The incorporation of transition metal Ni and rare-earth elements La and Y into Mg-based alloys significantly enhances hydrogen storage performance through synergistic effects. To optimize storage capacity and glass-forming ability (GFA), a Mg₉₀La₂Y₂Ni₆ alloy was designed and synthesized via induction casting and melt spinning. The amorphous alloy was further subjected to crystallization annealing at 400 ℃ to obtain a crystallized alloy. Structural analyses (XRD, SEM, HRTEM) revealed that the cast alloy comprised Mg, Mg₂Ni, La₂Mg₁₇, and YNi₃ phases. Melt spinning produced amorphous–nanocrystalline composites, with the amorphous fraction increasing with spinning rate. The crystallized alloy exhibited a phase composition similar to the cast alloy, but with finer, uniformly dispersed precipitates that provided enhanced diffusion pathways. Hydrogen storage properties were evaluated by Sievert apparatus and DSC. The crystallized alloy demonstrated markedly improved hydrogen absorption/desorption kinetics compared with the cast alloy. Specifically, the desorption activation energy decreased from 67.84 kJ/mol (cast) to 58.56 kJ/mol (crystallized, 30 m/s spinning rate). In addition, the initial hydrogen desorption temperature was reduced from 323.5 ℃ to 288.2 ℃. Thermodynamic analysis further confirmed a decrease in desorption enthalpy, indicating reduced hydride stability. Overall, the melt spinning–crystallization annealing route effectively tailors the microstructure and thermodynamics of Mg-based alloys, leading to lower activation energy, reduced desorption temperature, and enhanced hydrogen storage performance.

Rare earth (RE) elements have been successfully utilized in solid-state hydrogen storage as hydrogen-absorbing elements with excellent hydrogen storage properties in terms of safety and efficiency. RE-Mg-based hydrogen storage materials with high magnesium content are considered to be one of the most promising hydrogen storage materials for application due to their high mass/volume hydrogen storage density, moderate required hydrogen pressure, good reversibility, non-toxicity, and harmlessness. Furthermore, RE-Mg-based materials with low magnesium content and superlattice structure show great potential for application in the field of solid-state hydrogen storage. They are also widely used as anode materials for nickel-metal hydride batteries. In this paper, we comprehensively summarized and evaluated the organization and hydrogen storage properties of different RE-Mg system alloys (Mg-RE, Mg-RE-TM (TM=transition metals), and superlattice-type RE-Mg-TM) and the catalytic effect and mechanisms of catalysts on RE-Mg system alloys. The interactions between the types of RE elements, the contents of RE elements, the crystal structures, and the catalysts with the microstructure morphology and hydrogen storage properties of RE-Mg-based hydrogen storage alloys were established. The intrinsic mechanisms between microstructure morphology, phase structure, phase composition, and hydrogen storage properties of alloys with different RE-Mg-based systems were elucidated. By comparing the differences and characteristics between the organizational structures and hydrogen storage properties of different RE-Mg systems, a feasible idea and solution for the rational design and development of RE-Mg-based alloys with high hydrogen storage capacity, low cost, and fast hydrogen absorption and desorption kinetics was proposed.

To address the challenges posed by high reaction temperatures and the slow kinetics of Mg-based alloys with high hydrogen storage density, Mg−RE−TM (RE = rare earth, TM = metallic element) alloys have been extensively researched and hold great promise. In this study, a series of Mg−RE−TM based Mg₉₀Y₂Ce₂Ni₃Al_3-xSc_x (x = 0, 0.3, 0.6, 0.9, 1.2) alloys were prepared. The addition of Sc element has been found to enhance the activation and kinetic properties of the alloy. Compared with the significant differences in the first four dehydrogenation curves of the Sc0 sample, the first activated dehydrogenation curve of the Sc1.2 alloy overlaps with the fully activated dehydrogenation curve. The dehydrogenation activation energy decreased from 96.56 kJ/mol in the Sc0 alloy to 63.69 kJ/mol in the Sc0.9 alloy. Through analysis of the microstructure, phase composition, and hydrogen absorption and desorption kinetics of the alloy, the mechanisms for improving the hydrogen storage properties of the alloy were elucidated. The nucleation-growth-impingement Avrami model was employed to accurately simulate the hydrogen storage kinetics. The results showed that stage Ⅱ was prolonged and accelerated at high temperature, and the growth rate and hydrogen storage of stage Ⅰ were increased at low temperature in hydrogen absorption. Microstructure analysis revealed the presence of Mg, CeMg₁₂, Mg₄₇Y, and YNi₂Al₃ phases in the Sc0 sample. Upon the addition of Sc element, a new phase, ScNiAl, was formed, and the coarse grain size of the main phase was significantly refined. This refinement provides faster diffusion channels for hydrogen atoms, accelerating the phase transition between Mg alloys and hydrides. The microstructure changes explain the improved activation properties, effective hydrogen absorption and desorption capacity, and kinetic properties of the Mg-based samples.

The hydrolysis behavior of CaMg₂In_0.1, CaMg₂In_0.3, CaMg₂In_0.5, and CaMg₂In_0.7 ternary alloys in an MgCl₂ solution following casting and hydrogenation were investigated. The hydrolysis mechanism of these alloys is elucidated through an analysis of microstructure, phase composition, and kinetics before and after hydrolysis. The nucleation-growth Avrami model is employed to accurately model the hydrolysis kinetics, revealing improved hydrolysis yields and reaction rates following hydrogenation. Notably, CaMg₂In_0.1 has demonstrated exceptional hydrolysis characteristics, exhibiting a yield of 1140 mL/g, an initial hydrolysis rate of 113 mL/g·s, and an activation energy of 24.3 ± 1.7 kJ·mol⁻¹. The yield of H-CaMg₂In_0.1 further escalates to 1800 mL/g with a rate of 221 mL/g·s, attributed to the formation of Ca₄Mg₃H₁₄ and In phases subsequent to the hydrogenation of In₂Ca and Mg₃In phases in the alloy. These newly formed phases act as catalysts and actively participate in the hydrolysis process, providing active sites for hydrogen production, thus enhancing hydrolysis yields and kinetics. It is observed that with increasing In content, the order of hydrolysis performance of the alloy is as follows: CaMg₂In_0.1 > CaMg₂In_0.3 > CaMg₂In_0.5 > CaMg₂In_0.7, consistent with the trend after hydrogenation. These findings indicate that the addition of In significantly enhances the hydrolysis performance of CaMg₂ alloys, offering a promising strategy for preparing magnesium-based alloys with high yields and favorable kinetic properties.

Mg-based hydrides are too stable and the kinetics of hydrogen absorption and desorption is not satisfactory. An efficient way to improve these shortcomings is to employ reactive ball milling to synthesize the nanocomposite materials of Mg and additives. In this experiment, TiF₃ was selected as an additive, and the mechanical milling method was employed to prepare the experimental alloys. The alloys used in this experiment were the as-cast Ce₅Mg₈₅Ni₁₀, as-milled Ce₅Mg₈₅Ni₁₀ and Ce₅Mg₈₅Ni₁₀ + 3 wt.% TiF₃. The phase transformation, structural evolution, isothermal and non-isothermal hydrogenation and dehydrogenation performances of the alloys were inspected by XRD, SEM, TEM, Sievert apparatus, DSC and TGA. It revealed that nanocrystalline appeared in the as-milled samples. Compared with the as-cast alloy, ball milling made the particle dimension and grain size decrease dramatically and the defect density increase significantly. The addition of TiF₃ made the surface of ball milling alloy particles markedly coarser and more irregular. Ball milling and adding TiF₃ distinctly improved the activation and kinetics of the alloys. Moreover, ball milling along with TiF₃ can decrease the onset dehydrogenation temperature of Mg-based hydrides and slightly ameliorate their thermodynamics.