Graphene-CoO/PEG composite phase change materials with enhanced solar-to-thermal energy conversion and storage capacity

Composite phase change materials (PCMs) with excellent light adsorption and high thermal conductivity have great potentials in the efficient solar-to-thermal energy utilization. In order to improve the light absorption and solar-to-thermal conversion efficiency, reduced graphene oxide nanosheets decorated with CoO nanoparticles (rGO@Co) were used as support for polyethylene glycol (PEG) PCMs. The hierarchical structure composed of rGO nanosheets provides a large space to impregnate a high amount of PEG with good shape stability during the solid-liquid phase transition. Meanwhile, CoO nanoparticles and rGO nanosheets with high light absorption can provide rGO@Co with enhanced light absorption capacity and solar-to-thermal conversion capacities. In addition, the well distributed CoO nanoparticles on rGO nanosheets could contact PEG chains better, act as heat transfer intermediate and reduce the interface thermal resistance for the thermal energy transfer between rGO and PEG during the thermal energy storage/release process. Therefore, the prepared rGO@Co/PEG composite PCMs exhibit enhanced thermal conductivity with 51.79%~152.46% increasement as compared with pure PEG, high energy storage densities (131.94 J/g), good shape stability and high solar-to-thermal energy storage/release rates. Hence, the light-driven composite PCMs have great potentials for the efficient utilization of sustainable solar energy.