Heterointerface engineering in hierarchical assembly of the Co/Co(OH)₂@carbon nanosheets composites for wideband microwave absorption

Heterogeneous interface engineering strategy is an effective method to optimize electromagnetic functional materials. However, the mechanism of heterogeneous interfaces on microwave absorption is still unclear. In this study, abundant heterointerfaces were customized in hierarchical structures via a collaborative strategy of lyophilization and hard templates. The impressive electromagnetic heterostructures and strong interfacial polarization were realized on the zero-dimensional (0D) hexagonal close- packed (hcp)-face-centered cubic (fcc) Co/two-dimensional (2D) Co(OH)₂ nanosheets@three-dimensional (3D) porous carbon nanosheets (Co/Co(OH)₂@PCN). By controlling the carbonization temperature, the electromagnetic parameters were further adjusted to broaden the effective absorption bandwidth (EAB). Accordingly, the EAB of these absorbers were almost greater than 6 GHz (covering the entire Ku-band) in the thickness range of 2.0–2.2 mm except the sample S-1.0-800. As far as to the S-0.8-700 achieved an EAB up to 7.1 GHz at 2.2 mm and the minimum reflection loss (RL_min) value was −25.8 dB. Moreover, in the far-field condition, the radar cross section (RCS) of S-0.8-700 can be reduced to 19.6 dB·m². We believe that this work will stimulate interest in interface engineering and provide a direction for achieving efficient absorbing materials.