▎ 摘　　要

Electromagnetic (EM) waves absorbing materials with lightweight and unique 3D porous structure have been receiving greater attention due to their excellent EM shielding effects. Here, a low density, high porosity Ni/rGO composite foam has been facilely obtained by a combination of solution combustion, freeze-drying and high temperature annealing. The resulting Ni/rGO foam exhibits an interpenetrating network consisting of a 3D nickel skeleton and continuous rGO sheets. This unique configuration endows the foam excellent EM wave attenuation with a density of 38.54 mg/cm(3) and a porosity of 96.74%. The foam achieves a maximum reflection loss (RL) as high as -53.11 dB covering a bandwidth of 4.91 GHz for a thickness of 4.5 mm showing satisfying impedance matching. In addition, multiple loss mechanisms have been demonstrated in the Ni/rGO foam, including Debye dipole relaxation, conduction loss, interfacial polarization, ferromagnetic natural resonance, and multiple reflections resulted from this hierarchically porous structure. In short, the study provides a novel, economical, and efficient way to obtain 3D EM wave absorbing materials.