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

The introduction of axial-coordinated heteroatoms in Fe & horbar;N & horbar;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 & horbar;Fe & horbar;N & horbar;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 & horbar;Fe & horbar;N & horbar;C. As a result, the O & horbar;Fe & horbar;N & horbar;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 & horbar;Fe & horbar;N & horbar;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. A general gas phase surface treatment method is proposed for the preparation of X & horbar;Fe & horbar;N & horbar;C single-atom catalysts with axial-coordinated X heteroatoms on graphitic-N-rich carbon supports. This work reveals the construction of a charge transfer channel between single-atom Fe sites and the doped carbon supports in O & horbar;Fe & horbar;N & horbar;C for boosting oxygen reduction. image