Graphene Oxide‐Molten Salt Composite Material for High‐Temperature Photothermal Phase Change Energy Storage

ABSTRACT A series of graphene aerogel‐molten salt (GA/MS) composites were successfully synthesized using a directional freezing‐thermal reduction method, enabling the stable encapsulation of high‐melting‐point eutectic salts within a 3D graphene framework. Polyethylene glycol (PEG) was introduced during the process to enhance the uniform dispersion and in situ embedding of molten salts, ensuring superior heat storage and excellent thermal stability. The resulting composite exhibited a phase change enthalpy of 531.1 J/g and a rapid photothermal response, reaching 550°C within 25 s under concentrated solar irradiation. After 50 thermal cycles, 93.0% of the initial latent heat was retained, showcasing excellent durability. The light‐to‐heat conversion efficiency reached up to 91.6%, benefiting from the synergy between graphene and confined molten salts. This high‐temperature photothermal phase change material addresses limitations in current phase change materials (PCMs), with significant potential for applications in solar energy storage, concentrated solar thermal systems, aerospace, and waste heat recovery. The scalable and versatile approach presented here can be applied to various molten salt systems, advancing the development of next‐generation solar thermal energy storage materials.