Ni Doping in MnO₂/MXene (Ti₃C₂T_x) Composites to Modulate the Oxygen Vacancies for Boosting Microwave Absorption

Endowing composites with defects such as oxygen vacancies is an easy and effective strategy to determine the physical and chemical properties of nanomaterials. The influence of defects on microwave absorption remains a very open question. Herein, MnO2/Ti3C2Tx MXene composites are self-assembled, demonstrating the boosting of microwave absorption through Ni doping in MnO2 to modulate the oxygen vacancies. The Ni-doped MnO2 (Ni–MnO2) nanorods with diameters of about 40 nm are dispersed on the surface and interlay of MXene. As expected, the reflection loss (RL) value and effective absorption bandwidth (EAB) of Ni–MnO2/MXene composites are −55.9 dB and 6.32 GHz, which are greatly enhanced over pure MnO2/MXene with −18.8 dB and 4.56 GHz. This excellent microwave absorption is mainly attributed to the optimized impedance matching in Ni–MnO2/MXene composites. In addition, the random distribution of MnO2 nanorods and MXene layers will form a conductive network, leading to the inducing microcurrent to form conduction losses. Moreover, interfacial polarization between layered MXene and Ni–MnO2 and dipole polarization induced by oxygen defects yield a strongly dielectric loss. Thus, our work provides a novel principle of modulation in oxygen vacancies to develop efficient MXene-based multicomponent composites for electromagnetic wave absorption.