Prospect and advancement of high-entropy alloys as solid-state hydrogen storage materials for large-scale applications

High-entropy alloys (HEA) are emerging materials for hydrogen storage, moving toward sustainable and greener energy systems, owing to compositional tunability and structural stability, which arise from their four core effects. These features enable HEAs to operate at low temperature and pressure, overcoming the challenges of conventional metal hydrides (MH). However, their large-scale deployment is hindered by challenges, including uniform elemental distribution, balancing the trade-offs among storage capacity, kinetics, and stability, synthesis scalability, material synthesis costs, computational cost-accuracy optimization, and ensuring recyclability. This study systematically reviews HEAs' theoretical foundations, synthesis techniques, computational design approaches, and applications as MH or catalyst for MgH2. It critically examines recent developments and research trends while also addressing the existing research gaps. First, we examine the elemental impact on the material performance, highlighting that Ti-rich and Mg-rich HEAs exhibit enhanced hydrogen diffusion and storage capacity, respectively. Then, an operation-target classification framework is provided, including room-temperature, high-capacity, and reversible hydrogen storage systems. Fe/Co/Ni/Cr/Ti/Mo-catalyzed MgH2 demonstrates enhanced hydrogen diffusion, and Ti/V/Nb/Zr/Fe-based compositions exhibit superior structural stability. Finally, a multi-scale pipeline is proposed to incorporate computational modeling and machine learning to bypass conventional design limitations, shortening the design-to-fabrication timeline. Addressing these challenges is essential to unlocking the full potential of HEAs, positioning them as promising candidates for next-generation hydrogen storage technologies. This review integrates theoretical insights with practical developments, providing a decision-making strategy for targeted material design to scale-up from laboratory to industrial application.