Engineering Ti3C2 electronic structure via surface termination synergy for high-efficiency electromagnetic wave absorption

Abstract

Ti₃C₂ MXene has attracted considerable attention in the field of electromagnetic wave (EMW) absorption due to its conductive layered structure. In recent years, modulating the electromagnetic properties of MXene through surface functional group engineering has emerged as a research focus, yet the synergistic effects among different functional groups and their dominant mechanisms remain unclear. Here, accordion-like Ti₃C₂(Cl,O)x has been synthesized via a molten salt etching method. By adjusting the etching temperature, the surface Cl/O atomic ratio and total surface termination number of Ti₃C₂(Cl,O)_x can be precisely regulated while maintaining a stable interlayer spacing, which provides an ideal platform for revealing the intrinsic influence of surface chemistry on EMW absorbing performance. The surface chemistry effectively regulates the balance between conduction loss and polarization loss. At relatively low etching temperatures (550-650 °C), EMW absorption is dominated by polarization loss induced by surface terminations. In contrast, at higher etching temperatures (700 °C), the synergistic contribution of enhanced conduction loss and residual polarization endows the material with pronounced dielectric dispersion, enabling efficient EMW attenuation over a broader frequency range. The Ti ₃C₂(Cl,O)_x etched at 650 °C shows strong absorption with a minimum reflection loss of -52.3 dB, while the sample etched at 700 °C has an ultra-wide effective absorption bandwidth of 8.35 GHz, surpassing previously reported pristine MXene absorbers. This work provides an effective strategy for tailoring the EMW absorption performance of MXene at the atomic scale through surface chemistry engineering.