Rational design of hybrid Fe7S8/Fe2N nanoparticles as effective and durable bifunctional electrocatalysts for rechargeable zinc-air batteries

Rechargeable zinc-air batteries are promising next-generation energy storage systems due to their large energy density and high safety. However, air-cathodes based on Pt/C and RuO2 suffer from poor catalytic activity and stability in rechargeable zinc-air batteries. Here, we report novel bifunctional Fe7S8/Fe2N nanoparticle (Fe7S8/Fe2N NPs) electrocatalysts for the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) by carbonizing the metal-organic framework precursors. Due to the synergistic function between the Fe7S8 and Fe2N with high conductivity and high electrochemical stability, the Fe7S8/Fe2N NPs show outstanding OER and ORR electrocatalytic activities versus precious metal catalysts and pristine Fe2N nanoparticles. Prototype liquid and solid-state zinc-air batteries were also fabricated, and they both show significant rechargeable activities and cyclic stability.