N-doped defective carbon with trace Co for efficient rechargeable liquid electrolyte-/all-solid-state Zn-air batteries

Simple synthesis of multifunctional electrocatalysts with plentiful active sites from earth-abundant materials is especially fascinating. Here, N-doped defective carbon with trace Co (1.5 wt%) was prepared via a scalable one pot solid pyrolysis process. The sample exhibits efficient bifunctional OER/ORR activity in alkaline, mainly ascribed to the unique micro-mesoporous structure (1–3 nm), high population of graphitic-N doping (up to 49.0%), abundant defects and the encapsulated Co nanoparticles with graphitized carbon. The according rechargeable liquid Zn-air batteries showed excellent performance (maximum power density of 154.0 mW cm⁻²; energy density of 773 Wh kg⁻¹ at 5 mA cm⁻² and charging-discharging cycling stability over 100 cycles). As a proof-of-concept, the flexible, rechargeable all-solid-state Zn-air batteries were constructed, and displayed a maximum power density as high as 45.9 mW cm⁻², among the top level of those reported previously.