Structuring Hierarchically Porous Architecture in Biomass-Derived Carbon Aerogels for Simultaneously Achieving High Electromagnetic Interference Shielding Effectiveness and High Absorption Coefficient.

Developing high-performance electromagnetic interference (EMI) shielding materials with high absorption coefficient is highly desired for eliminating the secondary pollution of reflected electromagnetic wave (EMW). Nevertheless, it has long been a daunting challenge to achieve high shielding effectiveness (SE) and ultralow or no reflection SE simultaneously. Herein, highly porous and conductive carbon nanotube (CNT)-based carbon aerogel with a meticulously designed hierarchically porous structure from micro and sub-micro to nano levels is developed by specific two-stage pyrolysis and potassium hydroxide activation processes. The resultant activated cellulose-derived carbon aerogels (a-CCAs) exhibit an ultrahigh EMI SE of 96.4 dB in the frequency range of 8.2-12.4 GHz in conjunction with an exceptionally high absorption coefficient of 0.79 at a low density of 30.5 mg cm-3. The successful construction of hierarchically porous structure is responsible for the excellent "structurally absorbing" ability of a-CCAs, and the introduction of CNT-based heterogeneous conductive network can effectively dissipate the incident EMWs by interfacial polarization and microcurrent losses. Moreover, the as-prepared a-CCAs have a water contact angle of as high as 158.3°and a sliding angle of as low as 5.3°, revealing their superhydrophobic feature. The ingenious structure design proposed here provides a possible pathway to overcome the conflict between high EMI shielding performance and ultralow or no secondary reflection, and the as-prepared a-CCAs are exceedingly promising in the application of telecommunication, microelectronics, and spacecraft.