Efficient enhancement of photothermal conversion of polymer-coated phase change materials based on reduced graphene oxide and polyethylene glycol

Reduced graphene oxide (rGO) aerogel is frequently employed in support phase change material (PCM) and function as heat conductors in phasing-energy storage systems, absorbing and converting solar energy. However, their low filler content and insufficient reduction have caused a far inferior photothermal performance than graphene. Therefore, it is urgent to enhance light-heat conversion efficiency of rGO-based composite PCM. Herein, a photothermal coating material, polydopamine (PDA), has been selected as a coating for rGO aerogel to further increase the photothermal conversion efficiency of rGO-based composite PCM by conjugation effect. First, rGO aerogel is created by hydrothermal reduction and freeze-drying techniques, followed by dopamine self-polymerization on the rGO surface to form PDA-coated rGO (rGO-PDA) aerogel, and finally composite PCM (PEG (Polyethylene glycol) /rGO-PDA) are prepared by vacuum impregnation technique. The results indicate that PDA exhibits excellent photothermal conversion ability, increasing the absorption of PEG/rGO-PDA in the infrared band, thus resulting in the composite PCM exhibiting excellent photothermal conversion efficiency (88.9 %), which is 2.4 % higher compared to that of PEG/rGO. Furthermore, PDA has strong hydrophilicity, which enhances the affinity between rGO aerogel and PEG, and the large amount of hydrogen bonding provided by the addition of PDA contributes to maintain the morphology stability of composite PCM. The composite PCM with better form-stable and higher photothermal conversion efficiency could play a critical role in solar energy storage system.