Bifunctional oxygen electrodes of homogeneous Co4N nanocrystals@N-doped carbon hybrids for rechargeable Zn-air batteries

The development of transition metal nitrides/carbon hybrids with well-organized morphology, outstanding efficiency and durability for Zn-air batteries are of great urgency. Herein, a morphology-controlled strategy to efficiently fabricate uniform Co 4 N nanoparticles anchored on N -doped carbon (Co 4 N@NC-m) is reported. The diameters and distribution of Co 4 N nanocrystals can be tuned to be homogeneous profited by abundant N sources in melamine. Moreover, thanks to the advantages of higher nitrogen doping content, better electrical conductivity , higher degree of graphitization , and larger electrochemical surface area, Co 4 N@NC-m possesses excellent oxygen reduction reaction (half-wave potential of 0.87 V) and oxygen evolution reaction (overpotential of 398 mV at 10 mA cm −2 ) activities in basic solution. The Zn-air battery fabricated with Co 4 N@NC-m owns higher open circuit voltage (1.490 V), larger power density, and better rechargeability than those of the commercial IrO 2  + 20% Pt/C catalysts, which proves the potential application in practical energy conversion devices.