Synthesis of lightweight N-doped graphene foams with open reticular structure for high-efficiency electromagnetic wave absorption

Chemical doping of graphene with heteroatoms is expected to be a promising strategy to enhance the electromagnetic wave attenuation capability, however, the intrinsic mechanism is not investigated in-depth. In this manuscript, ultra-lightweight N-doped graphene foams (ρ ≈ 10.5–16.6 mg/cm3) with high porosity and open reticular structures are prepared via a self-assembled hydrothermal reaction and a freeze-drying process. Compared with pure graphene foams, the presence of N heteroatoms helps to build open reticular walls and tailors the electrical properties, leading to strong electromagnetic wave absorption capacity and broad absorption bandwidth simultaneously, and meanwhile, the investigation of N bonding configurations illustrates that the presence of pyrrolic/pyridinic N are mainly essential for the dipolar relaxation loss whereas graphitic N is beneficial to the conduction loss. When the bulk density is 11.6 mg/cm3, the maximum reflection loss of the absorber is −53.9 dB at 3.5 mm with a low filler loading of only 5 wt%, and the absorption bandwidth exceeding −10 dB is 4.56 GHz with a thickness of 2 mm, the highly efficient electromagnetic wave absorption performance strongly originates from the enhanced dipolar/interfacial polarizations, the multiple scatterings, the microscale circular conductive structures as well as the balanced impedance match. Furthermore, this monocomponent absorber can be an optimal candidate for ultra-lightweight and high-efficiency electromagnetic wave absorber without decorating other nanomaterials.