Unraveling the Charge Rearrangement-Driven Synergistic Mechanism in SiO ₂ @Ni–Co/CNTs: The Regulatory Role of Ni-Doping in the Bimetallic Shell

Metal-organic framework (MOF)-derived carbon-based composites have emerged as promising candidates for high-performance electromagnetic wave (EMW)-absorbing materials, yet the atomic-scale mechanism linking compositional doping to EMW energy dissipation remains to be clarified. Herein, core-shell SiO₂@Ni-Co/CNTs composites were fabricated via epitaxial Zeolitic imidazolate frameworks (ZIF) growth on monodisperse SiO₂ microspheres (∼1 μm) and controlled pyrolysis, focusing on the Ni-doping-driven charge rearrangement and synergistic mechanism. Material characterizations confirmed the well-defined core-shell structure, while electromagnetic analysis showed the optimized SiO₂@Ni-Co/CNTs-2 sample achieved ultrastrong performance: minimum reflection loss (RL_min) of -61.21 dB at 1.85 mm, ultrabroad effective absorption bandwidth (EAB) of 6.64 GHz (11.36-18 GHz) at 2.09 mm, and 25.5 dB radar cross-section (RCS) reduction at 60°. Crucially, off-axis electron holography visualized interfacial charge accumulation, and DFT calculations quantified Ni-induced charge rearrangement, which intensifies dipole/interfacial polarization to dielectric loss enhancement. Combined with the optimized bimetallic magnetic resonance, this charge rearrangement drives a powerful synergistic effect that maximizes EMW attenuation. This work clarifies the "charge rearrangement-synergistic loss" link and provides a "structure-composition-charge-function" design paradigm for high-performance EMW absorbers.