P-band center modulated and heterostructure stabilized 1T-MoS2 as bidirectional electrocatalyst for Lithium-Sulfur batteries

Lithium-sulfur batteries (LSBs) are considered as the most potential next-generation rechargeable energy storage devices due to their high theoretical energy density. However, the commercialization is severely hampered by the shuttle effect and sluggish sulfur redox kinetics of sulfur cathodes. Herein, we propose MoS2/C3N4 heterostructures as potential cathodes for LSBs. Based on the density functional theory (DFT), the "anchor-catalytic-diffusion" performance of 1T-phase and 2H-phase MoS2 monolayers as well as 1T-MoS2/C3N4 and 2H-MoS2/C3N4 heterostructures are systematically analyzed and compared. The results show that 1T-MoS2/C3N4 heterostructure exhibits stronger adsorption for lithium polysulfides (LiPSs), lower Gibbs free energy change of the rate-determining step and Li2S decomposition energy barrier, as well as faster Li-ion diffusion, which will significantly accelerate the sulfur reduction/oxidation reactions (SRR/SOR) kinetics during charge and discharge processes. The in-depth mechanism indicates the synergistic effect of phase engineering and built-in electric field (BIEF) effectively tune the p-band centers and local electrochemical reactivity of the basal S sites of 1T-MoS2/ C3N4 heterostructure, endowing it with excellent bidirectionally catalyze activity. This work provides valuable theoretical insights for the further development of catalytic cathodes of LSBs.