Form-stable phase change materials based on graphene-doped PVA aerogel achieving effective solar energy photothermal conversion and storage

Polyvinyl alcohol (PVA) aerogel is usually used to restrict the flow of liquid polyethylene glycol (PEG) for the preparation of composite phase change materials (PCM). Currently, the vacuum freeze-drying method is demonstrated to be the most valid way to prepare PVA aerogel. However, achieving a high thermal conductivity and optical thermal conversion efficiency in composite PCM remains challenging, due to the lack of effective thermal conductivity fillers and optical thermal conversion media within the reported PVA aerogel. Herein, we report a simple method to prepare PVA-reduced graphene oxide (rGO) aerogel by reductant reduction and vacuum freeze-drying methods. PVA-rGO aerogel is well suitable to accommodate PEG, and the consequent composite PCM (PEG/PVA-rGO) demonstrates an outstanding PEG loading rate of up to 96.9 wt%. In addition, due to the efficient light absorption and highly thermal conductivity of rGO, the photothermal conversion efficiency of PEG/PVA-rGO was increased to 88.2%, while also increasing its thermal conductivity to 0.348 W/(m·K). The melting enthalpy of PEG/PVA-rGO is measured to be as large as 155.5 J/g. Furthermore, the use of PEG/PVA-rGO for solar-thermal energy storage application is demonstrated. This work provides valuable guidance for preparing high-performance form-stable composite PCM and raises their potential for practical use in solar energy storage and energy-efficient buildings.