The impact of thiophene, a carbon growth promoter, was investigated when added to acetonitrile during pyrolysis over 2 wt%Fe/MgO to form nitrogen-containing carbon nanostructured (CNx) oxygen reduction reaction (ORR) catalysts. ORR activity and selectivity were studied using rotating ring disk electrode (RRDE) electrochemical testing. Catalysts were characterized using XPS, TEM, hydrophobicity testing and BET surface area. It was found that thiophene did increase CNx yield, but did not affect the ORR activity of the resulting catalysts. Characterization results revealed that sulfur was incorporated into the CNx catalyst. Viability of catalysts for use in a PEM or direct methanol fuel cell environment was further investigated using temperature programmed oxidation and desorption (TPO, TPD) techniques to determine the stability of sulfur in CNx catalyst. Post-synthesis treatment to prevent sulfur desorption during long-term use in a fuel cell was found to be feasible. (c) 2010 Elsevier B.V. All rights reserved.