We doped Vulcan XC-72 (VXC-72) with nitrogen by heating it under flowing NH3 gas in various conditions and investigated its oxygen reduction reaction (ORR) activity in 0.1 M H2SO4. The cyclic voltammograms, X-ray photoelectron spectra, and Brunauer-Emmett-Teller analyses indicated that the heating temperature greatly influenced ORR activity, nitrogen content, and surface area of VXC-72. Furthermore, the heating time also influenced the ORR activity. Therefore, the rate of cooling as well as that of heating at above 773 K was found to be fixed to evaluate ORR activity. Under controlled heating/cooling conditions, the maximum onset potential for ORR was 0.70 V vs normal hydrogen electrode when VXC-72 was heated at 1223 K for 24 h under NH3 gas (200 mL min(-1)). (c) 2010 The Electrochemical Society. [DOI: 10.1149/1.3489365] All rights reserved.