Diatomic Iron with\na Pseudo-Phthalocyanine Coordination\nEnvironment for Highly Efficient Oxygen Reduction over 150,000 Cycles

Abstract

Atomically dispersed Fe–N–C catalysts emerged\nas\npromising alternatives to commercial Pt/C for the oxygen reduction\nreaction. However, the majority of Fe–N–C catalysts\nshowed unsatisfactory activity and durability due to their inferior\nO–O bond-breaking capability and rapid Fe demetallization.\nHerein, we create a pseudo-phthalocyanine environment coordinated\ndiatomic iron (Fe₂-pPc) catalyst by grafting the core domain\nof iron phthalocyanine (Fe–N_α–C_α–N_β) onto defective carbon. <i>In situ</i> characterizations and theoretical calculation confirm\nthat Fe₂-pPc follows the fast-kinetic dissociative pathway,\nwhereby Fe₂-pPc triggers bridge-mode oxygen adsorption\nand catalyzes direct O–O radical cleavage. Compared to traditional\nFe–N–C and FePc-based catalysts exhibiting superoxo-like\noxygen adsorption and an *OOH-involved pathway, Fe₂-pPc\ndelivers a superior half-wave potential of 0.92 V. Furthermore, the\nultrastrong N_α–C_α bonds in\nthe pPc environment endow the diatomic iron active center with high\ntolerance for reaction-induced geometric stress, leading to significantly\npromoted resistance to demetallization. Upon an unprecedented harsh\naccelerated degradation test of 150,000 cycles, Fe₂-pPc\nexperiences negligible Fe loss and an extremely small activity decay\nof 17 mV, being the most robust candidate among previously reported\nFe–N–C catalysts. Zinc–air batteries employing\nFe₂-pPc exhibit a power density of 255 mW cm^–2 and excellent operation stability beyond 440 h. This work brings\nnew insights into the design of atomically precise metallic catalysts.