C14-Laves phase high entropy alloys for hydrogen storage: a review

Recently, solid-state hydrogen storage materials have attracted significant research attention within the hydrogen energy community owing to their higher hydrogen storage density and affordable safety compared to conventional systems (i.e., gaseous and liquid storage systems). Among these materials, high entropy alloys (HEAs) possessing C14-Laves single-phase structures have emerged as promising candidates for this application, attributed to their unique structural properties and superior performance. Unlike traditional alloys, the complex composition and high configurational entropy of C14-Laves phase HEAs reveal a new balanced design strategy for hydrogen storage that stabilizes single phase structures, encourages reversible hydrides, and provides exceptional cycling stability. Numerous remarkable studies have already demonstrated the potential of C14-Laves phase alloys, typically for stationary hydrogen storage applications. In this review, first, the definition and concept of HEAs as well as the evaluation of the compositional design strategies for the formation of a favorable C14-Laves single solid-solution phase are highlighted. Moreover, the thermodynamic modeling of the hydrogenation properties, manufacturing processes, and hydrogen storage properties in the latest state-of-the-art C14-Laves phase structured HEAs are presented and discussed. Finally, possible applications, potential challenges, and perspectives are outlined.