Abstract: Two-dimensional Ti₃C₂T_x MXene exhibits strong dielectric loss capabilities. However, its high electrical conductivity and dielectric response cause impedance mismatch, thereby limiting the effective electromagnetic wave absorption. To clarify the intrinsic electromagnetic response of Ti₃C₂T_x, a series of (Ti_1-xMo_x)₃C₂T_x MXene were prepared from the (Ti_1-xMo_x)₃AlC₂ (x=0, 0.03, 0.05, 0.10) precursors with different Mo contents through HCl/LiF etching. The results showed that Mo was effectively incorporated into the M sites with a controlled compositional gradient, while (Ti_1-xMo_x)₃C₂T_x samples retained the typical two-dimensional layered morphology. At a filler loading of 30% (in mass), (Ti_0.97Mo_0.03)₃C₂T_x exhibits the best microwave absorption performance, with a minimum reflection loss of -57.17 dB and a maximum effective absorption bandwidth of 3.92 GHz at a thickness of 1.45 mm. Compared with Ti₃C₂T_x, M-site Mo solid solution effectively regulated the excessively high electrical conductivity and dielectric response, thereby decreasing the reflection of incident electromagnetic waves on the material surface. Furthermore, (Ti_0.97Mo_0.03)₃C₂T_x still maintains a relatively high imaginary part of dielectric constant, tangent of dielectric loss and attenuation constant, indicating that it improvs impedance matching while still maintaining strong dielectric loss and internal attenuation capabilities. First-principle calculations further revealed that, with increasing Mo content, the total density of states (TDOS) near the Fermi level generally decreased, indicating a reduced contribution of electronic states to charge transport. In addition, Mo substitution induced local charge redistribution, providing electronic-structure-level support for the observed changes in charge transport and dielectric response. Overall, M-site Mo solid solution can regulate charge transport and dielectric response, optimize the balance between impedance matching and internal attenuation, and thereby enhance the electromagnetic wave absorption performance of Ti₃C₂T_x. This study demonstrates the feasibility of M-site Mo solid solution regulation of the intrinsic electromagnetic response of Ti₃C₂T_x, providing a new idea for the M-site design of highly conductive MXene.

Key words: Ti₃C₂T_x MXene, Mo solid solution, impedance matching, electromagnetic wave absorption