An oxygen-mediated galvanic battery reaction strategy has been developed to one-step synthesize carbon-supported Co@Pt core-shell nanostructures. Relying on this strategy, a structural evolution of 3-D Pt-on-Co bimetallic nanodendrites into Co@Pt core-shell configuration is readily achieved in our study. These well-supported and low-Pt-content nanostructures show superior electrocatalytic activities to oxygen reduction reaction. Especially, the supported Co@Pt core-shell electrocatalyst for oxygen reduction reaction shows a high activity with the maximal Pt-mass activity of 465 mA mg(-1) Pt at 0.9 V (vs. RHE). The present investigation clearly demonstrates that the design and synthesis of the core-shell nanostructures is a viable route for building Pt-based electrocatalysts with optimized utilization efficiency and higher cost performance. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.