Nanofibers comprising reduced graphene oxide (rGO) and Mo2C/Mo2N nanoparticles (Mo2C/Mo2N rGO NFs) were prepared for a functional interlayer of Li-S batteries (LSBs). The well-dispersed Mo2C and Mo2N nanoparticles in the nanofiber structure served as active polar sites for efficient immobilization of dissolved lithium polysulfide. The rGO nanosheets in the structure also provide conductive channels for fast ion/electron transport during charging-discharging and ensured reuse of lithium polysulfide during redox reactions through a fast charge transfer process. As a result, the cell assembled with Mo2C/Mo2N rGO NFs-coated separator and pure sulfur electrode (70 wt% of sulfur content and 2.1 mg cm–2 of sulfur loading) showed a stable discharge capacity of 476 mA h g-1 after 400 charge-discharge cycles at 0.1 C. Furthermore, it exhibited a discharge capacity of 574 mA h g-1 even at a high current density of 1.0 C. Therefore, we believe that the proposed unique nanostructure synthesis strategy could provide new insights into the development of sustainable and highly conductive polar materials as functional interlayers for high performance LSBs.