High-quality graphene aerogels for thermally conductive phase change composites with excellent shape stability

Abstract

Low thermal conductivity and poor shape stability have seriously limited the wide application of phase change materials (PCMs). To enhance the thermal conductivity without compromising the latent heat of fusion of PCMs, high-quality graphene aerogels (HGAs) with both a highly conductive network and high porosity are fabricated on the basis of highly processable graphene oxide (GO) pastes. Freeze-drying of the GO pastes fixes their shapes and endows the resultant GO aerogels with high porosity, and high-temperature annealing of the GO aerogels at 2800 °C efficiently removes the oxygen-containing groups of the GO component and heals its defects to get HGAs with high thermally conductive capacity. Due to the interconnecting network with high porosity constructed by the high-quality graphene sheets, the resulting HGAs are highly efficient in improving the thermal conductivity of PCMs at a low graphene loading. After impregnating the porous HGA with 1-octadecanol, the obtained composite with only ∼5.0 wt% of graphene exhibits a satisfactory shape stability, an exceptional thermal conductivity of ∼4.28 W m⁻¹ K⁻¹ that is 18-fold higher than that of neat 1-octadecanol, and a high latent heat of fusion of ∼225.3 J g⁻¹. Such a high performance phase change composite with an excellent shape stability would be very promising for thermal energy storage applications as latent heat storage/release units.