Pt-transition metal alloy catalysts with an active Pt surface have exceptional properties for use in oxygen electro-reduction reactions in fuel cells. Herein, we report the simple synthesis of dealloyed PtCu catalysts and their catalytic performance in oxygen reduction. The dealloyed PtCu catalysts consisted of a Pt-enriched shell with a Pt-Cu alloy core and were synthesized through a chemical co-reduction process followed by thermal annealing and chemical dealloying. During synthesis, thermal annealing leads to a high degree of formation of PtCu alloy particles (e.g., PtCu or PtCu3), and chemical dealloying causes selective dissolution of unstable Cu species from the surface layers of the PtCu alloy particles, resulting in a PtCu alloy@Pt-enriched surface core-shell configuration. Our PtCu3/C catalyst exhibits a great improvement in the oxygen reduction reaction with a mass activity of 0.501 A/mg(Pt), which is 2.24 times greater than that of a commercial Pt catalyst. In this article, the synthesis details, characteristics and performance improvements in ORR of chemically dealloyed PtCu catalysts are systemically explained. (C) 2015 Elsevier B.V. All rights reserved.