Ruthenium nanoparticles mounted on multielement co-doped graphene: an ultra-high-efficiency cathode catalyst for Li–O2 batteries

Abstract

Developing a high-performance Li–O₂ battery demands an air electrode with a high-efficiency bifunctional catalyst. Here we designed a new type of bifunctional cathode catalyst by mounting ruthenium nanoparticles on reduced graphene oxide co-doped with nitrogen, iron, and cobalt. The catalyst exhibited significantly higher ORR and OER activities than a commercial Pt/C catalyst in both aqueous and non-aqueous electrolytes. With this novel catalyst as the cathode, the battery exhibited an ultra-high reversible capacity of 23 905 mA h g⁻¹ at a current density of 200 mA g⁻¹. Furthermore, the battery also exhibited an excellent cycling stability—after 300 cycles of limited capacity, the discharge plateau potential decreased only slightly, and the energy efficiency was still above 60%. The battery also demonstrated good rate performance; with discharge current densities of up to 1000 and 2000 mA g⁻¹, the capacities still reached 14 560 and 6420 mA h g⁻¹, respectively. We suggest that the excellent performance of our catalyst can be ascribed to the excellent ORR performance of the multielement co-doped graphene and the excellent OER performance of the mounted Ru nanoparticles. In addition, the nanosheet structure with high surface area of the multielement co-doped graphene may result in the formation of uniform Li₂O₂ nanocrystals, which make the formation (discharge) and decomposition (charge) processes much more reversible.