Heterogeneous assembling 3D free-standing Co@carbon membrane enabling efficient fluid and flexible zinc-air batteries

Developing an efficient, interface-rich, and free-standing non-noble-metal electrocatalyst is vital for the flexible zinc-air batteries (ZABs). Herein, a three-dimensional (3D) heterogeneous carbon-based flexible membrane was assembled by Co@carbon nanosheets/carbon nanotubes and hollow carbon nanofiber (Co@NS/CNT-CNF) as an efficient oxygen reduction reaction (ORR) catalyst with a positive half-wave potential of 0.846 V and a small Tafel slope of 79 mV·dec⁻¹. Meanwhile, the Co@NS/CNT-CNF electrode also exhibits excellent open-circuit voltage, peak power density, and long-time cycling stability in liquid-state ZABs (1.605 V, 163 mW·cm⁻², and 400 h) and flexible ZABs under flat/bending condition (1.47 V, 102 mW·cm⁻², and 80 h). Such heterogeneous flexible membrane architecture not only optimizes the electrolyte infiltration, but also provides capacious possibility for O₂ and electrolyte transfer. Meanwhile, work-function analyses coupled with density functional theory (DFT) results demonstrate that the electron transfer capability and metal–support interaction can be well optimized in the obtained Co@NS/CNT-CNF catalyst.