Ultra-lightweight compositionally complex alloys with large ambient-temperature hydrogen storage capacity

In the burgeoning field of hydrogen energy, compositionally complex alloys promise unprecedented solid-state hydrogen storage applications. However, compositionally complex alloys are facing one main challenge: reducing alloy density and increasing hydrogen storage capacity. Here, we report TiMgLi-based compositionally complex alloys with ultralow alloy density and significant roomtemperature hydrogen storage capacity. The record-low alloy density (2.83 g cm-3) is made possible by multi-principal-lightweight element alloying. Introducing multiple phases instead of a single phase facilitates obtaining a large hydrogen storage capacity (2.62 wt% at 50 degrees C under 100 bar of H2). The kinetic modeling results indicate that three-dimensional diffusion governs the hydrogenation reaction of the current compositionally complex alloys at 50 degrees C. The here proposed approach broadens the horizon for designing lightweight compositionally complex alloys for hydrogen storage purposes.