Flame-retardant and form-stable phase change composites based on MXene with high thermostability and thermal conductivity for thermal energy storage

Phase change materials (PCMs) are promising candidates for enhancing the efficiency of solar thermal energy utilization owing to their excellent capacity of storing thermal energy. However, the issues of leakage, poor thermal conductivity, and high flammability have hindered their application. Here, we have successfully designed and prepared flame-retardant PCMs through chemical modification of stearyl alcohol (SAL) with a phosphorus-containing molecule. Form-stable phase change composites were then fabricated through a vacuum impregnation method, where an MXene with a porous architecture serves as the supporting skeleton for PCMs. As expected, benefiting from the high aspect ratio and strong capillary force of the MXene aerogel as well as the interfacial interaction between the PCM molecule and MXene, the resulting MXene-based PCMs (PSM-4) exhibit a large thermal conductivity (0.486 W m−1 K−1) and are form-stable upon heating up to 90°C. Additionally, the combination of phosphorus and MXene further strengthens the flame retardancy of PCMs, e.g., the peak heat release rate and total heat release are reduced by 42.8% and 32.1%, respectively. The improvement of flame retardancy can be assigned to the catalytic charring and barrier effect in the condensed phase as well as to the effect of free radical quenching in the gas phase. Hence, the obtained MXene-based flame-retardant PCMs can be potentially utilized for safe and efficient applications of solar energy storage.