Metal-organic framework derived Fe3C nanoparticles coupled single-atomic iron for boosting oxygen reduction reaction.

Abstract

Developing transition metal electrocatalysts, especially single-atom catalysts (SACs), is significant. However, most of the synthesis procedures of SACs involve the formation of nanoparticles (NPs), and the produced NPs always play an influential role during electrocatalytic processing, so exploring the synergistic effects between metallic and isolated metal species is of great interest. Herein, we report a Zn/Fe-metal-organic framework (MOF)-derived Fe3C coupling FeNx catalyst constructed via coordination confinement pyrolysis effect successfully. Compared with the Pt/C catalyst and most precious metal-free catalysts, the optimized catalyst Fe3C-FeNx/NC-7 demonstrates superior oxygen reduction reaction (ORR) activity in 0.1M KOH. The half-wave potential (E1/2) reaches up to 0.93V with the limiting current density (jL) of 5.65mA/cm2 at 5mV/s scanning rate and 1600rpm. The excellent performance originates from the synergistic effect of FeNx and Fe3C active units combined with wide-distributed nitrogen atoms. The Fe3C NPs further optimize the electronic structure and adsorption/desorption free energy of the catalyst. The assembled primary Zn-air battery (ZAB) displays a satisfying open-circuit potential of 1.53V and an excellent specific capacity of 835mA·h·g-1. The maximum power density achieves 283mW/cm2, outclassing the commercial Pt/C-based ZAB. This result demonstrates the promising application prospect of the catalyst-cooperated metallic NPs with isolated single metal species.