PdNi biatomic clusters from metallene unlock record-low onset dehydrogenation temperature for bulk-MgH 2 .

Hydrogen storage has long been a priority on the renewable energy research agenda. Due to its high volumetric and gravimetric hydrogen density, MgH 2 is a desirable candidate for solid-state hydrogen storage. However, its practical use is constrained by high thermal stability and sluggish kinetics. Here, we report PdNi bilayer metallenes as catalysts for hydrogen storage of bulk-MgH 2 near ambient temperature. Unprecedented 422 K beginning dehydrogenation temperature and up to 6.36 wt.% reliable hydrogen storage capacity were achieved. Fast hydrogen desorption was also provided by the system (5.49 wt.% in 1 h, 523 K). The in-situ generated PdNi alloy clusters with suitable d-band centers were identified as the main active sites during the de/re-hydrogenation process by AC-TEM and theoretical simulations, while other active species including Pd/Ni pure phase clusters and Pd/Ni single atoms obtained via metallene ball milling, also enhance reaction. These findings present fundamental insights into active species identification and rational design of highly efficient hydrogen storage materials. This article is protected by copyright. All rights reserved.