Phase-changing hydrogels incorporated with copper sulfide-carbon nanotubes for smart thermal management and solar energy storage

Organic phase change materials (PCMs) have great potential in solar energy storage and thermal management. Herein, a novel system of integrated photothermal-thermal storage function was designed and prepared based on sodium alginate (SA) hydrogel combined with photothermal materials (CuS-CNTs) and pure polyethylene glycol-6000 (PEG-6000). The CuS-CNTs composites were synthesized mainly by hydrothermal reaction, and the resulting CuS was a 3D nanoflower structure with excellent light absorption and photothermal conversion. When Ca2+ is introduced, SA underwent a cross-linking polymerization reaction to encapsulate CuS-CNTs and PEG-6000 to form light-thermal phase change hydrogel (LTPCH). With 93% PCM loading, the hydrogel exhibited a high latent heat of over 150.8 J/g and reliable thermal stability, as well as inherited the excellent photothermal properties of CuS. Inside the LTPCH, CuS-CNTs and PEG-6000 were in direct contact, and the heat energy generated from the photothermal conversion of CuS-CNTs can be immediately absorbed by PEG-6000, demonstrating efficient thermal management. The solar energy storage efficiency was as high as 91.4% under simulated sunlight. Light-thermal thermal storage composite hydrogels had great potential in solar energy storage systems, providing insights into the functional integration design of PCMs.