A Focused Mini-Review on High-entropy Intermetallics for Hydrogen Storage

Intermetallic compounds (IMCs) have long been considered as a type of desirable hydrogen storage material. However, there still exist many shortcomings in traditional hydrogen storage IMCs. High-entropy alloys (HEAs), composed of multiple metal elements, exhibit significant lattice distortion and large gap positions, which make them a promising class of hydrogen storage alloys. Among HEAs for hydrogen storage, the high-entropy intermetallics(HEIs) have exhibited enormous potential in hydrogen absorption kinetics, cycle stability, especially in the field of room temperature hydrogen storage. This review systematically summarizes the research progress of HEIs in the field of hydrogen storage. The article first conducts a statistical analysis of the composition design methods for these alloys, including empirical criteria based on parameters such as valence electron concentration and atomic size mismatch, as well as thermodynamic calculations like the CALPHAD method. It subsequently summarizes the characteristics and hydrogen storage performance of the reported alloys, with detailed discussions on their phase composition, microstructure, and corresponding effects on hydrogen storage properties. Particular emphasis is placed on the critical roles of phase boundaries, multiphase synergy, and specific microstructural features (e.g., networked/eutectic, morphologies) in enhancing activation performance and improving hydrogen diffusion kinetics. Although the current hydrogen storage capacity of HEIs (approximately 1 H/M) remains lower than that of BCC-structured high-entropy alloys, their exceptional reversible hydrogen absorption/desorption capability at room temperature, absence of activation requirements, and remarkable cycling stability render them highly promising for applications where moderate capacity suffices, such as mobile hydrogen storage. This review provides a systematic summary of the research progress on HEIs in the field of hydrogen storage, with a focus on the effects of alloy design strategies, phase composition, and microstructural regulation on their hydrogen storage properties. It points out that the primary challenge currently facing HEIs is their relatively low hydrogen storage capacity, and accordingly outlines future development directions to address this issue. This review provides a theoretical basis and guidance for the development of next-generation high-performance hydrogen storage materials.