Corn silk-derived biomass carbon materials for low-frequency microwave absorption and energy storage

Abstract

Biomass carbon (BC) materials derived from agricultural waste have shown great potential in microwave absorption (MA). However, current research mainly focuses on high-frequency (8–18 GHz) MA, and much less effort has been spent on low-frequency (2–8 GHz) MA and other important functionalities such as energy storage. Herein, corn silk rich in carbon is utilized to prepare BC materials with uniform pores and large specific surface area through a straightforward chemical activation and carbonization process. Attributed to its optimized impedance matching, interfacial polarization and (N and O) heteroatom-induced dipole polarization, the optimal sample exhibits superior low-frequency MA capability, including a strong reflection loss (RL) of −75 dB at 6.88 GHz, an effective absorption bandwidth (EAB, RL ≤ −10 dB) down to 2.8 GHz, and excellent radar cross-section reduction. Furthermore, it achieves a high initial discharge specific capacity of 1015.54 mA·h g⁻¹ and stable cycling performance at 0.5 A g⁻¹ in lithium-ion batteries owing to its heteroatom-rich porous structure with a large specific surface area. Our study offers a simple and low-cost way to fabricate high-performance multifunctional BC materials for low-frequency MA and lithium-ion energy storage.