Oxygen Reduction Kinetics of Fe–N–C Single Atom Catalysts Boosted by Pyridinic N Vacancy for Temperature-Adaptive Zn–Air Batteries

Abstract

The design of temperature-adaptive Zn-air batteries (ZABs) with long life spans and high energy efficiencies is challenging owing to sluggish oxygen reduction reaction (ORR) kinetics and an unstable Zn/electrolyte interface. Herein, a quasi-solid-state ZAB is designed by combining atomically dispersed Fe-N-C catalysts containing pyridinic N vacancies (FeNC-V_N) with a polarized organo-hydrogel electrolyte. First-principles calculation predicts that adjacent V_N sites effectively enhance the covalency of Fe-N_x moieties and moderately weaken *OH binding energies, significantly boosting the ORR kinetics and stability. In situ Raman spectra reveal the dynamic evolution of *O₂^- and *OOH on the FeNC-V_N cathode in the aqueous ZAB, proving that the 4e^- associative mechanism is dominant. Moreover, the ethylene glycol-modulated organo-hydrogel electrolyte forms a zincophilic protective layer on the Zn anode surface and tailors the [Zn(H₂O)₆]²⁺ solvation sheath, effectively guiding epitaxial deposition of Zn²⁺ on the Zn (002) plane and suppressing side reactions. The assembled quasi-solid-state ZAB demonstrates a long life span of over 1076 h at 2 mA cm^-2 at -20 °C, outperforming most reported ZABs.