French-fry-shaped carbon composites co-doped with S, N, and Br for ultra-wideband electromagnetic wave absorption

Structural modulation and element doping are well-established strategies for tailoring impedance matching in the development of high-performance electromagnetic-wave (EMW) absorbers. Nevertheless, the efficient synthesis of carbon absorbers with controlled morphologies and multi-element-doping remains a formidable challenge. In this study, novel S/N/Br multi-doped EMW absorbers featuring distinctive three-dimensional architectures were synthesized via a monomer-polymerization strategy. Specifically, S/N-containing ABHMA monomers via Friedel–Crafts alkylation and Br-containing PDM monomers via esterification reaction were synthesized for the first time, the radical copolymerization of these monomers at different ratios afforded three distinct precursors. Subsequent pyrolysis at 700 °C under N 2 yielded porous carbon materials with ball-like (P-A@P-CB-700), french-fry-like (P-A@P-CF-700), and popcorn-like (P-A@P-CP-700) morphologies. Among them, the french-fry-shaped P-A@P-CF-700 with a large specific surface area (550.81 m 2  g −1 ) and unique pore structure exhibits outstanding EMW absorption performance, achieving an ultralow minimum reflection loss ( RL min ) of −56.74 dB at a thickness of 3.5 mm, and an effective absorption bandwidth (EAB) of 6.62 GHz at 2.5 mm. Moreover, a maximum radar cross section (RCS) reduction of 49.36 dBm 2 was attained, underscoring its potential for practical stealth applications. The combination of the unique morphology with S/N/Br doping synergistically enhanced the cooperative effects of polarization loss, conductive loss, and multiple-scattering attenuation. This work not only provides an innovative pathway for precise morphology and composition control but also establishes a new paradigm for designing advanced EMW absorption materials.