Comprehensive structural and hydrogenation analysis of arc-melted and melt-spun Mg_1.95Ag_0.05Ni: Experimental and theoretical approaches

This study investigates the impact of silver (Ag) substitution on the microstructure and hydrogen storage properties of an Mg₂Ni-based alloy. Density functional theory (DFT) calculations as well as universal machine learning interatomic potentials are used to explore how Ag substitution leads to a decreased hydride desorption energy. Experimental analysis of arc-melted Mg_1.95Ag_0.05Ni alloys and melt-spun Mg_1.95Ag_0.05Ni ribbons reveals structural changes between the two different production methods. X-ray diffraction (XRD), scanning electron microscope (SEM), differential thermal analysis (DTA), thermogravimetric analysis (TGA), and transmission electron microscope (TEM) confirm refined microstructures. In addition, hydrogen properties of melt-spun ribbons were measured with Sievert type and electrochemical device. The Sieverts-type measurement demonstrates about 3wt% H₂ absorption and desorption, while electrochemical measurements show an initial discharge capacity of 80 mAh/g, with gradual fading over cycles. X-ray photoelectron spectroscopy (XPS) unambiguously confirms Ag substitution and provides detailed insight into surface oxidation processes induced by prolonged exposure to ambient conditions. The results demonstrate that Ag incorporation plays a key role in tailoring the microstructure and significantly enhancing the hydrogen storage performance.