Abstract
This study systematically investigates the modulation mechanism of transition metal elements (Ti, Nb, Ta, V) on the microwave absorption performance of MXenes (Ti(3)C(2)T(x), Ti(2)NbC(2)Tx, Ti(2)TaC(2)T(x), Ti(2)VC(2)T(x), Nb(2)CT(x), V(2)CT(x)). Using multiscale characterization techniques, the microstructure, elemental distribution, and surface chemical states of these materials are comprehensively analyzed. Integrated electromagnetic parameter measurements and theoretical calculations elucidate the physical mechanisms underlying their distinct microwave absorption behaviors. Experimental results reveal that the single-metal V-based MXene V(2)CT(x) exhibits outstanding X-band (8.2-12.4 GHz) absorption performance, achieving an ultralow RL of -53.8 dB and a broad effective absorption bandwidth of 3.4 GHz. Theoretical calculations indicate that V's multivalent d-orbitals generate pronounced density of states (DOS) peaks near the Fermi level, significantly enhancing carrier mobility and wave-carrier interactions. Normalized impedance analysis confirms excellent impedance matching with free space, a critical factor for minimizing microwave reflection and maximizing energy dissipation. In contrast, Ti-, Nb-, and Ta-based MXenes show limited performance, primarily relying on single loss mechanisms that fail to balance impedance and dissipation efficiently. The findings provide theoretical guidance for designing high-performance broadband microwave absorbers by tailoring atomic-scale composition to optimize impedance matching and multi-mechanistic energy dissipation in MXene-based materials.