Precious metals such as platinum are commonly used in polymer-electrolyte membrane fuel cells (PEMFCs) to enhance sluggish oxygen-reduction reactions. However, agglomerations of the nano-sized platinum and corrosions of the carbon supports degrade the performance and durability of the PEMFC during the long-term operation. Here, we present a highly active and durable catalyst for the oxygen-reduction reactions by covering carbon-supported platinum with nitrogen-doped carbons as a protective layer. The PEMFC with the NC-protected Pt/C cathode shows a power density of 1.06 W cm(-2) at 0.6 V in H-2-O-2, comparable with 0.67 W cm(-2) of the PEMFC with a commercial Pt/C cathode. Furthermore, the durability is remarkably enhanced over 50%, compared with the commercial carbon-supported platinum cathode. It suggests that the nitrogen-doped carbons as a protective layer are effective in enhancing the catalytic activity for oxygen-reduction reactions and durability of the PEMFCs. (C) 2016 Elsevier Ltd. All rights reserved.