Synergy of Spin States, Active Centers, and H Adsorption Sites on d - p Hybridized Fe–Sn–N ₆ –C Dual-Atom Catalysts for Enhanced Oxygen Reduction Reaction

Synergistic effects inherent to dual-atom catalysts (DACs) constitute a promising strategy for boosting the oxygen reduction reaction (ORR), yet the underlying regulatory mechanism─especially for heteronuclear DACs incorporating d-block and p-block metal centers─remains elusive. Herein, we investigate the ORR mechanism on Fe (d-block)–Sn (p-block)–N 6 –C catalysts via density functional theory (DFT) calculations under the IEFPCM solvation model, focusing on spin-state dependence, active-center specificity, and the pivotal role of H adsorption sites. Our calculations demonstrate that O 2 adsorption at the Sn active center triggers pronounced O–O bond elongation, which substantially reduces the kinetic barrier for direct O–O dissociation; notably, this dissociation barrier is minimized to a mere 0.44 eV in the high-spin state ( S = 2). Additionally, the single Sn active center selectively promotes the 4 electron (4e – ) pathway toward H 2 O, whereas both the 4e – and 2e – electron pathways are accessible at the single Fe active center and Fe,Sn dual active centers. Critically, ORR selectivity is strictly governed by the H adsorption site during H 2 O 2 formation: H binding to the Fe-side N site favors the 2e – pathway yielding H 2 O 2, while H adsorption at the Sn site directs the reaction toward the 4e – pathway producing H 2 O. More remarkably, we construct a set of integrated descriptors derived from spin-regulation parameters, including band gap, spin magnetic moment, interfacial charge transfer, and metal atomic charge. These innovative descriptors establish robust structure–property correlations, laying a rigorous theoretical framework for the rational design of heteronuclear DACs in electrochemical energy conversion, environmental remediation, and advanced synthetic chemistry.