Synthesis of layered double hydroxide derivative-decorated nitrogen-doped graphene composite aerogels with a unique hierarchical porous network structure for microwave absorption

Developing lightweight and high-performance microwave absorbing materials remains a huge challenge. In this work, nitrogen-doped reduced graphene oxide/nickel oxide/cobalt tetraoxide (NRGO/NiO/Co₃O₄) composite aerogels were prepared through a three-step method involving a hydrothermal reaction, calcination and hydrothermal self-assembly. The results showed that the prepared NRGO/NiO/Co₃O₄ composite aerogels had extremely low bulk density and a unique three-dimensional (3D) hierarchical porous network structure. Furthermore, the effect of the addition amount of NiO/Co₃O₄ on the complex permittivity and microwave absorption properties of NRGO/NiO/Co₃O₄ composite aerogels was studied. When the addition amount of NiO/Co₃O₄ was 30 mg, the ternary composite aerogel exhibited the best microwave absorption performance. Specifically, when the filling ratio was as low as 3 wt%, the minimum reflection loss reached −59.77 dB at a thickness of 3.05 mm, and the maximum effective absorption bandwidth was 6.8 GHz (11.2–18 GHz, covering the entire Ku band and partial X band) with a thickness of 2.63 mm. In addition, the results of radar cross-section simulations demonstrated that the prepared ternary composite aerogel had great potential for practical applications. The excellent microwave absorption performance of NRGO/NiO/Co₃O₄ composite aerogels was mainly attributed to the reasonable structural design and the synergistic effect of the components. It is believed that this study will provide deep insights into the construction of 3D graphene-based composites as lightweight, broadband and efficient microwave absorbers.