Atomically Regulated Symmetry-Breaking Sulfur-Bridged Dual Iron Sites Catalyst for High-Performance Oxygen Reduction...

Single-atom catalysts featuring metal-N₄ moieties hold great promise for promoting oxygen reduction reaction (ORR). However, their symmetric active sites often lead to suboptimal electronic structure and intermediate adsorption, thereby limiting intrinsic ORR performance. In this work, we construct a symmetry-breaking dual-atom site catalyst featuring Fe-S-Fe moieties (Fe₂-S@NHCS) through precise modulation of the coordination environment and electronic structure. The interaction between adjacent Fe atoms and the bridging S atom endows the catalyst with a high half-wave potential of 0.912 V and a turnover frequency of 1.45 s^-1 at 0.85 V, significantly surpassing other Fe-based catalysts. There is no significant performance degradation after 20,000 CV cycles or 100,000 s continuous testing. Combined theoretical and in situ spectroscopic analyses reveal that adjacent dual Fe atoms act as the active center to parallel adsorb oxygen molecule. Owing to the relatively low electronegativity of S, electron transfer from Fe to O₂ is enhanced, resulting in stronger covalent bonding and lower adsorption energy. Zinc-air batteries employing Fe₂-S@NHCS as the cathode catalyst demonstrate high power density of 210.66 mW cm^-2 and excellent stability over 900 charge-discharge cycling. This catalyst offers new insights into the design of atomic-scale catalysts and highlights their potential for electrocatalysis applications.