Carbon doped with binary heteroatoms (N,X-C, where X = P, B, or S) derived from polypyrrole for enhanced electromagnetic wave absorption at microwave frequencies

Dual heteroatom-doped carbon materials show great promise as electromagnetic wave absorbers. However, synthesizing carbons containing multiple heteroatoms at controlled heteroatom doping levels has provided challenges to date. Herein, we report a simple method for manufacturing dual heteroatom doped carbons (N,X-C, where X = P, B, or S) by direct carbonization of polypyrrole synthesized in the presence of H3PO4, H3BO3, or H2SO4, respectively. The heteroatom content of the N,X-C products could be precisely tuned by varying amounts of acid dopant used in the polypyrrole synthesis. The N,X-C materials showed excellent electromagnetic wave absorption properties, especially N,S1-C (prepared using equimolar amounts of pyrrole and H2SO4) which offered a wide absorption bandwidth up to 6.6 GHz (11.38-18 GHz), and a RLmin of-32.3 dB (14.2 GHz) at 2.5 mm at a filler loading of 9.0 wt%. The outstanding electromagnetic wave absorption performance of N,S1-C was attributed to the presence of N dopant species, defects, C-S, and C-Sa groups, which optimized dipole polar-ization and conduction loss in the dielectric loss leading to excellent impedance matching.