Engineering of Multiple Heterointerfaces in N, S‐Codoped Hollow Cu/Cu ₂ S/C Nanoboxes for Superior Electromagnetic Attenuation

The reasonable construction of hollow structures featuring multiple heterointerfaces is widely recognized as crucial for developing high‐performance electromagnetic wave (EMW) absorbers, owing to their advantages in lightweight and enhanced interfacial polarization. However, achieving precise structural control and obtaining deep understanding of associated dielectric loss mechanisms still remain challenging. To address this, we rationally designed and synthesized N, S‐codoped hollow Cu/Cu 2 S/C nanoboxes (H‐Cu/Cu 2 S@NSC) through a multi‐step process based on self‐sacrificing templates. This unique architecture ingeniously integrates interior hollow cavities, various heterointerfaces (including Cu/Cu 2 S, Cu/C, and Cu 2 S/C), and heteroatom doping within a single entity. Benefiting from the synergistic effect between hollow structure and heterointerfaces, the H‐Cu/Cu 2 S@NSC maintains lightweight characteristics while exhibiting enhanced interfacial polarization. Furthermore, N, S‐codoped carbon shell further improves conduction loss and dipole polarization. Density functional theory (DFT) calculations provide deep insights into the electronic interactions at the heterointerfaces, confirming promoted charge transfer and polarization effects. As a result, H‐Cu/Cu 2 S@NSC exhibits exceptional EMW absorption performance, with a minimum reflection loss ( RL min ) of ‐62.21 dB at 2.04 mm and a broad effective absorption bandwidth (EAB) of 4.8 GHz at merely 1.64 mm. This work provides a feasible strategy for the rational design of advanced hollow multi‐interface materials for efficient EMW attenuation.