Gaseous phase hydrogen storage and electrochemical properties of Zr8Ni21, Zr7Ni10, Zr9Ni11, and ZrNi metal hydride alloys

A systematic study of four important non-Laves phase alloys, Zr₈Ni₂₁, Zr₇Ni₁₀, Zr₉Ni₁₁, and ZrNi, commonly seen in the Zr-based AB₂ metal hydride alloys was presented. In order to investigate the synergetic effect between the major and secondary phases, an annealing treatment was used to change the abundances of various phases in the alloys. The structure, gaseous phase hydrogen storage, and electrochemical properties were obtained for each of the four alloy compositions before and after annealing, and the correlations among these properties were explored. Annealing generally suppressed secondary phases except for the case of Zr₉Ni₁₁, where its secondary ZrNi phase abundance increased. As the Zr/Ni ratio in the average composition increased, the maximum gaseous phase hydrogen storage capacity increased but maximized at Zr:Ni = 9:11. Comparing the properties before and after annealing, it was established that the change in phase distribution influenced the gaseous phase storage. Through the electrochemical measurements, it was found that the highest full discharge capacity was obtained at Zr:Ni = 7:10, which represents a compromise between the hydrogen desorption/discharge rate and the theoretical maximum gaseous phase hydrogen storage. As the Zr/Ni ratio increased, the high-rate dischargeability decreased, which followed the trend of the amount of metallic Ni in the surface oxide determined by magnetic susceptibility measurement. The synergetic effect was observed in the electrochemical environment by comparing the results before and after annealing. In general, annealing deteriorated and improved the electrochemical discharge capacity and high-rate dischargeability, respectively, due to the reduction in secondary phase abundance and consequent synergetic effect. Among all alloys investigated, the unannealed Zr₇Ni₁₀ demonstrated the best overall gaseous phase hydrogen storage and electrochemical capacity and could be considered as a candidate to replace the AB₅ and AB₂ metal hydride alloys in Ni/MH battery applications. Furthermore, the unannealed Zr₈Ni₂₁ showed a good balance between high-rate dischargeability and ease of formation.     

The structure, hydrogen storage, and electrochemical properties of Fe-doped C14-predominating AB2 metal hydride alloys

A series of Fe-substituting cobalt C14-predoninating AB₂ alloys with the general formula Ti₁₂Zr_21.5V₁₀Cr_7.5Mn_8.1Fe_xCo_8−xNi_32.2Sn_0.3Al_0.4 (x = 0-5) were studied for the impacts of Fe to structure, gaseous, and electrochemical hydrogen storage properties. All alloys exhibit hyper-stoichiometric C14 main phase due to the formation of A-rich non-Laves secondary phases and the loss of Zr and Ti in the melt. Lattice parameters together with the unit cell volume increases and then decreases with increasing Fe-content which indicates the existence of anti-site defects. The amount of TiNi secondary phase increases with the increase of Fe-content up to 4% and shows a detrimental effect to the high-rate dischargeability of the alloys. Most of the gaseous storage characteristics remain unchanged with the addition of Fe. In the electrochemical properties, Fe-addition in the AB₂ alloys facilitates activation, increases the total electrochemical capacity and effective surface reaction area, decreases the half-cell high-rate dischargeability and bulk hydrogen diffusion, and deteriorates both −10 and −40 °C low-temperature performance. Fe-substituting Co in AB₂ alloys as negative electrode of nickel metal hydride battery can reduce the raw material cost with the trade-off being mainly in the low-temperature performance.     

Study of the different ZrxNiy phases of Zr-based AB2 materials

Hydride-forming alloys are used as components of the negative electrode of nickel-metal hydride (NiMH) batteries. In previous works, the study of Zr-based AB₂-type alloys indicated that the material without heat treatment (annealing) had better electrochemical characteristics than the annealed one. The effect was attributed to the presence of secondary phases Zr_xNi_y formed during the solidification of the alloy button obtained by arc melting, and to the fact that these phases diminished their concentration or disappeared upon annealing. The main secondary phases formed by microsegregation are Zr₇Ni₁₀, Zr₉Ni₁₁ and Zr₈Ni₂₁.     

Study on the structure and hydrogen storage characteristics of as-cast La0.7Mg0.3Ni3.2Co0.35−XCuX alloys

In this paper, the structure, hydrogen storage performance, electrochemical discharge and cyclic characteristics of La_0.7Mg_0.3Ni_3.2Co_0.35−XCu_X alloys were investigated using X-ray diffraction (XRD), pressure composition isotherm (PCT) and electrochemical tests. XRD tests showed that all of the alloys were composed of La₂Ni₇ and LaNi phases. The ratio of LaNi phase in these alloys increased with increasing substitution of Cu for Co. PCT tests showed that increasing substitution of Cu for Co resulted in the decrease of hydrogen storage capacity and the increase of plateau pressure. Electrochemical discharge tests showed that the discharge capacity increased first and then decreased with increasing substitution of Cu for Co.     

Electrochemical performances of the as-melt La0.75−xMxMg0.25Ni3.2Co0.2Al0.1 (M = Pr,Zr; x = 0, 0.2) alloys applied to Ni/metal hydride (MH) battery

The partial replacement of La by M (M = Pr, Zr) has been performed in order to ameliorate the electrochemical hydrogen storage performances of La–Mg–Ni-based A₂B₇-type electrode alloys. For this purpose, we adopt melt spinning technology to prepare the La_0.75−xM_xMg_0.25Ni_3.2Co_0.2Al_0.1 (M = Pr, Zr; x = 0, 0.2) electrode alloys. Then systemically investigate the effects that the preparation methods and M (M = Pr, Zr) substitution have on the structures and electrochemical hydrogen storage characteristics of the alloys. The analysis of XRD and TEM reveals that the as-cast and spun alloys hold a multiphase structure, containing two main phases (La, Mg)₂Ni₇ and LaNi₅ as well as a trace of residual phase LaNi₂. Besides, the as-spun (M = Pr) alloy displays an entire crystalline structure, while an amorphous-like structure is detected in the as-spun (M = Zr) alloy, implying the replacement of La by Zr facilitates forming amorphous phase. Based upon electrochemical measurements, an impact engendered by melt spinning on the electrochemical performances of the alloys appears to be evident. The cycle stabilities monotonously augment with the growing of the spinning rate. The discharge capacity and high rate discharge ability (HRD), however, exhibit difference. For the (M = Pr) alloy, they first mount up and then fall with the rising of the spinning rate, whereas for the (M = Zr) alloy, they always decline as the spinning rate elevates. Furthermore, the replacement of La by M (M = Pr, Zr) considerably enhances the cycle stability of the alloys and the replacement of La by Pr clearly increases the discharge capacity, but the Zr replacement results in an adverse impact.     

Effect of Al and Mo substitution on the structural and hydrogen storage properties of CaNi5

A simple mechanical milling and annealing process has been used to synthesize CaNi₅-based hydrogen storage alloys. Heat treatment at 800 °C under vacuum results in the formation of a crystalline CaNi₅ phase. Secondary phases, including Ca₂Ni₇ and Mo–Ni, are formed when substituting Mo for Ni. Replacement of Ni by Al or Mo leads to an increase in the unit cell volume of the CaNi₅ phase. The hydrogen storage capacity of all substituted alloys is reduced and the plateau pressures are lower than those of pure CaNi₅. Fairly flat plateau regions are retained for all compositions except the CaNi_4.8Mo_0.2 composition where a Ca₂Ni₇ phase is dominant. The incorporation of Mo also causes slow sorption kinetics for the CaNi_4.9Mo_0.1 alloy. CaNi_4.9Al_0.1 maintains its initial hydrogen absorption capacity for 20 cycles performed at 85 °C but the other substituted alloys lose their capacity rapidly, especially the CaNi_4.8Mo_0.2 composition.     

Structural and electrochemical properties of Ti1.5Zr5.5VxNi10−x

Quaternary alloys with the formula Ti_1.5Zr_5.5V_xNi_10−x (x between 0 and 3.0) were studied as a potential replacement for Laves phase alloys used as the negative electrode active material in nickel metal hydride batteries. The V-containing alloys all show multi-phase structures. The major phase shifts from a Zr₇Ni₁₀ structure to a Zr₉Ni₁₁ structure and finally to a C14 structure as the vanadium content increases. Other minor phases with C15 and ZrNi crystal structures are also present. The solubility of vanadium is high in AB2 phases (both C14 and C15), moderate for the ZrNi phase and very low for Zr₇Ni₁₀ and Zr₉Ni₁₁ phases. The bulk hydrogen transport property of the alloys is dominated by synergetic effects between major and minor phases. Electrochemical testing shows that the highest discharge capacity, 357 mAh/g, was obtained from an alloy with a chemical composition of Ti_1.5Zr_5.5V_2.5Ni_7.5 and mainly C14 structure. Testing also shows the high rate dischargeability is controlled by the surface reaction and Ti_1.5Zr_5.5V_0.5Ni_9.5 has the best high rate dischargeability.     

Effect of processing parameter on hydrogen storage characteristics of as quenched Ti45Zr38Ni17 quasicrystalline alloys

The present study deals with the microstructural changes with respect to the processing parameter (quenching rate) and their correlation with hydrogen storage characteristics of Ti₄₅Zr₃₈Ni₁₇ quasicrystalline alloys. The ribbons of the alloy have been synthesized at different quenching rates obtained through different wheel speeds (35, 40, 45 and 50 m/s) and investigated for their hydrogen storage characteristics. The lower cooling rate obtained through low wheel speed (35 m/s) produces, i-phase grains whose size ranges from 300-350 nm, whereas higher cooling rates obtained through high wheel speed (45 and 50 m/s) promote the formation of grains with size ranges from 100-150 nm in Ti₄₅Zr₃₈Ni₁₇ ribbons. It has been found that the ribbons synthesized at 35 m/s absorbed ∼2.0 wt%, whereas ribbons synthesized at 50 m/s absorbed ∼2.84 wt. % of hydrogen. Thus the hydrogen storage capacity of ribbon increases for the ribbons produced at higher quenching rate. One of the salient features of the present study is that the improvement of hydrogen storage capacity obtained through higher quenching rates (∼45 to 50 m/s wheel speed) leading to the formation of lower grain size.     

Microstructure and electrochemical investigations of La0.76−xCexMg0.24Ni3.15Co0.245Al0.105 (x = 0, 0.05, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys

The effects of substitution of Ce for La on the microstructure and electrochemical performance of La_0.76−xCe_xMg_0.24Ni_3.15Co_0.245Al_0.105 (x = 0, 0.05, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) analyses showed that the main phases of the alloys consist of (La, Mg)Ni₃ phase (PuNi₃-type rhombohedral structure), LaNi₅ phase (CaCu₅-type hexagonal structure) and (La, Mg)₂Ni₇ phase (Ce₂Ni₇-type hexagonal structure). The cell volume of the (La, Mg)Ni₃ phase, (La, Mg)₂Ni₇ phase and LaNi₅ phase decreased monotonously with increasing Ce content. Electrochemical investigations showed a decrease in the discharge capacity, while high rate dischargeability (HRD) first increased and then decreased with increasing Ce content. The Ce substitution for La slightly enhanced the cyclic stability of the alloy electrodes. The pressure–composition (P–C) isotherms showed that the plateau region was broadened with Ce content increased in the alloys, meanwhile, two plateaus appeared and pressure of the hydrogen absorption and desorption increased accordingly.     

Microstructural characterization and hydrogenation properties of non-stoichiometric Zr0.9TixV2 alloys

The non-stoichiometric Zr_0.9Ti_xV₂ (x = 0, 0.2, 0.3, 0.4) alloys are designed to explore the effect of non-stoichiometry on phase constituent, microstructure and hydrogenation properties of Zr-based AB₂ Laves alloys. The alloys are prepared by non-consumable arc melting and annealed at 1273 K for 168 h in argon atmosphere to ensure the homogeneity. Phase structure investigation shows the α-Zr/β-Zr phase and V-BCC phase originating from the non-equilibrium solidification can be reduced after annealing, C15-type ZrV₂ becomes the dominant phase. Meanwhile, a small amount of Zr₃V₃O phase generates when x ≤ 0.2 and the β-Zr transforms to α-Zr when x > 0.2. High density annealing twins are observed in ZrV₂ matrix by TEM. Activation behavior, hydrogenation kinetics and PCT characteristics of annealed Zr_0.9Ti_xV₂ are investigated in the temperature range 673–823 K. With the decrease in B/A ratio or increase in Ti content, the initial hydrogen absorption speed decreases obviously, the plateaus of PCT curves become wide and flat, meanwhile the hydrogen absorption capacity and the stability of metal hydrides increases. Twin defects observed in these alloys play an important role in accelerating the hydrogenation kinetics. In addition, phase constituent after hydrogenation is analyzed.     

Improved electrochemical hydrogen storage properties of Ti49Zr26Ni25 quasicrystal alloy by doping with Pd and MWCNTs

Ti₄₉Zr₂₆Ni₂₅ quasicrystal was fabricated via mechanical alloying and subsequent annealing. The mixtures containing different amounts of Pd and MWCNTs were doped into the Ti₄₉Zr₂₆Ni₂₅ alloy by ball-milling method. The icosahedral quasicrystal and Ti₂Ni-type phases were the main phase compositions for the composite alloys. The composite alloy combined the large specific surface area and high conductivity of MWCNTs in conjunction with the excellent electrocatalysis ability of Pd, thus improving the discharge capacity and cycle stability of the matrix alloy. The Ti₄₉Zr₂₆Ni₂₅ + MWCNTs + Pd electrode possessed a maximum discharge capacity of 281.6 mAh/g, outstandingly higher than those for Ti₄₉Zr₂₆Ni₂₅ (206.1 mAh/g), Ti₄₉Zr₂₆Ni₂₅ + MWCNTs (248.4 mAh/g) and Ti₄₉Zr₂₆Ni₂₅ + Pd (259.3 mAh/g). The cycle stability and high-rate dischargeability were also enhanced. Furthermore, the studies on electrochemical reaction kinetics demonstrated that doping of Pd and MWCNTs accelerated the charge-transfer process, the two active materials played synergistic effect in enhancing the electrochemical activity and reaction kinetics for the Ti₄₉Zr₂₆Ni₂₅ electrode.     

Deuterium storage of Ti40Zr40Ni20 icosahedral quasicrystal

Ti₄₀Zr₄₀Ni₂₀ icosashedral quasicrystal was observed to load hydrogen in a much lower capacity than similar Ti–Zr–Ni alloys. To verify the result, the alloy is further studied by using deuterium instead of hydrogen in this work. With a home-made gas–solid reaction system, XRD and XPS techniques, the investigation was conducted on deuterium absorption and desorption properties of Ti₄₀Zr₄₀Ni₂₀ alloy and its phase stability during the deuteration course. It is shown that the quasicrystal can load deuterium rapidly in an elevated volume of 11.5 mmol·D₂/g·M (D₂ denotes deuterium molecular and M the metal). After the full storage of deuterium, the quasicrystal phase remained, however the quasilattice expanded at a rate of 6.28%, revealing the occurrence of severe quasilattice stress. The solution of deuterium in the alloy caused the increase of binding energy of the metal elements, as much as 0.4 eV for Ti, 0.6 eV for Zr and 0.1 eV for Ni, which reflects the location of deuterium near Ti and Zr. The deuterium release was very slow at low temperature and could be complete at least above 610 °C. Based on the gained results, the quasilattice shrink would be more reasonable to explain the big difficulty of the desorption.     

Improved hydrogen storage behaviours of nanocrystalline and amorphous Mg2Ni-type alloy by Mn substitution for Ni

The nanocrystalline and amorphous Mg₂Ni-type alloys with nominal compositions of Mg₂Ni_1−xMn_x (x = 0, 0.1, 0.2, 0.3, 0.4) were synthesized by melt spinning technique. The structures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The hydrogen absorption and desorption kinetics of the alloys were measured by an automatically controlled Sieverts apparatus. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that the as-spun (x = 0) alloy holds a typical nanocrystalline structure, whereas the as-spun (x = 0.4) alloy displays a nanocrystalline and amorphous structure, confirming that the substitution of Mn for Ni facilitates the glass formation in the Mg₂Ni-type alloy. The hydrogen absorption capacity of the alloys first increases then decreases with rising Mn content, but the hydrogen desorption capacity of the alloys grows with increasing Mn content. Furthermore, the substitution of Mn for Ni significantly improves the electrochemical hydrogen storage performances of the alloys, involving both the discharge capacity and the electrochemical cycle stability. With an increase in the amount of Mn from 0 to 0.4, the discharge capacity of as-spun (30 m/s) alloy grows from 116.7 to 311.5 mAh/g, and its capacity retaining rate at 20th charging and discharging cycle rises from 36.7 to 78.7%.     

Fabrication and electrochemical hydrogen storage performance of Ti49Zr26Ni25 alloy covered with Cd/Pd core/shell particles

A facile two-step reduction method is employed to obtain the Cd/Pd core/shell particles. Mechanical alloying and subsequent annealing are used to fabricate the Ti₄₉Zr₂₆Ni₂₅ quasicrystal. Composite materials of Ti₄₉Zr₂₆Ni₂₅ mixed with different contents of Cd/Pd particles are obtained via ball-milling. The electrochemical performance and kinetics properties of the alloy electrodes for Ni/MH secondary batteries are studied. Ultimately, a maximum discharge capacity of 272.9 mA h/g is achieved for 7% additive content of Cd/Pd. Ti₄₉Zr₂₆Ni₂₅ + Cd/Pd shows higher capacity than Ti₄₉Zr₂₆Ni₂₅ + Pd (246.8 mA h/g) and original Ti₄₉Zr₂₆Ni₂₅ (212.5 mA h/g). Moreover, the composites also exhibit improved cyclic stability and high-rate dischargeability. The Cd/Pd particles with special core/shell microstructure can enhance the electro-catalytic activity of Pd. The Cd/Pd material covered on the surface of alloy can further decrease the charge-transfer resistance and accelerate the hydrogen transmission, thus improving the electrochemical properties and reaction kinetics of the electrode.     

Effects of Zr addition on electrochemical characteristics of MgTiMnNi hydrogen storage alloys

The electrochemical hydrogen storage properties of 25 h milled Mg_0.80Ti_0.175Mn_0.025Zr_xNi_1-x (x = 0, 0.025, 0.05, 0.1) quinary alloys were investigated. The substitution of Zr for Mg or Ni leads to an increase in structural disorder and amorphization. Thus, the maximum discharge capacity and the cycling stability of MgNi-based alloys can be enhanced. The x-ray diffraction patterns indicate that all additive elements are entirely dissolved in the synthesized alloys, and amorphous structure was successfully obtained by 25 h milling. Among the milled alloys, the Mg_0.80Ti_0.175Mn_0.025Zr_0.10Ni_0.90 alloy exhibited the best discharge capacity of 604 mA h g⁻¹ at the initial charge/discharge cycle. The obtained results demonstrate that using multi-component compositions is beneficial for enhancing the structural and cyclic stability of MgNi-based alloys. Therefore, substituting additive elements for Mg or Ni may offer impressive performance for efficient hydrogen storage applications.     

Structure and electrochemical properties of (La1−xDyx)0.8Mg0.2Ni3.4Al0.1 (x = 0.0–0.20) hydrogen storage alloys

The structure and electrochemical characteristics of (La_1−xDy_x)_0.8Mg_0.2Ni_3.4Al_0.1 (x = 0–0.20) hydrogen storage alloys have been investigated. Dysprosium was adopted as a partial substitution element for lanthanum in order to improve electrochemical properties. The XRD, SEM and EDX results showed that the alloys were composed of (La, Mg)₂Ni₇, LaNi₅ and (La, Mg)Ni₂ phases. The introduction of Dy promoted the formation of (La, Mg)₂Ni₇ phase which possesses high hydrogen storage capacity, and controlling dysprosium content at 0.05 can obtain the maximum (La, Mg)₂Ni₇ phase abundance in the alloys. The maximum discharge capacity was heightened from 382.5 to 390.2 mAh/g, which was ascribed to (La, Mg)₂Ni₇ phase abundance increasing from 54.8% to a maximum (60.5%). Also, the biggest discharge capacity retention remained 82.7% after 100 cycles at discharge current density of 300 mA/g.     

Preparation and electrochemical hydrogen storage properties of Ti49Zr26Ni25 alloy covered with porous polyaniline

A facile saturated solution synthesis method is used to obtain the porous polyaniline (P-PANI). The materials exhibit unique sea urchin-like morphology and special porous structure. Ti₄₉Zr₂₆Ni₂₅ quasicrystal is fabricated via mechanical alloying followed by annealing treatment. Different amounts of P-PANI are coated on the surface of hydrogen storage alloy by ball milling. For comparison, Ti₄₉Zr₂₆Ni₂₅ alloy doped with conventional PANI (C-PANI) is also prepared. The electrochemical characterizations of the composites are conducted in the standard tri-electrode system. Ultimately, the P-PANI coated Ti₄₉Zr₂₆Ni₂₅ electrode shows preferable performance compared with the C-PANI modified alloy (230.6 mAh/g) and original alloy (209.3 mAh/g). As the additive content of P-PANI is 6 wt%, a maximum discharge capacity of 258.7 mAh/g is obtained. Furthermore, the cycle stability and high-rate dischargeability of the electrodes are also enhanced. The P-PANI materials with distinctive morphology and unique porous structure can not only improve the electrocatalytic activity of polyaniline but also increase the specific surface area of Ti₄₉Zr₂₆Ni₂₅ alloy. The P-PANI can further facilitate the hydrogen diffusion, expedite the charge transfer in/on the alloy and improve the corrosion resistance, thus enhancing the electrochemical performance and reaction kinetics of the hydrogen storage alloys.     

Crystallographic and electrochemical characteristics of Ti–Zr–Ni–Pd quasicrystalline alloys

Ti₄₅Zr₃₅Ni_20−xPd_x (x = 0, 1, 3, 5 and 7, at%) alloys were prepared by melt-spinning. The phase structure and electrochemical hydrogen storage performances of melt-spun alloys were investigated. The melt-spun alloys were icosahedral quasicrystalline phase, and the quasi-lattice constant increased with increasing x value. The maximum discharge capacity of alloy electrodes increased from 79 mAh/g (x = 0) to 148 mAh/g (x = 7). High-rate dischargeability and cycling stability were also enhanced with the increase of Pd content. The improvement in the electrochemical hydrogen storage characteristics may be ascribed to better electrochemical activity and oxidation resistance of Pd than that of Ni.     

Hydrogenation and electrochemical studies of La–Mg–Ni alloys

La–Mg–Ni alloys are potential candidates for hydrogen storage materials. In this study, mechanical alloying with subsequent annealing under an argon atmosphere at 973 K for 0.5 h, were used to produce La_2-xMg_xNi₇ alloys (x = 0, 0.25, 0.5, 0.75, 1). Shaker type ball mill was used. An objective of the present study was to investigate an influence of amount of Mg in alloy on electrochemical, hydrogenation and dehydrogenation properties of La–Mg–Ni materials. X-ray diffraction analyses revealed formation of material with multi-phase structure. Obtained materials were studied by a conventional Sievert's type device at 303 K. It was observed that electrochemical discharge capacity and gaseous hydrogen storage capacity of La–Mg–Ni alloys increases with Mg content to reach maximum for La_1.5Mg_0.5Ni₇ alloy. Moreover, all of La–Mg–Ni alloys were characterized by improved hydrogen sorption kinetics in comparison to La–Ni alloy.     

Hydrogen absorption characteristics of mechanically alloyed Ti–Zr–Ni and Ti–V–Ni powders

A first investigation into the production of amorphous and nanostructured Ti-based alloys with nominal compositions Ti_41.5Zr_41.5Ni₁₇, Ti₆₁Zr₂₂Ni₁₇, Ti_41.5V_41.5Ni₁₇ and Ti₆₁V₂₂Ni₁₇ by mechanical alloying (MA) technique is presented. This technique was adopted to produce alloys' powders with high fresh surface area that were active for hydrogen storage. Hydrogen absorption characteristics and structure changes in the alloys after hydrogenation were investigated. Gas phase hydrogenation of the Ti–Zr–Ni alloys, at 573 K and an initial hydrogen pressure of 2 MPa, exhibited good hydriding properties and started at a maximal rate without induction period with a hydrogenation capacity up to 1.2 wt%. However, hydriding of Ti–V–Ni alloys at the same conditions exhibited slower rates. The Ti₆₁V₂₂Ni₁₇ composition showed high hydrogen absorption capacity of 1.8 wt% and exceeded 4 wt% at 345 K. In addition, the Ti–V–Ni alloys showed structure stability after hydrogenation and retained the amorphous structure.