Biomass-based shape-stabilized phase change materials from artificially cultured ship-shaped diatom frustules with high enthalpy for thermal energy storage

The high adsorption capacity of the phase change mediums in porous supports is a key requirement for the shape-stabilized phase change materials (ss-PCMs) with high latent heat. Here, ship-shaped diatom (Pennales) frustule-based composite ss-PCMs with high polyethylene glycol (PEG) absorption capacity and high phase change enthalpy was prepared by a solution-assisted vacuum impregnation method for high-performance thermal energy storage. To improve the diatom frustules’ specific surface area and form a multi-level pore structure, the effects of calcination temperature on the microstructure of diatom frustules were studied. It was found that diatom frustules calcined at 400 °C (400CDF) had a relatively high specific surface area (~155.9 m2/g) with a well-maintained skeleton, which was a suitable PEG supporter. The devised PEG/400CDF composites with 72.7% loading of PEG4000 that had a latent heat value of 128.9 J/g for melting and 136.7 J/g for freezing, and the relative enthalpy efficiency reached up to 97.7%. The composite ss-PCMs exhibited thermal and chemical stability even after 200 thermal cycles. The current work demonstrated that ss-PCMs from biomass-based artificially cultured diatoms could slow the spread of heat by absorbing thermal energy. Moreover, the phase change mechanisms of the PEG/CDF composites under the nanoconfinement in the diatom frustules framework were also explored to explain the obtained high adsorption capacity.