Construction of an Axial Charge Transfer Channel Between Single‐Atom Fe Sites and Nitrogen‐Doped Carbon Supports for Boosting Oxygen Reduction

Abstract

AbstractThe introduction of axial‐coordinated heteroatoms in Fe─N─C single‐atom catalysts enables the significant enhancement of their oxygen reduction reaction (ORR) performance. However, the interaction relationship between the axial‐coordinated heteroatoms and their carbon supports is still unclear. In this work, a gas phase surface treatment method is proposed to prepare a series of X─Fe─N─C (X = O, P, and S) single‐atom catalysts with axial X‐coordination on graphitic‐N‐rich carbon supports. Synchrotron‐based X‐ray absorption near‐edge structure spectra and X‐ray photoelectron spectroscopy indicate the formation of an axial charge transfer channel between the graphitic‐N‐rich carbon supports and single‐atom Fe sites by axial O atoms in O─Fe─N─C. As a result, the O─Fe─N─C exhibits excellent ORR performance with a half‐wave potential of 0.905 V versus RHE and a high specific capacity of 884 mAh g−1 for zinc–air battery, which is superior to other X─Fe─N─C catalysts without axial charge transfer and the commercial Pt/C catalyst. This work not only demonstrates a general synthesis strategy for the preparation of single‐atom catalysts with axial‐coordinated heteroatoms, but also presents insights into the interaction between single‐atom active sites and doped carbon supports.