A facile method to fabricate macropores and high-content pyridine N-doped carbon in hollow Co/C toward high-efficient microwave absorption

Synchronizing the contents of N-doped carbon and porous structure modulation is an effective strategy for carbon-based absorbers to boost their microwave absorbing property. However, it is difficult to implement it with a simple method. In this work, hollow Co/C composites with macropores and N-doped carbon in shell were prepared by simple carbonization process using hollow ZnCo-ZIFs as precursors, and the density of macropores and N-doped carbon species were simultaneously regulated by facile adjusting the molar ratio of Zn to Co. Moreover, the obtained Co/C composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectra and nitrogen adsorption and desorption system. When the molar ratio of Zn/Co is 0.5, the obtained hollow Co/C possessed suitable density macropores and relative high content of pyridine N (77.34%) with low graphitic N (22.66%). Benefiting from the synergistic effect of macropores and high content of pyridine N, the high polarization loss and low conduction loss were achieved, and improved impedance match was realized, resulting in that the obtained composites displayed high-efficient microwave absorption with RLmax of - 56.7 dB and efficient absorbing bandwidth of 8 GHz. This work could serve as a reference for fabrication of other efficient MOFs-derived microwave absorbing materials.