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Copyright of Electric Power Automation Equipment / Dianli Zidonghua Shebei is the property of Electric Power Automation Equipment Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ZrCo alloy is considered as a promising candidate for hydrogen isotope storage in nuclear fusion reactors. However, severe poisoning caused by the impurities contained in hydrogen is an inevitable issue in engineering applications. Herein, the effects of Cr-doped ZrCo with segregated the reticular ZrCr 2 phase on the activation and oxidation resistance were investigated systematically. Experimental results show ZrCo 0·95 Cr 0.05 can achieve 1.71 wt% hydriding capacity within about 37 min under 1 mol% O 2 + 99 mol% H 2 , whereas ZrCo consumes more than 4 times (150 min) to reach the same capacity. Specifically, the improved anti-poisoning ability of the ZrCo–Cr system could be attributed to the three-step chain effect induced by Cr doping, including the hydrogenation-prone and oxygen resistance character of ZrCr 2 phases, sacrificial and catalysis of in-situ formed metallic Cr clusters, and protective effects of Cr oxide layers. Hence, the active sites for rapid hydrogen absorption were obtained and inferior oxygen resistance of ZrCo substrates was alleviated through the self-sacrifice of ZrCr 2 and Cr. This work not only proves the feasibility of the multi-component alloying strategy in the field of ZrCo alloy anti-poisoning modification, but also reveals that the core of the multi-component alloying strategy is to realize the modulation of the microstructure through the composition design. The layer-to-layer stacking relationship and oxidation dynamic behavior of Cr-doped ZrCo under the O 2 /H 2 mixed gas is vividly illustrated. [Display omitted] The Cr-doped ZrCo with a Cr-rich reticular second phase structure was constructed flexibly. •Facilitated activation kinetics under H 2 and poisoning resistance under 99% H 2 + 1% O 2 were obtained. •The stacking relationship and dynamic oxidation behavior of Cr-doped ZrCo are vividly illustrated. •The self-sacrificial mechanism of segregated ZrCr 2 phases and in-situ formed metallic Cr clusters under the action of oxygen was revealed. [ABSTRACT FROM AUTHOR]

Alkaline water electrolysis was performed using Ni(OH) 2 /NiOOH as an anode and MmNi 5 -based hydrogen storage alloy as a cathode removed from NiMH batteries at 303 K and 10 mA/cm2 for 2 h. The water decomposition voltage changed from 1.36 V to 1.48 V (thermoneutral voltage: 1.48 V). The hydrogen evolution reaction (HER) overpotentials of the practically used MmNi 5 -based alloy with low H 2 dissociation pressure 0.012 MPa were small (33–75 mV) at 10 mA/cm2. The HER overpotentials were similar to those of Pt-based electrocatalysts. The low dissociation pressure of the hydride was suggested to play a key role to decrease the HER overpotentials of the alloy. The alkaline water electrolysis voltage was 1.46–1.48V and stable at 50 mA/cm2 and 353K for 24h. Then, the MmNi 5 -based hydrogen storage alloy was found to be a new type of HER electrocatalyst for alkaline water electrolysis. [Display omitted] • Alkaline water electrolysis was performed using Ni(OH) 2 and MmNi 5 -based alloy. • HER overpotentials of the alloy with low dissociation pressure were 33–75 mV. • The overpotentials of the alloy were similar to those of Pt-based electrocatalysts. • The dissociation pressure of the alloy hydride increased with the overpotential. • The water electrolysis voltage was stable at 50 mA/cm2 and 353K for 24h. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the substitutional effect of typical A-side elements of Ce, Nd, Sm, and Gd on the crystal structure and hydrogen storage properties of an A 5 B 19 -type La 0. 72 Y 0. 13 Mg 0. 15 Ni 3. 70 Al 0.15 alloy aiming to provide further design for enhancing the commercial application of RE–Mg–Ni-based alloys for nickel-metal hydride (Ni/MH) batteries. The results reveal that Ce substitution significantly improves discharge ability at higher rates, delivering 283.3 mAh g−1 at 5C and 183.7 mAh g−1 at 10C, which present increases of 16.7% and 44.0% over the unsubstituted alloy, respectively. Additionally, Sm substitution effectively extends the alloy's cycling life, retaining 66.2% capacity after 500 cycles, representing a 14.4% increase compared to the original alloy. Moreover, the substitution of Nd increases the hydrogen storage capacity from 1.23 wt% to 1.50 wt%, while Gd reduces plateau hysteresis and slope factor during (de)hydrogenation. • Ce, Nd, Sm, and Gd substitution effects on A 5 B 19 -type alloy properties are revealed. • The high rate discharge ability of Ce-substituted alloy is elevated by 44.0% at 10C. • Nd substitution increases hydrogen storage capacity from 1.23 wt% to 1.50 wt%. • Sm substitution extends the 500th electrochemical cycling life from 14.4% to 66.2%. • Gd substitution reduces (de)hydrogenation plateau hysteresis and slope factor. [ABSTRACT FROM AUTHOR]

Hydrogen has been widely recognized as a promising new renewable energy source. Developing safe and efficient hydrogen storage technologies is crucial for scaling up hydrogen energy applications. AB 2 -type Ti–Mn-based hydrogen storage alloys have excellent kinetic and activation properties, but their comprehensive hydrogen storage performance, especially the hydrogen storage capacity, platform pressure, and cycling stability of low-cost Ti–Mn-based alloys without V, needs to be further optimized. Hence, the hydrogen storage properties of the Ti 1- x Zr x Mn 0.9 Cr 0. 7 Fe 0.1 (x ​= ​0.05, 0.16, 0.20, 0.25) were systematically studied. All of the series alloys contained a single C14-type Laves phase structure. Increasing the substitution of Zr for Ti resulted in higher hydrogen storage capacities and lower plateau pressures. Notably, the effective hydrogen storage capacity of x ​= ​0.16 alloy is significantly higher than that of the other alloys, and its platform pressure is the most suitable. This alloy achieved a hydrogen content of 1.8 ​wt% and demonstrated excellent cycling stability, retaining 98.6 ​% of its capacity after 100 cycles. This study provides a theoretical guideline for optimizing the properties of low-cost TiMn-based alloys without V. [ABSTRACT FROM AUTHOR]

In order to improve the detonation characteristics of RDX, a RDX-based composite explosive with TiH2 powders was prepared. The effects of content and particle size of TiH2 powders on thermal safety, shock wave parameters and thermal damage effects of RDX-based composite explosive were studied with the C80 microcalorimeter, air blast experiment system and colorimetric thermometry method. Experimental results showed that TiH2 powders could enhance the thermal stability of RDX-based composite explosive and increase its ultimate decomposition heat. The content and particle size of TiH2 powders also had significant effects on the thermal safety, detonation velocity, shock wave parameters, fireball temperature and duration of RDX-based composite explosives. Furthermore, the differences of TiH2 and Ti powders on the detonation energy output rules of RDX-based composite explosives were also compared, showing that TiH2 powders had better influences on improving the explosion power and thermal damage effect of RDX-based composite explosives than Ti powders, for the participation of free H2 released by TiH2 powders in the detonation process. TiH2 powders have important research values as a novel energetic additive in the field of military composite explosives.

Herein, a first-principles pseudopotential plane-wave method is used to investigate the effects of co-doping Sc with Cu (or Zn) on the structural stability and desorption temperature of Mg-based hydrogen storage alloys and their hydride phases, as well as the related microscopic mechanisms. Specifically, the cell volume, electronic density of states, bond order, differential charge density, charge spreading, enthalpy of generation, and hydrogen desorption temperature of Mg 1.75 Sc 0.25 Ni 1−x M x H 4 (M = Cu or Zn, x = 0.125, 0.25, 0.375, and 0.5) are analyzed. Results indicate that the Mg 2 Ni alloy cell expands with an increase in the concentration of Cu or Zn co-doped with Sc. This expansion avoids the formation of a hydrogen adsorption layer, thus facilitating the entry and exit of hydrogen atoms from the alloy, thus improving its hydrogen release performance. In addition, the Cu or Zn atoms attract the surrounding H atoms and weaken the H–Ni bonds. Thus, the stability and dehydrogenation temperature of the system decrease with increasing Cu or Zn content. [Display omitted] • First-principles pseudopotential plane-wave method used to investigate Mg-based hydrogen storage materials. • The cell volume of the Mg 2 Ni alloy increases with increasing dopant content. • Co-doping Sc and M (M: Cu or Zn) in Mg 2 Ni weakens the bonding order of the H–Mg and H–Ni bonds. • Sc and M co-doping in Mg 2 Ni improves hydrogen release from the hydride phase. [ABSTRACT FROM AUTHOR]

This study investigated the first hydrogenation behavior of TiFe-based hydrogen storage alloy with the laves phase. A TiFe 0.9 Cr 0.1 alloy was prepared through vacuum arc melting, and it had a dual-phase microstructure with B2 and laves phases. The first hydrogenation kinetics was measured by applying a hydrogen pressure of 40 bar at 30 °C, where the alloy absorbed hydrogen without thermal activation. The first hydrogenation kinetics was divided into three sections to understand the first hydrogenation behavior, and each section was analyzed using a solid–gas reaction model. The model's goodness of fit was evaluated by fitting each section. In the early hydrogen absorption stage, a surface-controlled mechanism (Chemisorption model) was analyzed to be the most dominant. In the second stage, where hydrogen was quickly absorbed, an interface-controlled mechanism (CV3D model) was most suitable. In the last hydrogen absorption stage, where hydrogen absorption was saturated, a diffusion-controlled mechanism (GB3D model) was most suitable. • The TiFe 0.9 Cr 0.1 alloy had a dual-phase microstructure with B2 and laves phases. • The alloy absorbed hydrogen without any thermal activation process. • The first hydrogenation kinetics was divided into three sections for analysis. • Hydrogen absorption behavior was analyzed through the solid-gas reaction model. [ABSTRACT FROM AUTHOR]

AB 3 -type La-Mg-Ni-based hydrogen storage alloys are known for their high electrochemical hydrogen storage capacity. However, their practical application has been hindered by fast capacity degradation. Herein, we managed to improve their cycle life by synchronizing the hydrogen absorption/desorption behaviors of [A 2 B 4 ] and [AB 5 ] subunits based on a series of AB 3 -type single-phase La 0.60 R 0.12 Mg 0.28 Ni 3 (R = La, Pr, Nd, Gd) superlattice alloys. This is achieved by the preferable occupation of Pr, Nd and Gd in [A 2 B 4 ] subunits rather than [AB 5 ] subunits compared to La, which decreases the volume difference between [A 2 B 4 ] and [AB 5 ], significantly reducing the mismatch between [A 2 B 4 ] and [AB 5 ] during hydrogen absorption/desorption. Resultantly, the microstrain of the R = Gd alloy is only half that of the R = La alloy, leading to enhanced anti-pulverization and anti-oxidation/corrosion resistance, as well as an improved cycle stability. The S 100 of the R = Gd alloy is more than 15 % higher than the R = La alloy. Moreover, the plateau pressure is adjusted to a proper level, enabling an increase in the high-rate dischargeability (HRD 1500) from 53.6 % (R = La) to 66.4 % (R = Gd). This work provides impressive insights into developing high-performance superlattice hydrogen storage alloys. [Display omitted] • Single-phase AB 3 -type superlattice alloys with different RE elements are acquired. • V [A2B4] and V [AB5] are equalized by selective occupation of RE elements. • H 2 absorption/desorption of [A 2 B 4 ] and [AB 5 ] subunits are synchronized. • Not only is cycle stability greatly enhanced, but HRD is also improved. [ABSTRACT FROM AUTHOR]

This investigation explores the solid-state hydrogen storage properties of two series of hydrogen storage alloys: (Ti 0.85 Zr 0.15) x Mn 0.8 CrFe 0.2 (x = 1.00∼1.10) and (Ti 0.85 Zr 0.15) 1.02 Mn y Cr 1.8-y Fe 0.2 (y = 1.00∼0.40) alloys. These alloys exhibit a single C14-Laves phase structure and demonstrate promising capabilities for solid-state hydrogen storage. The (Ti 0.85 Zr 0.15) x Mn 0.8 CrFe 0.2 (x = 1.00∼1.10) alloys display an increased hydrogen absorption capacity and a reduced plateau pressure at higher super-stoichiometric ratios of x. When x = 1.10, the alloy achieves a maximum capacity of 1.86 wt%. The hydrogen storage capacity of the (Ti 0.85 Zr 0.15) 1.02 Mn y Cr 1.8-y Fe 0.2 (y = 1.00∼0.40) alloys diminishes as the value of y decreases. Furthermore, the hydrogen absorption plateau pressure and hysteresis factor of the alloys increase with an escalating Mn/Cr ratio. The analysis of cyclic stability reveals that the primary factor contributing to poor cycling stability of the (Ti 0.85 Zr 0.15) 1.02 Mn 0.4 Cr 1.4 Fe 0.2 alloy is the compositional decomposition, rather than pulverization or alterations in the phase structure. In summary, this investigation enhances our understanding of the solid-state hydrogen storage properties of these alloys. It establishes a foundation for further research and development in this pivotal field of hydrogen storage. [Display omitted] • The alloys have a stable C14 single-phase structure as influenced by the size factor. • The alloys have a maximum hydrogen storage capacity of 1.86 wt%. • Cycling stability of the alloys is determined by compositional decomposition. [ABSTRACT FROM AUTHOR]

Rare earth-based superlattice alloys are essential anodes for high-performance nickel-metal hydride (Ni-MH) batteries. This study aimed to improve the overall electrochemical hydrogen storage properties of (La0.33Y0.67)5Ni18.1- x Mn0.9Al x alloys by adjusting the Al content. The alloys predominantly consist of the 2H–Pr5Co19 phase, with Al atoms mainly occupying the 12 k2 site at the [AB5]-1/[AB5]-2 boundary and subsequently the 12 k1 site at the [A2B4]/[AB5]-1 boundary. As a result, a minimum subunit volume difference of 2.08 Å3 is observed at x = 0.6. Therefore, the Al substitution is responsible for the decrease in the dehydriding plateau pressure and the increase in discharge capacity. Among them, the alloy (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 presents a discharge capacity of 361.2 mAh/g, a higher capacity retention S 200 of 69.80 %, and better rate performance owning to the enhanced hydrogen diffusion rate through the multi-phase interface. This work demonstrates the potential of the (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 alloy as high-performance Ni-MH battery anode. • Suitable Al substitution minimizes the subunit volume difference of the 2H–Pr 5 Co 19 phase. • The (La 0.33 Y 0.67) 5 Ni 17.5 Mn 0.9 Al 0.6 alloy has a rate discharge performance HRD 900 of 83.15 %. • The (La 0.33 Y 0.67) 5 Ni 17.5 Mn 0.9 Al 0.6 alloy has a capacity retention S200 of 69.80 %. [ABSTRACT FROM AUTHOR]

Due to the increased demand of environmentally sustainable energy resources, reliable energy storage technologies become more essential than ever. Other emerging energy storage applications include uninterruptible power supply, cell phone towers, and sensors/monitors for outdoor systems (utility line, traffic control, etc.), and automotive emergency call system. The common requirements for above-mentioned applications are high safety and durability, easy maintenance, and the most important of all, wide operating temperature range. With its proven reliability, nickel metal hydride (NiMH) battery has become very competitive in these fields. Although NiMH battery can function in a wide temperature range, extreme temperatures cause some operating difficulties. Exposure to elevated temperatures lead to premature NiMH battery material failure. At ultra-low temperature, NiMH battery's alloy anode experiences sluggish bulk reaction and decreased surface reactivity. In this review, the fundamentals of NiMH battery electrochemical reactions and failure mechanisms at extreme temperatures are explained, followed by a report focused on the research effort of hydrogen storage alloy for extreme temperature applications, and finally an alloy development plan for improved wide-temperature-range operation is discussed. [Display omitted] • Review of low-temperature metal hydride alloy development is presented. • Review of metal hydride alloy's stability/high-temperature property improvement is presented. • Metal hydride alloy's issues at extreme temperatures are discussed. • Future research plan for wide-temperature-range metal hydride alloy is presented. [ABSTRACT FROM AUTHOR]

Mg80Ni16−xAlxY4 (x = 2, 4, 8) alloys were prepared by induction levitation melting, and the effect of substitution of Al for Ni on the microstructure and hydrogen storage properties was studied in the present work. The results illustrated that the solidification path, phase constitution, and grain size were significantly altered by Al addition. Appropriate Al addition improved abundance and grain refinement of the Mg, Mg2Ni, and Mg15NiY ternary eutectic. But as Al further increased, Mg solidified independently rather than in the formation of the ternary eutectic. More Al favored the formation of Al3Ni2Y but suppressed Mg2Ni and YMgNi4. Although the hydrogen absorption activation and the kinetic property deteriorated, the thermodynamic stability of hydrides was enhanced by adding Al. Hydrogen absorption ability under low pressure was improved, and the Mg80Ni8Al8Y4 alloy could absorb nearly 3.5 wt% hydrogen under 1 bar hydrogen at 250 °C. [ABSTRACT FROM AUTHOR]

This study reports the development of a two-stage metal hydride hydrogen compressor (MHHC) capable of compressing hydrogen from 1 to 30 MPa through a temperature change between 20 and 150 °C. AB 2 -type hydrogen storage alloys in the C14 Laves phase are employed, where A = Ti and Zr and B = Cr, Mn, and V. The pressure transfer conditions between the two stages are investigated, and the composition of the AB 2 alloys is optimized accordingly: the Mn content x in Ti 0.8 Zr 0.2 Cr 1.9 − x Mn x V 0.1 and the Zr content y in Ti 1 − y Zr y Cr 1.2 Mn 0.8 , for the 1st and the 2nd stage materials, respectively. A laboratory-scale two-stage compressor is fabricated and operated using the selected alloys, whereby hydrogen is successfully compressed to 30 MPa. The compression capacity is analyzed to estimate the useable capacity of the materials. The results of this study can serve as a guide for the design and evaluation of multistage MHHCs. • A two-stage MHHC, compressing H 2 from 1 to 30 MPa in the 20–150 °C range, is reported. • AB 2 -type hydrogen storage alloys, (Ti, Zr)(Cr, Mn, V) 2 , are employed for the MHHC. • The transfer pressure from the 1st to 2nd stage is examined and optimized. • Linear coefficients to estimate the plateau pressures are derived. • The estimated useable capacities are compared with the compression capacities. [ABSTRACT FROM AUTHOR]

In this study, La15Fe2Ni72Mn7B2Al2 hydrogen storage was composited with grapheme and the effect of ball milling time on the microstructure and properties of the alloy were studied. XRD analysis shows that the as-milled composites alloy consists of LaNi5, La3Ni13B2 and (Fe, Ni) phases. No new phase is formed in the composites alloy with the milling time increases. The ball-milling treatment produced amorphous structure and refined the particle size of the alloy. Electrochemical studies revealed that the discharge capacity of composites alloy was significantly improved. The ball-milling process enhances the maximum discharge capacity and the dynamics performance, especially for the alloy with milling time of 30 min. Moreover, self-discharge behavior of the composites alloy were also increased by ball-milled. [ABSTRACT FROM AUTHOR]

The newly discovered AB 4 -type superlattice structure of rare earth–Mg–Ni-based (RE–Mg–Ni) alloys have extended cycle life and power performance, which are a promising anode material for nickel-metal hydride (Ni/MH) battery. However, the cycling stability still needs to be enhanced to meet the requirement of utilization. Herein, we design low cost single-phase AB 4 -type alloys and clarify the effect of merging Y on Mg on the electrochemical performance. Studies show that the cycling stability of the alloy is significantly enhanced after partial replacement of Y on Mg, where the discharge capacity of the La 0.65 Sm 0.12 Y 0. 10 Mg 0. 13 Ni 3. 60 Al 0.15 alloy maintains 234.5 mAh g−1 after cycling 500 times with a capacity retention of 61.8%, in contrast to 191.6 mAh g−1 with 50.6% of the La 0.65 Sm 0.12 Mg 0. 23 Ni 3. 60 Al 0.15 alloy. The prolonged cycling life relates to the reduction of pulverization due to the increased matching degree of the sublattice structure, and the prevention of oxidation in terms of the oxide film of Y. Whereas, the discharge ability at high rates and low temperatures of the alloy are deteriorated after Y replacement. The results pave the way to the component design of the RE–Mg–Ni-based alloys for long-life Ni/MH batteries. • Low-cost AB 4 -type La–Mg–Ni-based alloys with single-phase structures are obtained. • Effect of Y substituted Mg on electrochemical properties of the alloy is clarified. • The La 0.65 Sm 0.12 Y 0 10 Mg 0. 13 Ni 3. 60 Al 0.15 alloy is with improved matching sublattices. • Y replaced Mg enhances the cycling stability to from 50.6 to 61.8% after 500 cycles. • The AB 4 -type alloys possesses superior discharge ability at high rates. [ABSTRACT FROM AUTHOR]

The first-principle pane wave pseudopotential method in GGA-PBE generalized gradient approximation is aphid to study the lattice parameters, electronic properties and mechanical properties of hydrogen storage alloy LaNi4Ge under different pressures. The results show that the lattice parameters of LaNi4Ge compound decrease with the increase of pressure, and is a-axles is more easily compressed than taxes. There are no signal cant trend changes in the total density of states, the Fermi energy level decreases with the increase of pressure, and is hardness increases with the increase of pressure. The elastic properties show that the material is decisive in the pressure range, and the elastic constant Cu and elastic modulus E increase further with the increase of pressure, and maintain the mechanical stability in a certain pressure range. [ABSTRACT FROM AUTHOR]

In order to meet the demand of metal hydride–hydrogen compressors (MHHC) and their hydrogen compression materials for high-pressure hydrogen filling in a hydrogen energy field, four kinds of hydrogen storage alloys with low-grade heat source (<373 K) heating outputs and different hydrogen pressures (up to 80 MPa) were developed as hydrogen compression materials. The preliminary compositions of the hydrogen storage alloys were determined by using a statistical model and research experience. The rare earth series AB5 and Ti/Zr base AB2 hydrogen storage alloys were prepared using a high-temperature melting method. The composition, structure, and hydrogenation/dehydrogenation plateau characteristics of the alloys were tested by an inductively coupled plasma mass spectrometer (ICP-MAS), X-ray diffractometer (XRD), and pressure–composition isothermal (PCT) tester. The median output pressures of the four-stage hydrogen storage alloys at 363 K were 8.90 MPa, 25.04 MPa, 42.97 MPa, and 84.73 MPa, respectively, which met the requirements of the 20 MPa, 35 MPa, and 70 MPa high-pressure hydrogen injections for the MHHCs. In fact, due to the tilted pressure plateau of the PCT curve, the synergy between the adjacent two alloys still needed to be adjusted. [ABSTRACT FROM AUTHOR]

Rare-earth-based AB5-type alloys are strong candidates for use in solid state hydrogen storage applications; however, their capacity needs to be improved. To efficiently optimize the hydrogen storage performance of AB5-type alloys, the effects of the substitution of Ce and Ca for La (A side) and Mn and Al for Ni (B side) on the structural properties and hydrogenation/dehydrogenation performance of the (LaCeCa)1(NiMnAl)5 alloy series were studied systematically using the uniform design method. X-ray diffraction analysis and scanning electron microscopy showed that all the designed alloys consisted of a single uniform LaNi5 phase. The atomic radii and contents of the constituent elements had a determining effect on the cell volume and properties of the alloys. The maximum hydrogen storage capacity of the (LaCeCa)1(NiMnAl)5 alloy series is approximately 1.7 wt%, which is much higher than the theoretical hydrogen storage capacity of LaNi5 (1.39 wt%).

LaSm 0.4 Y 1.6 Ni 10.5 Mn 0.4 Al 0.2 hydrogen storage alloy with a Ce 2 Ni 7 -type single-phase has been prepared and its electrochemical properties and hydrogen storage properties are systematically investigated. The crystal structure of the alloy transformed completely into the Ce 2 Ni 7 -type single-phase via annealing at 1323 K for 16 h. The Ce 2 Ni 7 -type single-phase alloy has promising electrochemical properties, including 0.2C max = 385.8 mAh/g, 1C max = 356.8 mAh/g, and S 100 = 86.72%. The HRD of the Ce 2 Ni 7 -type single-phase alloy is primarily determined by the charge transfer rate, which is HRD 1500 = 75.75% and the corresponding electrochemical capacity at 1500 mA/g is 272.7 mAh/g. The PCT curves of the alloy present double pressure platforms owing to the hydrogen atoms occupying the [A 2 B 4 ] subunit preferentially and entering the [AB 5 ] subunit subsequently. Similarly, because the lattice expansion rates of the [A 2 B 4 ] and [AB 5 ] subunits vary discordantly throughout hydrogen absorption/desorption, the hydrogen storage capacity of the alloy experiences irreversible losses. • Ce 2 Ni 7 -type single-phase La-Sm-Y-Ni based hydrogen storage alloy with appreciable electrochemical properties is prepared. • The Ce 2 Ni 7 -type single-phase alloy shows excellent high-rate discharge capacity performance. • Hydrogen absorption/desorption performances and the mechanism of cyclic capacity decay are studied. [ABSTRACT FROM AUTHOR]

Pressure-composition-temperature (PCT) curves for hydrogen absorption and desorption of AB2-type hydrogen storage alloys at arbitrary temperatures are predicted by three machine learning models such as random forest, K-nearest neighbor and deep neural network (DNN). Two data generation methods are adopted to increase the number of data points. A new form of the PCT curve functions is suggested to fit experimental data, which greatly helps improve the prediction accuracy. A van't Hoff type equation is used to generate unmeasured temperature data, which improves the model performance on the PCT behavior at various temperatures. The results indicate that a DNN is the best model for predicting the PCT behavior with a high average correlation value R2 = 0.93070. [ABSTRACT FROM AUTHOR]

Oxidation of hydrogen storage alloy leads to the formation of a passive surface oxide layer, which deteriorates its performance. This study introduces a method utilizing polymethyl methacrylate (PMMA) nano-coating to improve the antioxidant properties of hydrogen storage alloys, including LaNi 5 , TiMn 2 , and Mg 2 Ni. PMMA nano-coating was achieved using a solution immersion method. The results show that the PMMA-coating promotes a stable capacity, kinetics, and thermodynamic properties compared to those of uncoated alloys. After 168 h of air exposure, the hydrogen storage capacities of PMMA-coated LaNi 5 , TiMn 2 , and Mg 2 Ni alloys show minor decreases. Moreover, cycling tests demonstrate that PMMA-coated LaNi 5 and PMMA-coated Mg 2 Ni have good cyclic stabilities. Our results show that the PMMA coating provides effective protection for variant hydrogen storage alloys from oxygen contamination and oxidation. • PMMA-coated LaNi 5 , TiMn 2 , and Mg 2 Ni were successfully prepared by a solution immersion method. • The antioxidant properties of LaNi 5 , TiMn 2 , and Mg 2 Ni were enhanced due to PMMA coating. • PMMA-coated alloys showed good performance retention after 168-hr air exposure. [ABSTRACT FROM AUTHOR]

La–Mg–Ni-based superlattice structure alloys are promising negative material candidates for nickel metal hydride (Ni-MH) batteries, but their application is challenged by cycling life. Herein, we propose Sm–Mg–Ni-based alloys beyond La–Mg–Ni-based alloys to promote long-term durability. Specifically, Ce 2 Ni 7 -type single-phase Sm 0.58 La 0.25 Mg 0.17 Ni 3.26 Al 0.18 and Sm 0.54 La 0.29 Mg 0.17 Ni 3.26 Al 0.18 alloys have been obtained, delivering significantly high-capacity retention rates over 70 % after 500 cycles at a 1C charge and discharge rate. Furthermore, the alloy's discharge ability has been optimized via manipulating Sm/La ratios, of which its effect on the structure and electrochemical properties is detailly studied. It is found that the discharge capacity of the Sm 0.58 La 0.25 Mg 0.17 Ni 3.26 Al 0.18 alloy with a higher Sm/La ratio outperforms the Sm 0.54 La 0.29 Mg 0.17 Ni 3.26 Al 0.18 alloy. However, the low Sm/La ratio Sm 0.54 La 0.29 Mg 0.17 Ni 3.26 Al 0.18 alloy is favorable for discharge ability at a high-rate current rate and features lower plateau pressure and enthalpy change compared with Sm 0.58 La 0.25 Mg 0.17 Ni 3.26 Al 0.18. The work is expected to offer new insights into the composition design of hydrogen storage alloys with long cycling life for Ni-MH batteries. • Two Ce 2 Ni 7 alloys single-phase Sm-Mg-Ni-based alloys are obtained. • Both alloys show outstanding cycling life with over 70 % capacity after 500 cycles. • HR-Sm 0.58 La 0.25 Mg 0.17 Ni 3.26 Al 0.18 alloy features higher discharge capacity. • LR-Sm 0.54 La 0.29 Mg 0.17 Ni 3.26 Al 0.18 has lower plateau pressure and lower Δ H value. • LR-Sm 0.54 La 0.29 Mg 0.17 Ni 3.26 Al 0.18 alloy features 210.0 mAh g−1 at high rate of 5C. [ABSTRACT FROM AUTHOR]

Mg80Ni16−xAlxY4 (x = 2, 4, 8) alloys were prepared by induction levitation melting, and the effect of substitution of Al for Ni on the microstructure and hydrogen storage properties was studied in the present work. The results illustrated that the solidification path, phase constitution, and grain size were significantly altered by Al addition. Appropriate Al addition improved abundance and grain refinement of the Mg, Mg2Ni, and Mg15NiY ternary eutectic. But as Al further increased, Mg solidified independently rather than in the formation of the ternary eutectic. More Al favored the formation of Al3Ni2Y but suppressed Mg2Ni and YMgNi4. Although the hydrogen absorption activation and the kinetic property deteriorated, the thermodynamic stability of hydrides was enhanced by adding Al. Hydrogen absorption ability under low pressure was improved, and the Mg80Ni8Al8Y4 alloy could absorb nearly 3.5 wt% hydrogen under 1 bar hydrogen at 250 °C.

Copyright of Inorganic Chemicals Industry is the property of Editorial Office of Inorganic Chemicals Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To investigate the influence of thermal effects on the hydrogen desorption performance of the metal hydride hydrogen storage system, a two-dimensional numerical model was established based on a small metal hydride hydrogen storage tank, and its accuracy was verified by the temperature variations in the reaction zone of the hydrogen storage tank during hydrogen desorption. In addition, the influence of the heat transfer medium on the heat and mass transfer performance of the hydrogen desorption reaction was analyzed. An external heat transfer bath was added to simulate the thermal effect of the model during the hydrogen desorption reaction. The temperature and type of heat transfer medium in the heat transfer bath were modified, and the temperature and reaction fraction variations in each zone of the hydrogen storage model were analyzed. The results showed that under heat transfer water flow, the reaction rate in the center region of the hydrogen storage tank was gradually lower than that in the wall region. The higher the temperature of water flow, the shorter the total time required for the hydrogen desorption reaction and the shortening amplitude is reduced. The variations in the temperature and hydrogen storage capacity during hydrogen desorption were similar, with water and oil as the heat transfer medium, under the same flow rate and heat transfer temperature, however, the heat transfer time and hydrogen desorption time of water were about 10% and 5% shorter than that of oil, respectively. When the air was used as the heat transfer medium, the heat transfer rate of the air convection in the channel was lower than the heat transfer rate of the tank wall, reducing the temperature difference between the air and alloy on both sides of the wall, decreasing heat transfer efficiency, and significantly prolonging the time required for hydrogen desorption. [ABSTRACT FROM AUTHOR]

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A study on the synthesis of black powder (La2NiO4) material using the solution combustion synthesis method at a variation of synthesis temperature of 60, 70, and 80°C was carried out. It produces a mass of black powder of 2 grams by four times of synthesis process. Then, material characterization was performed on the black powder samples obtained by using X-ray Diffraction (XRD) to determine the phases formed, Scanning Electron Microscopy - Energy Dispersive X-ray Spectroscopy (SEM-EDS) to determine the morphology and analyze the composition elemental on the microscale and Fourier Transform Infra-Red (FTIR) to determine chemical bonds. From the whole black powder sample, XRD analysis showed the phases of Dilantanum Nickel Tetraoxide (La2NiO4), Nickel Oxide (NiO), Lanthanum Oxide (La2O3), and Lanthanum Oxide Ht x-form (La2O3 Ht (x-form)). In addition, it was seen from the visible compositions of the phases that the NiO phase looks more dominant and the variation of the synthesis temperature shows that the La2O3 phase was increasing. This was supported by the EDS analysis, which showed that the EDS spectrum contains elements La, Ni, and O where the element O indicates that oxidation occurs in the elements Ni and La. On the other hand, the SEM analysis results confirm that the black powder sample contains the elements La and Ni, based on the high and low electron images contained in the morphology of the black powder sample. In addition, it was also known that the particles in the black powder sample were micron size and had porous morphology. This occurs due to rapid thermal decomposition events and excessive gas development. In addition, FTIR analysis showed that the O-H bond had been reduced and there are still C-O and C-H bonds indicating the presence of organic elements possessed by glycine.

Abstract With the continuous expansion of the high‐purity hydrogen application range, the performance degradation of hydrogen storage alloy (HSA) caused by impurities has attracted widespread attention in producing pure hydrogen from biomass. In this study, the lanthanum‐rich mischmetal alloy's purification ability on hydrogen sulfide impurities and cycling performance were studied. The hydrogen with different concentrations of hydrogen sulfide was used to investigate the purification performance, which assumes the gas derived from biomass. Besides, a cycling experiment was designed to analyze cycling performance. The results show that the HSA could remove high concentrations of hydrogen sulfide entirely. It was also found that impurities of 1 ppm hydrogen sulfide had little effect on the HSA. With hydrogen sulfide concentrations of 100 ppm, the hydrogen storage capacity, absorption rate, and release rate were reduced, but they became a stable state from the second cycle. The performance degradation mechanism was analyzed by Energy Dispersive X‐Ray Spectroscopy (EDS) and X‐ray Photoelectron Spectroscopy (XPS​).

Metal hydride hydrogen compression technology has the advantages of good safety, no moving parts, and the ability to use low-grade waste heat. However, this technology has high requirements for the hydrogen sorption plateau pressure, plateau slope, hysteresis of hydrogen storage alloys. In this paper, the influence of the addition of alloying elements on the hydrogen compression properties of BCC structure vanadium-based alloys is studied. The V75Ti20Cr5 (M=V, Ti, Cr or Zr) hydrogen compression alloys were prepared by the arc melting method, using volume adsorption method to determinate the PCT curve and kinetic properties, and the plateau slope, hysteresis effect, hydrogen compression ratio and hydrogen reaction rate of the alloy PCT curve were obtained by calculation to compare the hydrogen compression properties of alloys. The results show that the reversible hydrogen storage capacity of V75Ti20Cr5 alloy is 1.05 wt%. Compared with V75Ti25 alloy, the hydrogen compression rate is significantly improved, and V75Ti20Zr5 significantly reduces the reversible hydrogen storage, hydrogen compression ratio and hydrogen compression rate of the alloy. [ABSTRACT FROM AUTHOR]

Rare-earth AB 5 -type La–Ni–Al hydrogen storage alloys are widely studied due to their extensive application potentials in hydrogen isotope storage, hydrogen isotope isolation and hydrogen compressors, etc. Good hydriding/dehydriding kinetics, easily activation, high reversibility are important factors for their practical application. However, their overall hydrogen storage performance, especially plateau pressure and hydrogen absorption/desorption durability need to be further optimized. In this study, the microstructures and the hydrogen storage properties of as-cast, annealed, and melt-spun LaNi 3.95 Al 0.75 Co 0.3 alloys were investigated. The experimental results of XRD and SEM showed that all alloys contained a pure CaCu 5 type hexagonal structure LaNi 4 Al phase. The cell volume increased in an order of annealed ​> ​melt-spun ​> ​as-cast, resulting in a lower hydrogen absorption/desorption plateau pressure and a more stable hydride phase. The hydrogen storage capacity of three alloys was almost the same. The slope factor of the annealed and melt-spun alloys is smaller than the as-cast alloy, indicating that heat-treatment process can make the alloys more uniform. For the cycle stability of the alloys, the hydrogen absorption rate of the annealed alloy and melt-spun alloy was much faster than that of the as-cast alloy after 500 cycles. The melt-spun alloy showed high pulverization resistance during hydrogen absorption/desorption, and exhibited an excellent cycling retention of 99% after 500 cycles, suggesting that melt-spinning process can enhance the cycle stability and improve the cycle life of the alloy. [Display omitted] • Hydrogen storage performance of as-cast, annealed, and melt-spun LaNi 3.95 Al 0.75 Co 0.3 alloy are investigated. • The annealing treatment and melt-spun process improve the uniformity of LaNi 3.95 Al 0.75 Co 0.3 alloy. • The annealing treatment and melt-spun process increase the hydrogen absorption rate before and after 500th cycling. • After 500 cycles, the MS alloy presents a better pulverization resistance with high hydrogen cycling retention. [ABSTRACT FROM AUTHOR]

In this study, we investigated the microstructures, hydrogen absorption kinetics, and surface oxides of a Ti0.2Zr0.2Nb0.2V0.2Cr0.17Fe0.03 high entropy alloy (HEA). The prepared HEA had a dual phase microstructure consisting of body-centered cubic (BCC) phase (32.2Ti-13.1Zr-30.3Nb-18.6 V-5.8Cr) and face-centered cubic (FCC) phase (11.3Ti-19.6Zr-13.2Nb-24.7 V-25.7Cr-5.5Fe). The HEA ingot absorbed hydrogen under a hydrogen pressure of 5 bar at room temperature without any thermal activation process. After hydrogenation, the FCC and BCC phases were transformed to a monohydride and a dihydride phase, respectively. To examine the hydrogen absorption behavior of each phase, two ingots having the same compositions as the BCC and the FCC phases were separately prepared. Though the BCC phase ingot did not react with hydrogen, the FCC phase ingot absorbed hydrogen, which could result from the formation of a highly reactive oxide layer on the FCC phase ingot. From the X-ray photoelectron spectroscopy results of the two ingots, although the BCC phase ingot contained Cr, no Cr was detected in the oxide layer. In contrast, the oxide layer on the FCC phase ingot displayed a high Cr concentration, and it seems that the reactivity of the oxide layer with hydrogen could be improved by the presence of Cr in the surface oxides. [ABSTRACT FROM AUTHOR]

In order to meet the demand of metal hydride–hydrogen compressors (MHHC) and their hydrogen compression materials for high-pressure hydrogen filling in a hydrogen energy field, four kinds of hydrogen storage alloys with low-grade heat source (5 and Ti/Zr base AB2 hydrogen storage alloys were prepared using a high-temperature melting method. The composition, structure, and hydrogenation/dehydrogenation plateau characteristics of the alloys were tested by an inductively coupled plasma mass spectrometer (ICP-MAS), X-ray diffractometer (XRD), and pressure–composition isothermal (PCT) tester. The median output pressures of the four-stage hydrogen storage alloys at 363 K were 8.90 MPa, 25.04 MPa, 42.97 MPa, and 84.73 MPa, respectively, which met the requirements of the 20 MPa, 35 MPa, and 70 MPa high-pressure hydrogen injections for the MHHCs. In fact, due to the tilted pressure plateau of the PCT curve, the synergy between the adjacent two alloys still needed to be adjusted.

In recent years, hydrogen has been attracting attention as a long-term energy storage that can absorb fluctuations of the output of variable renewable energy sources. While there are several hydrogen storage methods, hydrogen storage alloy is one of the most suitable methods for stationary hydrogen storage. Since hydrogen storage alloy’s characteristics of absorption and desorption heavily depends on operating temperature, temperature control is one of the critical issues in the design of the hydrogen storage alloy system. As a new method for controlling alloy’s temperature, the authors have developed the air heat exchanged hydrogen storage alloy system that is supplying an air temperature for hydrogen storage alloy. In this study, the year-round hydrogen balance and the heat input required for temperature control of this air heat exchanged hydrogen storage alloy system are simulated for an independent electric power utilization system using photovoltaic power generation with hydrogen energy storage system assuming arbitrary regions and electric power demand patterns in Japan. Based on the simulation results, the external heat input of the system was systematically evaluated, and the energy-saving performance of the alloy temperature control of the storage alloy system in each region and the feasibility of seasonal energy shift by the hydrogen storage system were evaluated. The results show that the air heat exchanged hydrogen storage alloy system is a highly energy-efficient system that can adjust the temperature using less energy than the heat of alloy chemical reaction heat regardless of the regional variation of temperature or type of electric demand pattern, although the amount of energy input varies depending on the region.

Metal hydrides can theoretically store H 2 at extremely low temperatures in anodic nickel-metal hydride batteries (Ni-MHBs). However, the evolution kinetics of H 2 was retarded at low temperatures and the H 2 -storing capacity of the battery was reduced. Annealing temperature was hypothesized to be the key to regulate the phase composition and therefore, improve the electrochemical kinetics and performance in cold operating conditions. A new-type of La 1.9 Y 4.1 Ni 20.8 Mn 0.2 Al H 2 -storage alloy was prepared and annealed at 1098, 1148, 1223 and 1323 K. At the annealing temperature of 1148 K, the alloy exhibited various crystalline structures and H 2 channel modifications, a high H 2 desorption plateau, resistance to oxidation/corrosion and favourable kinetic characteristics. All the measurements was performed at a temperature of 243 K, resulting in a maximum discharge specific capacity of 298.6 mAh g−1, low-temperature discharge rate of 80.5%, and high-rate dischargeability of 62.8% at a current density of up to 300 mA g−1. • The effect of annealing temperature on low performance of the alloy is clarified. • The 1148 K-annealed alloy shows the best kinetics performances at 243 K. • The annealed alloy shows maximum discharge capacity of 298.6 mAh g−1 at 243 K. [ABSTRACT FROM AUTHOR]

The hydrogen emission characteristics of a hydrogen storage alloy operating system employing the Zr 0. 9 Ti 0. 1 Cr 0. 6 Fe 1. 4 alloy were analyzed under different temperatures and loading conditions for application in a rehabilitation system for motion assistance for the aged and disabled. After activating 8.56 g of a Zr 0. 9 Ti 0. 1 Cr 0. 6 Fe 1. 4 alloy under a 5.5 MPa hydrogen atmosphere, operation tests were conducted in the temperature range of 25–80∘C under the loading conditions of 5–45 kg. The lightest load of 5 kg was lifted by 150 mm when the system was heated from the initial test temperature of 25–80∘C and a 40 kg load was lifted by 12.5 mm at 80∘C, while a 45 kg load could not be lifted under any of the temperature conditions. The hydrogen storage alloy operating system developed in this study is expected to be useful in motion assistance for the socially underprivileged, as a rehabilitation tool for the hand, wrist, and elbow, as supplementary equipment, and in rehabilitation systems for daily life. [ABSTRACT FROM AUTHOR]

The catalytic effect of rare-earth hydrogen storage alloy is investigated for dehydrogenation of alane, which shows a significantly reduced onset dehydrogenation temperature (86 °C) with a high-purity hydrogen storage capacity of 8.6 wt% and an improved dehydrogenation kinetics property (6.3 wt% of dehydrogenation at 100 °C within 60 min). The related mechanism is that the catalytic sites on the surface of the hydrogen storage alloy and the hydrogen storage sites of the entire bulk phase of the hydrogen storage reduce the dehydrogenation temperature of AlH 3 and improve the dehydrogenation kinetic performance of AlH 3. This facile and effective method significantly improves the dehydrogenation of AlH 3 and provides a promising strategy for metal hydride modification. [Display omitted] • The dehydrogenation performance of the LaNi 5 -doped AlH 3 was investigated. • The onset dehydrogenation temperature of the composite decreased to 86 °C. • The composite released 6.3 wt% of hydrogen within 60 min at 100 °C. • The mechanism was provided according to the characterization. [ABSTRACT FROM AUTHOR]

To investigate the influence of thermal effects on the hydrogen desorption performance of the metal hydride hydrogen storage system, a two-dimensional numerical model was established based on a small metal hydride hydrogen storage tank, and its accuracy was verified by the temperature variations in the reaction zone of the hydrogen storage tank during hydrogen desorption. In addition, the influence of the heat transfer medium on the heat and mass transfer performance of the hydrogen desorption reaction was analyzed. An external heat transfer bath was added to simulate the thermal effect of the model during the hydrogen desorption reaction. The temperature and type of heat transfer medium in the heat transfer bath were modified, and the temperature and reaction fraction variations in each zone of the hydrogen storage model were analyzed. The results showed that under heat transfer water flow, the reaction rate in the center region of the hydrogen storage tank was gradually lower than that in the wall region. The higher the temperature of water flow, the shorter the total time required for the hydrogen desorption reaction and the shortening amplitude is reduced. The variations in the temperature and hydrogen storage capacity during hydrogen desorption were similar, with water and oil as the heat transfer medium, under the same flow rate and heat transfer temperature, however, the heat transfer time and hydrogen desorption time of water were about 10% and 5% shorter than that of oil, respectively. When the air was used as the heat transfer medium, the heat transfer rate of the air convection in the channel was lower than the heat transfer rate of the tank wall, reducing the temperature difference between the air and alloy on both sides of the wall, decreasing heat transfer efficiency, and significantly prolonging the time required for hydrogen desorption.

With the continuous expansion of the high‐purity hydrogen application range, the performance degradation of hydrogen storage alloy (HSA) caused by impurities has attracted widespread attention in producing pure hydrogen from biomass. In this study, the lanthanum‐rich mischmetal alloy's purification ability on hydrogen sulfide impurities and cycling performance were studied. The hydrogen with different concentrations of hydrogen sulfide was used to investigate the purification performance, which assumes the gas derived from biomass. Besides, a cycling experiment was designed to analyze cycling performance. The results show that the HSA could remove high concentrations of hydrogen sulfide entirely. It was also found that impurities of 1 ppm hydrogen sulfide had little effect on the HSA. With hydrogen sulfide concentrations of 100 ppm, the hydrogen storage capacity, absorption rate, and release rate were reduced, but they became a stable state from the second cycle. The performance degradation mechanism was analyzed by Energy Dispersive X‐Ray Spectroscopy (EDS) and X‐ray Photoelectron Spectroscopy (XPS​). [ABSTRACT FROM AUTHOR]

In this study, demonstration of a one-stage metal hydride hydrogen compressor (MH compressor) by using a BCC alloy was performed. It was estimated that V 40 Ti 22 Cr 38 could compress approximately 1.6 wt% of hydrogen from 1.0 to 10 MPa in 20–140 °C temperature range from equilibrium theory via pressure-composition-isotherm measurements. For demonstration of an actual MH compressor, a kg-scale experimental system was set up; V 40 Ti 22 Cr 38 (1.4 kg) was introduced into a 1-inch cylindrical vessel with a heat-medium flow tube outside. As a result, 1.0 MPa of hydrogen can be compressed into the hydrogen cylinder at >10 MPa by hydrogen absorption at 10 °C and desorption at 160 °C for 30 min each (1 cycle/h) to achieve a compression rate of 0.23 Nm3/h and indicate the potential of the practical MH compressors by using BCC alloy. • Thermodynamics of V 40 Ti 22 Cr 38 as MH compressor with H 2 ab/desorption was evaluated. • V 40 Ti 22 Cr 38 can compress 1.6 wt% of hydrogen from 1.0 to 10 MPa between 20 and 140 °C. • Demonstration of MH compressor with 1.4 kg of V 40 Ti 22 Cr 38 was performed. • Compression from 1.0 to >10 MPa at 0.23 Nm3/h was achieved between 10 and 160 °C. [ABSTRACT FROM AUTHOR]

Rare earth–Mg–Ni-based alloys with superlattice structures are novel anode materials for nickel metal hydride batteries, wherein A 5 B 19 -type alloys have been regarded as the replacement of the current commercialized A 2 B 7 -type alloys due to the superior discharge ability at high rates and cycling stability. However, it is still a challenge to further improve the hydrogen storage properties of the A 5 B 19 -type alloys in a low-cost approach. Herein, we select low-cost Mn and Fe elements to substitute Ni to further reduce the cost of an A 5 B 19 -type La 0.72 Y 0.13 Mg 0.15 Ni 3.70 Al 0.15 alloy and focus on their effects on the alloy's structure and hydrogen storage properties. Results show that the La 0.72 Y 0.13 Mg 0.15 Ni 3.65 Al 0.15 Fe 0.05 alloy features increased intrinsic gas-solid hydrogen storage ability of 1.44 wt% and hydrogen absorption enthalpy change of −22.9 kJ mol–1, which have been altered by 0.21 wt% and 7.3 kJ mol–1 in contrast to the La 0.72 Y 0.13 Mg 0.15 Ni 3.70 Al 0.15 alloy, respectively. Furthermore, the Fe substitution benefits capacity retention during electrochemical cycling compared to Mn, which maintains 87.5% and 62.4% after cycling 100 and 500 times. The Mn substitution results in superior rate capability compared to the alloy containing Fe. The work provides guidance for designing hydrogen storage alloys with superlattice structures to improve the electrochemical performance. • Pr 5 Co 19 -type alloys with low cost Mn and Fe substituted Ni are obtained. • Effect of Mn and Fe substituted Ni on hydrogen storage properties is clarified. • Fe substituted Ni increases hydrogen storage capacity from 1.23 wt% to 1.44 wt%. • Fe substitution rises the capacity retention from 52.6% to 62.4% at the 500th cycle. • Mn substitution optimizes the discharge ability at high rates. [ABSTRACT FROM AUTHOR]

The partially hydrogenated microstructure of an AB-type Ti–Fe–V–Ce hydrogen storage alloy was investigated using scanning electron microscopy (SEM) with electron backscatter diffraction (EBSD). For the first time, the formation of the orthorhombic β-TiFeH phase was directly observed by using SEM-EBSD. Lamellar structures consisting of TiFeH and body-centered cubic TiFe phases with a (100) TiFeH ∥ (100) TiFe habit-plane pair were observed. Pole figure analysis was performed to confirm the orientation relationship between the TiFeH and TiFe phases to be [011](100) TiFeH ∥ [010](100) TiFe. The formation of TiFeH was characterized by simple lattice expansion with a short-range arrangement of H atoms and surface relief. In addition, unidirectional microcracks along the (100) TiFe planes were observed, presumably owing to the dehydrogenation of the TiFeH phase. [Display omitted] • Microstructure of partially hydrogenated TiFeVCe alloy was observed by SEM-EBSD. • Lamellar structures consisting of orthorhombic TiFeH and BCC TiFe phases were identified. • An orientation relationship between TiFeH and TiFe phases was suggested for the first time. • Unidirectional cracks in a TiFe matrix seem to be associated with dehydrogenation of TiFeH. [ABSTRACT FROM AUTHOR]

Hydrogen storage properties and reactivity for hydrogenation of acetylene in a series of CeNi5-xGax (x = 0, 0.5, 0.75, 1, 1.25, 1.5) alloys and Mg2Ni were determined and compared. The structure of CeNi5 (CaCu5 type) was maintained up to CeNi3.5Ga1.5 when Ni was replaced by Ga. The replacement facilitated hydrogenation absorption by creating larger interstitial spaces through expansion of the lattice, allowing CeNi4.25Ga0.75 to absorb the greatest proportion of hydrogen atoms among the alloys under the same conditions. The results showed that the absorbed hydrogen in CeNi3.75Ga1.25 improved reactivity. In contrast, Mg2Ni formed a hydride upon hydrogenation of acetylene and thus possessed much lower activity. The difference of the activity of absorbed hydrogen between CeNi5-xGax and Mg2Ni was confirmed from transient response tests under reaction gases alternately containing He and H2.

This paper discusses the effect of AB 2 (Ti(Cr, Fe) 2) phase on the hydrogenation properties of a Ti–Fe–Cr alloy system. Five Ti–Fe–Cr based alloys were fabricated by varying the Cr content. The microstructural analysis results revealed that the fraction of the Ti(Cr, Fe) 2 phase increased with the increasing Cr content. The first hydrogenation test results indicated that all the alloys could absorb a significant amount of hydrogen at room temperature (30 °C) without a separate activation process. This behavior improved when the Ti(Cr, Fe) 2 phase existed in the AB phase; the kinetics of the first hydrogenation tended to increase with the fraction of Ti(Cr, Fe) 2 phase. The enhancement in the first hydrogenation kinetics of the Ti–Fe–Cr based alloys was attributed to the synergetic effect of the interface between the AB and Ti(Cr, Fe) 2 phases and the inherent fast hydrogenation of the Ti(Cr, Fe) 2 phase. However, the total hydrogen storage capacity decreased when the fraction of Ti(Cr, Fe) 2 phase increased. • AB single phase with Cr is hydrogenated at 30 °C without activation heat treatment. • Hydrogenation kinetics improves as the fraction of the AB 2 phase increases. • The interface between the AB and AB 2 phases also improves hydrogenation kinetics. [ABSTRACT FROM AUTHOR]