The Electron Sink Effect Driven by Work Function Gradient for Enhanced Interface Polarization and Broadband Microwave Absorption in Conductive Heterostructures

The traditional development of magnetic alloy‐based microwave absorbers has relied on trial‐and‐error, lacking systematic control over interfacial electronic behavior, which often leads to poor impedance matching, single loss mechanisms, and limited bandwidth. To address these issues, this work proposes a DFT‐guided design strategy for conductive heterogeneous interfaces. The work function analysis reveals a gradient energy level alignment among FeSiAl, Fe 3 C, Fe, and CNTs. A difference exceeding 0.4 eV drives spontaneous electron migration from low‐work‐function components (FeSiAl, Fe 3 C, Fe) to CNTs, forming localized electron‐rich regions, referred to as the “electron sink” effect. This electron accumulation induces intense interfacial polarization relaxation under alternating electromagnetic fields, providing a work‐function‐gradient‐driven mechanism for enhanced dielectric loss. Using alkaline etching activation and in situ CVD, a hierarchical all‐conductive FeSiAl@CNT‐Fe 3 C/Fe heterostructure was constructed. Leveraging the synergy of electron‐sink‐enhanced interface polarization, optimized conduction loss, and magnetic loss, the composite achieves a minimum reflection loss of −76.53 dB at 1.55 mm and an effective absorption bandwidth of 6.06 GHz at 1.72 mm, with a density only 18% of FeSiAl, demonstrating the “thin, lightweight, broadband, strong” advantages. This strategy was further validated in the CoNi alloy system, pioneering a rational design pathway for high‐performance electromagnetic protection materials beyond traditional trial‐and‐error.