3D graphene paraffin composites based on sponge skeleton for photo thermal conversion and energy storage

Multifunctional phase change composites, which have both high photo-thermal conversion capability and high latent-heat capacity, are in great demand for large number of applications. In this work, a shape-stabilized reduced graphene oxide sponge-based phase change composite that has reduced graphene oxide decorated melamine sponge as a support and paraffin wax as a filler was fabricated. Because of the lipophilicity of the reduced graphene oxide, paraffin wax is well adsorbed on the skeleton of the sponge. The loading percentage of paraffin wax could reach up to ~98%. Compared to pure sponge, the anti-leakage ability of the composite showed great improvements. The melting temperature and latent heat of the composite was 56 °C and 143.0 J/g, respectively. The reduced graphene oxide also gave the prepared phase change composites good solar absorption efficiencies that reached 95%. Under solar light irradiation, the composites could effectively harvest and convert solar energy into thermal energy. The phase change thermal storage efficiency reached up to 88.7%. Based on the heat storage characteristics of the phase change composites, a solar-driven thermoelectricity experiment was conducted, and results showed that the thermal energy was stored in the phase change materials and released over an elongated period, during which the open circuit voltage reached to 1.30 V. Therefore, the multifunctional phase change composites have potential for applications in various sustainable uses, including as solar thermal-energy storage, and waste-heat recovery.