Dual (N, O)-Doped MoS2 as a Cathode Host for Immobilizing Polysulfides and Enhancing Kinetics of Sodium–Sulfur (Na–S) Batteries

Room-temperature Na–S batteries (RT-NSBs) hold great promise for high-energy-density storage, but their practical deployment remains hindered by polysulfide dissolution (i.e., shuttle effect), sluggish sulfur redox reactions (SRR), and limited ionic transport. Rational design of electrocatalysts with a strong adsorption affinity toward polysulfides and high catalytic activity is therefore essential to address these issues. In this work, we employ density functional theory (DFT) to investigate N-, O-, and dual (N, O)-doped MoS₂ as potential electrocatalytic cathode hosts for RT-NSBs. Unlike most previous studies that solely assessed Na₂S_n adsorption in the gas phase, we utilized an implicit solvent model to incorporate intrinsic electrolyte effects on polysulfide stability. We show that this approach yields lower Na₂S_n binding energies on the cathode hosts as compared with the gas-phase approach due to solvent polarity and dielectric screening, indicating the importance of solvation in evaluating polysulfide dissolution. N-, O-, and (N, O)-doped MoS₂ exhibit sufficiently strong Na₂S_n adsorption to mitigate the shuttle effect. Nevertheless, their catalytic behaviors differ considerably. While N- and O-doped MoS₂ (monodoped MoS₂) provide limited SRR enhancement, (N, O)-doped MoS₂ delivers significantly improved catalytic activity. This is attributed to the significant population of antibonding states in the N–Na and O–Na bonds formed at the interface of (N, O)-doped MoS₂ and Na₂S_n, inducing s- and p-band shifting after interacting with Na₂S_n to catalytically activate the conversion of Na₂S_n in the SRR. Kinetic analysis quantitatively shows that (N, O)-MoS₂ markedly lowers the rate-determining barrier of the SRR from 0.93 eV in pristine MoS₂ to 0.57 eV. These results identify (N, O)-doped MoS₂ as a highly effective cathode host for RT-NSBs.