Ultrafine CoFe nanoparticles supported on nitrogen-doped carbon sheets boost oxygen electrocatalysis for Zn-air batteries

Efficient, durable and inexpensive electrocatalysts are urgently needed to mediate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in rechargeable Zn-air batteries (ZABs). Herein, ultrafine CoFe alloyed nanoparticles (NPs) homogeneously decorated on N-doped carbon nanosheets (CoFe@NCS) are synthesized by annealing the precursor of NCS supported CoFe-based Prussian-blue-analogues. The optimal CoFe@NCS delivers prominent electrocatalytic behaviors for both the ORR (0.88 V of half-wave potential) and OER (340 mV of overpotential at 10 mA cm−2) in an alkaline electrolyte. The outstanding bifunctional electrocatalytic activities are ascribed to the synergistic interplay of structural and compositional advantages, including the hierarchically porous structure as well as the strong coupling of ultrafine CoFe species and NCS. Simultaneously, the assembled flow ZAB with CoFe@NCS as the air-cathode catalyst manifests a superior battery performance to the device catalyzed by the noble-metal benchmark (Pt/C + RuO2). This work may pave an avenue for developing efficient bifunctional electrocatalysts and promoting the practical application of ZABs.