Morphology and Active-Site Engineering for Stable Round-Trip Efficiency Li–O₂ Batteries: A Search for the Most Active Catalytic Site in Co₃O₄

For the purpose of finding the catalytic active site for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in the crystal structure of Co₃O₄, a {100} faceted Co₃O₄ cube enclosed by only a Co²⁺ site and a {112} faceted Co₃O₄ plate also exposing a Co³⁺ site was adopted as a catalyst for lithium–oxygen (Li–O₂) batteries. Thus, we found that the Co³⁺ site plays the crucial role of determining the adsorption properties of reactants, enabling high round-trip efficiency and cyclic stability, as well as the morphology of discharge products such as Li₂O₂.