Single Semi‐Metallic Selenium Atoms on Ti₃C₂ MXene Nanosheets as Excellent Cathode for Lithium–Oxygen Batteries

Rechargeable Li–O 2 batteries are promising due to their superior high energy density but subject to sluggish oxygen reduction/evolution kinetics. Developing highly efficient catalysts to improve catalytic activity and alleviate oxidation–reduction overpotential of Li–O 2 batteries is of great challenge and importance. Herein, a CO 2 ‐assisted thermal‐reaction strategy is developed to fabricate isolated semi‐metallic selenium single‐atom‐doped Ti 3 C 2 MXene catalyst (SASe‐Ti 3 C 2 ) as cathodes for high‐performance Li–O 2 batteries. The isolated moieties of single Se atom catalysis centers can function as active catalytic centers to drastically enhance the intrinsic LiO 2 ‐absorption ability and thus fundamentally modulate the formation/decomposition mechanism of lithium peroxide (Li 2 O 2 ) discharge product, thus demonstrating greatly enhanced redox kinetics and efficiently ameliorated overpotentials. Theoretical simulations reveal that the interaction between Se‐involved moieties and Ti 3 C 2 substrate greatly enhances the intrinsic LiO 2 ‐absorption ability and fundamentally promotes the charge transfer between electrode and Li 2 O 2 product, deeply ameliorating the round‐trip overpotential. The well‐designed SASe–Ti 3 C 2 electrode exhibits decreased charge/discharge polarization (1.10 V vs Li/Li + ), ultrahigh discharge capacity (17 260 mAh g −1 at 100 mA g −1 ), and superior durability (170 cycles at 200 mA g −1 ) as cathode for Li–O 2 batteries. The promising results will shed light on the design of highly efficient catalysts for oxygen‐involved systems of future investigation.