Synergistic orbital coupling and descriptor-driven engineering of dual-atom catalysts on N-doped graphene for high-performance Li-S batteries: A first-principle perspective

Lithium‑sulfur (Li-S) batteries are regarded as promising next-generation energy storage systems due to their high theoretical specific energy and economic feasibility. Nevertheless, critical challenges such as the lithium polysulfide shuttle effect and sluggish redox kinetics continue to impede their practical implementation. To overcome these limitations, designing highly active and stable catalysts is crucial. Graphene with abundant pyridinic nitrogen sites and a two-dimensional porous framework provides an excellent substrate for supporting dual-atom catalysts (DACs). Herein, we designed 15 nitrogen-doped graphene-supported DACs, denoted as M₁M₂@N₆-G (M₁, M₂ = V, Fe, Cu, Zr, Nb, Pt). The potential of these materials as sulfur hosts was systematically investigated through density functional theory (DFT) calculations. The findings reveal that the coupling of distinct molecular orbitals between metal atoms in heteronuclear DACs effectively tunes the spin states, thereby enhancing polysulfide anchoring and catalytic activity beyond that of homonuclear and single atom counterparts. The results indicate that CuFe@N₆-G demonstrates superior catalytic performance, arising from its low Gibbs free energy (0.65 eV) in the rate-determining step of the discharge process and its reduced Li₂S decomposition energy barrier (0.97 eV) during charging. Specifically, the integrated crystal orbital Hamilton population (ICOHP) serves as an effective electronic descriptor, particularly in relation to the dissociation energy barrier of Li₂S during the charging process. This theoretical study offers actionable insights for developing advanced energy storage systems.