The Proportion of Fe-NX , N Doping Species and Fe3 C to Oxygen Catalytic Activity in Core-Shell Fe-N/C Electrocatalyst.

A bifunctional oxygen electrocatalyst composed of iron carbide (Fe3 C) nanoparticles encapsulated by nitrogen doped carbon sheets is reported. X-ray photoelectron spectroscopy and X-ray absorption near edge structure revealed the presence of several kinds of active sites (Fe-Nx sites, N doping sites) and the modulated electron structure of nitrogen doped carbon sheets. Fe3 C@N-CSs shows excellent oxygen evolution and oxygen reduction catalytic activity owing to the modulated electron structure by encapsulated Fe3 C core via biphasic interfaces electron interaction, which can lower the free energy of intermediate, strengthen the bonding strength and enhance conductivity. Meanwhile, the contribution of the Fe-Nx sites, N doping sites and the effect of Fe3 C core for the electrocatalytic oxygen reaction is originally revealed. The Fe3 C@N-CSs air electrode-based zinc-air battery demonstrates a high open circuit potential of 1.47 V, superior charge-discharge performance and long lifetime, which outperforms the noble metal-based zinc-air battery.