In situ growth of Co3O4 on nitrogen-doped hollow carbon nanospheres as air electrode for lithium-air batteries

Design and synthesis of efficient bifunctional electrocatalysts for both oxygen reduction reaction and oxygen evolution reactions are of great significant for metal-air batteries. In this work, bifunctional catalysts consisting of Co3O4 nanocrystals and nitrogen-doped hollow carbon nanospheres are synthesized through in situ growth of Co3O4 nanocrystals on the surface of nitrogen-doped hollow carbon nanospheres. The observed Co-N bond formation is an indication of the nucleation of Co3O4 nanocrystals starting from N-sites in nitrogen-doped hollow carbon nanospheres. The resulted hybrids exhibit improved activity towards oxygen reduction reaction compared to pristine nitrogen-doped hollow carbon nanospheres in terms of the 42 mV positive shift of half-wave potential and comparable activity towards oxygen evolution reactions with commercial RuO2 and IrO2 catalysts. The thus-assembled Li-O-2 battery delivers an initial discharge capacity of 3325 mAhg(-1) at 100 mAg(-1) using mixed gas of O-2 and Ar (20% of O-2 in volume). The battery fails after 27 discharge/charge cycles due to the accumulation of discharge products on electrode. (C) 2018 Elsevier B.V. All rights reserved.