The adsorption, diffusion and dissociation properties of O-2, as well as adsorption and diffusion properties of O on the Ih Cu@Pt12 core-shell nanoparticle are studied using the ab initio density functional theory (DFT) calculations. It is found that the O-2 can easily dissociate and the O can easily diffuse on the Ih Cu@Pt12 with much lower barriers as compared those on the Pt(1 1 1) surface, which demonstrates the much higher oxygen reduction activity of the Ih Cu@Pt12 core-shell nanoparticles. (C) 2011 Elsevier B. V. All rights reserved.