Oxygen-vacancy-rich Fe3O4/carbon nanosheets enabling high-attenuation and broadband microwave absorption through the integration of interfacial polarization and charge-separation polarization

Metal-oxide/carbon composites with remarkable dielectric-magnetic properties are promising as microwave absorption materials, but achieving high-attenuation and broadband microwave absorption properties still remains challenging. Herein, we develop a one-step carbonization of the ferric gluconate precursor to manufacture two-dimensional oxygen-vacancy-rich Fe3O4/carbon nanosheets (Fe3O4/C) for high-attenuation microwave absorption. The key to the synthesis is employing the Fe3+-gluconate complex as the precursor, which has the ability to release small molecules within the viscosity foaming window to spontaneously obtain a 3D self-foamed material. Followed by high-temperature annealing, the as-obtained Fe3O4/C hybrid composite features large lamellar (>20 mu m) carbon nanosheets with abundant yolk-shell heterostructures and highly dispersed and high-loaded (similar to 44%) oxygen-vacancy-rich Fe3O4 nanocrystals. The unique 2D structure could facilitate multiple scattering absorption and interconnect into a 3D conductivity-loss network. Meanwhile, the abundant yolk-shell heterostructures could trigger extra interfacial polarization. And density functional theory calculation results demonstrate that oxygen vacancies endow magnetic Fe3O4 nanocrystals with charge-separation induced polarizations. Consequently, Fe3O4/C exhibit superior microwave absorption capability with an impressive reflection loss (RL) of -65.4 dB and an ultra-broad effective absorption bandwidth of 6.24 GHz. The spontaneous foaming strategy in this work could provide feasible technological approaches for the practical fabrication of microwave absorption materials.

Automated summary

In this study, two-dimensional oxygen-vacancy-rich Fe3O4/carbon nanosheets were successfully synthesized for high-attenuation microwave absorption. The material features large lamellar carbon nanosheets with abundant yolk-shell heterostructures, which facilitate multiple scattering absorption and trigger extra interfacial polarization. The Fe3O4/C composite exhibits superior microwave absorption capability with an ultra-broad effective absorption bandwidth.