fig5

Figure 5. Insights into the sulfur cathode and anchoring role of V₂AB₄: (A) Adsorption energies of Na₂S_n clusters (n = 1, 2, 4, 6, and 8) and S₈; with the color scale representing the adsorption-energy values; (B) corresponding charge transfer to V₂MoS₄, V₂MoSe₄, V₂WS₄, and V₂WSe₄ hosts; with the color scale representing the transferred charge; (C) charge-density difference of intermediate-chain Na₂S₄ and long-chain Na₂S₆ polysulfides with all four topological materials. Yellow and cyan isosurfaces denote electron gain and electron loss, respectively. The atomic spheres represent V (light blue), Mo (dark blue), W (light purple), S (small yellow), Se (green), and Na (large yellow); (D) Decomposition energy barriers of Na₂S adsorbed on the V₂AB₄ monolayers; (E) Schematic illustration of the catalytic mechanism, highlighting strong polysulfide anchoring, accelerated redox conversion, suppressed shuttle effect, and rapid electron transport. In panel (E), purple and golden-yellow spheres represent Na and S, respectively; (F) Gibbs free-energy profiles for the S₈ to Na₂S sulfur reduction reaction on all monolayers.