Magnesium-based Hydrogen Storage Alloys Research Articles

Hydrogen storage properties of MgH2 + Mg2NiH4–Co/C ternary nanocomposite

The application of ternary nanocomposite synergetic catalysis has proven to be an effective modification strategy for enhancing MgH2 hydrogen storage performance. The ternary magnesium-based hydrogen storage alloy, composed of MgH2+Mg2NiH4–Co/C, is successfully prepared and characterized. Through the optimized preparation process and the optimal ratio, it is observed that the catalyst Mg2NiH4–Co/C significantly reduces the reaction activation energy, resulting in a the initial hydrogen desorption temperature is approximately 60 °C lower than that of pure MgH2. The enhanced hydrogen storage properties are attributed to the synergistic catalytic effect of carbon (C) combined with the formation of Mg2Ni and Mg2Co facilitated by Ni and Co elements. Furthermore, the reversible phase transitions of Mg2Co/Mg2CoH5 and Mg2Ni/Mg2NiH4 serve as "hydrogen pumps" further aiding in hydrogen storage. This study extends the investigation of the synergistic catalytic effect of ternary nanocomposites to enhance the hydrogen storage performance of alloys.

Magnesium-Based Hydrogen Storage Alloys: Advances, Strategies, and Future Outlook for Clean Energy Applications.

Magnesium-based hydrogen storage alloys have attracted significant attention as promising materials for solid-state hydrogen storage due to their high hydrogen storage capacity, abundant reserves, low cost, and reversibility. However, the widespread application of these alloys is hindered by several challenges, including slow hydrogen absorption/desorption kinetics, high thermodynamic stability of magnesium hydride, and limited cycle life. This comprehensive review provides an in-depth overview of the recent advances in magnesium-based hydrogen storage alloys, covering their fundamental properties, synthesis methods, modification strategies, hydrogen storage performance, and potential applications. The review discusses the thermodynamic and kinetic properties of magnesium-based alloys, as well as the effects of alloying, nanostructuring, and surface modification on their hydrogen storage performance. The hydrogen absorption/desorption properties of different magnesium-based alloy systems are compared, and the influence of various modification strategies on these properties is examined. The review also explores the potential applications of magnesium-based hydrogen storage alloys, including mobile and stationary hydrogen storage, rechargeable batteries, and thermal energy storage. Finally, the current challenges and future research directions in this field are discussed, highlighting the need for fundamental understanding of hydrogen storage mechanisms, development of novel alloy compositions, optimization of modification strategies, integration of magnesium-based alloys into hydrogen storage systems, and collaboration between academia and industry.

Thermal Effect and Heat Control Strategy of Magnesium-Based Hydrogen Storage Alloy System for Lightweight Automobile

The magnesium-based hydrogen storage alloy has a very good prospect to be applied in the market of lightweight automobile due to its merits of light weight, excellent discharge performance, long cycle life, and large hydrogen storage capacity. However, existing studies on magnesium-based hydrogen storage alloy have a series of shortcomings such as the insufficient works in terms of model reasonability analysis, heat transfer behavior analysis, heat control scheme design, and comparative experiment analysis, etc. In view of these problems, this paper studied the thermal effect and heat control strategy of the Mg-based Hydrogen Storage Alloy (MHSA) system for lightweight automobile. At first, this paper constructed numerical models for the fluid-solid coupled heat exchange region and the heat conduction region in the system; then, based on the law of energy conservation, a heat transfer behavior model of the MHSA system was established and used to analyze the thermal effect of the system. After that, according to the driving process of hydrogen fuel cell electric vehicle, the working process of the MHSA system was further analyzed to study the heat control process. Next, this paper proposed a new idea for the heat control of the MHSA system, gave a few tips for the simulations, and presented the flow of the heat control scheme of the system. At last, the experimental results were given and analyzed.

Excellent destabilization effect and ideal desorption temperature in the hydride Mg2FeH6 substituted with yttrium; a first principles study

We investigated some properties of the hydride Mg2FeH6 substituted with yttrium by a first principles calculation. Some experimental results showed that 4d transition metal, yttrium serves as a good catalyst for magnesium based hydrogen storage alloys, but there are a few theoretical studies about magnesium based hydrides substituted with it. Mg2FeH6 is regarded as a cheaper material than pure MgH2, while it is crystalized into Fm3m structure (space group 225). Although it has high hydrogen storage capacity, many investigations have not been devoted to it due to its extremely high thermodynamic stability. The yttrium substituted Mg2FeH6 exhibits very low energy of formation, and its desorption temperature, 75 °C is very suitable for practical hydrogen storage applications. Our results showed that Mg2FeH6 is destabilized effectively by yttrium substitution and introducing vacancy defects has additive effect to the improvement of dehydrogenation performance.

Enhanced electrochemical kinetics of magnesium-based hydrogen storage alloy by mechanical milling with graphite

Magnesium nickel alloy (Mg2Ni) which used as the negative electrode material in the nickel-metal hydride (Ni/MH) secondary battery is modified by graphite via mechanical milling. The effects of graphite on the Mg2Ni are systematically investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and a series of electrochemical tests. The results show that the cycle stability of the Mg2Ni alloy is improved with the addition of 10 wt.% graphite and the discharge capacity at the 20th cycle increase from 116.9 mA g−1 to 178.5 mA g−1. The Tafel polarization test indicates better corrosion resistance of the Mg2Ni/graphite composite. Meanwhile, the results of electrochemical tests indicate that both the charge-transfer reaction rate on the surface of the alloy and the hydrogen diffusion rate inside the bulk of alloy are boosted with the introduction of graphite.

Hydrogen storage properties and mechanisms of magnesium based alloys with mesoporous surface

A new kind of magnesium based hydrogen storage alloy with highly developed surface (HDS) was prepared using the technique of mechanical alloying followed by alkali washing in this paper. The phase composition, morphology, hydrogen storage properties and mechanisms of the alloy thus prepared, named HDS Mg-Ni, were further investigated by multiple methods including X-ray diffraction, scanning electron microscope, Sieverts volumetric method and differential scanning calorimeter. The specific surface area, average pore size and pore volume of the alloy are 50.95 m2 g−1, 36.2 nm and 0.34 cc g−1, respectively. Also, it was discovered that the HDS Mg-Ni powder takes in about 0.65 wt.% of hydrogen even at a low temperature of 323 K, at which the conventional Mg and Mg2Ni materials could not react with H2. It suggests that the highly developed surface remarkably improves the hydrogen storage properties at low temperatures. Besides, the synergistic effects between the HDS Mg-Ni powder and activated carbon(AC) on the improvement of low-temperature behaviors were discussed. The results showed that the addition of AC further improves the hydrogen capacity and absorption kinetics due to the increased specific surface area, providing easier and more paths for the diffusion of hydrogen into the alloy powder.

Method of Preparation Magnesium-Based Alloy Film and its Hydrogen Storage Performance

The problem of hydrogen storage is clearly connected to the necessity of development of reliable and effective methods of hydrogen compression. Efforts have been devoted to these materials to decrease their desorption temperature, enhance the kinetics and cycle life. Film for preparing hydrogen storage materials is a new method developed in recent years. The advantagesof thin film metal hydrides is obvious. For example, thin films provide large surface area, fast charging discharging rate for hydrogen. Mg films and Multilayered Mg films with rare earths, light elements and transition metals have also been studied by many researches. Preparation of Magnesium-based hydrogen storage alloy film and its hydrogen storage performance are summaried in this paper.

Development of the high performance magnesium based hydrogen storage alloy

Series of MgNi type alloys with Ti, Al, Zr, Pd and Co additive elements were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. Systematical alloy designing indicated that Mg 0.80Ti 0.15Al 0.05Zr 0.05Ni 0.95 alloy has the best electrode performance. The atomic fractions in this alloy were believed to be optimum to get the reasonable amount of hydrogen storage with the improved cyclic stability. Titanium was estimated to enter into Mg(OH) 2 layer during the discharging process and make this barrier layer more penetrable by elemental hydrogen. Al and/or Al-oxides were predicted to dissolve selectively throughout the barrier hydroxide layer and thus reduce the stability of this layer. The main contribution of Zr was estimated to arise from its large atomic size that Zr atoms can create extra sites for the elemental hydrogen in the alloy structure. As the alloy charge transfer resistances decreased, the alloy retention rates increased. Improvement in the alloy capacity retaining rate was also closely related with the hydrogen diffusion coefficients in the alloy.

Magnesium-nickel hydrogen storage alloys prepared by hydriding combustion synthesis followed by mechanical milling

Recent progress is reviewed in the preparation of highly active magnesium-based hydrogen storage alloys by the combined process of Hydriding Combustion Synthesis (HCS) and Mechanical Milling (MM). The structural transformation of the alloys during MM determined by means of X-ray Diffraction (XRD) and the hydrogen storage properties of the alloys measured by means of Pressure-Concentration-Temperature (PCT) are reported. The HCS alloy of Mg98Ni2 after MM showed the highest hydrogen capacity of 5.60 wt.% at 373 K within 100 s and the dehydriding onset decreased from about 640 K of the HCS product to 480 K of the HCS + MM product. Besides, the absorption capacity at 373 K in 30 s increased from 3.85 wt.% for the HCS + MM product of Mg95Ni5 without Nb2O5 to 5.09 wt.% for that with 1 at.% Nb2O5. The results demonstrated that the method of HCS + MM has potential in the preparation of magnesium-based materials for vehicular application.

Electrochemical properties of magnesium-based hydrogen storage alloys improved by transition metal boride and silicide additives

Transition metal borides and silicides prepared by mechanical alloying (MA) and chemical reduction methods (CR) were introduced to improve the corrosion resistance of magnesium-based hydrogen storage alloys. The additive of FeB prepared by MA can remarkably enhance the discharge capacity and cycling stability which has initial discharge capacity of 355.9 mA h g −1 and keeps 224 mA h g −1 after 100 cycles, and the exchange density I 0 of MgNi–NiB(CR) electrodes is 344.80 mA g −1 but MgNi is only 67.6 mA g −1 which leads to the better rate capability of the composite alloys. The results of SEM characterization, cyclic charge–discharge tests, potentiodynamic polarization, linear polarization and AC impedance experiment show that the corrosion inhibition property of MgNi in alkaline is improved by transition metal boride and silicide additives.

Synthesis mechanism and properties of Mg–Mg2Ni composite hydrogen storage alloy produced by hydriding combustion synthesis

Hydriding combustion synthesis (HCS) has been regarded as an innovative process to produce magnesium based hydrogen storage alloys. In the present paper, a Mg–Mg2Ni composite hydrogen storage alloy was prepared by the HCS process under moderate conditions. Phase composition, synthesis mechanism and hydrogen storage properties were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure composition temperature (PCT). The results indicated that the HCS product was composed mainly of MgH2, Mg2NiH4 and Mg2NiH0·3. A gas–solid reaction mechanism played an important role in the HCS process. The hydriding activity of the as synthesised product was very high so that it absorbed 4·61 mass% hydrogen in the first hydriding process without any activation treatment and the maximum hydrogen storage capacity achieved was 5·24 mass%. Moreover, the hydriding rate was excellent. For example, it could absorb >3·20 and 4·05 mass% hydrogen within 4 min in the first and forth hydriding/dehydriding cycle respectively. The relationships between the plateau pressure and temperature were: lgP(0·1 MPa)=−4250·5/T+7·9635 (hydriding), lgP(0·1 MPa)=−4125·4/T+7·6502 (dehydriding) for the lower plateau, and lgP(0·1 MPa)=−2894·6/T+5·9656 (hydriding), lgP(0·1 MPa)=−3855·9/T+7·3435 (dehydriding) for the higher plateau.

Structure and Properties of Magnesium-Based Hydrogen Storage Alloys

Hydrogen is the promising pollutant-free fuel of the near future. For various hydrogen applications, suitable storage systems have to be developed. One of the safe ways is the reversible storage of hydrogen in the form of light metal (lithium or magnesium) hydrides. MgH2 magnesium hydride shows very high storage capacity (approx. 7 wt. %), but its problem is high thermodynamic stability. Therefore, high temperature (over 400°C) is necessary for MgH2 to decompose producing hydrogen. The solution of this problem can be the utilization of the complex magnesium hydrides containing nickel, copper or other transition metals. In this work, the microstructure and hydrogen storage properties of the various magnesium alloys (Mg-Ni, Mg-Zn, Mg-Cu and Mg-Cu-Al) are described. The aim was to find suitable hydrogen storage system with good storage capacity and sufficient rate of formation and decomposition of hydrides. Microstructure, chemical and phase composition of the alloys were determined by the light and scanning electron microscopy, EDS and XRD. Hydrogen saturation was carried out by cathodic polarization in the alkaline solution. Hydrogen content in the material was estimated by XRD from the shift of the diffraction lines of present phases.

Effect of surface oxidation on the hydriding and dehydriding of Mg2Ni alloy produced by hydriding combustion synthesis

Hydriding combustion synthesis (HCS) has been regarded as an innovative process for the preparation of high active magnesium-based hydrogen storage alloys. For the purpose of understanding the interrelation of the unique hydrogen storage properties and the surface characteristics of the HCS product, the samples of Mg2Ni alloy/hydride with and without exposure to air were prepared from the HCS product of Mg2NiH4. The hydriding and dehydriding properties were compared and the surface compositions were analyzed by means of X-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES). It was shown that the air exposure considerably decreases the hydriding activity of Mg2Ni. Absorbing of 3.0 wt.% of hydrogen under the conditions of 603 K and 3.0 MPa after the air exposure takes 1500 s, which is six times longer than for the unexposed alloy. The hydrogen desorption of the hydride are also impeded by the air-exposure, which results in the increase of dehydriding temperature from 450 K to 540 K. XPS and AES analyses indicated that Mg segregates and exists in the form of hydroxide on the surface of the air-exposed sample, which is responsible for the degradation of the hydriding and dehydriding properties. It was confirmed that the fresh surfaces generated during the dehydriding process of the as-synthesized hydride product contributes to the high activity of the HCS product in the first cycle of the hydriding determination.

Hydriding characteristics of [formula omitted] prepared by mechanical milling of the product of hydriding combustion synthesis

Hydriding combustion synthesis (HCS) and mechanical milling (MM) are both well-known methods for production of magnesium-based hydrogen storage alloys. The former can produce high active hydride by a simple process, and the latter can synthesis various metastable hydrogen storage materials such as nanocrystalline, amorphous and extended solid solutions phases with excellent hydrogen sorption properties. In the present study, HCS and MM were combined, aiming to decrease sorption temperature for Mg 2 Ni . The high active Mg 2 NiH 4 , synthesized by HCS, was mechanically milled for 0.5, 6, 40 and 80 h with 5 wt% of graphite under argon atmosphere. The effect of the milling process on the morphology and crystal structural of Mg 2 NiH 4 were investigated by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The hydrogen storage properties were examined by a Sieverts type apparatus. The nanocrystalline Mg 2 NiH 4 milled for 40 h has the best sorption kinetics, which can absorb 2.4 wt% hydrogen at 303 K within 100 s in the first cycle. Several reasons are considered to explain the improvement in hydriding kinetics.

Mechanism of the high activity of [formula omitted] produced by hydriding combustion synthesis based on the analysis of phase composition, particle characteristic and grain size

Hydriding combustion synthesis (HCS) is well known as an innovative processing to produce magnesium-based hydrogen storage alloys, and the product Mg 2 NiH 4 , as synthesized, possesses excellent activity without any activation process. In this paper, the mechanism of the high activity of Mg 2 NiH 4 produced by HCS emphasized mainly on microstructure is discussed based on the analysis of phase composition, particle characteristic, crystal grain size and hydriding reaction by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure composition temperature (PCT). It is indicated that pure composition, loose and porous morphology, a large number of microfissures and small grain size are the intrinsic reasons for the high activity of Mg 2 NiH 4 produced by the process of HCS. The result is very helpful for us to control and improve the hydrogen storage properties of HCS product based on the microstructure further.

Intermediate products during the hydriding combustion synthesis of Mg2NiH4

Magnesium-based hydrogen storage alloy is one of the most attractive mediums, as a hydrogen storage tank for a fuel cell. However, the practical application is still limited because of its poor hydriding and dehydriding kinetics and relatively high reaction temperature. To overcome such problems, the hydriding combustion synthesis (HCS) was established in 1997, as one of the most effective production methods. The understanding of these microstructures is strongly related to the improvement of the reaction property. However, up to now, little efforts have been made as to the microstructures of final product and intermediate products. Therefore, the purpose of this paper is to prepare intermediate products at several stages during the HCS of Mg2NiH4, and to study their microstructures by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) for the first time. Interestingly, the results revealed that: (1) the intermediate product generated at lower temperature than 800K caused the unique particle morphology of final product of Mg2NiH4; (2) severe thermal corrosion, cotton-like material, was also observed on the surface of intermediate products at 705K, which became enhanced with increasing temperature; (3) after the dehydriding reaction of MgH2 at 750K, a large amount of the Mg2Ni phase existed in the intermediate product; (4) hydrogen present during the heating period makes the product to have smaller size. Further investigation on the mechanism of the gas–solid reaction deserves attention, because lowering of the synthesis temperature by as much as 100° is very attractive and significant for industrializing this process.

Hydriding behavior of magnesium-based hydrogen storage alloy modified by mechanical ball-milling

The structure and effects of mechanical ball-milling on hydriding behavior of LaMg 11Ni were studied. Structures of the alloys and the hydrides were determined by X-ray diffraction (XRD). By measuring hydrogen-storage capacity and hydrogen absorption kinetics of the material, hydriding behaviors of LaMg 11Ni prepared by different mechanical ball-milling time were compared. In this work, there is a 20% increase of hydrogen absorption capacity after 20 h milling, and the kinetics of hydrogen absorption was markedly improved. Nevertheless, further milling does not make good. When the milling time is too long, the situation will be deteriorated. For example, after 120 h milling, the material has very poor hydrogen-storage capacity and is difficult to activate. Explanation of the phenomenon is proposed on the basis of microstructure analysis.

Synthesis and characterization of nanocrystalline magnesium-based hydrogen storage alloy electrode materials

Nanocrystalline Mg 2Ni-type hydrogen storage alloys were synthesized using the powder metallurgical technique and mechanical milling with nickel powder under an argon atmosphere. Changes in phase structures with mechanical treatment were studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM) with selected-area electron diffraction (SED). As expected, the phase structure of the synthesized material changes with milling time, from crystallite to nanocrystallite and amorphous. The electrochemical behavior of these materials with various phase structures in alkaline media, such as electrochemical capacity, high rate dischargeability and cycle life, were investigated and compared. The Mg 2Ni type alloy electrode with nanocrystalline structure showed superior discharge characteristics compared with those with crystallite and amorphous structure. It was also found that the electrochemical hydriding/dehydriding behavior of Mg 2Ni-type hydrogen storage alloys has been further improved by a new approach of particle inlay developed in this study. The analysis of the electrochemical impedance spectroscopy (EIS) reveals that for the nanocrystalline Mg 2Ni type alloy electrode, both the charge transfer resistance of the hydrogen redox reaction on the surface and the diffusion resistance of the hydrogen atom in the bulk alloy were greatly reduced by mechanical treatment with nickel addition. The rate-determining step of the electrode reaction changed with the electrode nanocrystalline structure.

Discharge behaviour of Mg 2Ni-type hydrogen-storage alloy electrodes in 6 M KOH solution by electrochemical impedance spectroscopy

The discharge behaviour of Mg 2Ni-type hydrogen-storage alloy electrodes in 6 M KOH is investigated by a.c. impedance at room temperature. Comparative measurements are also performed on an LaNi 5 electrode. The rate-determining step of the discharge process for the magnesium-based hydrogen-storage alloy electrode is dependent on the alloy composition and depth-of-discharge. The unmodified Mg 2Ni has a high charge-transfer and mass-transfer resistance compared with LaNi 5. Additions of yttrium and aluminium in Mg 2Ni reduced considerably both the resistances and, thereby, produce a remarkable improvement in discharge capacity and rate-dischargeability.

Effects of yttrium additions on the electrode performance of magnesium-based hydrogen storage alloys

The effects of yttrium additions on the electrode performance of Mg 1.9Al 0.1Ni 1− x Y x alloys have been investigated. The addition of yttrium substantially increases the discharge capacity of the electrodes and effectively improves the electrode high-rate dischargeability. For Mg 1.9Al 0.1Ni 0.7Y 0.3 alloy electrodes, a discharge capacity of 170 mAh g −1 at room temperature has been achieved. On the other hand, the addition of yttrium results in a negative effect on the cycling stability for the Mg 2Ni-type alloy electrodes.