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-N x 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-N 4 sites in an Fe/N/C catalyst. One-step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe-N 4 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-N 4 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-N 4 sites is controlled by precise tuning of the chemical structure of the iron complex precursor.