Effect of MXene Surface Structures on the Absorption Component in Reflection-Dominated Electromagnetic Interference Shielding.

MXene nanoflakes have attracted significant attention due to their outstanding electromagnetic interference (EMI) shielding effectiveness (SE). However, understanding the relationship between shielding performance and complex surface microstructures of MXene nanoflakes remains challenging. In this study, flexible selfstanding Ti3C2Tx films were synthesized under various preparation conditions, achieving an ultrahigh EMI shielding effectiveness exceeding 70 dB. The morphology and microstructure were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), synchrotron radiation X-ray diffraction (SR-XRD), X-ray absorption fine structure spectroscopy (XAFS), and X-ray photoelectron spectroscopy (XPS). Based on the layered structure of MXene and the nearest- and next-nearest-neighbor coordination numbers around Ti atoms, an XAFS-based model was developed to estimate the surface Ti-vacancy rate (p) and average surface Tx-termination number (m). The results reveal that the shielding performance is jointly influenced by p and m through nonlinear coupling, with m exerting a more pronounced influence. Furthermore, the correlations among EMI absorption shielding performance, electrical conductivity, attenuation constant, surface structural parameters, and synthesis conditions were systematically analyzed, and the mechanism by which the surface structures affect the absorption shielding effectiveness was briefly discussed. We anticipate that this work will contribute to the surface engineering and optimization of advanced MXene-based shielding materials.