Porous N-doped Ni@SiO2/graphene network: Three-dimensional hierarchical architecture for strong and broad electromagnetic wave absorption

Abstract

Electromagnetic wave absorber is critical for reducing increasingly serious electromagnetic wave pollution, however, the development of lightweight and broadband microwave absorbers remains a pressing challenge. We report here the rational design and synthesis of N-doped [email protected]2/graphene composite constructed from 3D interconnected porous graphene network and [email protected]2 core-shell architecture, which fulfills lightweight and broadband requirements while exhibiting highly efficient electromagnetic wave absorption. The porous graphene network, functioning both as lightweight support and dielectric mediator, was synthesized via NaCl template-assisted high-temperature calcination method. Upon uniformly attached with core-shell [email protected]2 on the surface, the resulting abundant heterogeneous interfaces constructed by graphene-Ni and Ni-SiO2 strongly reinforce polarization loss. The presence of low dielectric SiO2 allows facile tuning of the complex permittivity of ternary composite by adjusting coating thickness to balance the attenuation ability and impedance matching. Moreover, further N-doping of graphene assists in the optimization of dielectric loss ability. Taking account of the advantages arising from the porous hierarchical architecture, multiple absorption centers and diverse interfaces, the lightweight composite exhibits an ultra-strong reflection loss (RL) value of - 71.13 dB at 13.76 GHz with a thickness of 2.46 mm and broad effective absorption bandwidth of 7.04 GHz at a low filler content of 15 wt.%. More importantly, the effective absorption range covers 13.28 GHz (4.72–18 GHz) with the optimized thickness of 1.6–5 mm, representing 83% of the whole range of frequencies. Our results demonstrate that the novel 3D porous N-doped [email protected]2/graphene network with hierarchical architecture is a promising candidate for high-performance electromagnetic wave absorption.