Layered Perovskite Oxide: A Reversible Air Electrode for Oxygen Evolution/Reduction in Rechargeable Metal-Air Batteries

For the development of a rechargeable metal-air battery, which is expected to become one of the most widely used batteries in the future, slow kinetics of discharging and charging reactions at the air electrode, i.e., oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), respectively, are the most critical problems. Here we report that Ruddlesden–Popper-type layered perovskite, RP-LaSr₃Fe₃O₁₀ (<i>n</i> = 3), functions as a reversible air electrode catalyst for both ORR and OER at an equilibrium potential of 1.23 V with almost no overpotentials. The function of RP-LaSr₃Fe₃O₁₀ as an ORR catalyst was confirmed by using an alkaline fuel cell composed of Pd/LaSr₃Fe₃O_{10–2<i>x</i>}(OH)_2<i>x</i>·H₂O/RP-LaSr₃Fe₃O₁₀ as an open circuit voltage (OCV) of 1.23 V was obtained. RP-LaSr₃Fe₃O₁₀ also catalyzed OER at an equilibrium potential of 1.23 V with almost no overpotentials. Reversible ORR and OER are achieved because of the easily removable oxygen present in RP-LaSr₃Fe₃O₁₀. Thus, RP-LaSr₃Fe₃O₁₀ minimizes efficiency losses caused by reactions during charging and discharging at the air electrode and can be considered to be the ORR/OER electrocatalyst for rechargeable metal-air batteries