A bi-functional metal-free catalyst composed of dual-doped graphene and mesoporous carbon for rechargeable lithium–oxygen batteries

Abstract

Mesoporous carbon on nitrogen and sulfur co-doped graphene nanosheets (NSGC) was synthesized and its bi-functional catalytic activity toward oxygen reduction reaction and oxygen evolution reaction was investigated. The NSGC material showed high bi-functional catalytic activity due to the synergistic effect of co-doping of sulfur and nitrogen, as well as the presence of a hierarchical porous structure. The enhanced bi-functional catalytic activity of NSGC facilitated the efficient formation and decomposition of Li₂O₂ on the air cathode. The lithium–oxygen cell assembled with the NSGC-based air cathode delivered a high initial discharge capacity of 11 431 mA h g⁻¹ and exhibited good cycling stability. The hybrid structure consisting of mesoporous carbon with co-doped graphene nanosheets can be an effective strategy to improve the round-trip efficiency and cycle life of lithium–oxygen batteries.