Sodium oxalate-induced hydrothermal synthesis of wood-texture-column-like NiCo₂O₄ with broad bandwidth electromagnetic wave absorption performance

Single-component absorbent with wide-band absorption and strong attenuation capability is a challenge for efficient electromagnetic wave absorption. Morphology manipulation is an effective pathway to enhance electromagnetic wave absorption. Herein, naked NiCo₂O₄ with novel morphology of wood-texture-column-like nanostructure was synthesized for the first time through sodium oxalate-induced hydrothermal synthesis. The electromagnetic parameters are adjusted by controlling the amount of sodium oxalate to optimize absorbing performance. The optimum absorption performance occurs when the molar ratio of sodium oxalate to metal ions is 1.5, in which the effective absorption bandwidth is up to 7.10 GHz (10.90–18 GHz) at only 2.20 mm and the minimum reflection loss is low to −49.78 dB. Notably, the qualified EAB can cover the entire C, X and Ku bands by adjusting the thickness from 1.7 to 5.0 mm. Excellent absorbing performance is attributed to appropriate impedance matching originating from numerous cracks and pores in nanostructures and strong dipole polarization induced dominantly by oxygen vacancy together with lattice distortion. This study provides an excellent candidate for the study of single-component electromagnetic wave absorbents.