Assembling and characterizing of high-loading and steady-shape graphene aerogel composite phase change material with nano-AlN─as an efficient thermal conductivity enhancer

Phase change materials (PCMs) have the advantages of high heat storage density and wide phase transition temperature, which can effectively solve the intermittent and random problems of solar energy. However, problems such as low light conversion efficiency and easy leakage of PCMs limit their application in the field of solar water heating. In this work, graphene nanoplatelets (GNPs) aerogel is prepared by mixing GNPs with solidum alginate by freeze-drying method. Then, composite PCMs with high latent heat and photothermal conversion efficiency are successfully prepared by impregnation polyethylene glycol (PEG) mixed with aluminum nitride (AlN) into GNPs aerogel. GNPs aerogel exhibits lighter mass and obvious pore structure, and the adsorption rate of PEG can be as high as 87%. The prepared composite PCM with 1% AlN (mass fraction) exhibits 176.6 J/g and the photothermal conversion efficiency is 80.3%. Moreover, the encapsulated PEG maintains good shape stability and only loses 0.4% in heat storage capacity after 100 cycles. These properties make it present great potential in the practical application of solar water heaters.