Directional Construction of Low-Coordination Fe–N<sub>3</sub> Coupled with Intrinsic Carbon Defects for High-Efficiency Oxygen Reduction
Xinrui Li, Guanying Ye, Weiwei Zhu, Min Tian, Ruiting Wang, Suqin Liu, Zhen He
Abstract
Regulating the coordination environment of Fe–N x sites is an efficient but challenging approach for promoting the intrinsic catalytic activity of single-atom Fe/N-codoped carbon (Fe–N–C) toward the oxygen reduction reaction (ORR). Herein, low-coordination Fe–N 3 sites coupled with carbon vacancies (Fe–N 3 /C V ) are directionally constructed in Fe–N–C via pyrolysis of a metal–organic framework (MOF) precursor with N 3 –Zn–O–Fe moieties, which are delicately prefabricated by chemically anchoring Fe 3+ onto a H 2 O-etching induced linker-missing Zn–N 3 site in the MOF precursor. The optimized Fe–N–C with the Fe–N 3 /C V sites displays a high ORR half-wave potential of 0.92 V (vs RHE), which is attributed to the optimized electronic structure and binding strengths of the active Fe center toward the ORR intermediates stemming from the synergy of the asymmetric configuration of Fe–N 3 as well as the adjacent carbon vacancies. This work could be enlightening for the design and construction of high-activity coupling sites in metal and nitrogen-codoped carbon catalysts.