Bifunctional Catalytic Activity Guided by Rich Crystal Defects in Ti3C2 MXene Quantum Dot Clusters for Li–O2 Batteries

Abstract Ameliorating round‐trip efficiency and mitigating parasitic reaction play a key role in enhancing the activity and durability of lithium–oxygen batteries. Herein, it is first reported that Ti 3 C 2 MXene quantum dot clusters full of rich crystal defects anchored on N‐doped carbon nanosheets (Ti 3 C 2 QDC/N‐C) can operate well as bifunctional catalyst for Li–O 2 batteries. The well‐defined grain boundary and edge defects make crucial contributions in modulating the local unsaturated coordination state of active titanium atoms and thus the electronic structure of Ti 3 C 2 QDC/N‐C, greatly enhancing the catalytic capability. Furthermore, density functional theory calculations disclose that the fruitful crystal defects governed catalytic centers endow substantial benefits for inducing charge density delocalization, regulating the Li x O y intermediate adsorption and reducing the oxidation‐reduction energy barriers. The geometric morphology and distribution of final Li 2 O 2 accommodations are distinctly altered with optimized decomposition reversibility, which strengthens electro‐catalytic kinetics and lowers redox voltage gaps. As expected, Li–O 2 cells based on Ti 3 C 2 QDC/N‐C show favorable long‐period stability (240 cycles at 200 mA g −1 ) with minimal side reactions and distinguished discharge/charge overpotential (0.62 V). Critically, this crystal defect strategy paves a new way for expanding the active sites in MXenes for catalytic applications.