Flame-retardant wood-based composite phase change materials based on polydopamine functionalized carbon dots for efficient solar-to-thermal energy storage

To address the low efficiency and flammability of wood-based phase change materials (WPCMs) in solar energy storage, this study developed a series of WPCMs (PEG/TPP/DW-P) with both flame retardancy and solar-thermal energy storage properties by vacuum-impregnating polyethylene glycol (PEG), triphenyl phosphate (TPP), and polydopamine (PDA)-functionalized carbon dots (PCDs) into delignified wood (DW). In addition to surface tension and capillary forces, the polyhydroxy structures of cellulose and hemicellulose in DW formed strong hydrogen bonds with PCDs, PEG, and TPP, further hindering the leakage of phase change materials (PCMs) during the “solid–liquid” phase Change process. The leakage rate was lower than that of most studies, at 4.67%, and the composite material could still maintain shape stability after 150 heating–cooling cycles. The PDA with a larger specific surface area in PCDs conducted efficient electron transfer with the carbon dots (CDs) loaded on it, resulting in the occurrence of non-radiative transitions. The photothermal energy storage efficiency was 90.68%, far exceeding those of pure CDs. The P-containing PCM-TPP synergistically interacted with the N in PCDs to generate a flame-retardant carbon layer. Compared with PEG/DW, the peak heat release rate and total heat release of PEG/TPP/DW-P were reduced by 28.19% and 13.45%, respectively. We also explored the practical application of WPCMs in simulating roofs, which showed good flame-retardant and thermal insulation properties. This study achieved the integration of the photothermal agent and flame retardant in WPCMs into the same nanomaterial-PCDs, minimizing the reduction in latent heat value caused by the addition of multiple components. The current research has very broad application potential in the practical application of WPCMs as buildings. Wood-based composite phase change materials based on polydopamine functionalized carbon dots for efficient solar-to-thermal energy storage and flame-retardant applications.