Heterophasic cobalt sulfide heterogeneous interfaced carbon nanospheres with enhanced electromagnetic wave absorption and thermal insulation performance

• The heterophasic cobalt sulfide (CoS, Co 9 S 8 , Co 3 S 4 )/carbon nanospheres rich in heterogeneous interfaces was prepared; • Enormous heterogeneous interfaces formed among multiple heterophasic cobalt sulfides and carbon induce dipole and interfacial polarisation; • Excellent EM wave absorption with RL min of -62.68 dB and EAB of 5.44 GHz was obtained; • The EM wave absorption performance was proved by radar reflectance cross section simulation. • Satisfactory thermal insulation performance was achieved by thermal conductivity test. Heterogeneous interfaces can significantly improve interface polarization loss, promote multiple reflections or scatter of incident electromagnetic waves; simultaneously, the mutual diffusion of constituent elements introduces interface states and defects, which results in the asymmetric localized electric field effect and dipole polarization effect, promoting electromagnetic wave (EW) absorption performance. Various cobalt sulfides (Co x S y ) with heterogeneous interfaces formed by the variable stoichiometric ratios of cobalt and sulfide, producing high dielectric loss, which has received considerable attention in the microwave absorption (MA) field. Nevertheless, preparation of Co x S y EW absorbers with a broadened effective absorption bandwidth (EAB) is still a challenge. Herein, the heterophasic cobalt sulfide (CoS, Co 9 S 8 , Co 3 S 4 )/carbon nanospheres rich in heterogeneous interfaces were synthesized. Numerous heterogeneous interfaces in prepared composites enhanced the interfacial polarizability, which plays an important role in optimizing the electromagnetic parameters and absorption performance. An EAB value of 5.44 GHz at 1.8 mm, which essentially covers the entire Ku band, and an excellent minimum reflection loss (RL min ) of −62.68 dB at 2.8 mm was achieved. Furthermore, the dissipation capability of the absorber in practical applications was verified by radar scattering cross-sectional (RCS) simulation results. Besides, the high thermal insulation performance of the prepared composites was achieved, which proves its possible application under extreme conditions. The heterophasic cobalt sulfide (CoS, Co 9 S 8 , Co 3 S 4 )/carbon nanospheres rich in heterogeneous interfaces was sythesized by the solvothermal method with calcination process. Numerous heterogeneous interfaces in multiple heterophasic cobalt sulfide/carbon constructs enhance the interfacial polarizability to enhance the electromagnetic wave absorption performance.