Constructing Fe–N-doped porous carbon nanofibers for a pH-universal ORR and switchable, superior Zn–air batteries

Abstract

Mechanically stable air cathodes with exceptional oxygen reduction reaction (ORR) activities serve as a highly significant component of metal–air batteries. Herein, we have proposed and prepared a porous air electrode consisting of well-dispersed Fe nanoparticles (Zn assisted formation) embedded in nitrogen-rich 3D carbon nanofibers (called Fe(Zn)–N–C) derived from Fe, Zn–metal–organic frameworks (MOFs) by a facile and scalable approach. The obtained Fe(Zn)–N–C with a distinctly continuous porous structure presented a comparable or even better performance than the commercial 20 wt% Pt/C and previously reported non-noble electrocatalysts for Zn–air batteries, which includes (1) effective in the universal-pH range (E_1/2 = 0.86, 0.74, and 0.67 V in alkaline, acidic, and neutral media, respectively), (2) extremely high stability (∼85%, 80%, and 82% activity retention for 86 400 s in alkaline, acidic, and neutral media, respectively), (3) a high power density (193 and 48 mW cm⁻² in alkaline and neutral media, respectively), and (4) an excellent specific capacity (800 and 688 mA h g⁻¹ in alkaline and neutral media, respectively). This design strategy of porous non-precious metal-doped pH-universal ORR electrocatalysts could also be extended to fabricate other novel, stable, and easy-to-use multi-functional electrocatalysts for clean-energy technology.