Hierarchical Graphene Aerogels as Wide-Range Thermal Management Switches

Graphene aerogels (GAs) have been widely recognized as ideal candidate materials for numerous applications; however, they still face drawbacks in terms of low strength and insufficient elasticity. Inspired by cellular structures, this study employs a high-melting-point aromatic oil phase to prepare the stable graphene oxide Pickering emulsion. Owing to its special sequential freezing behavior, the emulsion effectively suppresses ice crystal growth and successfully constructs a hierarchical microsphere/wall structure. Besides, due to the strong interaction between the oil molecules and graphene, the adsorbed oil phase can provide a healing effect for graphene nanosheets during the thermal reduction process. Based on these findings, the obtained pure GA exhibits significantly improved compression strength, which is more than 6 times higher than that of the common GA (CGA). More importantly, this GA exhibits a decreasing apparent density, resulting in an outstanding specific strength as high as 31.9 kN·m/kg and a recovery rate of 93.7% after 90% strain compression, a performance not yet achieved in reported studies. The formation and enhancement mechanism of the hierarchical microsphere/wall structure of GA is also studied in detail. Benefiting from its pure graphene composition and reversible compression properties, this aerogel serves as a potential material for thermal switches, achieving an ultrahigh switching ratio of 38.6 and enabling wide-range regulation of heat transfer capabilities. Therefore, this study demonstrates an accessible strategy to prepare lightweight, high strength, and elastic GAs, which can be excellent candidates for thermal management systems.