Carbon dots efficiently enhance photothermal conversion and storage of organic phase change materials through interfacial interaction

Polymer phase change materials (PCMs) often suffer from the attenuation of thermal storage capacities and the shrinkage of storage duration after adding conventional high heat conduction matters, resulting in low efficiency of heat storage and utilization. Here we report a novel strategy in which carbon dots (CDs) evenly distributed into polyethylene glycol (PEG) act as local self-heating agents to shorten thermal transfer distances. As a result, CDs enhance the phase change enthalpies of PEG-related PCMs by their interface interaction, resulting in 13.7% higher than the theoretical value. Moreover, the hybrids of CDs and PEG are impregnated into the melamine sponge modified with CDs and polydimethylsiloxane through vacuum induced infiltration technique to prevent the liquid leakage. The obtained composite shows the long heat storage duration and achieves 82.57% of solarto-thermal storage efficiency as well as 92.27% of the heat release efficiency. In particular, its outstanding hydrophobicity and stability in shape and heating-cooling cycles allows it to practically apply in solar-thermal energy conversion and storage.