In Situ Fabricating Oxygen Vacancy-Rich TiO2 Nanoparticles via Utilizing Thermodynamically Metastable Ti Atoms on Ti3C2Tx MXene Nanosheet Surface To Boost Electrocatalytic Activity for High-Performance Li-O2 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-O2) batteries. Herein, utilizing thermodynamically metastable Ti atoms on the Ti3C2Tx MXene nanosheet surface as the nucleation site, oxygen vacancy-rich TiO2 nanoparticles were in situ fabricated on Ti3C2Tx nanosheets (V-TiO2/Ti3C2Tx) and used as the oxygen electrode of Li-O2 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-TiO2/Ti3C2Tx-based Li-O2 battery shows improved performance including the ultralow overpotential of 0.21 V, high specific capacity of 11 487 mA h g-1 at a current density of 100 mA g-1, and excellent round-trip efficiency (93%). This work proposes an effective strategy for researching high-performance oxygen electrodes for Li-O2 batteries via introducing Vo-rich oxides on two-dimensional MXene.