Biomass-based honeycomb-like architectures for preparation of robust carbon foams with high electromagnetic interference shielding performance

Honeycomb-like lignin-derived carbon (LC) foams doped with reduced graphene oxide (RGO) are fabricated via unidirectional ice-templating followed by freeze-drying and carbonization. The dimensions, constituent contents, and density of the foams could be easily adjusted. By manipulating the density, high electrical conductivity and good mechanical properties could be achieved at relatively low RGO contents. In addition to the high conductivity and interfaces between LC and RGO, aligned pores also boost electromagnetic interference (EMI) shielding effectiveness (SE) of the foams owing to induced multiple reflections. X-band EMI SE of the LC-based foams with 2-mm thickness could reach 28.5–70.5 dB at very low densities. Furthermore, the normalized surface specific SE (SE divided by density and thickness) could be as high as 28750 dB cm²/g, which is much higher than those of other types of carbon foams and most shielding materials ever reported. With the outstanding EMI shielding performance, good mechanical properties and more sustainable raw material, the biomass-based carbon foams offer promising prospects for lightweight, robust and high-performance EMI shielding materials.