Phase Equilibrium and Thermophysical Properties of Hydrochar–Metal Composites: In‐Depth Analysis and Application Prospects

ABSTRACT Hydrochar–metal composites exhibit significant potential in catalysis and energy storage due to their tunable pore structures, high surface areas, and adjustable physicochemical properties. This review systematically examines preparation methods, phase equilibrium behavior, and thermophysical properties of these composites. Microstructural control is achieved by varying biomass types, hydrothermal conditions (temperature, time, pH), and metal incorporation approaches (direct addition or pretreatment). Metal type and content critically influence phase equilibrium, governing thermal conductivity (TC), specific heat capacity (SHC), and thermal expansion coefficient (CTE). Uniform metal dispersion and stable integration with the carbon matrix enhance catalytic activity and energy storage performance. High TC improves thermal management in catalysis, while high SHC and low CTE enhance energy storage stability by mitigating thermal fluctuations and mechanical stress. Challenges include phase equilibrium modeling, thermophysical characterization under extreme conditions, and scalable synthesis optimization. Future research should leverage machine learning, multifield coupling experiments, and advanced characterization to guide high‐performance composite design.