Electrical conductivity of Ce0.8Gd0.2−xDyxO2−δ (0 ≤ x ≤ 0.2) co-doped with Gd and Dy for intermediate-temperature solid oxide fuel cells

High-quality nano-sized Ce_0.8Gd_0.2−xDy_xO_2−δ (0 ≤ x ≤ 0.2) powders are synthesized by a solution combustion process. The calcined powders are composed of a ceria-based single phase with a cubic fluorite structure and are nanocrystalline nature, i.e., 15-24 nm in crystallite size. The addition of an intermediate amount of Dy³⁺ (0.03 ≤ x ≤ 0.16) for Gd³⁺ in Ce_0.8Gd_0.2O_2−δ decreases the electrical conductivity. On the other hand, the doping of a small amount of Dy³⁺ (0.01 ≤ x ≤ 0.02) and of a large amount of Dy³⁺ (0.17 ≤ x ≤ 0.19) leads to an increase in conductivity. The Ce_0.8Gd_0.03Dy_0.17O_2−δ shows the highest electrical conductivity (0.215 S cm⁻¹) at 800 °C.     

Novel Nd2WO6-type Sm2−xAxM1−yByO6−δ (A = Ca, Sr; M = Mo, W; B = Ce, Ni) mixed conductors

In the present work, we have explored novel Nd₂WO₆-type structure Sm_2−xA_xM_1−yB_yO_6−δ (A = Ca, Sr; M = Mo, W; B = Ce, Ni) as precursor for the development of solid oxide fuel cells (SOFCs) anodes. The formation of single-phase monoclinic structure was confirmed by powder X-ray diffraction (PXRD) for the A- and B-doped Sm₂MO₆ (SMO). Samples after AC measurements under wet H₂ up to 850 °C changed from Nd₂WO₆-type structure into Sm₂MoO₅ due to the reduction of Mo^VI that was confirmed by PXRD and is consistent with literature. The electrical conductivity was determined using 2-probe AC impedance and DC method and was compared with 4-probe DC method. The total electrical conductivity obtained from these two different techniques was found to vary within the experimental error over the investigated temperature of 350-650 °C. Ionic and electronic conductivity were studied using electron-blocking electrodes technique. Among the samples studied, Sm_1.8Ca_0.2MoO_6−δ exhibits total conductivity of 0.12 S cm⁻¹ at 550 °C in wet H₂ with an activation energy of 0.06 eV. Ca-doped SMO appears to be chemically stable against reaction with YSZ electrolyte at 800 °C for 24 h in wet H₂. The ionic transference number (t_i) of Sm_1.9Ca_0.1MoO_6−δ in wet H₂ at 550 °C (pO₂ = 10^−25.5 atm) was found to be about 0.012 after subtraction of electrical lead resistance from the 2-probe AC data and showed predominate electronic conductors.     

Characterization of perovskite-type cathode,La0.75Sr0.25 Mn0.95−xCox Ni0.05O3+δ (0.1 ≤ x ≤ 0.3), for intermediate-temperature solid oxide fuel cells

Phase evolution, structure, thermal property, morphology, electrical property and reactivity of a perovskite-type cathode system, La_0.75Sr_0.25 Mn_0.95−xCo_xNi_0.05O_3+δ (0.1 ≤ x ≤ 0.3), are reported. The samples are synthesized using metal acetates by the Pechini method. A perovskite-type phase is formed after calcination at ∼700 °C and a rhombohedral symmetry of R – 3c space group is stabilized at ∼1100 °C. An increase in x decreases the unit cell volume linearly, accompanying with a linear decrease in bond lengths and tilt angle. The differential thermal analysis suggests the phase stabilization for a temperature range, 50–1100 °C. The thermo-gravimetric, thermal expansion, and electrical and ionic conductivities studies suggest presence of a Jahn–Teller transition at ∼260–290 °C. The samples with x = 0.1 mol exhibit electrical conductivity of ∼55 S cm⁻¹ at ∼600 °C, activation energy of ∼0.13 eV, coefficient of thermal expansion of ∼12 × 10⁶ °C⁻¹, crystallite size of ∼45 nm, Brunauer–Emmett–Teller (BET) surface area of 1.26 m² g⁻¹ and average particle size of ∼0.9 μm. A fairly high ionic conductivity, 5–9 × 10⁻² S cm⁻¹ makes the sample with x = 0.1 mole suitable for intermediate-temperature solid oxide fuel cell cathode applications. The experimental results are discussed with the help of the defect models proposed for La_1−xSr_xMnO_3+δ.     

Nanospheres and nanorods structured Fe2O3 and Fe2−xGaxO3 photocatalysts for visible-light mediated (λ ≥ 420 nm) H2S decomposition and H2 generation

This article reports our investigation on H₂ generation from visible light (λ ≥ 420 nm) photodecomposition of H₂S by nanomaterial catalysts, α-Fe₂O₃ and its chemically modified Fe_2−xGa_xO₃ (Ga substitution at x = 0.6, FeGaO₃-I and x = 1.0, FeGaO₃-II). Simple template-free hydrothermal technique was employed to synthesize the three photocatalysts. XRD study reveals rhombohedral nanocrystalline structure and FESEM shows nanospheres morphology for Fe₂O₃ and nanosticks/nanorods for both FeGaO₃-I, and FeGaO₃-II. In H₂ generation, Fe₂O₃ and FeGaO₃-II perform moderate and almost same activities in the fresh and used conditions (quantum yield, QY = 6.0–6.8% at 550 nm). Contrarily, fresh FeGaO₃-I exhibits a greater activity (11.2% QY) and the activity is further enhanced (QY = 15.3%) on regeneration and reuse. The intricacy, as resolved by XRD and FESEM, appears to take place through morphology transformation. The present work, thus, successfully demonstrates H₂ generation from H₂S by nanostructured photocatalysts involving morphology dependent activity enhancement.     

Evaluation of A-site cation-deficient (Ba0.5Sr0.5)1−xCo0.8Fe0.2O3−δ (x > 0) perovskite as a solid-oxide fuel cell cathode

A-site cation-deficient (Ba_0.5Sr_0.5)_1−xCo_0.8Fe_0.2O_3−δ ((BS)_1−xCF) oxides were synthesized and evaluated as cathode materials for intermediate-temperature solid-oxide fuel cells (ITSOFCs). The material's thermal expansion coefficient, electrical conductivity, oxygen desorption property, and electrocatalytic activity were measured. A decrease in both the electronic conductivity and the thermal expansion coefficient was observed for increasing values of the stoichiometric coefficient, x. This effect was attributed to the creation of additional oxygen vacancies, the suppression of variation in the oxidation states of cobalt and iron, and the suppression of the spin-state transitions of cobalt ions. The increase in A-site cation deficiency resulted in a steady increase in cathode polarization resistance, because impurities formed at the cathode/electrolyte interface, reducing the electronic conductivity. A single SOFC equipped with a BS_0.97CF cathode exhibited peak power densities of 694 and 893 mW cm⁻² at 600 and 650 °C, respectively, and these results were comparable with those obtained with a Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ cathode. Slightly A-site cation-deficient (BS)_1−xCF oxides were still highly promising cathodes for reduced temperature SOFCs.     

Ln0.6Sr0.4Co1−yFeyO3−δ (Ln = La and Nd; y = 0 and 0.5) cathodes with thin yttria-stabilized zirconia electrolytes for intermediate temperature solid oxide fuel cells

The electrochemical performances of the solid oxide fuel cells (SOFC) fabricated with Ln_0.6Sr_0.4Co_1−yFe_yO_3−δ (Ln = La, Nd; y = 0, 0.5) perovskite cathodes, thin yttria-stabilized zirconia (YSZ) electrolytes, and YSZ–Ni anodes by tape casting, co-firing, and screen printing are evaluated at 600–800 °C. Peak power densities of ∼550 mW cm⁻² are achieved at 800 °C with a La_0.6Sr_0.4CoO_3−δ (LSC) cathode that is known to have high electrical conductivity. Substitution of La by Nd (Nd_0.6Sr_0.4CoO_3−δ) to reduce the thermal expansion coefficient (TEC) results in only a slight decrease in power density despite a lower electrical conductivity. Conversely, substitution of Fe for Co (La_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ or Nd_0.6Sr_0.4Co_0.5Fe_0.5O_3−δ) to reduce the TEC further reduces the cell performance greatly due to a significant decrease in electrical conductivity. However, infiltration of the Fe-substituted cathodes with Ag to increase the electrical conductivity increases the cell performance while preserving the low TEC.     

Microstructure and hydrogen storage characteristics of nanocrystalline Mg + x wt% LaMg2Ni (x = 0–30) composites

The nanocrystalline Mg + x wt% LaMg₂Ni (x = 0, 5, 10, 20, 30) composites were prepared by reactive ball-milling, their microstructure and hydrogen storage characteristics were investigated. The results show that the addition of LaMg₂Ni improves the hydriding rate and capacity. The hydriding capacity of the Mg + x wt% LaMg₂Ni (x = 5, 10, 20, 30) composites are all above 4.1 wt% at 120 °C and above 4.3 wt% at 180 °C within 6000 s. Moreover, the addition of LaMg₂Ni also improves the dehydriding performance of the composites. The main reason for the improvement of hydriding/dehydriding properties investigated by XRD and SEM shows that the synergistic effect among the multiphase nanocrystalline Mg-based structures make hydrogen easily absorbed/desorbed on the interface of the matrix.     

Preparation and characterization of La0.9Sr0.1Ga0.8Mg0.2O3 − δ thin film on the porous cathode for SOFC

A dense and crack-free La_0.9Sr_0.1Ga_0.8Mg_0.2O_3 − δ thin film has been prepared by RF magnetron sputtering. The XRD, FESEM, XPS and four-probe technique are employed to characterize the La_0.9Sr_0.1Ga_0.8Mg_0.2O_3 − δ film. Results show that after annealing at 1000 °C, the La_0.9Sr_0.1Ga_0.8Mg_0.2O_3 − δ film presents a polycrystalline perovskite structure with grain size of 100–300 nm. XPS data show that both La and Ga are in their +3 state. Sr element has two chemical states which are related to Sr²⁺ in the perovskite lattice and SrO_1 − δ suboxide. The O 1s spectrum also shows two chemical states which can be assigned to molecularly adsorbed O₂ species and O²⁻ in the lattice. The electrical conductivity reaches to 0.093 S cm⁻¹ at 800 °C. The microstructure and conductivity analysis indicates that the La_0.9Sr_0.1Ga_0.8Mg_0.2O_3 − δ thin film prepared by RF magnetron sputtering is suitable for intermediate temperature Solid oxide fuel cell.     

Properties and performance of Ba0.5Sr0.5Co0.8Fe0.2O3−δ + Sm0.2Ce0.8O1.9 composite cathode

The properties and performance of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) + Sm_0.2Ce_0.8O_1.9 (SDC) (70:30 in weight ratio) composite cathode for intermediate-temperature solid-oxide fuel cells were investigated. Mechanical mixing of BSCF with SDC resulted in the adhesion of fine SDC particles to the surface of coarse BSCF grains. XRD, SEM-EDX and O₂-TPD results demonstrated that the phase reaction between BSCF and SDC was negligible, constricted only at the BSCF and SDC interface, and throughout the entire cathode with the formation of new (Ba,Sr,Sm,Ce)(Co,Fe)O_3−δ perovskite phase at a firing temperature of 900, 1000, and ≥ 1050 °C, respectively. The BSCF + SDC electrode sintered at 1000 °C showed an area specific resistance of ∼0.064 Ω cm² at 600 °C, which is a slight improvement over the BSCF (0.099 Ω cm²) owing to the enlarged cathode surface area contributed from the fine SDC particles. A peak power density of 1050 and ∼382 mW cm⁻² was reached at 600 and 500 °C, respectively, for a thin-film electrolyte cell with the BSCF + SDC cathode fired from 1000 °C.     

Desirable performance of intermediate-temperature solid oxide fuel cell with an anode-supported La0.9Sr0.1Ga0.8Mg0.2O3 − δ electrolyte membrane

An anode-supported La_0.9Sr_0.1Ga_0.8Mg_0.2O_3 − δ (LSGM) electrolyte membrane is successfully fabricated by simple, cost-effective spin coating process. Nano-sized NiO and Ce_0.8Gd_0.2O_3 − α (GDC) powders derived from precipitation and citric-nitrate process, respectively, are used for anode support. The dense and uniform LSGM membrane of ca. 50 μm in thickness is obtained by sintering at relatively low temperature 1300 °C for 5 h. A single cell based on the as-prepared LSGM electrolyte membrane exhibits desirable high cell performance and generates high output power densities of 760 mW cm⁻² at 700 °C and 257 mW cm⁻² at 600 °C, respectively, when operated with humidified hydrogen as the fuel and air as the oxidant. The single cell is characterized by field-emission scanning electron microscope (FESEM), X-ray diffraction (XRD) and electrochemical AC impedance. The results demonstrate that it is feasible to fabricate dense LSGM membrane for solid oxide fuel cell by this simple, cost-effective and efficient process. In addition, optimized anode microstructure significantly reduces polarization resistance (0.025 Ω cm² at 700 °C).     

The structure and 233 K electrochemical properties of La0.8−xNdxMg0.2Ni3.1Co0.25Al0.15 (x = 0.0–0.4) hydrogen storage alloys

The effect of neodymium content on the structure and low-temperature (233 K) electrochemical properties of the La_0.8−xNd_xMg_0.2Ni_3.1Co_0.25Al_0.15 (x = 0.0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys was investigated systematically. The result of the Rietveld analyses suggested that all these alloys mainly consist of two phases: the (La, Mg)₂Ni₇ phase and the LaNi₅ phase. The electrochemical studies revealed that, at temperature 233 K, the maximum discharge capacity first increased from 188.5 mAh/g (x = 0.0) to 201.7 mAh/g (x = 0.1) and then decreased to 153.9 mAh/g (x = 0.4). The low-temperature dischargeability (LTD) first increased and then decreased with increasing x, also reaching an extreme when x was 0.10. The LTD was in agreement with the I₀, but was irrespective of the diffusion of hydrogen. From our work, the optimum composition of the La_0.8−xNd_xMg_0.2Ni_3.1Co_0.25Al_0.15 (x = 0.0–0.4) alloy electrodes was found to be x = 0.10.     

Performance of SrSc0.2Co0.8O3−δ + Sm0.5Sr0.5CoO3−δ mixed-conducting composite electrodes for oxygen reduction at intermediate temperatures

In order to improve the electrical conductivity of the SrSc_0.2Co_0.8O_3−δ (SrScCo) electrode, a composite of 70 wt% SrSc_0.2Co_0.8O_3−δ and 30 wt% Sm_0.5Sr_0.5CoO_3−δ (SrScCo + SmSrCo) was prepared and investigated for electrochemical oxygen reduction at intermediate temperatures. The phase reaction between SrScCo and SmSrCo and its effect on the electrical conductivity, oxygen vacancy concentration and oxygen mobility were examined by XRD, 4-probe DC conductivity measurement, iodometry titration and O₂-TPD experiment, respectively. The results showed that the composite reached a maximum conductivity around 123 S cm⁻¹ at 600 °C, nearly five times that of SrScCo. AC impedance results showed that the electron charge-transfer process was greatly improved by forming the composite electrode, while the oxygen-ion charge-transfer process was somewhat deteriorated. By firing at 1000 °C for 2 h, a SOFC with the SrScCo + SmSrCo cathode and thin-film SDC electrolyte delivered peak power densities of 1100 and 366 mW cm⁻² at 600 and 500 °C, respectively, which were only modestly lower than those of a similar cell with a pure SrScCo cathode.     

Structures and electrochemical hydrogen storage behaviours of La0.75−xPrxMg0.25Ni3.2Co0.2Al0.1 (x = 0–0.4) alloys prepared by melt spinning

In order to improve the electrochemical performance of the La–Mg–Ni system A₂B₇-type electrode alloys, La in the alloy was partially substituted by Pr and melt spinning technology was used for preparing La_0.75−xPr_xMg_0.25Ni_3.2Co_0.2Al_0.1 (x = 0, 0.1, 0.2, 0.3, 0.4) electrode alloys. The microstructures and electrochemical performance of the as-cast and spun alloys were investigated in detail. The results obtained by XRD, SEM and TEM show that the as-cast and spun alloys have a multiphase structure which consists of two main phases (La, Mg)Ni₃ and LaNi₅ as well as a residual phase LaNi₂. The substitution of Pr for La leads to an obvious increase of the (La, Mg)Ni₃ phase and a decrease of the LaNi₅ phase in the alloys. The results of the electrochemical measurement indicate that the discharge capacity of the alloys first increases and then decreases with variation of the Pr content. The cycle stability of the alloy monotonically rises with increasing Pr content. When the Pr content rises from 0 to 0.4, the discharge capacity increases from 389.4 (x = 0) to 392.4 (x = 0.1) and then drops to 383.7 mAh/g (x = 0.4) for the as-cast alloy. Discharge capacity increases from 393.5 (x = 0) to 397.9 (x = 0.1), and then declines to 382.5 mAh/g for the as-spun (5 m/s) alloys. The capacity remaining after 100 cycles increases from 65.32 to 79.36% for the as-cast alloy, and from 73.97 to 93.08% for the as-spun (20 m/s) alloy.     

The structure and high-temperature (333 K) electrochemical performance of La0.8−xCexMg0.2Ni3.5 (x = 0.00–0.20) hydrogen storage alloys

The microstructures and electrochemical properties of La_0.8−xCe_xMg_0.2Ni_3.5 (x = 0.00–0.20) hydrogen storage alloys are investigated systematically. XRD and Rietveld analyses indicate that all these alloys mainly consist of two phases: (La, Mg)₂Ni₇ phase with the hexagonal Ce₂Ni₇-type structure and LaNi₅ phase with the hexagonal CaCu₅-type structure. The lattice parameters of the component phases gradually decreased with increasing Ce content. It is concluded that, compared to that of room temperature (298 K), the deterioration in capacity is due to the enhanced corrosion of electrode active material and self-discharge at 333 K. The electrode corrosion was alleviated effectively with the increasing x, whereas the high-temperature dischargeability decreases from 92.7% (x = 0.00) to 80.5% (x = 0.20) accordingly. As the discharge current density is 1000 mA g⁻¹, the high-rate dischargeability (HRD) increases from 77.2% (x = 0.00) to 89.7% (x = 0.10) and then decreases to 73.5% (x = 0.20).     

Hydrogen-storage property characterization of Mg–15 wt%Ni–5 wt%Fe2O3 prepared by reactive mechanical grinding

Mg–15 wt%Ni–5 wt%Fe₂O₃ (Mg155) was prepared by reactive mechanical grinding (RMG). Mg155 exhibited high hydriding and dehydriding rates even at the first cycle, and its activation was completed after only two hydriding–dehydriding cycles. The activated Mg155 absorbed 5.06 and 5.38 wt% of hydrogen, respectively, for 5 and 60 min at 573 K under 12 bar H₂. It desorbed 1.50 and 5.28 wt% of hydrogen, respectively, for 5 and 60 min at 573 K under 1.0 bar H₂. The initial hydrogen absorption rate decreased, but the hydrogen desorption rate increased rapidly with an increase in temperature from 563 K to 603 K. The rate-controlling step for the dehydriding reaction in a range from F ? 0.20 to F ? 0.75 is considered to be the chemical reaction at the Mg hydride/α-solid solution interface. The absorption and desorption PCT curves exhibited two plateaus at 573 K. The hydrogen-storage capacity of the activated Mg155 was about 6.43 wt% at 573 K.     

Microstructure and hydrogen storage properties of Ti10V84−xFe6Zrx (x = 1–8) alloys

Ti₁₀V_84−xFe₆Zr_x (x = 1, 2, 4, 6, 8) hydrogen storage alloys were prepared by induction melting with magnetic levitation, and the effects of Zr content on the microstructures and hydrogen storage properties have been investigated systematically. The results show that the alloy with x = 1 has a single V-based solid solution phase with BCC structure, while other alloys with x = 2–8 consist of a BCC main phase and a C14 type Laves secondary phase, and the abundance ratio of the secondary phase increases with increasing Zr content. As the Zr content in the alloy increases, the activation behavior is improved, but the hydrogen absorption and desorption capacities decrease gradually. For the alloy with the Zr content of x = 1, the best overall hydrogen storage properties are obtained.     

Effects of addition of manganese and LmNi4.1Al0.25Mn0.3Co0.65 alloy on electrochemical characteristics of Ti0.32Cr0.43−xMnxV0.25 (x = 0–0.08) alloys as anode materials for nickel–metal-hydride batteries

This study examines the effects of the addition of Mn and LmNi_4.1Al_0.25Mn_0.3Co_0.65 (Lm: lanthanum-rich mischmetal) alloy on the electrochemical characteristics of body centered cubic (BCC) type Ti_0.32Cr_0.43−xMn_xV_0.25 (x = 0–0.08) alloys as negative electrode (anode) materials for nickel–metal-hydride (Ni-MH) batteries. The activation behaviour and discharge capacity of the BCC alloys are improved significantly by ball-milling with LmNi_4.1Al_0.25Mn_0.3Co_0.65 alloy because this AB₅ alloy acts as a path for hydrogen on the surface of the BCC alloy. Among the Mn-substituted alloys, a Ti_0.32Cr_0.38Mn_0.05V_0.25 alloy ball-milled with the AB₅ alloy yields the greatest discharge capacity of 340 mAh g⁻¹. In addition, compared with the alloy without Mn, the Mn-substituted alloys exhibit a lower plateau pressure for hydrogen, a better hydrogen-storage capacity in the pressure–composition isotherms and faster surface activation.     

A high rate,high capacity and long life (LiMn2O4 + AC)/Li4Ti5O12 hybrid battery–supercapacitor

A hybrid battery–supercapacitor (LiMn₂O₄ + AC)/Li₄Ti₅O₁₂ using a Li₄Ti₅O₁₂ anode and a LiMn₂O₄/activated carbon (AC) composite cathode was built. The electrochemical performances of the hybrid battery–supercapacitor (LiMn₂O₄ + AC)/Li₄Ti₅O₁₂ were characterized by cyclic voltammograms, electrochemical impedance spectra, rate charge–discharge and cycle performance testing. It is demonstrated that the hybrid battery–supercapacitor has advantages of both the high rate capability from hybrid capacitor AC/Li₄Ti₅O₁₂ and the high capacity from secondary battery LiMn₂O₄/Li₄Ti₅O₁₂. Moreover, the electrochemical measurements also show that the hybrid battery–supercapacitor has good cycle life performance. At 4C rate, the capacity loss in constant current mode is no more than 7.95% after 5000 cycles, and the capacity loss in constant current–constant voltage mode is no more than 4.75% after 2500 cycles.     

Ba1−xCo0.9−yFeyNb0.1O3−δ (x = 0-0.15, y = 0-0.9) as cathode materials for solid oxide fuel cells

Perovskite oxide Ba_1.0Co_0.7Fe_0.2Nb_0.1O_3−δ has been reported as oxygen transport membrane and cathode material for solid oxide fuel cells (SOFCs). In this study, the effects of A-site cation deficiency and B-site iron doping concentration on the crystal structure, thermal expansion coefficient (TEC), electrical conductivity and electrochemical performance of Ba_1−xCo_0.9−yFe_yNb_0.1O_3−δ (x = 0-0.15, y = 0-0.9) have been systematically evaluated. Ba_1−xCo_0.9−yFe_yNb_0.1O_3−δ (x = 0-0.10, y = 0.2 and x = 0.10, y = 0.2-0.6) can be indexed to a cubic structure. Increased electrical conductivity and decreased cathode polarization resistance have been achieved by A-site deficiency. No obvious variation can be observed in TEC by A-site deficiency. The electrical conductivity and TEC of Ba_0.9Co_0.9−yFe_yNb_0.1O_3−δ decrease while the cathode polarization resistance increases with the increase in iron doping concentration. The highest conductivity of 13.9 S cm⁻¹ and the lowest cathode polarization resistance of 0.07 Ω cm² have been achieved at 700 °C for Ba_0.9Co_0.7Fe_0.2Nb_0.1O_3−δ. The composition Ba_0.9Co_0.3Fe_0.6Nb_0.1O_3−δ shows the lowest TEC value of 13.2 × 10⁻⁶ °C⁻¹ at 600 °C and can be a potential cathode material for SOFCs.     

An electrochemical investigation of melt-spun nanocrystalline Mg20Ni10−xCux (x = 0–4) electrode alloys

The nanocrystalline Mg₂Ni-type electrode alloys with nominal compositions of Mg₂₀Ni_10−xCu_x (x = 0, 1, 2, 3, 4) were synthesized by the melt spinning technique. The microstructures of the as-cast and spun alloys were characterized by XRD, SEM and HRTEM. The electrochemical hydrogen storage performances were tested by an automatic galvanostatic system. The results show that all the as-spun alloys hold typical nanocrystalline structure instead of an amorphous phase. The melt spinning does not modify the major phase Mg₂Ni, but it leads to the formation of crystal defects such as stacking faults, dislocations, sub-grain boundary and twin-grain boundary. The melt spinning significantly improves the electrochemical hydrogen storage capacity of the alloys, whereas it slightly impairs the electrochemical cycle stability of the alloys. The substitution of Cu for Ni significantly ameliorates the electrochemical hydrogen storage performances of the alloys, involving both the electrochemical hydrogen storage capacity and the electrochemical charging and discharging stability.