Ultralight Coral-like hierarchical Fe/CNTs/Porous carbon composite derived from biomass with tunable microwave absorption performance

[Display omitted] •The hierarchical coral-like Fe-NPC/CNTs composite was fabricated from renewable biomass.•The composite exhibited strong RL (-70 dB) at an ultrathin thickness (1.9 mm).•The EAB can reach 5.0 GHz with low filler loading (12.5 wt%).•This provides a low-cost and sustainable strategy to prepare high-performance absorber. In order to widen the application field of microwave absorption (MA) materials, it is still challenging to obtain high-performance MA materials with wide frequency bandwidth, lightweight, thin thickness, and strong absorption by an economical and sustainable method. Herein, the novel coral-like hierarchical structure with zero-dimensional Fe nanocrystals, one-dimensional N-doped carbon nanotubes (CNTs) and three-dimensional porous carbon (PC) matrix is rationally constructed to enhance MA performance. Based on renewable biomass residues, the composite consisted of PC as matrix, bamboo-shaped CNTs with magnetic nanoparticles at the top grow on the surface of PC. By controlling the growth conditions of carbon nanotube, the microstructure and dielectric loss capacity of composite can be manipulated to optimize the impedance matching, reflection loss (RL), and effective absorption bandwidth (EAB, the bandwidth of RL