Lignin-derived porous carbon microspheres via interfacial self-assembly for superior electromagnetic wave absorption

Carbon-based electromagnetic wave (EMW) absorbers possess advantageous properties such as low density, tunable conductivity, and excellent environmental stability. However, their EMW absorption capabilities are typically limited due to inherent insufficient loss mechanisms. Morphology optimization represents a promising approach for overcoming this limitation by tuning microstructures to enhance electromagnetic attenuation. Herein, we propose a cost-effective interfacial self-assembly strategy, utilizing interfacial tension among lignin, tetrahydrofuran and water molecules to fabricate spherical carbon-based EMW absorbers. Employing lignin as an abundant and renewable carbon precursor, the resulting microspheres exhibit improved dielectric properties owing to their structural refinement. Control of the rotational speed of stirring during self-assembly further improves sphere size distribution, thereby remarkably enhancing the EMW absorption performance. Specifically, the optimal sample achieves strong reflection loss of −44.28 dB at a thickness as thin as 1.8 mm and effective absorption bandwidth of 3.9 GHz, verifying the considerable performance enhancement by uniform spherical morphology. Radar cross-section simulations additionally confirm its superior far-field EMW absorption capability, further demonstrating the potential of this approach for developing renewable, low-cost and morphology-optimized carbon-based EMW absorbers.