Ti₃C₂T_X MXene Nanosheets Decorated with Magnetic Co Nanoparticles and CoO Nanosheets for Microwave Absorption

As a recently emerging 2D material, Ti3C2TX MXene, with some distinct characters, might bring opportunities for developing advanced microwave absorption materials (MAMs). Although the multilayered MXene with an accordion-like structure has been used as the building blocks to obtain composite MAMs, the exfoliated MXene (eMXene) nanosheets have rarely been explored. Herein, we construct a hierarchically structured MXene-based composite by simultaneously decorating magnetic nanosheets/particles onto eMXene sheets for an efficient microwave absorption. Systematic ex situ characterizations reveal that the eMXene sheets can act as a structure-directing agent and host to allow an interlaced growth of ultrathin CoO nanosheets and spherical Co@C nanoparticles onto their surfaces. Such structural design impedes the agglomeration of eMXene sheets and magnetic nanounits while guaranteeing the adequate exposure of polar functional groups on MXene surfaces. Meanwhile, the introduction of dual magnetic phases enables an additional magnetic loss capability and also builds massive void spaces and rich heterointerfaces between various nanounits for a significantly enhanced dielectric polarization loss, resulting in a superior impedance matching and attenuation capability. Accordingly, the optimal composite exhibits a minimum reflection loss of −73.4 dB at a thin thickness of 2.1 mm and an effective absorption bandwidth up to 5.6 GHz (12.4–18.0 GHz) at a thin thickness of 1.8 mm. This study might stimulate the further development of exfoliated MXene-based composite microwave absorbers with hierarchical structures.