Inducing Fe 3d Electron Delocalization and Spin-State Transition of FeN4 Species Boosts Oxygen Reduction Reaction for Wearable Zinc–Air Battery

The strong interaction between Ti 3 C 2 S x and FeN 4 species induces the central metal Fe(II) in FeN 4 species with intermediate spin state transferred to high spin state, in which the latter is favorable to initiate the reduction of oxygen. This strong interaction induces a remarkable Fe 3 d electron delocalization with d band center upshift, boosting oxygen-containing groups adsorption on FeN 4 species and oxygen reduction reaction kinetics. The resulting FeN 4 –Ti 3 C 2 S x with FeN 4 moieties in high spin state exhibits high half-wave potential of 0.89 V vs. RHE and high limiting current density of 6.5 mA cm −2 , enabling wearable zinc–air battery showing a good discharge performance with a maximum power density of 133.6 mW cm −2 .