Highly accessible atomically dispersed FeNx sites coupled with Fe3C@C core-shell nanoparticles boost the oxygen catalysis for ultra-stable rechargeable Zn-air batteries

It is significant but challenging to develop a cost-effective, high-efficiency, and stable bifunctional electrocatalyst of oxygen reduction and evolution reactions (ORR and OER) for rechargeable Zn-air batteries. Herein, we present a novel bifunctional catalyst constructed by highly accessible atomically dispersed MNx sites coupled with core-shell nanoparticles (M-Phen-800; M = Fe, Co, and Ni) from easily accessible M-Phenanthroline (M-Phen) com-plexes. Due to the synergistically induced symmetric charge distribution around FeNx sites by Fe3C@C core-shell nanoparticles, Fe-Phen-800 exhibits exceptional onset (E-onset = 0.994 V) and half-wave (E-1/2 = 0.878 V) potentials for ORR and a very low overpotential of 285 mV @ 10 mA cm(-2) (E-j=10) for OER, indicating excellent bifunctional activity (Delta E = E-j=10 - E-1/2 = 0.637 V) over the state-of-the-art Pt/C-RuO2 (0.702 V) combination. Moreover, the Fe-Phen-800-based Zn-air battery demonstrates a remarkable energy density of 1022 Wh kg(-1) and greater cycling stability (>800 cycles) than the commercial Pt/C-RuO2 battery.