Sulfur‐doped biomass‐derived hollow carbon microtubes toward excellent microwave absorption performance

Micro/nanocarbon materials have been regarded as one of the most desirable microwave absorbents due to their unique physical and chemical properties, whereas their unsatisfactory intrinsic complex permittivity and poor impedance matching severely hinder the further application in microwave adsorption. Herein, novel sulfur-doped hollow carbon microtubes (S-HCMTs) are successfully prepared through a facile one-step pyrolysis process using poplar catkin as a carbon precursor and sulfur powder as a doping agent. The poplar catkin-derived carbon materials exhibit a novel hollow microtubular structure, which is hard to be realized by the conventional chemical synthesis, and meanwhile the one-dimensional hollow structure can be well preserved after the sulfur doping treatment. Note that the introduction of sulfur atoms is beneficial to the adjustment of the electrical conductivity, thereby leading to superior impedance matching characteristics and dipolar relaxation loss capacity in comparison with pure hollow carbon microtubes (HCMTs). The as-obtained S-HCMTs exhibit excellent microwave absorption performance. The minimum reflection loss (RLmin) of S-HCMTs is as high as − 37.4 dB at 6.72 GHz, and the broadest effective absorption bandwidth reaches 8.0 GHz. The high-efficiency microwave absorption is mainly originated from the unique hollow structures, enhanced dipolar/interfacial polarization, multiple scatterings, as well as the excellent impedance match. The results demonstrate that the S-HCMTs can be considered as a promising candidate in high-performance microwave absorbers integrating lightweight and strong absorption intensity.