Green electromagnetic interference shielding films with unique and interconnected 3D magnetic/conductive interfaces

Magnetic nanoparticle-decorated biomass-derived carbon films are intriguing green electromagnetic interference shielding composites because of their eco-friendly, high shielding effectiveness, low reflection loss, etc. However, it is still difficult to uniformly decorate magnetic nanoparticles onto a whole interconnected carbon skeleton. Herein, to overcome this difficulty, a novel in situ coprecipitation approach was developed to construct the 3D Fe3O4@carbon core-shell network with interconnected magnetic/conductive interfaces. Briefly, common filter papers (CFPs) decorated with metal ions were immersed into ammonia solutions, to in situ generate Fe3O4 nanoparticles on whole CFPs. Subsequently, Fe3O4-decorated CFPs are carbonized to obtain magnetic and conductive biomass-derived carbon films. The novel structure endows the resultant films with excellent electrical conductivity (673–732 S/m), excellent shielding (30.6 dB) and low reflection coefficient (R = 0.354). The specific SE of our films is as high as 191.3 dB/mm, exceeding that of the reported biomass-derived carbon materials.