Asymmetric Mn/Fe Dual Single‐Atom Catalysts for pH‐Universal Oxygen Electroreduction and Sustainable Metal‐Air Batteries

Abstract

AbstractConquering the sluggish kinetics of the oxygen reduction reaction (ORR) is significantly important for sustainable metal‐air batteries. However, the synthesis of advanced Pt‐free ORR electrocatalysts still remains challenging owing to the intrinsic activity, site accessibility, and structural stability. Herein, a catalyst of asymmetric N, P‐coordinated Mn and Fe dual single atoms supported on hollow carbon polyhedra (MnFe‐PNC) is synthesized via a metal‐organic framework pyrolysis strategy, which displays excellent pH‐universal ORR performance with half‐wave potentials of 0.923 V in 0.1 m KOH, 0.803 V in 0.1 m HClO4, and 0.774 V in 1 m phosphate buffer solution. Theoretical calculations reveal that the distance‐dependent electronic interaction between Mn‐N3P and Fe‐N3P structures at the atomic level plays a crucial role in optimizing the adsorption strength of *OH intermediate and consequently boosts ORR performance. Furthermore, the aqueous Zn/Al‐air batteries using MnFe‐PNC cathode catalyst show ultralong discharge stability and wide‐temperature adaptability. Meanwhile, combined with an anti‐freezing and zincophilic organohydrogel electrolyte, the MnFe‐PNC‐based quasi‐solid‐state Zn‐air batteries exhibit robust cycling stability (130 h at 50 mA cm−2 and 70 h at 100 mA cm−2), an unprecedented discharge capacity of 1.30 Ah at −40 °C, and smooth operation over a broad temperature range of −40 to 60 °C.