Ruthenium oxide modified hierarchically porous boron-doped graphene aerogels as oxygen electrodes for lithium–oxygen batteries

Abstract

Suitable catalysts and reasonable structures for oxygen electrodes can effectively improve the electrochemical performance of lithium–oxygen batteries. In this work, ruthenium oxide modified boron-doped hierarchically porous reduced graphene aerogels (RuO₂-B-HRG) are prepared by a sol–gel and subsequent low temperature annealing method and used as oxygen electrodes. The RuO₂ nanoparticles (5–10 nm) are uniformly anchored in the three-dimensional B-HRG continuous electric network. The RuO₂-B-HRG aerogel possesses a large specific surface area (287.211 m² g⁻¹) and numerous mesopores and micropores. The pores facilitate electrolyte impregnation and oxygen diffusion, and they provide greatly increased accommodation space for the discharge products. Electrochemical tests show that the RuO₂-B-HRG/KB enables the electrode overpotential to decrease, and the rate capability and the cycling stability are enhanced compared with pure HRG. The enhanced performance is ascribed to the bifunctional catalytic activity of RuO₂-B-HRG and its unique three-dimensional porous architecture. The method is proved to be an effective strategy to combine porous carbon materials and nanoscale catalysts as electrodes for Li–O₂ batteries.