Dual‐Mode MXene‐Based Phase‐Change Composite Towards Enhanced Photothermal Utilization and Excellent Infrared Stealth

Abstract Solar thermal collectors based on phase change materials (PCMs) are important to promote the civilian use of sustainable energy. However, simultaneously achieving high photothermal efficiency and rapid heat transfer of the PCM carrier typically involves a high proportion of functional materials, contradicting a satisfying energy storage density. In this work, a surface‐engineered anisotropic MXene‐based aerogel (LMXA) integrated with myristic acid (MA) to produce phase change composites (LMXA‐MA) is reported, in which the laser‐treated surface composed of the hierarchically‐structured TiO 2 /carbon composites act as a light absorber to improve solar absorption (96.0%), while the vertical through‐hole structure allows for fast thermal energy transportation from surface to the whole. As a result, LMXA‐MA exhibits outstanding thermal energy storage (192.4 J·g −1 ) and high photothermal conversion efficiency (93.5%). Meanwhile, benefiting from the intrinsic low emissivity of MXene material, thermal radiation loss can be effectively suppressed by simply flipping LMXA‐MA, enabling a long‐term temperature control ability (605 s·g −1 ). The excellent heat storage property and switchable dual‐mode also endow it with an infrared stealth function, which maintains camouflage for more than 240 s. This work provides a prospective solution for optimizing photothermal conversion efficiency and long‐term thermal energy preservation from surface engineering and structural design.