Adjusting the 3d Orbital Occupation of Ti in Ti 3 C 2 MXene via Nitrogen Doping to Boost Oxygen Electrode Reactions in Li-O 2 Battery.

Rationally designing efficient catalysts is the key to promote the kinetics of oxygen electrode reactions in lithium-oxygen (Li-O 2 ) battery. Herein, nitrogen-doped Ti 3 C 2 MXene prepared via hydrothermal method (N-Ti 3 C 2 (H)) is studied as the efficient Li-O 2 battery catalyst. The nitrogen doping increases the disorder degree of N-Ti 3 C 2 (H) and provides abundant active sites, which is conducive to the uniform formation and decomposition of discharge product Li 2 O 2 . Besides, density functional theory calculations confirm that the introduction of nitrogen can effectively modulate the 3d orbital occupation of Ti in N-Ti 3 C 2 (H), promote the electron exchange between Ti 3d orbital and O 2p orbital, and accelerate oxygen electrode reactions. Specifically, the N-Ti 3 C 2 (H) based Li-O 2 battery delivers large discharge capacity (11 679.8 mAh g -1 ) and extended stability (372 cycles). This work provides a valuable strategy for regulating 3d orbital occupancy of transition metal in MXene to improve the catalytic activity of oxygen electrode reactions in Li-O 2 battery.