Using density functional theory (DFT) calculations, we rationally designed metallic nanocatalysts with ternary transition metals for oxygen reduction reactions (ORRs) in fuel cell applications. We surrounded binary core—shell nanoparticles with a Pt skin layer. To overcome surface segregation of the core 3-d transition metal, we identified the binary alloy Cu_0.76Ni_0.24 as having strongly attractive atomic interactions by computationally screening 158 different alloy configurations using energy convex hull theory. The Pt_skinCu_0.76Ni_0.24 nanoparticle showed better electrochemical stability than pure Pt nanoparticles ~3 nm in size. We propose that the underlying mechanism originates from favorable compressive strain on Pt for ORR catalysis and atomic interactions among the nanoparticle shells for electrochemical stability. Our results will contribute to accurate identification and innovative design of promising nanomaterials for renewable energy systems.