Biomass-Derived Spherical Carbon Materials for Efficient Electromagnetic Wave Absorption

Biomass-derived carbon materials are hot in electromagnetic wave (EMW) absorption due to their wide sources, low cost, and unique structures. Yet, obtaining high-performance EMW absorbers from pure biomass via simple methods is challenging. In this work, a watermelon-derived spherical carbon material (SC-X) with a particle size distribution ranging from 2 to 10 μm was successfully synthesized using a combination of hydrothermal and carbonization methods. By increasing the carbonization temperature, the number of carbon defects in SC-X can be effectively increased, and the polarization loss capacity can be improved, achieving excellent EMW attenuation and impedance matching. The SC-4 carbonized at 900 °C achieved a minimum reflection loss value of −58.7 dB at 12.5 GHz frequency, with an effective absorption bandwidth of 3.5 GHz covering 10.8–14.3 GHz, and the corresponding thickness was only 1.7 mm. This work provides an effective strategy for the large-scale preparation of low-cost and high-performance EMW-absorbing materials derived from biomass.