MXene aerogel-based phase change materials toward solar energy conversion

Two-dimensional transition-metal carbides/carbonitrides (MXenes) have demonstrated wide application prospect in energy conversion and storage , mostly in the form of electrochemical energy storage . Compared with the conversion between chemical energy and electrical energy, an energy conversion process initiated by solar energy and driven by the physical change of energy materials will be a sustainable and environmentally friendly strategy. Therefore, a high-performance MXene aerogel-based phase change material for solar energy conversion and thermal energy storage is constructed. MXene nanosheets with an extinction coefficient of 25.67 L/(g.cm) at 808 nm demonstrate excellent light absorption performance , which can spontaneously convert the solar energy into thermal energy . The polyethylene glycol (PEG) possessing high affinity with MXene acts the medium for thermal energy storage and release in the process of fusion and solidification. The MXene@PEG aerogels are lightweight, with a density about 30 mg/cm 3 . The MXene skeleton is introduced as supporting materials to keep the shape of MXene@PEG aerogel stable during the phase change process . The MXene nanosheets improve the thermal stability of PEG, the thermal decomposition temperatures can be increased by 40 °C. The actual fusion and solidification enthalpies of MXene@PEG aerogels can reach 167.72 and 141.51 J/g, respectively. The photothermal storage efficiency of MXene@PEG aerogels reaches a relatively high value of 92.5%. This work provides a new type of scaffold for lightweight and shape-stable photothermal carrier and paves the way for the application of non-graphene 2D materials toward solar energy utilization.