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 Na 2 S 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., Fe 2, Co 2, and FeCo pairs supported on boron-doped graphene (B 5 G), nitrogenated holey graphene (C 2 N), graphdiyne, and MoS 2, are systematically evaluated with respect to Na 2 S oxidation kinetics, sulfur species adsorption, sulfur reduction reaction (SRR), and structural stability. Our results demonstrate that Co 2 @B 5 G and Fe 2 @C 2 N exhibit the lowest Na 2 S 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 Δ G (∼0.87 eV) for the rate determining step (Na 2 S 8 → Na 2 S 6 ) on Fe 2 @C 2 N than that in vacuum (1.44 eV), suggesting the enhanced feasibility of SRR on it during the discharge process. Furthermore, Fe 2 @C 2 N 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.