Synthesis of three-dimensional porous nitrogen-doped reduced graphene oxide/multi-walled carbon nanotubes composite aerogel as lightweight and high-performance electromagnetic wave absorbers

In this work, nitrogen-doped reduced graphene oxide/multi-walled carbon nanotubes (NRGO/MWCNTs) composite aerogel was synthesized through a hydrothermal self-assembly and freeze-drying two-step method. Results of micromorphology and structure analysis showed that three-dimensional (3D) porous network structure with a pore size of several microns was well constructed and numerous MWCNTs were on top of wrinkled surfaces of flake-like RGO and lots of nitrogen atoms were doped into RGO. Significantly, the obtained NRGO/MWCNTs composite aerogel with the density of 7.4 mg/cm3 exhibited the integrated optimal EMW absorption capacity that was the minimum reflection loss of −46.3 dB at 11 GHz (X-band), and broad absorption bandwidth of 4.2 GHz (from 13.3 to 17.5 GHz) under an ultrathin matching thickness of merely 1.4 mm and low filler content of 15 wt%. Meanwhile, the reflection loss values were all less than −10 dB (90% absorption) with matching thickness changing from 1.4 to 4.5 mm. The possible EMW absorption mechanisms were further proposed. Therefore, the as-fabricated NRGO/MWCNTs composite aerogel could be exploited as promising lightweight and high-efficient absorbers in the field of EMW absorption.