Cl-terminated decoration to modulate the permittivity of MXene for enhanced electromagnetic-absorbing performance

The explosive growth of communication technology has given rise to a large number of high-quality electromagnetic wave (EMW) absorbing materials, and single-component materials are often difficult to satisfy the demand. In this study, we propose an etching method of molten chlorine salts under vacuum to prepare Cl-terminated MXene (MX-Cl) which can meet the requirements of "thin, light, wide and strong" and realize the application of single-component absorbing materials. In the X and Ku bands, MX-Cl achieves a strong reflection loss of –42.99 dB and an effective absorption bandwidth of 3.44 GHz with the 1.2 mm matching thickness. The presence of Cl groups restricts the free electron movement of surface-Ti, which controls the conductivity of the MX-Cl and optimizes its permittivity. Dipole polarization induced by Ti–Cl, interfacial polarization between MXene layers and multiple scattering effects inside the layers all significantly increase the dielectric loss of the MX-Cl considerably. This study provides a new approach to investigating the effect of single atoms on the dielectric properties of materials. This work also offers a simple and low-cost process for the preparation of single-component MXene EMW-absorbing materials.