Heterointerface engineering of bimetallic sulfides for augmented polarization loss with electromagnetic wave absorption

To overcome the limitations of single-component electromagnetic wave (EMW) absorbers in achieving broadband impedance matching and synergistic loss mechanisms, this study proposes a bimetallic heterointerface engineering strategy. A CoS₂/NiS₂@HCNFs composite with a gradient electronic structure was fabricated via solvothermal-electrospinning technology, enabling systematic regulation of heterointerfaces and sulfur vacancies in the transition metal sulfides (TMS). Experimental and theoretical analyses reveal that band offset at the bimetallic heterojunction induces a strong built-in electric field (BIEF), driving interfacial charge gradient transfer. Sulfur vacancies act as high-frequency relaxation dipoles that couple with the BIEF, significantly enhancing Maxwell–Wagner–Sillars (MWS) interfacial polarization. Concurrently, the three-dimensional conductive network and multi-scattering structure of the hollow carbon nanofibers (HCNFs) synergistically optimize impedance matching and electromagnetic wave dissipation pathways. The optimized CNSF-1 sample achieves an effective absorption bandwidth (EAB) of 10.08 GHz (covering X to Ku bands) at a thickness of 2.6 mm and a minimum reflection loss (RL_min) of −48.04 dB at 2.4 mm, demonstrating significantly superior performance to single-metal systems. This strategy offers a novel approach for designing “heterointerface-defect synergy” EMW absorption materials.