Review of hydrogen storage using AB, AB2, HEA, and solid solution metal hydrides

Achieving Net Zero CO 2 emissions by 2050 requires efficient and reliable energy storage solutions. Hydrogen is considered a key energy vector, but its practical deployment depends on safe and compact storage systems. Metal hydrides offer high volumetric density and moderate operating pressures, but their performance is often limited by thermodynamics, kinetics, activation requirements, and cost. This review presents a cross-family comparison of hydrogen storage in AB-type, AB 2 -type, high-entropy alloys (HEAs), and body-centered cubic solid-solution hydrides. Rather than treating these alloy systems independently, they are compared using consistent metrics, distinguishing maximum and reversible hydrogen capacities and relating performance to reported pressure-temperature conditions. An indicative cost normalization (US$/kg H 2 ), based on raw element prices, is also incorporated to contextualize material selection. • A critical comparison of AB, AB 2 , HEA and solid-solution hydrides is presented. • Links between capacity, thermodynamics and cycling stability are clarified. • Key degradation pathways controlling long-term reversibility are identified. • Research priorities beside maximum hydrogen capacity is outlined.