NiO/NiFe2O4@N-doped reduced graphene oxide aerogel towards the wideband electromagnetic wave absorption: Experimental and theoretical study

Constructing the ferromagnetic N-doped reduced graphene oxide aerogel (N-rGA) with broadband and low filler loading is essential for absorbing electromagnetic waves (EMWs). In this work, an unique hierarchical structure of NiO/NiFe2O4 (NFO) with specific porous derived from NiFe layered double hydroxide (LDH) and N-rGA composite is successfully prepared through a facile hydrothermal method and freeze-drying technique. The NiO/NFO embedded into N-rGA (NNGA) possesses a hierarchical porous structure, abundant defects, and multiple interfaces, which can significantly enhance the EMW absorption capability of the composite. Here, when the mass ratio of NiO/NFO to N-rGA is 1:2.5, NNGA-2 exhibits excellent EMW absorption property, and its minimum reflection loss (RLmin) can reach -57.7 dB with an effective absorption bandwidth (EAB) of 6.58 GHz (10.34-16.92 GHz), appearing at 1.93 mm. Besides, NNGA-3 manifests a suitable EMW absorption property in a low-frequency band. To ulteriorly expose the inner EMW absorption mechanism of composites, the N-doped reduced graphene oxide (N-rGO) layer is constructed following the Lerf-Klinowski model, which uses a 2 x 2 unit cell of graphene to simulate the effects of polarization of N-rGA in our experiment. The combination of experimental and theoretical research clarified the mechanism of NNGA composites, indicating that NNGA composites can develop a novel mute to build a 3D hierarchical porous structure to promote EMW absorption abilities.