Multiscale regulation of thermodynamics and kinetics in high-entropy BCC-type hydrogen storage alloys

The thermodynamic and kinetic properties of BCC-type hydrogen storage alloys are highly dependent on the chemical composition, making high-entropy alloying a promising strategy for performance optimization. However, it remains difficult to clarify how multi-principal-element composition regulates multiscale structure and thereby influences hydrogen storage performance, limiting the rational design of high-performance BCC high-entropy alloys (HEAs). This review provides a comprehensive overview of recent advances in BCC HEAs for hydrogen storage, with an emphasis on the multiscale regulation of thermodynamics and kinetics. Empirical descriptor-guided composition screening, CALPHAD-based thermodynamic modeling, and data-driven and machine-learning-assisted approaches are discussed. In addition, the roles of melting-based processing, mechanical alloying, and emerging fabrication strategies in controlling chemical homogeneity, defect structures, and microstructure stability are examined. Hydrogen storage performance is analyzed in terms of activation behavior, thermodynamics, kinetics, and cyclic stability, with a focus on their underlying governing factors and mechanistic origins. Finally, key challenges and future research directions are proposed to guide the design and processing of BCC HEAs.