Simultaneously tuning structural defects and crystal phase in accordion-like Ti_xO_2x−1 derived from Ti₃C₂T_x MXene for enhanced electromagnetic attenuation

Single Ti₃C₂T_x MXene (MTO) materials are not suitable for electromagnetic (EM) wave absorption due to their high conductivity and impedance mismatch. To address this issue, we ingeniously took advantage of easily oxidized characteristics of Ti₃C₂T_x MXene to establish structural defects and multiphase engineering in accordion-like Ti_xO_2x−1 derived from Ti₃C₂T_x MXene by a high-temperature hydrogen reduction process for the first time. Phase evolution sequences are revealed to be Ti₃C₂T_x MXene/anatase TiO₂ → Ti₃C₂T_x MXene/rutile TiO₂ → Ti_xO_2x−1 (1 ≤ x ≤ 4) during a hydrogen reduction reaction. Benefiting from conductance loss caused by hole motion under the action of an external electric field and heterointerfaces caused by interfacial polarization, the impedance match and EM attenuation capability of accordion-like Ti_xO_2x−1 absorbers derived from Ti₃C₂T_x MXene are superior to that of pristine Ti₃C₂T_x MXene/TiO₂ materials. Additionally, simulated whole radar cross section (RCS) plots in different incident angular of the Ti₃C₂T_x MXene/rutile TiO₂ product are lower than −20 dBm², and the minimum RCS value can reach −43 dBm², implying a great potential for practical applications in the EM wave absorption. Moreover, the relationship among charges, defects, interfaces, and EM performances in the accordion-like Ti_xO_2x−1 materials is systematically clarified by the energy band theory, which is suitable for the research of other MXene-derived semiconductor absorbing composites.