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We doped Vulcan XC-72 ͑VXC-72͒ with nitrogen by heating it under flowing NH 3 gas in various conditions and investigated its oxygen reduction reaction ͑ORR͒ activity in 0.1 M H 2 SO 4 . 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 NH 3 gas ͑200 mL min −1 ͒.