Absorption-Dominated Asymmetric Graphene/Carbon Nanotube Network Composite Aerogel for Efficient Electromagnetic Shielding

With the rapid development of electronic devices, it has become important to develop highly efficient absorption-dominant electromagnetic interference (EMI) shielding materials to prevent electromagnetic waves (EMWs) from harming the environment and human health. In this study, a graphene (GR)/chitosan (CS) composite aerogel (GC) was prepared via directional freezing, and carbon nanotubes (CNT) were grown within the GC matrix by chemical vapor deposition (CVD) to fabricate a GC/CNT aerogel, which was further assembled into a bilayer composite structure. The optimized bilayer composite exhibits a high total electromagnetic shielding effectiveness of 70.02 dB, an exceptional absorption coefficient (A) of 0.91, and a minimum reflection loss (RL) of −18.95 dB at 9.187 GHz in the X-band, while also demonstrating a maximum compressive strength of 8.0 MPa. The GC/CNT aerogel achieved a high EMI shielding efficiency of up to 82.55 dB in the X-band at a thickness of 4.0 mm, while also possessing Joule heating performance and organic solvent adsorption function, demonstrating multifunctional characteristics. By integrating a GC absorption layer, the GC-GC/CNT bilayer structure allows tunable absorption efficiency through variation of the GC layer thickness, thereby shifting the shielding mode from predominantly reflective to predominantly absorptive. The developed bilayer composite, with its outstanding shielding efficiency and low reflection characteristics, employs a unique “absorption-reflection-reabsorption” electromagnetic wave dissipation mechanism, offering an effective strategy for the design of high-performance, absorption-dominant EMI shielding materials.