Defect-Triggered Orbital Hybridization in FeMn Dual-Atom Catalysts Toward Sabatier-Optimized Oxygen Reduction

Dual single-atom catalysts (DSAs), leveraging synergistic dual-site interactions, represent a promising frontier in electrocatalysis. However, the precise synthesis of dual-atom pairs and fine-tuning of their electronic structures remain significant challenges. Herein, we construct a defect-engineered heteronuclear FeMn-DSA anchored on a porous nitrogen-doped carbon matrix (FeMn_{D SA}/dNC) through a customized trinuclear-defect trapping strategy. This defect modulation strategy effectively stabilizes dual atomic pairs while optimizing electronic structures to approach Sabatier's optimality, significantly boosting oxygen reduction reaction (ORR) performance. The FeMn_{D SA}/dNC achieves a high half-wave potential of 0.921 V in alkaline media, with assembled zinc-air batteries demonstrating 291 mW cm^-2 peak power density and stable charge/discharge cycling for over 500 h. Theoretical calculations reveal that defect-mediated coordination adjacent to Fe-Mn diatomic centers triggers charge redistribution, suppressing antibonding orbital populations while strengthening Fe 3d_z ² with O 2p orbital hybridization. This modulation weakens O─O bonding through optimized ^*OOH adsorption configurations, thereby enhancing ORR kinetics. The present work provides valuable insights into the precise modulation and the underlying mechanisms of DSAs, advancing the design of electrocatalysts for energy storage and conversion applications.