large free Ag crystallites was observed. As temperature increased, oxidation of Pd became more intensive and dominating, which attracted more Pd to the surface for reaction, resulting in fewer and smaller free Ag particles on the surface. © 2005 Elsevier B.V. All rights reserved.