Controllable construction of one-dimensional Co/Co3O4@NC nanorods for enhanced low-frequency microwave absorption

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In the field of electromagnetic wave absorption (EMWA), a long-sought objective is still the deliberate construction of absorbers with lightweight, low loading, strong absorption, and broad bandwidth, especially in the low-frequency regime of 2–8 GHz. Herein, one-dimensional Co/Co 3 O 4 @N-doped carbon (Co/Co 3 O 4 @NC) nanorods were synthesized by a strategy involving high-temperature carbonization of Co-NTA nanowires in argon followed by low-temperature oxidation in air. By controlling the oxidation temperature, the mass ratio of Co to Co 3 O 4 can be effectively adjusted, which favors the optimization of impedance matching. At an oxidation temperature of 230 °C, the Co/Co 3 O 4 @NC-230 nanocomposite demonstrates strong low-frequency EMWA performance at an ultralow filling rate of 6 wt%. The minimum reflection loss (RL min ) reaches −50.95 dB at 6.1 GHz, and the effective absorption bandwidth (EAB) is approximately 3.0 GHz, covering 75% of the C-band. Furthermore, Co/Co 3 O 4 @NC-230 nanocomposite also shows outstanding EMWA behavior in the high-frequency range. When the matching thickness is 2.35 mm, a maximum EAB of 6.55 GHz can be achieved, and the RL min can reach −52.00 dB at 3.05 mm. Furthermore, by constructing a step-like periodic structure using Co/Co 3 O 4 @NC-230 nanocomposite, the EAB can be extended to 13.41 GHz, representing a 205.2% increase and covering 83.8% of the 2–18 GHz frequency band. To conclude, this study presents a new and effective approach to develop absorbers for low-frequency microwave absorption.