Improved oxygen reduction activity on the Ih Cu@Pt core-shell nanoparticles

► Ih Cu@Pt12 is the most stable among the symmetric Cu@Pt12 core-shell isomers. ► O2 prefers to be adsorbed on the Ih Cu@Pt12 with the t-b-t configuration. ► The Ih Cu@Pt12 has enhanced activity for O2 dissociation and O diffusion. ► Ih Cu@Pt12 nanoparticle is a good candidate for being the ORR catalyst.