Heterogeneous N-doped carbon composite NiSe₂–FeSe double-shell hollow nanorods for tunable and high-efficient microwave attenuation

To develop high-performance microwave absorbing materials, a heterogeneous NiSe₂–FeSe@NC double-shelled hollow nanorods (NiSe₂–FeSe@NC DSHNs) is constructed based on the strategies of morphology structure optimization and multicomponent recombination. First, NiSe₂–FeSe DSHNs are prepared through the cation exchange of Fe-based MOFs and subsequent selenization process. After that, the surface is coated with polydopamine (PDA) and annealed at high temperature to obtain NiSe₂–FeSe@NC DSHNs composite absorber. By changing the addition amount of DA, the microstructure, magnetic content and N doped carbon content of the material are effectively optimized. The minimum reflection loss (RL_min) of designed optimal NiSe₂–FeSe@NC DSHNs reaches −52.84 dB, and the overall effective absorption bandwidth (EAB, RL < −10 dB) covers 14.1 GHz (3.9–18 GHz). The maximum EAB at 1.7 mm is 4.5 GHz (13.1–17.6 GHz). The excellent microwave absorption (MA) performance is mainly attributed to the enhanced dielectric loss capability and optimized impedance matching, which are supported by the unique double-shell hollow structure, abundant channels and heterointerfaces, complementary magnetic/dielectric compositions, and suitable N heteroatom doping. The investigation of this work provides a convenient and environmentally friendly way for the construction of double-shell hollow structures, and provides a new idea for the design and preparation of lightweight and efficient absorbing materials.