In this paper, we demonstrate that oxygen-containing carbon nanoparticles (O-CNPs) obtained from diffusion flame display notable ORR electrocatalytic activities in alkali media. The O-CNPs were the incomplete combustion product of hydrocarbon fuels. Electrochemical results showed that the O-CNP catalyst prepared from n-hexane could display very positive ORR peak potential of -0.24 V vs. Ag/AgCl, which was higher than the reported oxygen-containing carbon materials and common carbon black of below -0.35 V. Moreover, the ORR peak potential was varied with the unsaturation degree of the hydrocarbon fuels. It was further proposed that the remarkable ORR electrocatalyic activities of the O-CNPs was attributed to semiquinone groups bonded to the edge of the graphitic carbon layer. (C) 2014 Elsevier Ltd. All rights reserved.