Review and outlook on high-entropy alloys for hydrogen storage

Recently, a new class of alloys, namely, high-entropy alloys (HEAs), started to be investigated for hydrogen storage as they can form metal hydrides. Considering that the properties of metal hydrides are greatly influenced by the type of phase formed, and chemical composition, HEAs (with their vastness of compositions) present a high potential for developing promising materials for this application. A crucial aspect in assessing the potential of these alloys is the effective compositional design and synthesis. Here, we evaluate the methods used for obtaining HEAs for hydrogen storage and, based on the most advanced discussions of phase formation and stability in HEAs, we expose some strategies for a better assessment of the vast compositional field. Moreover, we present and discuss the first attempts to model the hydrogenation properties of HEAs using thermodynamics and data science. The development of these kinds of predictive tools is paramount for exploring HEAs' potential for hydrogen storage. To date, the most promising HEA compositions can be classified into three classes: body-centered cubic HEAs, lightweight HEAs, and intermetallic HEAs.