In-situ spatial-embedding construction of FeCo nucleus-bound carbon skeletons for durable rechargeable liquid and flexible Zn-air batteries

Metal-organic frameworks (MOFs) and porous organic polymers (POPs) have received increasing attention for their attractive features of compositional/functional designability and high structural orderliness. However, the rational construction of the MOFs@POPs heterostructures to achieve the desired performance remains a challenging issue. Herein, an in-situ spatial-embedding strategy is proposed to construct FeCo nucleus-bound carbon skeletons (FeCo-MI@TAP-900), successfully meeting the requirements of high activity yet outstanding stability for bifunctional oxygen electrocatalysts. The effective molecular-level coordination of MOFs and POPs can not only prevent the collapse and aggregation of MOFs, but also endows the derived FeCo-MI@TAP-900 with enhanced porosity and electrochemical activity. Benefiting from abundant MOFs-derived highly-active FeCo nanoparticles and robust POPs-derived 3D porous carbon frameworks, the as-constructed FeCo-MI@TAP-900 manifests satisfactory oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) activity with a E0 of 0.991 V and a EJ=10 of 1.615 V (vs RHE). Notably, the as-assembled rechargeable liquid Zn-air battery (ZAB) delivers good rate performance and remarkable cycling stability (2100 cycles for 1400 h at 5.0 mA cm−2), and the corresponding flexible ZAB renders appealing flexibility, mechanical integrity and battery performance. This in-situ spatial-embedding strategy offers a new insight to design state-of-the-art bifunctional oxygen electrocatalysts for metal-air batteries and beyond.