Fast activation of Na micro-alloyed Mg–Ni-Gd-Y-Zn-Cu alloys for solid-state hydrogen storage

Abstract

The role of Na in influencing the microstructure, phase evolution, and hydrogen storage behavior of Mg-based alloys remains insufficiently understood. This study explores the impact of Na on the hydrogen storage performance of Mg–Ni-Gd-Y-Zn-Cu alloys. The addition of 0.2 wt.% Na significantly enhanced activation behavior by eliminating the incubation period and accelerating hydrogen absorption during the first cycle. Na-added alloys exhibited improved hydrogenation and dehydrogenation kinetics with a little sacrifice in hydrogen storage capacity, driven by enhanced catalytic activity from Na's distribution in the eutectic regions and Mg₂Ni phases. In-situ PXRD revealed that Na facilitates rapid phase transformations, while XPS analysis indicated surface enrichment of Na₂O, which altered the alloy's surface chemistry and further improved hydrogenation behavior. These results demonstrate that Na addition is a simple yet effective strategy for enhancing the activation and kinetics of Mg-based hydrogen storage materials, paving the way for the development of advanced materials for solid-state hydrogen storage applications.