Controlled-etching assisted fabrication of yolk–shell Co/C nanocubes with dual loss mechanisms to improve electromagnetic wave absorption abilities

Rational design and fabrication of yolk–shell structure is evolving as an effective approach to improve electromagnetic wave absorption performance by enhancing the impedance matching, multiple reflections and scatterings, as well as promoting interfacial polarizations. However, due to the complexity of synthesis, it is still challenging to develop an absorber with yolk–shell structures intergrating two types of losses (dielectric and magnetic loss) simultaneously in the yolk and shell. Herein, novel yolk–shell Co/C nanocubes were successfully constructed via a controlled-etching with tannic acid followed by direct pyrolysis, in which the magnetic component Co and dielectric component C were uniformly distributed in the yolk as well as the shell. It was found that the pyrolysis temperature can adjust the graphitization degree of carbon and the crystallinity of metal Co, which effectively regulated the electromagnetic properties of the YS-Co/C nanocubes. The reflection loss was − 57.34 dB by increasing the pyrolysis temperature to 700 ℃ under a frequency of 11.76 GHz. The corresponding effective absorption bandwidth was 5.6 GHz (9.52–15.12 GHz) at a thickness of only 2.5 mm. The findings obtained from this study lay a solid foundation for novel design of yolk–shell absorbers applied in EMW absorption.