MXene-Integrated Solid-Solid Phase Change Composites for Accelerating Solar-Thermal Energy Storage and Electric Conversion.

The high thermal storage density of phase change materials (PCMs) has attracted considerable attention in solar energy applications. However, the practicality of PCMs is often limited by the problems of leakage, poor solar-thermal conversion capability, and low thermal conductivity, resulting in low-efficiency solar energy storage. In this work, a new system of MXene-integrated solid-solid PCMs is presented as a promising solution for a solar-thermal energy storage and electric conversion system with high efficiency and energy density. The composite system's performance is enhanced by the intrinsic photo-thermal behavior of MXene and the heterogeneous phase transformation properties of PCM molecular chains. The optimal composites system has an impressive solar thermal energy storage efficiency of up to 94.5%, with an improved energy storage capacity of 149.5 J g, even at a low MXene doping level of 5 wt.%. Additionally, the composite structure shows improved thermal conductivity and high thermal cycling stability. Furthermore, a proof-of-concept solar-thermal-electric conversion device is designed based on the optimized M-SSPCMs and commercial thermoelectric generators, which exhibit excellent energy conversion efficiency. The results of this study highlight the potential of the developed PCM composites in high-efficiency solar energy utilization for advanced photo-thermal systems.