Reduced graphene oxide and zirconium carbide co-modified melamine sponge/paraffin wax composites as new form-stable phase change materials for photothermal energy conversion and storage

Highlights: • A new strategy to enhance photothermal conversion and storage of composite PCMs. • Reduced Graphene oxide and ZrC co-modified Melamine sponge are prepared firstly. • The thermal conductivity of composite PCMs is 121% higher than pure paraffin wax. • The composite PCMs show high photothermal conversion efficiency up to 81%. • The composite PCMs exhibit high phase change enthalpies and low enthalpies loss. -- Abstract: Photothermal energy conversion and storage are crucial in solar collection systems. However, it is difficult for traditional media to balance high photothermal conversion, thermal conductivity and thermal energy storage. Considering the advantages of nanofluids (volumetric absorption systems) and PCMs (high latent storage density), we develop novel form-stable PCMs for solar collection systems and overcome the disadvantages of current systems, which take melamine sponge as supporting materials, paraffin wax as solid-liquid PCMs, reduced graphene oxide and zirconium carbide as solar absorption and thermal conduction additives. The results demonstrate that the rich network skeleton structure of reduced graphene oxide modified melamine sponge provides huge surface tension and capillary force to support paraffin wax for achieving the shape-stability before and after phase transition, and the latent enthalpy reaches 137 J/g. The composites PCMs with different content zirconium carbide show good photoabsorption, high thermal storage capacity and excellent heat transfer property. The photothermal conversion efficiency is up to 81% when doped with 0.01 wt% zirconium carbide. The maximum thermal conductivity of composites PCMs is 121% higher than that of paraffin wax. The reduced graphene oxide and zirconium carbide co-modified melamine sponge/paraffin wax composites show its great potential in solar energy utilization and storage.