Effect of Co loading on the hydrogen storage characteristics of hollow glass microspheres (HGMs)

The use of hydrogen as a fuel either direct combustion in an IC engine or for power generation in fuel cells continues to be a topic of significant interest. Developing and popularizing fuel cells for vehicular or other stationary applications depends upon the availability of safe and reliable hydrogen storage method. The greatest challenge as of now in this regard is the production of a light weight, nontoxic and easily transportable material which can store hydrogen. World-wide research is being conducted on developing newer materials for hydrogen storage. Hollow glass microspheres (HGMs) can be considered to be a potential hydrogen carrier which can store and deliver hydrogen for energy release applications. In this paper, we are reporting the preparation and characterization of cobalt loaded HGMs from amber glass powder for hydrogen storage applications. The feed glass powder with different percentage of cobalt loading was prepared by soaking and drying the feed glass powder in required amount of cobalt nitrate hexahydrate solution. Further, the dried feed glass powder was flame spheroidised to get cobalt loaded HGMs. Characterizations of all the HGMs samples were done using SEM, FTIR and XRD techniques. Hydrogen adsorptions on all the samples were done for 10 bar pressure at room temperature and 200 °C for 5 h. The results showed that the hydrogen adsorption capacity on these samples increased with increase in cobalt wt% from 0.2 to 2.0%. The hydrogen storage capacity of HACo2 was found to 2.32 wt% for 10 bar pressure at 200 °C.     

Fabrication of zinc‐loaded hollow glass microspheres (HGMs) for hydrogen storage

The greatest challenge for a feasible hydrogen economy lies on the production of pure hydrogen and the materials for its storage with controlled release at ambient conditions. Hydrogen with its great abundance, high energy density and clean exhaust is a promising candidate to meet the current global challenges of fossil fuel depletion and green house gases emissions. Extensive research on hollow glass microspheres (HGMs) for hydrogen storage is being carried out world‐wide, but the right material for hydrogen storage is yet underway. But many other characteristics, such as the poor thermal conductivity etc. of the HGMs, restrict the hydrogen storage capacity. In this work, we have attempted to increase the thermal conductivity of HGMs by ZnO doping. The HGMs with Zn weight percentage from 0 to 10 were prepared by flame spheroidization of amber‐colored glass powder impregnated with the required amount of zinc acetate. The prepared HGMs samples were characterized using field emission‐scanning electron microscope (FE‐SEM), environmental SEM (ESEM), high‐resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy and X‐ray diffraction (XRD) techniques. The deposition of ZnO on the microsphere walls was observed using FE‐SEM, ESEM and HRTEM which was further confirmed using the XRD and ultraviolet–visible absorption data. The hydrogen storage studies done on these samples at 200 °C and 10‐bar pressure for 5 h showed that the hydrogen storage increased when the Zn percentage in the sample increased from 0 to 2%. The percentage of zinc beyond 2, in the microspheres, showed a decline in the hydrogen storage capacity. The closure of the nanopores due to the ZnO nanocrystal deposition on the microsphere surface reduced the hydrogen storage capacity. The hydrogen storage capacity of HAZn2 was found 3.26 wt% for 10‐bar pressure at 200 °C. Copyright © 2015 John Wiley & Sons, Ltd.     

Production and characterization of hollow glass microspheres with high diffusivity for hydrogen storage

A process is developed to produce high diffusivity hollow glass microspheres (HGMs) with high concentration of silica for applications in hydrogen storage by volatilizing alkali and boron oxides in shell-forming process. We investigate the effects of the initial glass compositions of gel particles, the pressure and composition of furnace atmosphere, the temperature and length of refining zone on the diffusivity, quality and yield of the resulting HGMs. The results show that with the preferred total contents of alkali oxides and the ratios of potassium to sodium in the initial glass compositions, the ultimate concentrations of SiO₂ in the resulting HGMs can be up to 95%, with most alkali and boron oxides being volatilized in the refining process. The quality and yield of the high silica HGMs change significantly with the initial glass compositions of the gel particles. The total alkali oxide concentrations ranging from 15% to 20% in the initial glass compositions are preferred to obtain high silica HGMs with high quality and yield. The permeability coefficients of the resulting HGMs can be improved remarkably by increasing the temperature and length of the refining zone. The permeability coefficients of the high silica HGMs to hydrogen gas at ambient temperature are between 3 and 4 × 10⁻²⁰ (mol·m)/(m²·s·Pa).     

Effects of different palladium content loading on the hydrogen storage capacity of double-walled carbon nanotubes

The effects of different amounts palladium loading on the hydrogen sorption characteristics of double-walled carbon nanotubes (DWCNTs) have been investigated. The physical properties of the pristine DWCNTs and Pd/DWCNTs were systematically characterized by X-ray diffraction, transmission electron microscopy, and Brunauer–Emmett–Teller surface area measurements. Pd nanoparticles were loaded on DWCNT surfaces for the dissociation of H₂ into atomic hydrogen, which spills over to the defect sites on the DWCNTs. When we use different Pd content, the particle size and dispersion will be different, which affects the hydrogen storage capacity of the DWCNTs. In this work, the hydrogen storage capacities were measured at ambient temperature and found to be 1.7, 1.85, 3.0, and 2.0 wt% for pristine DWCNTS, 1.0 wt%Pd/DWCNTs, 2.0 wt%Pd/DWCNTs, and 3.0 wt%Pd/DWCNTs, respectively. We found that the hydrogen storage capacity can be enhanced by loading with Pd nanoparticles and selecting a suitable content. Furthermore, the sorption can be attributed to the chemical reaction between the atomic hydrogen and the dangling bonds of the DWCNTs.     

Nanostructured hydrogen storage materials prepared by high-energy reactive ball milling of magnesium and ferrovanadium

Hydrogen storage nanocomposites prepared by high energy reactive ball milling of magnesium and vanadium alloys in hydrogen (HRBM) are characterised by exceptionally fast hydrogenation rates and a significantly decreased hydride decomposition temperature. Replacement of vanadium in these materials with vanadium-rich Ferrovanadium (FeV, V80Fe20) is very cost efficient and is suggested as a durable way towards large scale applications of Mg-based hydrogen storage materials. The current work presents the results of the experimental study of Mg–(FeV) hydrogen storage nanocomposites prepared by HRBM of Mg powder and FeV (0–50 mol.%). The additives of FeV were shown to improve hydrogen sorption performance of Mg including facilitation of the hydrogenation during the HRBM and improvements of the dehydrogenation/re-hydrogenation kinetics. The improvements resemble the behaviour of pure vanadium metal, and the Mg–(FeV) nanocomposites exhibited a good stability of the hydrogen sorption performance during hydrogen absorption – desorption cycling at T = 350 °C caused by a stability of the cycling performance of the nanostructured FeV acting as a catalyst. Further improvement of the cycle stability including the increase of the reversible hydrogen storage capacity and acceleration of H₂ absorption kinetics during the cycling was observed for the composites containing carbon additives (activated carbon, graphite or multi-walled carbon nanotubes; 5 wt%), with the best performance achieved for activated carbon.     

The processing of Mg–Ti for hydrogen storage; mechanical milling and plasma synthesis

A study was carried out into the processing of Mg-10 vol.% Ti powder mixture for hydrogen storage purposes. Two processing routes were evaluated; mechanical milling and plasma synthesis. Mechanical milling, carried out with a high speed planetary mill, yielded a particulate structure made up of large Mg agglomerates, 90–100 μm, with embedded Ti fragments of approx. 1 μm in size with a uniform distribution. Mg agglomerates were made up of coherently diffracting volumes that were less than 50 nm in size. Plasma processing was carried out with an RF plasma torch of 25–27 kW applied power, the powder mixtures fed with 1–3 g/min axially into the torch. The mixture Mg-10 vol.% Ti after plasma processing comprised Mg powders which were extremely fine, <100 nm. Ti occurred as separate particles mixed with Mg nanopowders. The powders had a coherently diffracting volumes that were comparable to the size of the particles themselves indicating that the plasma processing yields relatively defect free crystals. The formation of the nano-size particulate structures is evaluated with regard to their possible implications on the hydrogenation of Mg–Ti alloys.     

Reversible hydrogen storage in vapour deposited Mg-5 at.% Pd powder composites

Mg-5 at.% Pd powder composites derived from multilayered films of Mg and Pd deposited in Pd/Mg/Pd/Mg/Pd layer configuration by thermal evaporation reversibly store about 3.5 wt.% hydrogen up to 15 cycles under mild conditions of pressure and temperature. Hydrogenation takes place at 0.15 MPa hydrogen pressure while dehydrogenation occurs in a dynamic rotary vacuum. Each process is completed in about three hours. The temperature of a dehydrogenation or hydrogenation step is about 5–10 K higher than the preceding hydrogenation or dehydrogenation step. The hydrogenation temperature of the first cycle is 343 K whereas the dehydrogenation temperature of the 15th cycle is 423 K. The hydrogen storage capacity of composite is the manifestation of fine-grained microstructure of Mg and the catalytic properties of Pd. It declines beyond 423 K due to the exhaustion of metallic Pd as a result of the formation of Mg–Pd intermetallic compounds. This approach presents a simple and rapid method of preparing Mg–Pd composites for hydrogen storage applications.     

Hydrogen storage properties of Mg–TM–La (TM = Ti,Fe, Ni) ternary composite powders prepared through arc plasma method

For the first time, Mg based Mg–Transition metal (TM) –La (TM = Ti, Fe, Ni) ternary composite powders were prepared directly through arc plasma evaporation of Mg–TM–La precursor mixtures followed by passivation in air. The composition, phase components, microstructure and hydrogen sorption properties of the composite powders were carefully investigated. Composition analyses revealed a reduction in TM and La contents for all powders when compared with the compositions of their precursors. It is observed that the composites are all mainly composed of ultrafine Mg covered by nano La₂O₃ introduced during passivation. Based on the Pressure–Composition–Temperature measurements, the hydrogenation enthalpies of Mg are determined to be −68.7 kJ/mol H₂ for Mg–Ti–La powder, −72.9 kJ/mol H₂ for Mg–Fe–La powder and −82.1 kJ/mol H₂ for Mg–Ni–La powder. Meantime, the hydrogen absorption kinetics can be significantly improved and the hydrogen desorption temperature can be reduced in the hydrogenated ternary Mg–TM–La composites when compared to those in the binary Mg–TM or Mg–RE composites. This is especially true for the Mg–Ni–La composite powder, which can absorb 1.5 wt% of hydrogen at 303 K after 3.5 h. Such rapid absorption kinetics at low temperatures can be attributed to the catalytic effects from both Mg₂Ni and La₂O₃. The results gathered in this study showed that simultaneous addition of 3d transition metals and 4f rare earth metals to Mg through the arc plasma method can effectively alter both the thermodynamic and kinetic properties of Mg ultrafine powders for hydrogen storage.     

Hydrogenation properties of pure magnesium and magnesium–aluminium thin films

We have studied the hydrogenation/dehydrogenation behaviour of multilayered stacks of Pd/Mg/Pd and Pd–Fe(Ti)–Mg–Al–Mg–Fe(Ti)–Pd grown by electron beam physical vapour deposition. The palladium coating was deposited at both sides of the structure to ensure a fast dissociation rate and good transport properties for hydrogen as well as to avoid oxidation of magnesium either from atmosphere as from the substrate surface. Fe and Ti layers were included in the stack composition in order to assess their possible catalyst effect as well as to prevent the formation of Mg_xPd_y intermetallics during the thermal treatments. We have studied the structure evolution after thermal treatments as well as after the hydrogenation and dehydrogenation processes using XRD. We have also followed the reactions kinetics by resistometry and differential scanning calorimetry. The nanostructured Mg films have been hydrogenated at temperature as low as 50 °C in few minutes. Adding aluminium to magnesium has improved its hydrogenation capacity. We have also observed that the formation of an Mg_xAl_y intermetallic before hydrogenation improves the storage capacity. We have confirmed that titanium is a better catalyst for the hydrogenation/dehydrogenation of the Mg films.     

Structural and hydrogenation studies of ZnO and Mg doped ZnO nanowires

In this work, Mg doped zinc oxide (Mg_xZn_1−xO, x = 5, 10 and 20 at. %) nanowires were successfully prepared by two step process. Initially, ZnO nanowires were grown by thermal evaporation of Zn powder under oxygen atmosphere. Mg powder was doped in as grown ZnO through solid state diffusion at low temperature. Energy dispersive x-ray spectroscopy (EDAX), transmission electron microscopy (TEM), X-ray diffraction (XRD) and UV–Visible absorption spectra analysis reveals that the Mg doping on ZnO nanowires induces lattice strain in ZnO. Rietveld analysis of XRD data confirms the wurtzite structure and a continuous compaction of the lattice (in particular, the c-axis parameter) as x increases. The hydrogenation properties of ZnO nanowires and Mg doped ZnO (Mg_xZn_1−xO, x = 0, 5, 10 and 20 at. %) nanowires were studied. The hydrogenated samples were further investigated through XRD and Fourier transform infrared spectroscopy (FTIR). The hydrogen storage capacity of as grown ZnO nanowires has been estimated to be 0.57 wt. % H₂ at room temperature. However, the hydrogen storage capacity gets increased to ∼1 wt. % upon doping ZnO with 10 at. % Mg. Further increase in Mg concentration decreases the hydrogen storage capacity of ZnO nanowires. Thus for 20 at. % Mg doped ZnO; the hydrogen absorption capacity gets decreased from ∼1 wt. % to 0.74 wt. %. The mechanism of hydrogen storage in ZnO nanowires and Mg doped samples of ZnO has been discussed.     

Hydrogen storage properties of a Mg–Ni–Fe mixture prepared via planetary ball milling in a H2 atmosphere

A sample composition has been designed based on previously reported data. An 80 wt%Mg–13.33 wt%Ni–6.67 wt%Fe (referred to as Mg–13.33Ni–6.67Fe) sample exhibited higher hydriding and dehydriding rates after activation and a larger hydrogen storage capacity compared to those of other mixtures prepared under similar conditions. After activation (at n = 3), the sample absorbed 4.60 wt%H for 5 min and 5.61 wt%H for 60 min at 593 K under 12 bar H₂. The sample desorbed 1.57 wt%H for 5 min and 3.92 wt%H for 30 min at 593 K under 1.0 bar H₂. Rietveld analysis of the XRD pattern using FullProf program showed that the as-milled Mg–13.33Ni–6.67Fe sample contained Mg(OH)₂ and MgH₂ in addition to Mg, Ni, and Fe. The Mg(OH)₂ phase is believed to be formed through the reaction of Mg or MgH₂ with water vapor in the air. The dehydrided Mg–13.33Ni–6.67Fe sample after hydriding-dehydriding cycling contained Mg, Mg₂Ni, MgO, and Fe.     

Chemical processing of double-walled carbon nanotubes for enhanced hydrogen storage

Double-walled carbon nanotubes (DWCNTs) were modified for enhanced hydrogen storage by employing a combination of two techniques: KOH activation for the formation of defects on DWCNT surfaces and loading of the DWCNTs with nanocrystalline Pd. The physical properties of the pristine DWCNTs and chemically modified DWCNTs were systematically characterised by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and Brunauer–Emmett–Teller (BET) surface area measurements. The amounts of hydrogen storage capacity were measured at ambient temperature and found to be 1.7, 2.0, 3.7, and 2.8 wt% for pristine DWCNTS, 2 wt% Pd DWCNTs, activated DWCNTs, and 2 wt% Pd activated DWCNTs, respectively. Hydrogen molecules could be adsorbed on defect sites created by chemical activation in DWCNTs through van der Waals forces. For Pd nanoparticle loaded DWCNTs, H₂ molecules could be dissociated into atomic hydrogen and adsorbed on defect sites. We found that the hydrogen storage capacity of DWCNTs can be significantly enhanced by chemical activation or loading with Pd nanoparticles.     

Modeling and optimization of composite thermal insulation system with HGMs and VDMLI for liquid hydrogen on orbit storage

The passive thermal insulation system for liquid hydrogen (LH₂) on orbit storage mainly consists of foam and variable density multilayer insulation (VDMLI) which have been considered as the most efficient and reliable thermal insulation system. The foam provides main heat leak protection on launch stage and the VDMLI plays a major role on orbit stage. However, compared with the extremely low thermal conductivity of VDMLI (1 × 10⁻⁵ W/(m·K)) at high vacuum, the foam was almost useless. Recently, based on hollow glass microspheres (HGMs) we have proposed the HGMs-VDMLI system which performs better than foam-VDMLI system. In order to improve insulation performance and balance weigh and environmental adaptability of passive insulation system, the HGMs-VDMLI insulation system should be configured optimally. In this paper, the thickness of HGMs and the number and arrangement of spacers of VDMLI were configured optimally by the “layer by layer” model. The effective thicknesses of HGMs were 25 mm for 60 layers MLI and 20 mm for 45 layers VDMLI. Compared with 35 mm foam and 45 layers VDMLI system, the heat flux of 20 mm HGMs and 45 layers VDMLI system was reduced by 11.97% with the same weight, or the weight of which was reduced by 9.91% with the same heat flux. Moreover, the effects of warm boundary temperature (WBT) and vacuum pressure on thermal insulation performance of the system were also discussed.     

Hydrogen storage properties of Mg–Ni–C system hydrogen storage materials prepared by hydriding combustion synthesis and mechanical milling

Mg–Ni–C composite hydrogen storage materials were prepared by first ball milling the powder mixtures of carbon aerogel and nano-Ni, and then mixed with magnesium powder followed by hydriding combustion synthesis (HCS). The HCS product was further treated by mechanical milling for 10 h. The effect of Ni/C ratio on the structures and hydrogen absorption/desorption properties of the materials were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure–composition–temperature (PCT) measurements. It is found that 90Mg–6Ni–4C system shows the best hydriding/dehydriding properties, which absorbs hydrogen at a saturated capacity of 5.23 wt.% within 68 s at 373 K and desorbs 3.74 wt.% hydrogen within 1800 s at 523 K. Moreover, the dehydriding onset temperature of the system is 430 K, which is 45 K lower than that of 90Mg–10Ni system or 95 K lower than that of 90Mg–10C system. The improved hydriding/dehydriding properties are related greatly to the Ni/C ratio and the structures of the composite systems.     

A hybrid hydrolytic hydrogen storage system based on catalyst‐coated hollow glass microspheres

Hydrogen‐pressurized hollow glass microspheres (HGMs) in combination with a hydride bear the potential of storing hydrogen in feasible amounts. Therefore, the approximately 20‐µm diameter spheres are heated up and pressurized with hydrogen at a pressure of 85 MPa, so hydrogen diffuses into the spheres. After the spheres are cooled down, hydrogen can be stored at room temperature without excessive security measures. To release the stored hydrogen, heat has to be applied again to reach temperatures of about 250 °C (523.15 K). To reach this temperature, it is suggested in this work to use an exothermal chemical reaction, which produces hydrogen as a by‐product. In this case, an NaBH₄–water reaction will be discussed, which has to be initialized by a catalyst deployed on the HGMs. It will be shown that hydrogen storage densities of up to 20 wt% and 50 kg/m³ can be theoretically achieved with the proposed hydrogen storage system consisting of hydrogen‐pressurized HGMs and a hydride, that is, NaBH₄. Volumetric storage density and other aspects, such as water management, temperature restriction, stoichiometric restriction and hydrogen diffusion through glass, will be discussed. Due to resulting high water vapour pressures, a pressure vessel will still be needed in the concept. This paper shall give an overview of theoretically achievable storage densities with the proposed system. Experiments were carried out regarding catalytic promoted hydrolysis with HGMs, and resulting storage densities were determined. These experiments show good agreement with theory. However, they will be addressed only briefly in the outlook of the paper because a detailed discussion would go beyond the scope of this work. Copyright © 2016 John Wiley & Sons, Ltd.     

Improved desorption temperature of magnesium hydride via multi-layering Mg/Fe thin film

Hydrogen sorption property of Mg in Pd-capped thin film nanoconfined with Fe is investigated. Two methods of depositing the thin films were utilised, i.e., resistive heating method and pulsed laser deposition (PLD) method. In the thinnest Mg film prepared by resistive heating, hydrogen content was observed to be the highest among all samples and the hydrogen desorption temperature is 230 °C. Using pulsed laser deposition method, Mg/Fe nanoconfined multilayers are easily prepared. The hydrogen desorption temperature of Mg film with 12 Mg/Fe layers prepared via PLD method was significantly reduced to 155 °C, and the hydrogen storage capacity is improved as compared to the Mg/Fe with only several layers of same overall thickness. This study showed that the desorption temperatures correlate with the film thickness, thinner films react with hydrogen at lower temperatures. In addition, multi-layering Mg with Fe improves the desorption temperatures and hydrogen capacity, due to the higher grain boundary density, which acts as diffusion pathways for Pd in hydrogenation and dehydrogenation process.     

Effect of different reductants for palladium loading on hydrogen storage capacity of double-walled carbon nanotubes

The effects of different reductants for palladium loading on the hydrogen sorption characteristics of double-walled carbon nanotubes (DWCNTs) have been investigated. Pd nanoparticles were loaded on DWCNT surfaces for dissociation of H₂ into atomic hydrogen, which spills over to the defect sites on the DWCNTs. When we use different reductants, the reduction capabilities and other effects of the different reductants are different, which affects the hydrogen storage capacity of the DWCNTs. In this work, the amount of hydrogen storage capacity was determined (by AMC Gas Reactor Controller) to be 1.7, 2.0, 2.55, and 3.0 wt% for pristine DWCNTS and for 2.0%Pd/DWCNTs using H₂, l-ascorbic acid, and NaBH₄ as reductants, respectively. We found that the hydrogen storage capacity can be enhanced by loading with 2% Pd nanoparticles and selecting a suitable reductant. Furthermore, the sorption can be attributed to the chemical reaction between atomic hydrogen and the dangling bonds of the DWCNTs.     

The role of Al and Mg in the hydrogen storage of electrospun ZnO nanofibers

Pure and doped ZnO nanofibers with Al and Mg were successfully synthesized via an electrospinning method using a sol–gel containing Polyvinylpyrrolidone as a spinning aid and a zinc nitrate precursor. Calcination of the doped and undoped electrospun nanofibers was conducted at 500 °C in air, and the resultant structures were analyzed by X-ray diffraction (XRD) and Raman spectroscopy. The diameter of the doped nanofibers decreased with increasing viscosity and conductivity, as measured by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Energy dispersive spectroscopy (EDS) showed that Mg and Al are present in ZnO nanofibers. The pressure composition isotherm (PCI) demonstrated that the capacity of hydrogen storage in pure zinc oxide nanofibers is a factor of two greater than that of zinc oxide nanoparticles. However, Al-doped ZnO nanofibers have the highest capacity of hydrogen storage (2.81 wt%) at room temperature.     

Hydrogen generation by the hydrolysis of magnesium–aluminum–iron material in aqueous solutions

Highly activated Mg–Al–Fe materials are prepared from powder by mechanical ball milling method for hydrogen generation. The hydrolysis characteristics of Mg–Al–Fe materials in aqueous solutions under different experimental conditions are carefully investigated. The results show that the hydrolysis reactivity of Mg–Al–Fe material can be significantly improved by increasing the ball milling time and Fe content. The increase of NaCl solution concentration and initial temperature is also found to promote the hydrogen generation reaction. At 25 °C, the Mg60–Al30–Fe10 (wt%) material ball-milled for 4 h shows the best performance in 0.6 mol L⁻¹ NaCl solution, and the reaction can produce 1013.33 ml g⁻¹ hydrogen with a maximum hydrogen generation rate of 499.50 ml min⁻¹ g⁻¹. In comparison to NaCl solution, natural seawater is found to have an inhibiting effect on the hydrolysis of Mg–Al–Fe material. Especially, the presence of Mg²⁺ and Ca²⁺ in seawater can greatly reduce the hydrogen conversion yield, and the SO₄²⁻ can decrease the hydrogen generation rate.     

High-performance La–Mg–Ni-based alloys prepared with low cost raw materials

La–Mg–Ni-based hydrogen storage alloys showed good application prospects owing to their high hydrogen storage capacity. However, the poor cycling stability was a key problem. In order to improve the cycling stability, low cost YFe_0.85 master alloy was used as raw material to prepare La–Mg–Ni-based La_0.8-xY_xMg_0.2Ni_3-0.85xFe_0.85x (x = 0.50, 0.55, 0.60) hydrogen storage alloys by powder sintering method. The alloys were mainly composed of PuNi₃ phase and MgCu₄Sn phase. With the increase of Y and Fe, the cell parameters of PuNi₃ phase decreased. Lower mismatch coefficient promoted the cycling stability. As the case of x = 0.60, the capacity retention rate rose up to 95.45%. Aside from the cycling stability, appropriate substitution content contributed to higher capacity and satisfactory kinetics. As the case of x = 0.55, the hydrogen storage capacity reached 1.529 wt%, and hydriding time for the x = 0.60 alloy shrank to 76.7% of that for alloys without Y and Fe at 303 K.