Novel properties of stearic acid / MXene - Graphene oxide shape - Stabilized phase change material: Ascended phase transition temperature and hierarchical transition

To develop novel materials with active photothermal conversion and latent heat storage properties, the shape-stabilized phase change material was fabricated via self-assembly method employing stearic acid (SA) as heat storage medium, graphene oxide and MXene as hybrid matrix (GM) and photothermal conversion agent. The morphology, structure, properties and phase transition behavior were investigated by various techniques. The results shown that SA/GM has sandwich-like structure and SA is confined between matrix nanosheets in multiple crystallographic forms. Due to the superposition of host-guest interaction and intrinsic van der Waals force between nanosheets, the primary melting temperature of SA/GM climbs 27.7 °C approximately than that of SA, as well as the total latent heat decreases by 28.55%–30.85% compared with theoretical values. The confinement effect increases the crystallization activation energy of confined SA, and leads to the formation of non-phase transition layer, transitional confinement layer and proximate bulk layer. However, the above observations are applicable to fatty acids/GM, only the suppressed latent heat occurs in all GM-matrix composites. In addition, the SA/GM7 has excellent photothermal conversion efficiency, as high as 93.34%, and gradient latent heat storage capacity, 45.96 J g−1 at 74.43 °C and 91.19 J g−1 at 92.37 °C.