In Situ Construction of MXene Derivatives and Rare Metal Doping in Nanofibers for Multifunctional and Ultrathin Electromagnetic Responses

Abstract Electromagnetic systems capable of achieving multifunctional integration are essential for advancements in electromagnetic protection. Herein, a 1D PCN/MXene‐TiO 2 ‐RM (RM = Gd, Ce, Pr, Er, Sm) nanocomposite nanofiber is meticulously designed with a 3D spatial network structure. During the heat treatment process, polyacrylonitrile (PAN) is carbonized to nitrogen‐doped carbon (PCN) to form 1D nanofibers with excellent conductive pathways and high conductivity. MXene is in situ oxidized to rutile phase TiO 2 , forming a heterogeneous interface and regulating the dielectric constant. At the same time, the incorporated rare metal further balances the dielectric constant of the nanofiber and promotes the EMW attenuation ability. Therefore, at ultrathin matching thickness of 1.7, 2.245, and 2.88 mm, PCN/MXene‐TiO 2 ‐Gd inherits strong reflection loss ( R L ) of −64.01, −71.32, and −65.4 dB, respectively, covering the Ku, X, and C bands, demonstrating its outstanding EMW response characteristics. Further investigation reveals the universality of this strategy, as doping with other rare metals (Ce, Pr, Er, Sm) also significantly improved the performance of PCN/MXene‐TiO 2 nanofibers. Additionally, the designed 1D nanofibers also exhibit multifunctional properties such as lightweight, flexibility, hydrophobicity, seawater corrosion resistance, heat dissipation, and radar stealth.