Bifunctional oxygen electrocatalysts enriched with single Fe atoms and NiFe2O4 nanoparticles for rechargeable zinc–air batteries

Rechargeable zinc–air batteries (ZABs) have stimulated extensive interests, but the slow reaction kinetics of oxygen reactions hinder their further development. Here a bifunctional oxygen electrocatalyst enriched with both single Fe atoms and NiFe2O4 nanoparticles is designed to mitigate this issue. Specifically, iron phthalocyanine with single–atom Fe–N4 moiety is coupled with graphene by π−π stacking interaction to accelerate the oxygen reduction reaction (ORR) during discharging, while NiFe–based Prussian blue analogue derived NiFe2O4 nanoparticles are anchored on graphene to promote the oxygen evolution reaction (OER) during charging. The catalyst shows a small overpotential difference of 0.72 V between OER potential at 10 mA cm–2 and ORR half–wave potential. When used as an oxygen electrode catalyst, the corresponding ZAB exhibits a large power density of 185 mW cm–2, a small charge–discharge voltage gap of 0.717 V at 5 mA cm–2, and outstanding discharge–charge durability without any decay after 1035 cycles. This work offers a new concept to design multifunctional catalysts and stimulates the development of ZABs.