Spatial rotation-freeze-cast bilayer graphene aerogels with orthogonal gradients for switchable EMI shielding and thermal regulation

Abstract

We present a strategy to prepare bilayer reduced graphene oxide aerogels with hierarchical structure (rGAH) via two-step directional freeze-casting with spatial rotation, addressing the limitations of conventional homogeneous counterparts in achieving absorption-dominant and tunable electromagnetic interference (EMI) shielding. The architecture synergistically integrates an upper layer with vertically aligned pores for optimized impedance matching (reduce reflection loss) and a lower honeycomb-structured reflective shield, synergistically enhancing microwave absorption through dual electrical-structural gradients. Orthogonal pore alignment enables ultra-low in-plane thermal conductivity (0.012 W/(m·K)), surpassing most reported graphene aerogels. Incorporating 50% carbon nanotubes into the reflective layer yields exceptional EMI shielding effectiveness (54.2 dB) with a high absorption coefficient (A = 0.88). The compressible design permits dynamic modulation of EMI shielding (absorption-reflection ratio: 1.9–3.7) and electrothermal performance, featuring rapid Joule heating (58 °C at 3.5 V within 10 s) and compression-dependent tunability (0–90% strain). This orthogonally engineered bilayer platform, extendable to diverse 2D nanomaterials (e.g., MXenes), provides a scalable strategy for multifunctional shielding materials with programmable thermal/electrical properties. By structurally optimizing aerogels with dynamic responsiveness, our work advances excellent electromagnetic protection systems, demonstrating potential for next-generation shielding technologies.