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

Abstract

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