Doping-engineered Fermi level modulation in MXenes: Multiphysics field coupling enabled electron-pathway design for electromagnetic optimization

Doping-engineered Fermi level modulation in Ti₃C₂T_x-MXene is demonstrated through controlled in-situ nitrogen doping, which effectively tailors electronic structures to enhance dipole polarization. By constructing biomimetic aerogels with Prussian blue-derived FeCo bimetallic units, we establish hierarchical electron pathways that address critical limitations in conventional aerogel absorbers, including unstable connectivity and uncontrolled pore geometry. This electron-pathway design optimizes conductive networks while mitigating MXene stacking, as confirmed by interfacial charge transport analysis. Density functional theory calculations confirm a nitrogen doping-dependent Fermi level shift, which underlies the exceptional electromagnetic wave absorption of the FeCo-PBA/N-Ti₃C₂T_x aerogels. Sample PM-2 achieves a minimum reflection loss (R_Lmin) of −67.05 dB with 3.24 GHz effective absorption bandwidth (EAB) at 25 wt% loading and 2.30 mm thickness, supported by its ultralow density (9.8 mg/cm³) and high pore connectivity. Sample PM-1 attains the widest EAB of 4.56 GHz with an R_Lmin of −58.65 dB, while sample PM-4 maintains strong performance (R_Lmin = −50.52 dB, EAB = 4.12 GHz) at a low filler loading of 15 wt%. COMSOL Multiphysics simulations further elucidate multi-field coupled energy conversion dynamics, revealing that optimized polarization efficiency contributes dominantly to the absorption enhancement. This work provides a validated Fermi-level-centric strategy for electromagnetic functional materials, with demonstrated applicability in flexible multifunctional integrated electronic devices.