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 *O-2(-) 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 degrees C, outperforming most reported ZABs.