In Situ Fabricating Oxygen Vacancy-Rich TiO Nanoparticles via Utilizing Thermodynamically Metastable Ti Atoms on TiCTx MXene Nanosheet Surface To Boost Electrocatalytic Activity for High-Performance Li-O Batteries.

Catalysts with high performance are urgently needed in order to accelerate the reaction kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in lithium-oxygen (Li-O) batteries. Herein, utilizing thermodynamically metastable Ti atoms on the TiCTx MXene nanosheet surface as the nucleation site, oxygen vacancy-rich TiO nanoparticles were in situ fabricated on TiCTx nanosheets (V-TiO/TiCTx) and used as the oxygen electrode of Li-O batteries. Oxygen vacancy (Vo) can boost the migration rate of electrons and Li as well as act as the active sites for catalyzing the ORR and OER. Based on the above merits, V-TiO/TiCTx-based Li-O battery shows improved performance including the ultralow overpotential of 0.21 V, high specific capacity of 11 487 mA h g at a current density of 100 mA g, and excellent round-trip efficiency (93%). This work proposes an effective strategy for researching high-performance oxygen electrodes for Li-O batteries via introducing Vo-rich oxides on two-dimensional MXene.