Zinc-assisted MgO template synthesis of porous carbon-supported Fe-Nx sites for efficient oxygen reduction reaction catalysis in Zn-air batteries

Atomically dispersed iron-nitrogen-carbon catalysts offer great potential in oxygen reduction reaction (ORR), yet the poor exposure and low density of Fe-Nx sites causes relatively low ORR activity. Herein, a zinc-assisted MgO template strategy is reported to construct porous carbon-supported Fe-N4 sites (Fe-N-C). Iron atoms surrounded by zinc species are converted to abundant Fe-N4 sites rather than Fe containing nanoparticles. Meanwhile, both the zinc species and the MgO template can effectively produce porous structure so as to increase the utilization of Fe-N4 sites. Fe-N-C achieves superior ORR performance and stability in alkaline medium. Theoretical calculations manifest that Fe-N4 sites can narrow the energy barrier for ORR. Moreover, finite element simulation exhibits the porous framework in Fe-N-C could significantly accelerate the diffusion of O2. Therefore, Fe-N-C provides a high peak power density and superior discharge ability toward Zn-air batteries.