Grafting thin N-doped carbon nanotubes on hollow N-doped carbon nanoplates encapsulated with ultrasmall cobalt particles for microwave absorption

• Unique nanostructure microwave absorber with ultrasmall magnetic particles was prepared. • A reflection loss of –41.08 dB at a matching thickness of 2.0 mm was achieved. • The effective absorption bandwidth of the designed absorbers reached 4.26 GHz. • The origin of increased microwave absorption performance has been explored. • The microwave absorption ability under actual conditions of absorbents has been considered. It is desirable but challenging to integrate 0D, 1D and 2D materials into 3D nanostructures for the microwave absorption. Herein, short and thin N-doped carbon nanotubes (NCNTs) encapsulated with sub-2-nm magnetic Co particles grafted on hollow nanoplates (HCNP) are fabricated after ZIF-67 nanoplates were annealed at a lower temperature relative to conventional chemical vapor deposition methods. The as-fabricated HCNP/NCNT assembled with 0D, 1D and 2D nanostructures features 3D interconnected open structure, endowing them with abundant interfaces and defects that facilitate its microwave absorption. The minimum reflection loss ( RL min ) of −41.08 dB with a thickness of 2 mm and effective absorption bandwidth (EAB) of 4.26 GHz with a thickness of 1.8 mm were achieved by the HCNP/NCNT, superior to the counterparts without NCNTs. Besides its unique structural feature, density functional theory (DFT) calculations demonstrate that the increased microwave absorbability of the HCNP/NCNT is also relevant to the additional dipole polarization and interfacial polarization caused by the NCNTs. Based on the computer simulation technology (CST) results, the HCNP/NCNT can attenuate microwave energy under the actual conditions. The proposed controllable synthesis method may open a new avenue for the reasonable design of high-performance microwave absorbers.