Investigation of sulfur poisoning of CNx oxygen reduction catalysts for PEM fuel cells

► The role of Fe used to catalyze N-containing carbon nanostructures was examined. ► H2S poisoning was used as a probe for active sites in CNx and Pt ORR catalysts. ► Pt catalyst showed significant activity loss following H2S treatment. ► CNx prepared with Fe as a growth catalyst showed no activity loss toward ORR. ► If Fe were the active site, there should be a significant activity loss with H2S.