Multiscale regulation of thermodynamics and kinetics in high-entropy body-centered cubic type hydrogen storage alloys

Abstract

The thermodynamic and kinetic properties of body-centered-cubic (BCC) hydrogen storage alloys highly depend on their chemical compositions, making high-entropy alloying a promising strategy for performance optimization. However, clarifying how multi-principal element compositions regulate multiscale structures and thereby influence their hydrogen storage performance remains challenging, which limits the rational design of high-performance BCC high-entropy alloys (HEAs). This review provides a comprehensive overview of the recent advances in BCC HEAs for hydrogen storage, with emphasis on the multiscale regulation of their thermodynamics and kinetics. Empirical descriptor-guided composition screening, thermodynamic modeling based on the CALculation of PHAse Diagrams, 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 the chemical homogeneity, defect structures, and microstructural stability of materials are examined. The hydrogen storage performance is analyzed in terms of activation behavior, thermodynamics, kinetics, and cyclic stability, with a focus on the underlying governing factors and mechanistic origins. Finally, prospective challenges and research directions are outlined to guide the design and processing of BCC HEAs.

1. Introduction

Owing to its high gravimetric energy density and zero point-of-use carbon emissions, hydrogen is widely regarded as a potential secondary energy carrier for future low-carbon energy systems [1–6]. However, hydrogen storage and transportation in the form of a compressed gas or cryogenic liquid suffer from high energy consumption, high cost, and safety concerns, which severely limit its large-scale deployment [7–11]. Solid-state hydrogen storage materials, particularly metal and alloy hydrides, offer high volumetric hydrogen storage density and improved safety and are therefore considered one of the most promising candidates for hydrogen storage across multiple application scenarios [12–18]. However, conventional metal hydrides are generally constrained by intrinsic trade-offs among hydrogen capacity, desorption temperature, absorption/desorption kinetics, and cycling stability [19–25]. For example, Mg/MgH2 possesses a high theoretical gravimetric hydrogen capacity of 7.6wt% [26–27]; however, strong Mg–H bonding leads to increased desorption temperatures and sluggish kinetics [28–34]. By contrast, intermetallic compounds, such as TiFe and LaNi5, can reversibly absorb and desorb hydrogen under mild conditions but typically exhibit low gravimetric hydrogen storage capacities [35–39].

By incorporating multiple principal elements, the resulting high configurational entropy stabilizes simple solid-solution phases. Lattice distortion and diverse local chemical environments provide unique flexibility for tuning hydrogen occupancy, diffusion pathways, and metal–hydrogen interactions [35,40–41]. The tuned characteristics introduce additional degrees of freedom for regulating hydride active sites, hydrogen diffusion pathways, and metal–hydrogen interactions, thereby offering new opportunities and design strategies for advanced hydrogen storage materials.

The Web of Science Core Collection was searched on December 31, 2025, using “high entropy alloys for hydrogen storage” as the topic search term. To ensure a fair comparison, the annual publication statistics in Fig. 1(a) are plotted by year and limited to the 1996–2025 period. As Fig. 1(a) shows, the number of annual publications on high-entropy alloys (HEAs) for hydrogen storage has been increasing significantly since 2019, reaching 129 by 2025. This trend demonstrates the notable development and growing research interest in the field. Fig. 1(b) presents the keyword co-occurrence network of research on high-entropy hydrogen storage alloys, revealing four closely interconnected research themes: alloy design (magenta clusters), synthesis and processing (blue clusters), microstructure regulation (cyan clusters), and fundamental mechanisms (red clusters). Keywords related to alloy design, such as HEAs, multi-principal element alloys, body-centered-cubic (BCC) alloys, and Laves phases, form a prominent cluster.