Tailoring of bifunctional microencapsulated phase change materials with CdS/SiO2 double-layered shell for solar photocatalysis and solar thermal energy storage

Abstract

A novel type of bifunctional microcapsules was tailored by encapsulating an n-eicosane phase-change material (PCM) into a CdS/SiO2 hybrid via the interfacial polycondensation of silica precursors, followed by an in-situ precipitation between Cd2+ and S2− ions. Structural characterizations indicated that a double-layered shell based on an amorphous SiO2 inner layer and a crystalline CdS outer layer was fabricated successfully onto the n-eicosane core. Transmission and scanning electron microscopy demonstrated that the n-eicosane@SiO2/CdS double-layered microcapsules had a regularly spherical morphology with a perfect core-shell structure. Thermal analysis revealed that the n-eicosane@SiO2/CdS microcapsules achieved high energy-storage efficiency and reliable phase-change properties. Most of all, the n-eicosane@SiO2/CdS microcapsules not only exhibited good solar thermal energy-storage and thermoregulatory capabilities but also showed a high solar photocatalytic activity to organic dyes under the natural sunlight. Additionally, the microcapsules presented a fluorescent function due to the CdS outer layer. With these unique bifunctional characteristics, the n-eicosane@SiO2/CdS double-layered microcapsules developed by this work can serve for energy efficiency, sustainable chemistry and green processes, and therefore they exhibit an application potential for solar thermal energy collection and storage, solar photocatalytic depuration of industrial waste water, the solar photochemical detoxification of organic water pollutants, etc.