d-s/p orbital hybridization-driven synergy in heteronuclear dual-atom catalysts on CN/C2N for high-efficiency lithium-sulfur batteries

Graphene-like CN and C₂N, characterized by their high pyridinic nitrogen content and two-dimensional porous structure, serve as ideal substrates for dual-atom catalysts (DACs). In this study, homonuclear and heteronuclear DACs (M₁M₂@CN/C₂N, M = Mg/Co/Sn) were constructed by synergistically combining main-group metals (Mg/Sn) with the transition metal Co. The potential of these materials as sulfur hosts was systematically evaluated using density functional theory (DFT) calculations. The results indicate that the coupling of different molecular orbitals between metal atoms in heteronuclear DACs can modulate spin states, resulting in superior anchoring and catalytic performance for polysulfides compared with homonuclear systems. Specifically, the Co sites in MgCo@CN/C₂N and CoSn@CN/C₂N exhibited significantly enhanced sulfur reduction reaction (SRR) activity due to the d-s and d-p orbital hybridization effects of the adjacent Mg/Sn atoms. Notably, the Gibbs free energy for the SRR in CoSn@CN is as low as 0.31 eV, while MgCo@C₂N requires only 0.21 eV, with Li₂S dissociation barriers of 0.39 eV and 1.10 eV for the two structures, respectively. This theoretical research provides further insights into the design of high-performance lithium battery catalysts and carbon-based DACs composites.