Achieving Sustainable Ultralight Electromagnetic Absorber from Flour by Turning Surface Morphology of Nanoporous Carbon

It is well known that the surface architecture of an absorber has a significant effect on the final electromagnetic (EM) wave attenuation behavior. Herein, a series of nanoporous carbon media with different surface morphologies, including a honeycomb-like structure, three dimension (3D) interrelated network, and irregular lump shape, were obtained by a facile one-step strategy employing the green biomass of wheat flour as the precursor. By optimizing the surface architecture, it is demonstrated that the elaborate 3D interrelated skeleton makes a crucial contribution on the eventual EM absorption performance. At the identical low filler content of only 8 wt %, the nanoporous carbon media with a 3D interrelated skeleton shows the minmium reflection loss (RLmin) of −51 dB, almost 9 times higher than that of the other two nanoporous carbon media with honeycomb-like structures and irregular lump shapes. The corresponding effective frequency bandwidth (fe, RL exceeding −10 dB) of 4.8 GHz was achieved at a thin thickness of 1.8 mm. Moreover, when slightly changing the mass percentage to 9 wt % in the paraffin matrix, the broad fe region of 6 GHz could cover the whole Ku band. This work provides a facile, sustainable, and low-cost approach for developing ultralight and highly efficient absorption media by means of a renewable biomass as te source, and the derived 3D carbon skeleton displays a great potential for dealing with EM interference.