•Mg9Ag alloy is employed for both hydrogen generation and Ag NPs preparation.•Hydrogen yield reaches 730 mL g−1 within 25 min at 298 K for H2-milled Mg9Ag.•Ag NPs with a size of less than 50 nm were obtained for H2-milled Mg9Ag.A Mg9Ag alloy is employed as a medium for both production of hydrogen and preparation of Ag nanoparticles through hydrolysis. Mg9Ag milled under H2 exhibits very favorable structural characteristics, i.e., yielding a fine nanocrystal powder and partial hydrogen-induced phase decomposition. As a result, a hydrogen yield of 730 mL g−1 is obtained in 25 min at 298 K, a much higher rate than produced by samples not milled or milled under argon. Moreover, the hydrolysis by-product can be recycled to obtain Ag nanoparticles by removing insoluble Mg(OH)2 using an added HCl solution. These results show that this process provides a highly efficient method for economically produce hydrogen and Ag nanoparticles.

For the first time, component segregation during cycling was demonstrated to be responsible for the deterioration in the kinetics of bimetallic hydride NaMgH3. To solve this problem, we propose a method involving in situ embedding of Mg2NiH4 and YH3 into NaMgH3, which is accomplished with a solid-phase reaction using amorphous Mg12YNi alloy and NaH as starting materials under a H2 atmosphere. Using this novel method, 12 wt % of the Mg2NiH4 phase and 11 wt % of the YH3 phase were homogeneously embedded in the NaMgH3 matrix. In comparison to those of pure NaMgH3, this composite material exhibits no change in thermodynamics but shows greatly enhanced kinetics for hydrogen absorption and desorption cycling. In addition, reasonable mechanisms for the enhanced kinetics have been proposed including the prevention of macroscopic segregation of metallic Na, grain refinement, and a synergistic catalytic effect. All of these mechanisms rely on the intimately interdispersed Mg2NiH4 and YH3 nanoparticles embedded in the NaMgH3 matrix.

The ternary compound Ca4Al3Mg was successfully synthesized by induction melting of appropriate amounts of pure metals followed by annealing at 773 K for 14 days. The crystal structure was determined by X-ray powder diffraction. Ca4Al3Mg crystallizes in space group Pbcm (No. 57); cell parameters: a = 6.1792(1) Å, b = 24.2113(5) Å, c = 5.8864(1) Å; Z = 4. This structure can be built up of the alternating layers of two types of chains. The first type of chains consists of Al3 triangles sharing one corner and the second one contains AlMg2 triangles sharing one of the Mg corners. Both of them run along the crystallographic c-axis, forming atomic layers normal to the b-axis.

The hydriding behavior of the Mg17Al12 intermetallic compound was studied in detail. It was found that the Mg17Al12 compound can initially react with hydrogen to form Mg2Al3, MgH2 and Al at 573 K. Increasing the hydrogenation temperature to 623 K, further hydriding leads to the decomposition of Mg2Al3 into the hydride MgH2 and the Al-based solid solution Al0.9Mg0.1.

The pure Ca8Al3 intermetallic compound was prepared by induction melting of appropriate amounts of pure metals and subsequent annealing. Furthermore, the hydrogenation behavior of the Ca8Al3 compound was studied in detail. It was found that the Ca8Al3 compound can react with hydrogen to form CaH2 and Al starting from 373 K, but the process is very sluggish at a low temperature. Prior to the decomposition, the lattice parameters of Ca8Al3 do not change, indicating that the compound does not absorb hydrogen to form solid solution. Increasing hydrogenation temperature to 523 K, the hydrogen-induced decomposition of Ca8Al3 occurs entirely.

The phase relations and hydrogenation characteristics of the Ca8(Al1−xNix)3 (x=0, 0.1, 0.2, 0.3 and 0.4) alloys were studied. It was found that the maximum solid solubility of Ni in the Ca8Al3 phase is about x=0.09. In the Ni-substituted Ca8(Al0.91Ni0.09)3 phase, the Ni atoms occupy the Al sites but the occupation factor of Ni in 1c site is larger than that in 2i site. The lattice parameters of the Ca8Al3 phase have no obvious change after the partial substitution of Al by Ni because of the small solid solubility of Ni. However, further increasing x leads to a decrease in the amount of the Ca8Al3 phase and an increase in the amount of Ca and NiAl. When x=0.4, the Ca8Al3 phase disappears entirely and only the NiAl phase and the Ca-based solid solution with a solid solubility of about 0.05 at.% Al exist in the alloy. Both the binary Ca8Al3 phase and the Ni-substituted Ca8Al3 phase can be hydrogenated into CaH2 and Al at 473 K, but the former shows a slower hydrogenation reaction than the latter.

The phase relations and hydriding characteristics of the Ca(Al1−xNix)2 (x = 0, 0.1, 0.2, 0.3 and 0.4) alloys were studied. It was found that partially substituting Al by Ni in CaAl2 alloy leads to the co-existence of multiple phases. When x = 0.1, 0.2 and 0.3, the alloys consist of C15, Ca13Al14 and NiAl phases. The amount of the C15 phase decreases with the increase of x. Further increasing x to 0.4, the C15 phase disappears entirely and the alloy contains Ca8Al3, NiAl and Ca. The partial substitution of Al by Ni cannot effectively improve the hydrogen storage properties of CaAl2 because the lattice parameter of the C15 phase decreases slightly after the substitution.

The crystal structures and electrochemical properties of the multi-component TiNi-based alloys Ti0.7Zr0.2V0.1Ni, Ti0.6Zr0.2V0.1Mn0.1Ni and Ti0.55Zr0.2V0.1Mn0.1Cr0.05Ni were studied. It was found that these alloys consist of a major phase with the B2 structure and a secondary Laves phase. However, the structure type of the secondary phase, C14 or C15, can be changed because of the simultaneous substitution of different elements for Ti. The existence of the secondary Laves phase leads to an increase of discharge capacity and an improvement of high-rate dischargeability even though their activation property becomes worse. The effect of the secondary phase on electrochemical properties is caused not only by the abundance of the secondary phase but also by its lattice parameters.