Title: Advanced graphene aerogel embedded phase change materials (PCMs) for energy harvesting

Abstract

Phase change material (PCM) has been attracted to the thermal energy storage (TES) application due to the high latent heat, chemical stability, and high thermal density. Pure PCM is never utilized directly when occurs leakage problem during phase transition process. Supporting materials such as shell material, and porous aerogels can restrict the mobility of PCM upon melting and cooling. Thus, form-stable PCM composite is fabricated and still sustain the intrinsic solid state under the change of external temperature. These supporting materials stop PCM from occurring the leakage problem that the PCM composite can absorb or release a large amount of heat effectively. Comparing with shell material, aerogels can hold plenty of pure PCM because of high porosity. High weight percentage of pure PCM has an excellent TES ability during the phase transition process and even increases the efficiency of thermo-electric energy harvesting. However, the capillary force brings to the volume shrinkage of supporting material while infiltrating pure PCM into the porous internal structure. This volume shrinkage causes some weight loss of pure PCM and even decrease the efficiency of thermo-electric energy harvesting. Hence, the supporting material with high mechanical property and flexibility is vital to reduce the volume shrinkage. In this work, graphene aerogel is selected as a supporting material, and polydimenthylsiloxane (PDMS) is embedded to the graphene aerogel by solution spray treatment. The PDMS/n-Hexane solution is sprayed into the graphene aerogel and after n-Hexane is evaporated, the PDMS- embedded graphene aerogel is fabricated completely. Consider the mechanical requirement of PCM composite, cross-linked graphene aerogel is synthesized by using cysteamine vapor method, and graphene/cysteamine aerogel (GCA) is utilized as an advanced supporting material. These modified graphene aerogel can reduce the volume shrinkage, and PCM composites show high efficiency of thermo-electric energy harvesting.