Synergistic microwave absorption in MXene/MnO2 composites achieved through interfacial engineering and controlled MnO2 morphology

Two-dimensional metal carbide Ti₃C₂T_x MXene has emerged as a promising material for electromagnetic pollution protection. Multilayered MXene, featuring a unique accordion-like structure, offers a natural advantage as a microwave absorber by extending the attenuation path of incident electromagnetic waves. In this study, the controlled growth of MnO₂ morphology is achieved by the two-parameter synergistic strategy of ‘hydrogen ion concentration-temperature’, and the composite structure with synergistic wave-absorbing effect is constructed by combining the interlayer interfacial engineering of MXene. By precisely controlling hydrogen ion concentration and hydrothermal temperature, MnO₂ pillars with distinct morphologies were achieved. All composite series exhibited significantly superior microwave absorption performance compared to pure multilayered MXene or MnO₂, highlighting the crucial role of component design and structural synergy in enhancing electromagnetic wave absorption (EWA). Notably, the composite incorporating hollow tetragonal MnO₂ pillars with larger apertures demonstrated optimal performance, attributed to maximized acceleration of electron transport. This composite achieved a minimum reflection loss (RL_min) of -60.04 dB at 16.64 GHz with an ultra-thin thickness of only 1.0 mm. The variations in EWA performance across the composite series are comprehensively discussed based on their microscopic loss mechanisms. This study paves a new avenue for designing high-performance MXene-based microwave absorbers through structural engineering.