PANI‐Promoted Controlled Synthesis of CoO/Co/Hollow C Fibres: Microstructural Regulation and Electromagnetic Wave Absorption Optimization

The rational use of biomass microstructures, combined with the engineering design of controllable magnetic nanoparticle synthesis for precise electromagnetic parameter modulation, is fundamental for advancing the development of next-generation electromagnetic wave (EMW) absorbing materials. In this study, biomass fibers with unique hollow structures are used as carbon templates, modified by the conductive polymer polyaniline (PANI) to induce controllable growth of ZIF-67 particles on their surfaces, and systematically regulate the carbonization temperature to comprehensively investigate the tanδ_ε design principle of hollow carbon composite fibers for EMW absorption. As a result, the minimum reflection loss (RL_min) of CoO/Co /CP@TCF and CP@TCF can reach -55 and -53 dB, respectively, and the maximum effective absorption bandwidth (EAB_max) is 6.5 and 5.4 GHz, respectively, while maintaining the ultra-thin thickness of 2.38 and 2.18 mm. The significant charge carrier separation and interfacial polarization of CoO/Co@hollow carbon composite fibers are further confirmed using electron hologram analysis. In addition, the proposed magnetic nanoparticle loading strategy (microstructure, composition, and carbonization temperature) and the established electromagnetic parameter-EMW absorption property modulation mechanism have broad applicability in various biomass-derived materials. These findings broaden the strategies for developing high-performance biomass-derived carbon/magnetic composites in electromagnetic wave absorption.