Coordination Engineering Induced d-Band Center Shift on Single-Atom Fe Electrocatalysts for Enhanced Oxygen Reduction.

Part of the performance of single-atom catalysts (SACs) is greatly influenced by the microenvironment around a single metal site, of which the oxygen reduction reaction (ORR) is counted as one of them. However, an in-depth understanding of the catalytic activity regulation by the coordination environment is still lacking. In this study, a single Fe active center with axial fifth hydroxyl (OH) and asymmetric N,S coordination embedded in a hierarchically porous carbon material (Fe-SNC) are prepared. Compared to Pt/C and most of the reported SACs, as-prepared Fe-SNC has certain advantages in terms of ORR activity and maintains sufficient stability. Furthermore, the assembled rechargeable Zn-air battery exhibits impressive performance. The combination of multiple findings revealed that the introduction of S atoms not only facilitates the formation of porous structures but also facilitates the desorption and adsorption of oxygen intermediates. On the other hand, with the introduction of axial OH groups, the bonding strength of the ORR intermediate is reduced, and even the central position of the Fe d-band is optimized. The developed catalyst is expected to lead to further research on the multiscale design of the electrocatalyst microenvironment.