Atomic spin engineering of Fe-N-C by axial chlorine-ligand modulation for lightweight and efficient electromagnetic wave absorption

Introducing atomic magnetic factors to regulate the electromagnetic parameters of graphene is essential to achieving new-generation electromagnetic wave (EMW) absorbing materials. Herein, a new strategy of endowing graphene with atomic magnetic moments was developed by implanting high-spin FeN₄ moieties with axial Cl ligands into 3D N-doped graphene (Cl-Fe-NG). The design facilitates the multi-reflection loss, dielectric loss and magnetic loss of EMW at ultra-low filling. Its minimum reflective loss (RL) is up to −65.9 dB with the biggest effective absorption bandwidth (EAB) of up to 5.5 GHz in the thin thickness of 1.9 mm and a low filler loading of 5 wt%. Meanwhile, a waterborne polyurethane wave-absorbing coating filled with 5 wt% Cl-Fe-NG demonstrates its high absorption performance with a dominant absorption loss of 90 %. Additionally, theory calculations reveal that introducing axial Cl-ligand FeN₄ moiety with high-spin Fe into graphene not only generates additional electric dipoles but also induces an atomic magnetic moment, effectively enhancing the dielectric and magnetic loss of graphene for EMW absorption. This work provides a new approach to designing graphene with atomic magnetic moments for developing EMW absorbing materials with “thin, wide, light, and strong” characteristics instead of the conventional route of graphene with magnetic nanoparticles.