Template-Free Formation of Uniform Fe₃O₄ Hollow Nanoflowers Supported on Reduced Graphene Oxide and Their Excellent Microwave Absorption Performances

Iron oxides (Fe₂O₃, Fe₃O₄) are highly desirable for electromagnetic (EM) microwave absorption applications because of their high magnetization, low toxicity and good magnetic loss. Herein, we repot an effective strategy to improve the reflection loss (R_L) of iron oxides-based materials via a delicate design of distinctive hybrid nanostructures, where uniform magnetite (Fe₃O₄) hollow nanoflowers organized from ultrathin nanosheets are supported on the reduced graphene oxide (rGO) matrix (MHF-rGO). The designed MHF-rGO exhibits excellent microwave absorption performance with a low R_L of −53.3 dB at 4.96 GHz and a wide bandwidth of 5.68 GHz (< − 10 dB). The top level microwave absorption properties are associated with the high surface areas, ultrathin nanosheets and hollow structures of magnetic Fe₃O₄ nanoflowers, which present a good synergetic role with lightweight rGO. Furthermore, the controllable permittivity in MHF-rGO is developed by adjusting the rGO content, which can balance the permeability to obtain a good impedance matching. This study paves an effective way to improve and extend the microwave absorption performances of iron oxides-based materials through a delicate hybrid nanostructures design strategy.