Composite phase change materials with efficient solar-thermal energy conversion, storage and superior shape stability by interfacial enhancement

Phase change materials have broad applications in thermal management, but their applications in new energy conversion and storage are limited due to low solar-thermal conversion efficiency and leakage issues. This study fabricates a vertically oriented poly(vinyl alcohol) /MXene/N-octacosane composite phase change materials via solution blending, directional freezing, chemical vapor deposition treating, and vacuum impregnating methods. The integration of MXene broadens the light absorption spectrum and increases the surface roughness of composite phase change materials, facilitating the formation of additional thermal conductive pathways and enhancing the loading capacity. Following modification with methyltriethoxysilane via chemical vapor deposition method, the interaction between the poly(vinyl alcohol)/MXene aerogels and N-octacosane was significantly strengthened, further improving loading capacity, solar-thermal conversion efficiency, anti-leakage properties, and thermal conductivity. The resulting composite phase change materials, comprising 50 wt% MXene (PM50Oc), achieved a high enthalpy of 236 J/g, an impressive solar-thermal conversion efficiency of 97.1 %, a minimal leakage rate of 0.7 %, exceptional thermal stability (with only a 4.7 % decrease in enthalpy after 2000 cycles) and a thermal conductivity of 0.42 W/(m·K). In a simulated house heating system, the PM50Oc maintained water temperatures (25 °C) and air temperatures (0 °C) near 60 °C and 22 °C, respectively, under a light intensity of 1000 W/m². Upon removal of the light source, the PM50Oc effectively delayed the decrease in indoor temperature by releasing latent heat, with a cooling rate of 1/6 that of natural cooling. This research presents a new strategy to developing high-performance composite phase change materials, particularly those with improved anti-leakage property.