Phytic acid–decorated κ-carrageenan/melanin hybrid aerogels supported phase change composites with excellent photothermal conversion efficiency and flame retardancy

Organic phase change materials (PCMs) have been widely applied to thermal energy storage systems; however, poor solar–thermal conversion performance, high flammability, and liquid leakage issues considerably limit their practical application in efficient solar energy utilization. Herein, phytic acid–decorated melanin/κ-carrageenan aerogels (PMCAs) with excellent solar–thermal effect and satisfactory flame retardancy were developed using the cationic induction method. Then, form-stable PCM composites (PMPCMs) were fabricated by integrating molten n-octacosane into PMCAs through vacuum impregnation. The PMCAs effectively supported n-octacosane and avoided liquid leakage during the solar–thermal storage process owing to their strong surface tension and capillary force. The PMPCMs exhibited considerably high encapsulated efficiency (up to 97.73%), satisfactory thermal storage ability (246.7–257.7 J/g), and excellent thermal reliability. The introduction of natural melanin (natural photothermal conversion compound) and phytic acid (bio-based phosphorus-rich compound) significantly enhanced the solar–thermal conversion efficiency (from 61.7% to 89.4%) and flame retardancy of the PMPCMs. Thus, the synthesized form-stable composites possess tremendous potential for solar energy utilization.