A binary single atom Fe3C|Fe N C catalyst by an atomic fence evaporation strategy for high performance ORR/OER and flexible Zinc-air battery

An oxygen reduction/evolution reaction (ORR/OER) electrocatalyst with a high intrinsic activity is vital and challenging for a flexible zinc-air battery (ZAB). Herein, we prepared a binary single atom Fe3C|FeNC electrocatalyst through a facile atomic fence evaporation strategy using Zn atoms as the fence and eutectic NaCl/ZnCl2/NaNO3 as a reaction medium/porogen. The single atom FeNC active site promotes the onset potential of ORR/OER, and the atomically dispersed Fe3C boosts the FeNC activity further. Fe3C|FeNC shows a superior bifunctional activity, with an ORR half-wave potential of 0.888 V, an OER overpotential of 338 mV at 10 mA cm−2, and a reversible oxygen overpotential of 0.68 V. The theoretical calculation reveals that the synergy between the binary FeNC and Fe3C sites reduces the energy barriers of reaction-determining steps in the electrocatalytic reactions. The Fe3C|FeNC based solid ZAB delivers a stable recharge process over 1000 cycles at 2 mA cm−2, implying the vast applications to portable electronics.