HCl induced structure evolution and dual-frequency broadband microwave absorption of PANI hierarchical microtubes

Abstract

High-performance absorbers are in urgent demand for dealing with the increasing electromagnetic wave (EMW) pollution caused by the rapid development of information technology. Herein, we developed a simple SDS/HCl-assisted oxidative polymerization method for the controllable synthesis of nanorod-coated PANI hierarchical microtubes as an efficient EMW absorber. The morphological evolution can be expediently achieved from hierarchical microtubes and solid nanofibers to nanorods by adjusting the HCl concentration. The formation of PANI hierarchical microtubes is caused by the cooperation of SDS and the minimum surface energy. What is more, morphology-dependent conductivity and EMW absorption properties were systematically investigated. Owing to the hierarchical 1D hollow structure and carrier concentration, the ultimate conductivity reached 0.08 S/cm at [HCl] = 7.5 mM. The corresponding HCl-doped PANI hierarchical microtubes exhibited superior EMW absorption properties (EMWAPs) with a large absorption of −43.6 dB and a wide absorption band of 5.84 GHz in relation to a 1.55 mm thick sample. The excellent EMWAPs are the consequence of the high conductivity and distinctive 1D, hierarchical, and hollow structure, which generate enhanced permittivity, multiple resonances, strong attenuation capability, multiple scattering, and EM radiation. Owing to their tunable morphology, tunable conductivity, and excellent EMWAPs, the PANI hierarchical microtubes offer great promise for fields such as sensors, electronics, optics, catalysis, energy storage, and EMW absorption and shielding.