The Elaborate Design of Multi-Polarization Effect by Non-Edge Defect Strategy for Ultra-Broad Microwave Absorption

Anion defect engineering is proven to be an efficient approach to reconstruct the electronic configuration of carbon-based magnetoelectric materials for targeted modulation of electromagnetic (EM) performance. However, traditional mono-anionic doping suffers from low defect concentration and lacks diverse polarization mechanisms. In this work, multi-anions (N/S/F) stepwise-doped carbon/Fe 3 C magnetoelectric composites are elaborately constructed, wherein the predesigned N defects serve as activated sites for anomalously adopting S anions (Step I) and subsequent F anions (Step II) in non-marginal areas of the carbon layer. It is found that S prefers to replace pyrrolic N defects while F tends to form dangling bonds with the C site adjacent to the pyridinic N. Intriguingly, besides the inherent polarized resonance of N defect at ≈15 GHz, customized S and F defects induce new polarization resonances at ≈10 GHz and ≈15+ GHz, respectively. Under a typical multi-polarization effect with the synergetic magnetic response, the carbon/Fe 3 C composites with N/S/F defects harvest the broadest bandwidth of 8.28 GHz (9.72–18 GHz) at 2.55 mm, covering a wide frequency range almost from X to Ku bands. This work demonstrates the positive impact of localized multi-defects customization and multi-polarization effect on expanding microwave absorption bandwidth, providing valuable insights for the advanced design of ultra-broadband absorbers.