Design of 3D-network montmorillonite nanosheet/stearic acid shape-stabilized phase change materials for solar energy storage

Abstract Phase change materials (PCMs) that have the ability to convert and store solar energy could take full advantage of clean and renewable energy. However, the large-scale commercial application of PCMs was seriously limited due to the leakage, low thermal energy storage capacity and poor thermal transfer ability. In this work, natural montmorillonite (Mt) has been exfoliated into two-dimensional montmorillonite nanosheets (MtNS) and then being self-assembled into three-dimensional network montmorillonite framework (3D-MtNS), which was applied to encapsulate stearic acid (SA) for the fabrication of composite PCMs to significantly promote solar energy conversion and storage performances. This novel 3D-MtNS framework provides super porosity and huge specific surface area to encapsulate more than 95 wt% SA without leakage, resulting in the highest latent heat capacity (198.78 J/g) among clay mineral based composite PCMs. Besides, the cross-linked MtNS throughout the PCM composites provided rapid heat transfer paths, leading to outstanding thermal transfer ability and excellent photo-thermal conversion performances. In addition, due to the protection of the 3D-MtNS framework, the composite PCMs exhibit superior form stability, thermal stability and cycling stability. Compared with previous prepared clay minerals based composite PCMs, the present 3D-network MMT/SA composite PCMs showed dramatic latent heat capacity and good heat transfer ability simultaneously, which enable the direct solar energy conversion, storage and utilization.