Heterostructure Made of Multilayer MXene (Ti₃C₂T_x) and Vertically Grown CoFe₂O₄ Nanosheets for Microwave Absorption at 2–40 GHz

The development of microwave-absorbing materials (MAMs) with excellent performance is crucial for addressing electromagnetic (EM) interference issues. Two-dimensional (2D) Ti 3 C 2 T x MXene has been considered to be a promising candidate for microwave absorption owing to its distinctive structure and performances. In this study, a “house of cards” heterostructure comprising multilayer Ti 3 C 2 T x and vertically grown CoFe 2 O 4 nanosheets (NSs) is fabricated by inducing an in situ vertical growth of positively charged CoFe-LDH NSs on Ti 3 C 2 T x and a subsequent thermal treatment. The combination of Ti 3 C 2 T x and CoFe 2 O 4 NSs affords dielectric–magnetic synergistic effects on the overall EM properties of the heterostructure. On the one hand, vertically grown CoFe 2 O 4 NSs on Ti 3 C 2 T x shape the three-dimensional (3D) conductive network to consolidate conductive loss and generate numerous heterointerfaces to trigger intensive polarization loss. On the other hand, vertically grown CoFe 2 O 4 NSs on Ti 3 C 2 T x introduce additional loss mechanisms, such as magnetic loss and multiple reflection loss, thereby improving the impedance matching characteristic and reinforcing the loss capability of the composite. Most current studies on microwave absorption have focused on the frequency range of 2–18 GHz only, while we have extended this range to 40 GHz to explore the potential of the composite working in the higher frequency bands. The obtained optimal composite delivers satisfactory microwave absorption performance, including a minimum reflection loss (RL min ) value of −49.4 dB and a maximum effective absorption bandwidth (EAB max ) value of 10.8 GHz. It is believed that this study will pave the way for the design of Ti 3 C 2 T x -based MAMs and deepen the cognition of dielectric–magnetic synergistic mechanisms in the frequency range of 18–40 GHz.