N-doped graphene-wrapped carbon nanoparticles (NGCNPs) are in situ synthesized by a facile bottom-up method. The heat treatment boosts the conversion of N-containing species from the pyrollic N to graphitic N and pyridinic N, thus improving the electrocatalytic activity towards the oxygen reduction reaction (ORR). The physical characterization including X-ray photoelectron spectroscopy, Raman spectra, specific surface area and charge transfer resistance indicates that 600 degrees C is a pivotal temperature for remarkably improving the electrochemical activity for ORR in terms of onset potential, half-wave potential, electron transfer number and peroxide yields. (C) 2016 Elsevier Ltd. All rights reserved.