ARTICLE Spinel-type lithium cobalt oxide as a bifunctional electrocatalyst for the oxygen evolution and oxygen reduction reactions

Development of efficient, affordable electrocatalysts for the oxygen evolution reaction and the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present lithium cobalt oxide, synthesized at 400°C (designated as LT-LiCoO 2 ) that adopts a lithiated spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction. The catalytic activity of LT-LiCoO 2 is higher than that of both spinel cobalt oxide and layered lithium cobalt oxide synthesized at 800°C (designated as HT-LiCoO 2 ) for the oxygen evolution reaction. Although LT-LiCoO 2 exhibits poor activity for the oxygen reduction reaction, the chemically delithiated LT-Li 1 À x CoO 2 samples exhibit a combination of high oxygen reduction reaction and oxygen evolution reaction activities, making the spinel-type LTLi 0,5 CoO 2 a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The high activities of these delithiated compositions are attributed to the Co 4 O 4 cubane subunits and a pinning of the Co 3 þ /4 þ :3d energy with the top of the O 2 À :2p band