Heterointerface Engineering in Bimetallic Sulfides Cuts Polarization Loss for Better Microwave Absorption

Wireless technology has become inseparable from everyday life, but the electromagnetic radiation emitted by smartphones, routers, and smart devices can interfere with sensitive electronics and raise concerns about exposure. One promising route to mitigate these issues is electromagnetic wave (EMW) absorption—materials that convert incoming radio-frequency energy into heat rather than reflecting it back.

Yet conventional EMW absorbers often face a structural trade-off. Carbon-rich systems can reflect waves too efficiently, preventing deep penetration, while metal-based materials can suffer from impedance mismatch, limiting how effectively energy is dissipated. In practical terms, a successful absorber must both “invite” waves in and ensure they are ultimately consumed inside the material.

A research team from Qingdao University addresses this problem with a “heterointerface–defect synergy” strategy. They used solvothermal-electrospinning methods to couple bimetallic sulfides—CoS₂ and NiS₂—with hollow carbon nanofibers (HCNFs), building a composite engineered for a gradient electronic structure that promotes energy loss pathways.

The key mechanism begins at the CoS₂/NiS₂ heterointerface. There, a strong built-in electric field forms, promoting directional charge transfer. This field accelerates conversion of EMW energy into thermal dissipation through polarization and interfacial charge dynamics.

To further intensify losses, the design introduces sulfur vacancies that act as “energy traps.” These defect sites interact with the built-in electric field, strengthening dipole polarization and improving the coupling between structural imperfections and electromagnetic energy.

Meanwhile, the three-dimensional hollow network of HCNFs supports more effective impedance matching and increases the effective propagation length of waves within the absorber. Together, these features enhance multiple reflections and scattering, giving waves more opportunities to be attenuated.

Performance results are striking. At a thickness of 2.6 mm, the effective absorption bandwidth (EAB) spans 8.32–18.4 GHz, covering the full X-band and Ku-band. At 2.4 mm, the minimum reflection loss (RLmin) reaches −48.04 dB, corresponding to absorption of over 99.99% of incident EMW energy.

Compared with single-metal sulfide systems, the EAB increases by 61%. Importantly for real-world deployment, the material maintains excellent absorption even at a low filler loading of 15 wt% under 60° oblique incidence.

The findings were published in Nano Research on 14 May 2026, offering a lightweight, broadband, and highly lossy platform that could support next-generation shielding for civilian electronics and potentially improve stealth-relevant radar mitigation technologies.

Keywords

bimetallic sulfides; heterointerface engineering; sulfur vacancies; hollow carbon nanofibers; built-in electric field; polarization loss; electromagnetic wave absorption