An all-nanosheet OER/ORR bifunctional electrocatalyst for both aprotic and aqueous Li-O₂ batteries

Rechargeable lithium-oxygen (Li-O2) batteries are receiving intense interest because of their high energy density. A highly efficient catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a key factor influencing the performance of Li-O2 batteries. In this work, a facile synthesis of an all-nanosheet architecture electrocatalyst constructed from a monolayer ruthenium dioxide (RuO2) nanosheet with a nitrogen doped sulfonated graphene nanosheet (RuO2-NS-GNS) has been developed for Li-O2 batteries. This complex catalyst displays excellent activity towards the ORR and OER in both aprotic and aqueous Li-O2 batteries. A low overpotential around 1.0 V during the discharge/recharge process is obtained for the aprotic Li-O2 battery with RuO2-NS-GNS. Meanwhile, linear sweep voltammetry curves show that the OER and ORR potentials are 1.45 V and 0.81 V in an alkaline solution (1 M LiOH-5 M LiNO3) for RuO2-NS-GNS, respectively. Both aprotic and aqueous Li-O2 batteries with RuO2-NS-GNS exhibit stable cyclability and low round-trip overpotential without obvious degradation at a limited specific capacity of 1000 mA g-1. The advanced electrochemical performance of RuO2-NS-GNS in both aprotic and aqueous Li-O2 batteries can be attributed to the increased catalytic sites and synergistic effect arising from RuO2 and NS-GNS nanosheets.