Ce-4f/N double-doped Mo-MXene for regulating dielectric polarization response

Double transition metal nitrides and carbides (MXene) have garnered significant attention in the field of electromagnetic wave (EMW) absorption due to their distinctive structural properties. The design of efficient MXene-based EMW absorbers remains a formidable challenge in light of the high conductivity and strong van der Waals forces. In this work, we report for the first time the approach of the double-doping non-metal N and rare earth metal Ce-4f into Mo-MXene to construct Mo-MXene/MoO₂-N/Ce system. This process enables partial in-situ oxidation of Mo-MXene, thereby forming a heterostructure and enhancing the interface polarization. The introduction of Ce facilitates the hybridization between the 4f orbitals of rare earth Ce and the 4d orbitals of Mo, altering the electronic structure of Ce and Mo-MXene and promoting electron migration, which contributes to polarization loss. Furthermore, incorporating melamine into the precursor can induce N doping in Mo-MXene, thereby promoting dipolar polarization. Consequently, the double-doping of N and Ce enables the synergistic effects of interface polarization, dipole polarization, and conduction loss, leading to efficient EMW absorption. Therefore, at a frequency of 13.43 GHz and a matching thickness of 4.685 mm, the optimal reflection loss (R_L) value of Mo-MXene/MoO₂-N/Ce reaches -57.46 dB, which exceeds a large number of reported MXene-based absorbers. This research confirms that Mo-MXene/MoO₂-N/Ce is a promising EMW absorption material and provides valuable insights into modulating MXene-based EMW absorbers using rare earth elements.