Lamellar-structured phase change composites based on biomass-derived carbonaceous sheets and sodium acetate trihydrate for high-efficient solar photothermal energy harvest

Abstract

Inorganic salt hydrates have a great potential for solar photothermal energy storage due to their high energy-storage density and low cost. However, there are some major drawbacks such as high supercooling degree, shape/form instability, phase segregation, and poor long-term durability found in salt hydrates. These greatly limit their practical applications. Herein, we designed and fabricated a type of eco-friendly and cost-efficient phase-change system based on sodium acetate trihydrate (SAT) as an inorganic phase change material and biomass-derived carbonaceous sheets (BDCSs) as a supporting material for high-efficient solar photothermal energy storage and shape stabilization. Derived from a biomass waste of watermelon rind, the BDCSs show some unique characteristics such as a stacking lamellar structure and a compact surface with some corrugations and ripples as well as the presence of abundant oxygen-rich groups. These can lead to a significant enhancement in photothermal conversion efficiency of solar energy when used as a supporting material for a SAT-based phase-change composite system. This type of composite system not only presents a high thermal energy capacity of 212.2 J/g and a very low supercooling degree of 0.9 °C, but also has a high photothermal conversion efficiency of up to 80.18% for solar energy. Moreover, the composite system exhibits high thermal conductance, good shape stability without phase segregation, and excellent thermal cycle stability for long-term solar photothermal energy storage and release. This study provides a simple and facile methodology for the development of bio-based phase-change composites for high-efficient solar energy utilization. • Biomass-derived carbonaceous sheets (BDCSs) were obtained from watermelon rind. • BDCSs exhibit a stacking lamellar structure with rich oxygen groups on their surface. • BDCSs/sodium acetate trihydrate composites were fabricated for solar photothermal energy harvest. • This type of phase-change composite system has high photothermal conversion efficiency. • This composite system reveals enhanced thermal conductance and reduced supercooling.