Radial Dielectric Gradient Core–Shell Ce/NiCo@C Composites for Simultaneous Electromagnetic Wave Absorption and Antibacterial Activity via Ce³⁺/Ce⁴⁺ Valence Modulation

Abstract The increasing demand for multifunctional materials that combine electromagnetic wave (EMW) absorption and antibacterial properties has driven the development of novel materials capable of meeting these challenges. Here, a core–shell Ce/NiCo@C composite with a radial dielectric gradient structure is presented, designed to enhance EMW absorption and exhibit potent antibacterial activity. The material's unique architecture, which includes a multilayered core–shell configuration and a gradient distribution of Ce³⁺/Ce⁴⁺ valence states, modulates the dielectric constant and promotes electron migration polarization under EMW exposure. This design results in a broad effective absorption bandwidth of 7.12 GHz, with a minimum reflection loss (RL_min) of −67.2 dB at a thickness of 1.94 mm. Additionally, the reversible valence transition between Ce³⁺ and Ce⁴⁺ generates reactive oxygen species (ROS), which disrupt microbial cell membranes and inhibit bacterial growth. The Ce/NiCo@C composite demonstrates a sterilization rate exceeding 99% against E. coli and a significant bactericidal effect against S. aureus. This work highlights the potential of integrating valence‐modulated, dielectric gradient materials for advanced EMW absorption and antimicrobial applications, offering a promising approach for future multifunctional materials in diverse EMW technological fields.