Abstract: Microencapsulation of phase change materials (MPCM) is an effective way to achieve solar energy man-agement. However, the crystallization of phase change materials (PCMs) in microcapsules will produce supercooling, which will affect the energy storage efficiency of MPCM. The incorporation of TiO₂ nanopar-ticles into MPCM can alleviate supercooling. In this work, octadecyltrimethoxysilane (ODTMS) was used to modify the solid nucleating agent TiO₂ (m-TiO₂) to improve its compatibility with n-Octadecane. Then, MPCM based on m-TiO₂ nucleating agent, melamine-formaldehyde resin (MF) shell material, and n-Octadecane core material was prepared. Differential scanning calorimetry (DSC) results demonstrate that the supercooling degree (△T ) of MPCM (MPCM-02) decreases to 0 ℃ with a tiny level of 0.25 wt% m-TiO₂, while the MPCM with unmodified TiO₂ is 6.1 ℃ and the MPCM without nucleating agent is 4.1 ℃. Be-sides, the phase change enthalpy (△Hm) and encapsulation efficiency (E ) of MPCM-02 remain at 183.7 J/g and 95.3 %, respectively. Finally, phase change composite materials with photothermal conversion capa-bilities were constructed by MXenes, MPCM, and polyurethane acrylate (PUA). When 1 wt% MXenes and 30 wt% MPCM were incorporated into PUA matrix, the thermal conductivity and surface temperature af-ter 1200s of infrared light irradiation were 48.8 % and 8.2 ℃ higher than pure PUA matrix. These results demonstrate the good solar energy storage capabilities of the MPCM, which possesses promising applica-tion potential in the field of solar energy thermal management and human thermal regulation.

Key words: Microcapsules, Supercooling degree, Thermophysical properties, Solar energy storage, Thermal management