Fe,N-modulated carbon fibers aerogel as freestanding cathode catalyst for rechargeable Zn–Air battery

Freestanding air cathode catalyst with exceptional catalytic bifunctions for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desirable for exploring rechargeable Zn–air batteries (ZABs) with low cost and high reliability. Here, a facile and scalable approach is demonstrated to prepare efficient and robust freestanding cathode catalyst that consists of dispersed Fe3C nanoparticles, rich Fe-Nx/N-C species and carbon fibers networks with large specific surface area, which is based on one-pot in-situ coupling of Fe and N induced active sites within bacterial cellulose-derived carbon fibers networks. Its bifunctional activity parameter (ΔE) for ORR and OER is 0.79 V, superior to those of single Fe- or N- modulated counterparts, and comparable to the state-of-the-art Pt/C + RuO2 catalyst (0.79 V). This material can be directly used as freestanding and binder-free catalyst layer, and as-assembled ZABs exhibit a larger peak power density (173 mW cm−2), higher specific capacity (717 mA h g−1, 10 mA cm−2) and better cycle stability (negligible activity decay after 165 h charge/discharge cycles) than those of Pt/C + RuO2-based devices, representing their potential applications in advanced energy conversion systems.