Constructing dual-atom catalysts by replacing N atoms with heteronuclear transition metals as efficient sulfur host materials for lithium-sulfur batteries: A first-principles study

Dual-atom catalysts (DACs) have shown remarkable electrochemical performance as cathode materials in lithium-sulfur batteries (LSBs), and carbon-nitrogen compounds are highly effective support materials for these catalysts. In previous studies, catalytic atoms were often introduced into the cavities of carbon-nitrogen compounds, but this structure generally lacked stability. This work employs first-principles calculations to investigate the application potential of DACs (TM-TM@g-C3N4) supported on monolayer g-C3N4 through atomic substitution in LSBs. Molecular dynamics simulations and electronic structure analyses indicate that TM-TM@g-C3N4 structures possess good structural stability and exhibit enhanced conductivity. Adsorption studies reveal that, due to the d-electron configuration of heteronuclear dual atoms, the constructed DACs display excellent anchoring performance for LiPSs (with adsorption energies ranging from -1.02 to -5.67 eV). Notably, the strong hybridization of Mn and Co d-orbitals in Mn-Co@g-C3N4 at the Fermi level enhances its catalytic performance in the sulfur reduction reaction kinetics, particularly crossing the Fermi level. The reduction of Li2S2 to Li2S, the rate-limiting step, shows a low free energy barrier (-0.09 eV). Additionally, weakened Li-S bonds facilitate the decomposition of Li2S on Mn-Co@g-C3N4 (0.77 eV). With its suitable adsorption energy and superior catalytic activity in both directions, Mn-Co@g-C3N4 emerges as an optimal support material with strong application potential. This work paves the way for developing high-activity host materials for LiPSs and provides valuable insights for designing homonuclear and heteronuclear DACs in LSBs.