Interface Engineering of MXene via In Situ Growth of TiO ₂ : Lightweight Core–Shell Microspheres for High-Performance Microwave Absorption

Two-dimensional transition-metal carbides and nitrides (MXenes) have attracted tremendous attention in the field of microwave absorption. However, their practical application is inevitably impeded by intrinsic drawbacks such as severe nanosheet restacking and poor impedance matching. In this work, PMMA@Ti 3 C 2 T x /TiO 2 core–shell microspheres were successfully fabricated via a facile self-assembly and hydrothermal strategy, where TiO 2 nanoparticles were in-situ grown on Ti 3 C 2 T x MXene nanosheets through controlled partial oxidation. This unique structural design effectively alleviates the restacking of MXene nanosheets, optimizes impedance matching by mitigating the excessive conductivity of pristine MXene, and introduces strong interfacial polarization via an atomic-level integration of the dielectric TiO 2 phase within the conductive MXene shell. Benefiting from these synergistic effects, the prepared PMMA@Ti 3 C 2 T x /TiO 2 spheres exhibit outstanding microwave absorption performance, achieving a minimum reflection loss (RL min ) of –52.5 dB and an effective absorption bandwidth of 5.4 GHz at a thin thickness of 3 mm. This study offers a reference for designing high-performance MXene-based microwave absorbers through strategic interface engineering.