Sulfidation-induced phase engineering of NiCo2S4/MXene-nitrogen-doped carbon aerogels for boosting electromagnetic wave absorption

The growing demand for electromagnetic compatibility in modern electronics requires the development of lightweight absorbers featuring strong attenuation and broad bandwidth. Although significant progress has been made, achieving optimal impedance matching while maintaining high dielectric loss remains a significant challenge for MXene-based composites. Herein, we tackled this issue using a sulfidation-induced phase engineering approach to construct NiCo 2 S 4 /MXene-nitrogen-doped carbon (NiCo 2 S 4 /MXene-NC) hierarchical aerogels. In this design, the chitosan (CS) biopolymer serves as an eco-friendly cross-linker, stabilizing few-layer MXene nanosheets and facilitating the formation of a robust three-dimensional (3D) conductive network via hydrothermal assembly and freeze-drying. Subsequent sulfidation treatment induced an in situ phase transition from urchin-like NiCo 2 O 4 to NiCo 2 S 4 , enhancing electrical conductivity and generating numerous heterogeneous interfaces and defects. This innovative design orchestrates a synergistic interplay of dipole polarization, interfacial polarization, and multiple internal reflections within the porous network, optimizing both impedance matching and electromagnetic attenuation capability. As a result of these structural and compositional advantages, the optimized NiCo 2 S 4 /MXene-NC-4 aerogel exhibited outstanding electromagnetic wave (EMW) absorption performance. It achieved a minimum reflection loss (RL min ) of -55.7 dB at a thickness of 3.5 mm and a maximum effective absorption bandwidth (EAB max ) of 5.56 GHz at a thickness of 2.0 mm. Moreover, radar cross-section (RCS) simulations confirmed its superior electromagnetic dissipation capability across various incident angles. This work sets a paradigm for engineering high-performance EMW absorbers through integrated structural design and phase modulation, providing valuable insights for next-generation electromagnetic compatibility applications.