Fe3C coupled with Fe-Nx supported on N-doped carbon as oxygen reduction catalyst for assembling Zn-air battery to drive water splitting

Fe-N-C structures have been considered as a candidate to replace noble metal catalysts towards oxygen reduction reaction (ORR) due to their excellent electrocatalytic activity and durability. Herein, a zinc-mediated synthesis strategy is proposed for N-doped graphitic porous carbon encapsulated uniform dispersed Fe3C nanoparticles coupled with atomically dispersed Fe-N-x moieties (NPC/Fe-N-C) derived from biomass coconut shell. The introduction of zinc species could be conductive to the dispersion of iron species and formation of porous structures. Density functional theory calculations demonstrate that the N-doped carbon coating structures can weaken the oxygen intermediates adsorption energy barrier of Fe3C. Beside, the graphitic carbon could promote the electron transfer during the electrochemical reaction. These special structures enable NPC/Fe-N-C to have excellent ORR activity with an Eonset of 1.0 V, which is much better than Pt/C. Furthermore, the zinc-air battery assembled by pairing NPC/Fe-N-C with a high-efficiency oxygen evolution reaction (OER) catalyst can continuously and stably operate a charge-discharge potential gap of 0.8 V at 10 mA/cm(2) for more than 600 h. More importantly, the assembled batteries could drive overall water splitting device, realizing the effective energy conversion. (C) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

A zinc-mediated synthesis strategy was used to prepare N-doped graphitic porous carbon encapsulated Fe3C nanoparticles and atomically dispersed Fe-N-x moieties from biomass coconut shell. The resulting structure exhibited excellent ORR activity and stability, and could be used in zinc-air batteries for long-lasting charge-discharge operation and overall water splitting.