High-Performance Double-Atom Catalysts with Accelerated Na ₂ S Oxidation and Sulfur Reduction for Improved Cathode Performance in Na−S Batteries

Designing materials with tunable electronic structure to optimize Na polysulfide adsorption, suppress shuttle effects, enhance sulfur redox kinetics, and lower Na2S oxidation barriers is at the forefront of advancing the sodium−sulfur (Na−S) battery technology. Herein, we report a comprehensive first-principles investigation on double-atom catalysts (DACs) anchored on two-dimensional substrates as efficient sulfur redox electrocatalysts for Na−S batteries. Twelve DAC systems, i.e., Fe2, Co2, and FeCo pairs supported on boron-doped graphene (B5G), nitrogenated holey graphene (C2N), graphdiyne, and MoS2, are systematically evaluated with respect to Na2S oxidation kinetics, sulfur species adsorption, sulfur reduction reaction (SRR), and structural stability. Our results demonstrate that Co2@B5G and Fe2@C2N exhibit the lowest Na2S oxidation barriers of 0.14 and 0.74 eV respectively; outperforming all reported single- and double-atom catalysts. More importantly, the simulated free energy profiles for the SRR on these catalysts reveal a significantly low ΔG (∼0.87 eV) for the rate determining step (Na2S8 → Na2S6) on Fe2@C2N than that in vacuum (1.44 eV), suggesting the enhanced feasibility of SRR on it during the discharge process. Furthermore, Fe2@C2N demonstrates excellent thermal stability and electronic properties, suggesting its promise for further investigation in experimental Na−S battery applications. Given very few reports on the application of DACs for Na−S batteries, this study provides valuable insights into DAC design and is expected to stimulate further research in this direction.