Dual-phase CoFe2S4/CoFe2O4 nanoflowers with multiple interfacial polarization responses for superior electromagnetic wave absorption

Transition metal sulfides and oxides with suitable dielectric features have been considered as significant candidates for advanced electromagnetic wave (EMW) absorption systems. However, there is still an urgent need to realize controllable regulation of their interfacial polarization behavior. Herein, we prepared dual-phase CoFe2S4/CoFe2O4 composites with an average size of similar to 1.43 mu m through a hydrothermal method. The unique nanoflower morphology promoted the multiple reflection and scattering of the incident EMW, contributing to the improvement of the loss ability. By varying the temperature during the solvothermal reaction, a facile adjustment of the CoFe2O4 to CoFe2S4 ratio can be realized. The difference in electronegativity and band gap facilitated the directional electron transfer from CoFe2O4 side to CoFe2S4 side at the dual-phase heterogenous interfaces, leading to spatial charge redistribution and optimized in-plane interfacial polarization. Moreover, the different distribution of CoFe2O4 and CoFe2S4 phases on different nanosheets exaggerated the deviation of interlayer positive/negative charges from the original equilibrium centers, thereby contributing to the enhancement of interlayer polarization. As a result, CoFe2S4/CoFe2O4 with higher dual-phase density exhibited strongest absorption intensity of -77.2 dB with an effective absorption bandwidth of 7.2 GHz at 1.8 mm. This work demonstrates the effective EMW attenuation optimization in transition metal sulfides and oxides and paves the way for modulating multiple interfacial polarization responses in inhomogeneous absorber systems.