Composition-Dependent Dielectric Response and Broadband Electromagnetic Wave Absorption in Sulfide/rGO Composites

Broadband electromagnetic wave absorption depends on the frequency dependence of the composite response, not simply on the magnitude of dielectric loss. Here, CuS, CoS, and CuCo2S4 are combined with reduced graphene oxide (rGO) at a fixed sulfide-to-carbon mass ratio to examine how sulfide composition affects dielectric response and thickness-dependent absorption. Compared with CoS@rGO and CuS@rGO, CuCo2S4@rGO exhibits superior electromagnetic wave absorption, which is attributed to the synergistic effects of interfacial polarization and balanced dielectric and magnetic losses. It achieves an effective absorption bandwidth of 6.84 GHz at 2.4 mm and a minimum reflection loss of -46.7 dB at 2.9 mm. The CuCo2S4@rGO is also processed into poly(vinylidene fluoride) films. Electromagnetic measurements on stacked and pressed film specimens establish the response of the PVDF-based composite, while individual films show bendability, altered infrared thermal contrast, and self-extinguishing behavior under the tested conditions. This study relates sulfide-dependent dielectric response to broadband absorption and examines the processing of the absorber into a polymer composite.