Multiscale mechanistic insights into Er-driven phase reconfiguration and hydrogen diffusion in Mg–Ni alloys
Junqi Qiu, Haiyi Wan, Yuting Li, Ziyi Guo, Zhao Ding, Yu’an Chen, Fusheng Pan
Abstract
Improving the hydrogen storage performance of Mg-based alloys requires overcoming fundamental limitations in hydrogen sorption kinetics and thermodynamic stability. Herein, we report a comprehensive investigation into the effects of Er doping on the phase evolution, hydrogen diffusion dynamics, and storage behavior of Mg–Ni–Er ternary alloys using a multiscale experimental-theoretical framework. A series of alloys with systematically varied Ni and Er content were synthesized via melt casting and ball milling, enabling compositional modulation of multiphase architectures. Structural analyses reveal that Er preferentially partitions into the Mg 2 Ni phase rather than the α-Mg matrix, facilitating refined intermetallic networks and promoting the formation of long-period stacking ordered phases under low Ni conditions. Kinetic measurements demonstrate that the Mg-7.8Ni-2.2Er alloy achieves a hydrogen absorption capacity of 6.15 wt% at 300 °C, significantly outperforming binary Mg–Ni alloys. Rate-limiting step analysis using the Chou model identifies a transition from surface penetration to hydrogen diffusion control during sorption, which is further corroborated by first-principles calculations showing a reduction in hydrogen diffusion barrier from 0.505 eV (pure Mg) to 0.278 eV (ErH 2 -doped Mg). These findings elucidate the catalytic and microstructural roles of Er in reconfiguring hydrogen diffusion pathways and provide actionable insights for designing high-performance Mg-based material.