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