The marriage of two-dimensional materials and phase change materials for energy storage, conversion and applications

Benefiting from high thermal storage density, wide temperature regulation range, operational simplicity, and economic feasibility, latent heat-based thermal energy storage (TES) is comparatively accepted as a cutting-edge TES concept, especially solid-liquid phase change materials (PCMs). However, liquid phase leakage, low thermal/electrical conductivities, weak photoabsorption capacity, and intrinsic rigidity of pristine PCMs are long-standing bottlenecks in both industrial and domestic application scenarios. Towards these goals, emerging two-dimensional (2D) materials containing regions of empty nanospace are ideal alternatives to efficiently encapsulate PCMs molecules and rationalize physical phase transformation, especially graphene, MXene and BN. Herein, we provide a timely and comprehensive review highlighting versatile roles of 2D materials in composite PCMs and relationships between their architectures and thermophysical properties. In addition, we provide an in-depth understanding of the energy conversion mechanisms and rationalize routes to high-efficiency energy conversion PCMs. Finally, we also introduced critical considerations on the challenges and opportunities in the development of advanced high-performance and multifunctional 2D material-based composite PCMs, hoping to provide constructive references and facilitate their significant breakthroughs in both fundamental researches and commercial applications.