2D MXene/MBene Superlattice with Narrow Bandgap as Superior Electrocatalyst for High‐Performance Lithium–Oxygen Battery

Lithium–oxygen (Li–O2) battery with large theoretical energy density (≈3500 Wh kg−1) is one of the most promising energy storage and conversion systems. However, the slow kinetics of oxygen electrode reactions inhibit the practical application of Li–O2 battery. Thus, designing efficient electrocatalysts is crucial to improve battery performance. Here, Ti3C2 MXene/Mo4/3B2‐x MBene superlattice is fabricated its electrocatalytic activity toward oxygen redox reactions in Li–O2 battery is studied. It is found that the built‐in electric field formed by a large work function difference between Ti3C2 and Mo4/3B2‐x will power the charge transfer at the interface from titanium (Ti) site in Ti3C2 to molybdenum (Mo) site in Mo4/3B2‐x. This charge transfer increases the electron density in 4d orbital of Mo site and decreases the d‐band center of Mo site, thus optimizing the adsorption of intermediate product LiO2 at Mo site and accelerating the kinetics of oxygen electrode reactions. Meanwhile, the formed film‐like discharge products (Li2O2) improve the contact with electrode and facilitate the decomposition of Li2O2. Based on the above advantages, the Ti3C2 MXene/Mo4/3B2‐x MBene superlattice‐based Li–O2 battery exhibits large discharge specific capacity (17 167 mAh g−1), low overpotential (1.16 V), and superior cycling performance (475 cycles). Ti3C2/Mo4/3B2‐x superlattice is synthesized via electrostatic self‐assembly. The built‐in electric field in the superlattice structure formed by the difference of work function between Ti3C2 and Mo4/3B2‐x allows the redistribution of charge near the Mo sites, which optimizes the adsorption of different oxygen species on the Mo sites and finally accelerates the oxygen electrode reactions in Li–O2 battery.