Superhydrophobic halloysite-based porous foamed geopolymer for efficient phase change material encapsulation with enhanced thermal management performance

Exploiting inexpensive and highly porous materials for phase change materials (PCMs) encapsulation is identified as a promising strategy for addressing the shape collapse and leakage of organic PCMs. Herein, a hierarchical porous foamed geopolymer (MH) was prepared by alkali activation of meta-halloysite (MHNT) with hollow glass spheres as templates, which was then modified by polydimethylsiloxane (PDMS) to obtain superhydrophobic MH (PMH). The PMH demonstrates excellent encapsulation efficiency of 67.23% for paraffin wax (PW), exceeding that of MH (57.74%) and most reported geopolymers. The reason is attributable to the highly porous structure and superhydrophobic feature of PMH, which provides enough space for PW encapsulation and enhances the affinity between PW and PMH, respectively. Additionally, PW@PMH reveals remarkable thermal cycling stability, good thermal storage and thermal insulation performance. This work proposes a creative strategy to prepare highly porous geopolymer for PCMs encapsulation for application in thermal energy storage and thermal insulation fields.