Diatomic Iron with a Pseudo-Phthalocyanine Coordination Environment for Highly Efficient Oxygen Reduction over 150,000 Cycles
Zechuan Huang, M. Li, Xinyi Yang, Tao Zhang, Xin Wang, Wanqing Song, Jinfeng Zhang, Haozhi Wang, Yanan Chen, Jia Ding, Wenbin Hu
Abstract
Atomically dispersed Fe–N–C catalysts emerged as promising alternatives to commercial Pt/C for the oxygen reduction reaction. However, the majority of Fe–N–C catalysts showed unsatisfactory activity and durability due to their inferior O–O bond-breaking capability and rapid Fe demetallization. Herein, we create a pseudo-phthalocyanine environment coordinated diatomic iron (Fe 2 -pPc) catalyst by grafting the core domain of iron phthalocyanine (Fe–N α –C α –N β ) onto defective carbon. In situ characterizations and theoretical calculation confirm that Fe 2 -pPc follows the fast-kinetic dissociative pathway, whereby Fe 2 -pPc triggers bridge-mode oxygen adsorption and catalyzes direct O–O radical cleavage. Compared to traditional Fe–N–C and FePc-based catalysts exhibiting superoxo-like oxygen adsorption and an *OOH-involved pathway, Fe 2 -pPc delivers a superior half-wave potential of 0.92 V. Furthermore, the ultrastrong N α –C α bonds in the pPc environment endow the diatomic iron active center with high tolerance for reaction-induced geometric stress, leading to significantly promoted resistance to demetallization. Upon an unprecedented harsh accelerated degradation test of 150,000 cycles, Fe 2 -pPc experiences negligible Fe loss and an extremely small activity decay of 17 mV, being the most robust candidate among previously reported Fe–N–C catalysts. Zinc–air batteries employing Fe 2 -pPc exhibit a power density of 255 mW cm –2 and excellent operation stability beyond 440 h. This work brings new insights into the design of atomically precise metallic catalysts.