Correlating the gradient nitrogen doping and electromagnetic wave absorption of graphene at gigahertz

Nitrogen doping has been proved an effective strategy to improve the microwave absorption performance of graphene. However, the detailed investigations correlating the role of nitrogen dopants with dielectric properties and microwave absorption of graphene has not been available. In this work, the gradient nitrogen doped graphene (NG with 0 wt%, 3.7 wt% and 6.86 wt% N content) were prepared via a facile hydrothermal strategy. The effect of nitrogen dopant on microstructure, morphology, chemical composition, complex permittivity, attenuation factor, impedance matching degree and microwave absorption of graphene were systematically investigated. The electromagnetic characterization and CST simulation results reveal that the moderate N-doped graphene (NG-100) endows the optimal microwave absorbing performance, which was attributed to the moderately introduced dipole polarizations, as well as the better balance between attenuation factor and impedance matching degree. The maximum reflection loss (RL_max) of NG-100 is ∼ -55 dB under 3.2 mm, which is five times higher than that of non-doped graphene. Meanwhile, the effective attenuation bandwidth (EAB: < −10 dB) of NG-100 is up to ∼6.82 GHz under 2.6 mm. More importantly, by correlating gradient N-doped graphene with attenuation factor and impedance characteristics, this work provide an approach to the design and construction of graphene-based composites as efficient microwave absorber for realizing practical applications.