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<br>the oxygen reduction reaction is critical for rechargeable metal-air batteries. Here we present<br>lithium cobalt oxide, synthesized at 400 C (designated as LT-LiCoO2) that adopts a lithiated<br>spinel structure, as an inexpensive, efficient electrocatalyst for the oxygen evolution reaction.<br>The catalytic activity of LT-LiCoO2 is higher than that of both spinel cobalt oxide and layered<br>lithium cobalt oxide synthesized at 800 C (designated as HT-LiCoO2) for the oxygen evolution<br>reaction. Although LT-LiCoO2 exhibits poor activity for the oxygen reduction reaction,<br>the chemically delithiated LT-Li1 xCoO2 samples exhibit a combination of high oxygen<br>reduction reaction and oxygen evolution reaction activities, making the spinel-type LTLi0,5CoO2<br>a potential bifunctional electrocatalyst for rechargeable metal-air batteries. The<br>high activities of these delithiated compositions are attributed to the Co4O4 cubane subunits<br>and a pinning of the Co3 þ /4 þ :3d energy with the top of the O2 :2p band.<br>DO