Ultrafine Ru nanoparticles anchored on N-doped mesoporous hollow carbon spheres as a highly efficient bifunctional catalyst for Li-CO2 batteries

Rechargeable Li-CO2 battery is a facilitative and promising device for the conversion of CO2 to electrochemical energy. However, it remains a challenge to enhance the sluggish decomposition kinetics of lithium carbonate as the discharge product. Herein, the Ru nanoparticles anchored on N-doped mesoporous hollow carbon nanospheres (Ru-AHCNs) are designed as cathode to enhance the electrochemical performance of Li-CO2 battery. The Ru-AHCNs cathode displays a high discharge specific capacity of 11194.4 mA h g(-1) at the current density of 100 mA g(-1). In addition, the Ru-AHCNs cathode can stably run over 50 cycles and maintain a small overpotential (<1.38 V) with a limited capacity of 1000 mA h g(-1) at 100 mA g(-1). The excellent stability and catalytic activity of the cathode are ascribed to the following factors: (i) Uniform deposition of Ru nanoparticles in hollow carbon nanospheres can enhance the decomposition of Li2CO3 and provide considerable exposure to active sites. (ii) N-doped mesoporous hollow carbon nanospheres can provide abundant electron transport channels and promote the nucleation of discharge products. These results evidently prove the reversible formation and decomposition of the discharge products, indicating that Ru-AHCNs cathode possesses excellent bifunctional catalytic activity.