Enhanced thermal conductivity and photothermal effect of microencapsulated n-octadecane phase change material with calcium carbonate-polydopamine hierarchical shell for solar energy storage

The development of microencapsulated phase change materials with excellent photothermal conversion and storage performances is significant for solar energy utilization. Herein, a kind of the novel n-octadecane microcapsules with calcium carbonate-polydopamine (CaCO 3 -PDA) hierarchical shell was fabricated through a simple one-pot synthetic strategy. The n-octadecane droplets were firstly encapsulated into inorganic CaCO 3 shell in the SDBS-templating emulsion, and subsequently the formed n-octadecane microcapsules were further modified by adhesive PDA. The resultant composite microcapsules displayed a regular and compact spherical morphology with a well-defined core-shell microstructure, and the light-absorption PDA coating uniformly deposited onto the CaCO 3 shell surface. The phase change microcapsules possessed a satisfactory latent heat storage capability of more than 140 J g −1 and a favorable energy storage efficiency of about 60%. Owing to the existence of CaCO 3 shell, the as-prepared n-octadecane microcapsules achieved a remarkable enhancement in the thermal conductivity compared to pristine n-octadecane. With the surface modification of PDA, the composite microcapsules demonstrated not only superior thermal stability and phase change reliability but also improved photothermal effect. Moreover, the microcapsules exhibited stable photothermal conversion and storage performances under the cycling sunlight irradiation. Therefore, the developed composite n-octadecane microcapsules in this work present a promising prospect in the field of solar-to-thermal energy utilization and storage.