Thermal Evaporating-Trapping Strategy to Synthesize Flexible and Robust Oxygen Electrocatalysts for Rechargeable Zinc-Air Batteries

Great efforts have been devoted to the development of bifunctional electrocatalysts to accelerate the sluggish kinetics of cathodic oxygen reduction/evolution reactions (ORR/OER) in zinc–air batteries (ZABs). Here we report a thermal evaporating-trapping synergistic strategy to fabricate bifunctional electrocatalyst of flexible N-doped carbon fiber cloth loaded with both CoFe-oxide nanoparticles and single-atom Co/Fe-Nx sites, in which the thermal evaporation process functions in both downsizing CoFe-oxide nanoparticles and trapping the evaporated Co/Fe species to generate Co/Fe-Nx sites. The obtained flexible electrocatalyst, directly served as an oxygen electrode, displays a small potential gap of 0.542 V for OER/ORR, large peak power densities (liquid-state ZAB: 237.4 mW cm–2; solid-state ZAB: 141.1 mW cm-2), and excellent charge-discharge cycling stability without decay after 1000 cycles. Furthermore, in situ Raman spectroscopy characterization reveals that CoFe2O4 species is responsible for the OER catalysis.