Hierarchical Design of MXene Architectures for Photothermal Phase-Change Energy Storage: From Nanosheet Synthesis to Ordered 3D Composites

Solar energy is clean and abundant but intermittent, and the mismatch between solar energy supply and demand leads to significant energy waste. Phase-change materials (PCMs) can store solar energy as thermal energy, but conventional PCMs suffer from leakage, low thermal conductivity, and poor energy conversion ability. MXenes, a family of two-dimensional transition metal carbides/nitrides, possess high electrical and thermal conductivity, large specific surface area, abundant surface functional groups, and high photothermal conversion efficiency. Represented by Ti3C2Tx, MXene achieves efficient photothermal conversion through localized surface plasmon resonance (LSPR)-enhanced broadband photon capture, electron-phonon coupling-induced non-radiative relaxation, and interlayer phonon transport, offering new opportunities for photothermal phase-change energy storage. This review focuses on MXene-based photothermal conversion phase-change energy storage materials. It summarizes MXene preparation/etching methods and photothermal conversion mechanisms, discusses the relationship between photothermal energy storage and oxidation resistance in light of practical applications, and analyzes the factors of performance degradation in MXene-based three-dimensional structures. It then reviews ordered structural design strategies and surface modification/composite preparation methods, with emphasis on MXene aerogels and hydrogels and their applications in solar thermal energy storage, thermal management, sensing, supercapacitors, electromagnetic shielding, and batteries. Finally, effective solutions for specific applications and future development directions are proposed. This review aims to provide insights into the rational design and practical application of next-generation MXene-based photothermal phase-change materials.