One‐Step Preparation of Fe/N/C Single‐Atom Catalysts Containing Fe−N4 Sites from an Iron Complex Precursor with 5,6,7,8‐Tetraphenyl‐1,12‐Diazatriphenylene Ligands.

Fe/N/C single‐atom catalysts containing Fe−Nx sites prepared by pyrolysis are promising cathode materials for fuel cells and metal‐air batteries due to their high oxygen reduction reaction (ORR) activities. We have developed iron complexes containing N2‐ or N3‐chelating coordination structures with preorganized aromatic rings in a 1,12‐diazatriphenylene framework tethering bromo substituents as precursors to precisely construct Fe−N4 sites in an Fe/N/C catalyst. One‐step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe−N4 sites without iron aggregates. X‐ray absorption spectroscopy (XAS) and electrochemical measurements revealed that the iron complex with N3‐coordination is more effectively converted to Fe−N4 sites catalyzing ORR with a TOF value of 0.21 e site−1 s−1 at 0.8 V vs. RHE. This indicates that the formation of Fe−N4 sites is controlled by precise tuning of the chemical structure of the iron complex precursor. [ABSTRACT FROM AUTHOR]