Bimetal heterostructured nanoparticles anchored hierarchical carbon nanospheres with abundant active sites for high-performance liquid/flexible zinc-air batteries

The development of highly active bifunctional electrocatalysts is crucial to the sluggish oxygen reduction reaction/oxygen evolution reaction (ORR/OER) for efficient wearable Zn–air batteries (ZAB). The Fe-N x -C moieties anchored on carbon supports emerge as a desirable alternative to ORR catalysts but its OER activity suffers from low catalytic performance and stability. Herein, a N-doped carbon-encapsulated Fe 3 C and MnO nanoparticles composite (FeMn-NC) was developed using a simple one-step pyrolysis of the self-sacrificial template. The obtained FeMn-NC possesses a hierarchical porous structure with a large specific surface area and rich pyridinic N, which are favorable for the exposure of the active sites. The introduction of the Fe 3 C/MnO interface can regulate the charge redistribution to promote ORR/OER kinetics, which is confirmed by theoretical calculations. The obtained FeMn-NC exhibits an excellent bifunctional ORR/OER activity in alkaline electrolytes. The assembled liquid ZAB with the FeMn-NC as the cathode can achieve an ultrahigh specific capacity of 792.7 mAh g −1 and charge-discharged stability up to 800 h at 10 mA cm −2 (2400 cycles). Furthermore, the corresponding flexible solid-state ZAB provides a stable open-circuit voltage of 1.50 V and a specific capacity of 676.1 mAh g −1 at 1.0 mA cm −2 with good cycling stability. This work offers a simple strategy to synthesize hierarchical porous materials with highly active bifunctional properties, which can be applied in other electrochemical energy devices.