Emerging urchin-like core-shell mineral microspheres with efficient photothermal conversion and solar energy storage

Enormous challenges still seriously restrict the application of phase change materials (PCMs) in thermal energy storage and heat management systems, such as their leakage, low thermal conductivity, and low photothermal conversion efficiency. We reported an effective strategy for the morphology-controlled synthesis of the composite microsphere with an urchin-like core-shell structure for encapsulated paraffin, which synergistically enhanced efficient solar thermal conversion and heat energy storage. The SCGT was prepared by coating a layer of urchinlike TiO2 on the core composed of sepiolite, cellulose nanocrystals, and graphite (SCG). The synergistic effect of the core-shell structure makes paraffin-SCGT (P-SCGT) composites possess a high photothermal conversion efficiency of 94 % and outstanding heat energy storage capacity, with the melting and crystallization enthalpy of 137.4 J/g and 127.5 J/g. Furthermore, the mortar cylinder developed with the P-SCGT and mortar (P-SCGT-M) indicated exceptional thermal management abilities in attenuating the temperature fluctuations between diurnal and nocturnal periods, even multiple heating and cooling cycles. Therefore, the prepared materials with comprehensive properties would be perspective applied in solar collector systems and energy-saving buildings.