Well-dispersed ultrafine CoFe nanoalloy decorated N-doped hollow carbon microspheres for rechargeable/flexible Zn-air batteries

[Display omitted] •Efficient route has been developed for synthesis of ultrafine MOF-derived nanoalloy.•The hollow carbon nanospheres were used as conductive support.•CoFe/N-HCSs exhibit enhanced activity and stability for ORR and OER.•CoFe/N-HCSs deliver potential feasibility in liquid and all-solid-state Zn-air batteries. Metal-organic frameworks (MOFs) offer great advantages for construction of bimetallic alloys as efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts for rechargeable/flexible Zn-air batteries. Herein, a template-assisted method is developed to reduce the crystal size of CoFe-ZIF via in-situ growing on hollow polypyrrole spheres (h-PPy). As a result, the well-dispersed ultrafine CoFe nanoalloy were obtained with N-doped hollow carbon microspheres (N-HCSs) as support. Owing to the unique alloy structure with ultrafine size, uniform dispersion of the CoFe nanoalloy on the highly conductive N-HCSs support via strong interactions, the proposed CoFe/N-HCSs afford high catalytic activity and stability toward ORR. Interestingly, the CoFe/N-HCSs also deliver a low overpotential of 292 mV at 10 mA cm−2 for OER in alkaline electrolyte, demonstrating their superior bifunctional catalytic performance. Moreover, the CoFe/N-HCSs can endow the liquid Zn-air batteries with better energy density (882.3 Wh kgZn−1) and cycling stability than those of Pt/C catalyst and exhibit potential feasibility in all-solid-state Zn-air batteries.