High-temperature annealing enables the dielectric modulation of MXene for enhanced electromagnetic wave absorption and shielding

Ti₃C₂T_<i>x</i> MXene is widely used in electromagnetic (EM) wave absorption coatings and shielding devices due to its excellent dielectric properties. However, achieving high-performance absorption and shielding requires a high loading. Therefore, optimizing the dielectric properties of Ti₃C₂T_<i>x</i> MXene is crucial for expanding its lightweight applications in EM wave protection. Herein, this study employs an annealing process in a nitrogen (N₂) atmosphere to achieve <i>in situ</i> modification of TiO₂ nanoparticles on the Ti₃C₂T_<i>x</i> surface. Varying the annealing temperature modulates the crystal form and size of TiO₂ nanoparticles, thereby enabling the tuning of dielectric properties. Annealing at 350 °C for 2 hours introduced abundant, low-conductivity, uniform anatase-type TiO₂ nanoparticles (TiO₂-A-NP), improving the impedance matching and enhancing the interfacial polarization. The effective absorption bandwidth of 1 mm-thick TiO₂-A-NP@Ti₃C₂T_<i>x</i> increased by 117% compared with Ti₃C₂T_<i>x</i>. The incorporation of abundant anatase-rutile TiO₂ heterojunctions (TiO₂-AR-HJ) <i>via</i> annealing at 500 °C for 2 h significantly increased the conductivity. The average total EM shielding effectiveness of TiO₂-AR-HJ@Ti₃C₂T_<i>x</i> improved by 45.9% compared with Ti₃C₂T_<i>x</i>. In summary, this work provides a guiding approach for the application of Ti₃C₂T_<i>x</i> MXene in lightweight EM wave absorption and shielding.