Broadband Microwave Absorption of Nb₂CT_<i>x</i> Nanosheets by a One-Step Hydrothermal Method

As an emerging two-dimensional material, MXene holds great potential as a microwave-absorbing material due to its unique layered structure and flexibly tunable surface functional groups. Therefore, research on surface chemistry and interlayer engineering represents an effective strategy for optimizing the performance of MXene. In this work, we synthesized high-quality Nb₂CT_<i>x</i> nanosheets via a hydrothermal method. Detailed material characterization techniques have confirmed the synthesis of high-quality niobium-based nanosheets. The interlayer spacing, surface termination, and structural defects of the Nb₂CT_<i>x</i> nanosheets could be flexibly regulated by adjusting the duration of the hydrothermal etching process. This work reveals the etching time-dependent correlation of the electromagnetic parameters of Nb₂CT_<i>x</i>. It is noteworthy that the optimal impedance matching and microwave absorption performance were achieved after etching for 96 h, with a minimum reflection loss of -43.4 dB at an ultrathin thickness of 1.3 mm and an effective absorption bandwidth of 4.4 GHz at a thickness of 1.4 mm. This work presents a meaningful route to simultaneously adjust the nanoarchitecture and surface chemistry of MXene for advanced microwave absorption applications.