Asymmetric Zn–Sn Dual-Atom Sites with Sulfur Doping for Efficient Oxygen Reduction Reaction: Insights from First-Principles Calculations

The interaction of p–d orbitals among multiheteroatomic coordination sites plays a decisive role in governing the catalytic activity toward the oxygen reduction reaction (ORR). In this work, a heteroatom-coordination strategy is proposed to construct asymmetric Zn–Sn dual-atom sites (ZnSnS-NC) embedded within a N,S-codoped carbon matrix. In this structure, the p-block element Sn partially coordinated with N and S atoms couples synergistically with the d-block element Zn, forming an asymmetric Zn–S–Sn–N coordination environment that enables efficient p–d orbital hybridization. Benefiting from this electronic synergy, ZnSnS-NC exhibits outstanding ORR catalytic performance with a theoretical overpotential of 0.51 V, significantly outperforming the single-atom counterparts Sn-NC (0.83 V) and SnS-NC (0.62 V). Projected density of states (PDOS) and charge density difference analyses reveal that the cooperative coupling between Zn-3d and Sn-5p orbitals effectively promotes O 2 activation and achieves a balanced OH adsorption and desorption by optimizing adsorption strength. This theoretical study provides fundamental insights into the regulation mechanism of asymmetric p–d orbital interactions on ORR kinetics and offers valuable theoretical guidance for the rational design of multiheteroatomic synergistic electrocatalysts.