Axial Chlorine Engineering of p-Block Antimony Atomic Sites Boosts Oxygen Reduction

The main-group metals characterized by closed d shells are generally regarded as catalytically inert for oxygen reduction reactions (ORR) due to the delocalized valence orbitals. Modulating the coordination environment of metal sites is critical to gaining highly active electrocatalysts for ORR. Herein, atomically dispersed Sb site catalysts were successfully constructed with SbN₄-Cl configuration for highly efficient ORR. Density functional theory (DFT) calculations reveal that the introduction of an axial Cl ligand regulates the p electron structure of the Sb active center, thereby alleviating the binding energy of the HO* intermediate and lowering the energy barrier of the ORR process. Remarkably, the as-prepared SbN₄Cl/NC catalysts exhibited excellent ORR activity with a half-wave potential (E_1/2) of 0.921 V and exceptional durability, superior to most 3d transition-metal-based single-atom catalysts and commercial Pt/C. Moreover, Zn-air battery tests also verified the outstanding discharge performance and ultralong charge/discharge durability of SbN₄Cl/NC catalysts, demonstrating significant promise for energy storage and conversion applications.