Engineering axial Cl-coordinated asymmetric Fe-Sb dual-atom sites for high-performance oxygen reduction and Zn-air batteries

Iron-based single-atom catalysts are promising alternatives to platinum for the oxygen reduction reaction (ORR), but their performance is limited by the symmetrical electronic configuration of conventional Fe-N 4 sites. To overcome this constraint, we rationally designed a novel Cl-Fe/Sb-NC catalyst featuring an asymmetric Fe-Sb diatomic architecture with axial chlorine coordination. This unique active site endows the catalyst with enhanced ORR performance, achieving half-wave potentials of 0.932 V in alkaline medium and 0.808 V in acidic medium, along with remarkable stability in both environments. The superior catalytic activity translates directly into a high-performance Zn-air battery, delivering higher power density and cycling stability than Pt/C-based counterparts. Density functional theory calculations reveal that the synergistic effect of the asymmetric Fe-Sb site and axial Cl ligand optimizes the electronic structure of the Fe center through charge redistribution and d -band center modulation, facilitating more efficient adsorption and desorption of oxygenated intermediates and thereby enhancing catalytic performance. This work provides insights for the development of active and stable iron-based atomic-scale catalysts.