La0.75Sr0.25MnO3-based perovskite oxides as efficient and durable bifunctional oxygen electrocatalysts in rechargeable Zn-air batteries

Efficient and durable bifunctional oxygen electrocatalysts are critical for advanced rechargeable zinc-air (Zn-air) batteries. However, the obstacle to the development of bifunctional electrocatalysts for the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) lies in the different requirements of the ORR and OER for catalytic materials. Herein, La0.75Sr0.25Mn0.5X0.5O3 (X = Co, Ni, and Fe) perovskite nanoparticles were created by rationally screening targeted ORR/OER components and precisely controlling their electronic structures to achieve bifunctional oxygen electrocatalysis, in which La0.75Sr0.25Mn0.5Fe0.5O3 (LSFMO) displayed superior ORR performance (Eonset of 0.932 V and n of 3.59) and significantly enhanced electrocatalytic activity in the OER process (an Ej=10 of 1.658 V and overpotential of 428 mV), corresponding to excellent bifunctional properties (ΔE = 0.94 V). Furthermore, density functional theory (DFT) calculations demonstrated that Mn and Fe dual sites generated by partial substitution had a significant synergistic effect on the electrocatalytic process. The rechargeable Zn-air batteries delivered an unprecedented small charge-discharge voltage polarization (0.76 V), high reversibility and stability over many charge-discharge cycles (60 h). These excellent results demonstrate that Mn-based perovskites with Fe doping are undoubtedly promising bifunctional electrocatalysts for rechargeable Zn-air batteries.