Rational Generation of Fe−Nx Active Sites in Fe−N−C Electrocatalysts Facilitated by Fe−N Coordinated Precursors for the Oxygen Reduction Reaction

Abstract Fe−N−C catalysts synthesized by pyrolysis of Fe and N precursors have been intensively studied due to their remarkable activities for the electrochemical oxygen reduction reaction (ORR). Although Fe−N4 coordinated structures have been suggested as active sites by recent spectroscopic studies, the influence of precursor coordination on the generation of the active sites during high‐temperature pyrolysis is not well understood. In this work, phenanthroline isomers were used as systematic model precursors to reveal the correlation between precursor coordination and active site formation in Fe−N−C catalysts. Coordination between Fe and each phenanthroline isomer was effectively controlled by the molecular structure: monodentate (1,7‐ and 4,7‐phenanthroline) and bidentate coordination (1,10‐phenanthroline). Through X‐ray absorption spectroscopy and X‐ray photoelectron spectroscopy st…