Biomass-Derived\nSpherical Carbon Materials for Efficient\nElectromagnetic Wave Absorption

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