Cationic etching of ZIF-67 derived LaCoO3/Co3O4 as high-efficiency electromagnetic absorbents

Given the urgent requirement of electromagnetic (EM) radiation defensive and self-power EM energy infinite vitality deliverers, high-efficiency EM absorbents are highly proposed. Herein, a series of hierarchical N-hybridized carbon-based polycrystalline EM absorbents containing perovskite type LaCoO3 and spinel type Co3O4 have been successfully synthesized via a controllable cationic etching technique based on ZIF-67. By adjusting the molar ratio between water and ethanol in etching solvents, polycrystals with tunable morphologies, crystalline structures, dielectric and magnetic properties can be obtained. Especially, the multiple phase properties were studied via a refinement treatment (Rietveld analysis) of X-ray diffraction (XRD), illustrating the existence of heterogeneous interfaces and lattice stress and distortions in details. The non-stoichiometric lattice O (O vacancy) in LaCo3+1-2δCo2+2δO3-δ/Co3O4 polycrystals and LaCo3+1-2δCo2+2δO3-δ single crystalline perovskite were characterized by XPS (δ = 0.19, 0.12 and 0.03). Responsible to the synergistic optimization of EM attenuation and impedance matching effect caused by the strengthening of interfacial polarization and dipoles polarization, the polycrystalline samples exhibited excellent EM absorbability. In details, the minimum reflection loss (RLmin) and effective absorption band width (fE) reached −45.91 dB and 5.6 GHz respectively at 12.48 GHz with a thickness at 2.7 mm, when there were 25% water in etching solution. Noteworthily, the fE of polycrystal obtained via 50% water reached 6.88 GHz with a device thickness of 2.8 mm.