Fabrication of Graphene/TiO2/Paraffin Composite Phase Change Materials for Enhancement of Solar Energy Efficiency in Photocatalysis and Latent Heat Storage

To enhance the solar energy utilization efficiency of microencapsulated phase change materials (PCMs), a novel composite system was designed by combination of graphene nanosheets and the microencapsulated n-eicosane with a brookite TiO2 shell. A series of n-eicosane@TiO2@graphene microcapsules were fabricated through interfacial polycondensation in an emulsion templating system, and their microstructures, chemical compositions and crystallinity were investigated extensively. The composite system presented a spherical core–shell structural morphology, where graphene nanosheets were attached onto the microcapsule surfaces through hydrogen bonding. The composite system achieved phase-change enthalpies over 160 J/g, and its thermal conductivity was also improved from 0.64 to 0.98 W·m–1·K–1 due to highly thermally conductive graphene nanosheets. This study confirmed that the introduction of graphene nanosheets was an effective way not only to improve the structural stability and serving durability of the composite system but also to enhance its solar photocatalytic activity by promoting the electrons transfer and charges separation of TiO2. The composite system developed by this work exhibits a great potential for direct solar energy utilizations such as solar thermal energy storage in a natural environment, solar photodegradation and detoxification for the water containing organic pollutants, and solar thermal energy collection and decontamination for industrial hot wastewater.