Magnetic Microcapsules with Carbon Nanotubes-Fe ₃ O ₄ for Enhanced Solar Thermal Energy Storage

This study successfully fabricated multifunctional n-eicosane@CNTs-Fe3O4/CaCO3 phase-change microcapsules with enhanced photothermal conversion and thermal energy storage capabilities. The microcapsules were constructed via a Pickering emulsion-templating method combined with in situ interfacial precipitation, exhibiting a well-defined core–shell structure, a uniform spherical morphology, and a narrow size distribution. The incorporation of the CNTs-Fe3O4 composite not only endowed the microcapsules with superparamagnetic behavior but also significantly improved their thermal conductivity and broadband light absorption, yielding a high photothermal conversion efficiency of 63.85% under solar irradiation. Furthermore, the microcapsules achieved a latent heat of 131.2 J/g with an encapsulation efficiency exceeding 54.5% and demonstrated thermal reliability and cycling stability over 400 repeated thermal cycles. This work provides a feasible strategy for designing multifunctional phase-change materials that integrate magnetic responsiveness, efficient solar-to-thermal conversion, and high-capacity energy storage, thereby demonstrating promising potential for applications in solar thermal harvesting and intelligent thermal management.