Phase Change Microcapsules Shelled with Silica Functionalized with CNTs for Enhanced Thermal Conductivity and Solar Thermal Conversion

Advanced phase-change materials (PCMs), as novel energy-storage technologies, offer a practical solution to addressing the global energy crisis by improving both energy efficiency and sustainability. In this study, silica (SiO₂)-shelled phase-change microcapsules functionalized with carboxylated carbon nanotubes (CNTs) were designed and prepared to enhance thermal conductivity, photothermal conversion, and operational durability. The silica shell, featuring a Janus structure with exterior amine groups, facilitates covalent bonding with CNTs, effectively increasing thermal transfer and maintaining structural integrity. The as-prepared PCMs are characterized by an encapsulation efficiency exceeding 66% and a phase-change enthalpy over 120 J/g, besides the enhanced thermal conductivity, solar thermal conversion, and profound resistance to leakage. Long-term stability tests reveal that the SiO₂-shelled phase-change microcapsules coated with CNTs (S0/CNTs) maintain thermal performance after 100 heating-cooling cycles, showing sustained reliability. These advantages highlight the potential of S0/CNTs in sustainable thermal energy storage applications, offering a versatile solution for enhancing the efficiency and durability of energy storage systems.