Highly thermally conductive phase change composites with excellent solar-thermal conversion efficiency and satisfactory shape stability on the basis of high-quality graphene-based aerogels

Abstract

Although nontoxic organic phase change materials (PCMs) with high energy densities are promising for storing and releasing latent heat reversibly during their melting and solidifying processes, their major shortcomings of melt leakage and poor thermal conduction limit their wide applications. To accommodate a typical PCM of 1-octadecanol and enhance its thermal conduction and structural stability, high-quality graphene-based aerogels are fabricated by hydrothermally reducing graphene oxide/graphene nanoplatelets (GNPs) suspensions followed by air-drying and thermal annealing at 2800 °C. The hydrothermally reduced graphene oxide (RGO) sheets construct an interconnecting network during the hydrothermal reduction process. By varying the content of GNPs, shrinkage of the RGO/GNP hydrogel during air-drying could be regulated effectively. Crucially, graphitization of the air-dried RGO/GNP hybrid aerogel removes residual oxygen-containing groups of RGO and heals its lattice defects. The high-quality graphene aerogel is well suitable for accommodating 1-octadecanol, and the resultant phase change composite exhibits an ultrahigh thermal conductivity of 9.50 W m−1 K−1 at a graphene content of 13.3 wt%. Furthermore, thanks to the efficient light absorption feature and highly conductive network of the graphene-based aerogel, its 1-octadecanol phase change composite possesses an excellent solar-thermal energy conversion ability with a high efficiency of 84%. The phase change composites on the basis of the high-quality graphene-based aerogels would be highly promising for solar-thermal energy conversion and storage.