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 O₂ 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.