Transition metals have attracted particular research interest for sustainable ORR electrocatalysis but zero-valent ones have been often ignored. In this work metallic cobalt nanoparticle decorated graphene aerogel (CoNPs/rGO aerogel) was synthesized via a facile hydrothermal reaction, followed by thermal annealing in reducing H-2 atmosphere. As prepared CoNPs/rGO aerogel demonstrates commercial Pt/C-comparable ORR activity through a predominant four-electron pathway, as well as excellent durability and methanol tolerance superior to Pt/C in alkaline medium. This work suggests that metallic cobalt nanoparticle is highly efficient to boost the ORR activity of neighboring carbon besides various cobalt compounds. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.