Ni Hydrogen Storage Alloys Research Articles

Retracted: Preparation of Mg2Ni Hydrogen Storage Alloy Materials by High Energy Ball Milling

Retracted: Preparation of Mg₂Ni Hydrogen Storage Alloy Materials by High Energy Ball Milling

Synthesis of La–Mg–Ni@Ag composite catalyst and its catalytic performance for borohydride

Direct borohydride fuel cells (DBFC) have a promising future as a new type of fuel cell with a high energy conversion rate and a green profile, the performance of which is mainly determined by the anode catalyst. Precious metals as anode catalysts have better catalytic ability but are expensive, limiting their application. Hydrogen storage alloys as anode catalysts can inhibit hydrolysis and enhance the conversion efficiency, but have poor catalytic ability. On this basis, Ag modified La–Mg–Ni hydrogen storage alloy catalyst (La–Mg–Ni@Ag) was synthesized by photo-deposition method in this study. The microstructures and surface morphologies of Ag, La–Mg–Ni alloy and La–Mg–Ni@Ag composite alloy were investigated in detail by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Their catalytic and electrochemical properties towards BH4− were evaluated by cyclic voltammetry (CV) and chronoamperometry (CA). The results show that the La–Mg–Ni@Ag composite catalyst is composed of Ag and La–Mg–Ni alloy phase structure, and La–Mg–Ni alloy particles are closely covered by tiny particles of Ag. In addition, the La–Mg–Ni@Ag composite catalyst has better catalytic activity and stability than those of La–Mg–Ni hydrogen storage alloy catalyst, with an increase in peak oxidation current density of about 50% and an increase in the number of transferred electrons of about 3.

Phase forming law and electrochemical properties of A2B7-type La–Y–Ni-based hydrogen storage alloys with different La/Y ratios

The effects of different proportions of La and Y elements in the A-side on the structure and properties of A2B7-type La–Y–Ni hydrogen storage alloys were investigated. The (La,Y)2Ni7 hydrogen storage alloys with different La/Y ratios were prepared by sintering the Y2Ni4 precursor and different AB5-type precursors at 1298 K for 5 h and subsequently annealed for 20 h at 1248 K. All the alloys only contain Ce2Ni7 (2H-type) and Gd2Co7 (3R-type) phases with different mass ratios. As the La/Y ratio decreases, the cell volume of the two phases declines and the corresponding plateau pressure gradually increases. As the proportion of Y in the alloy increases, the hydrogen storage capacity increases gradually from 1.309 wt% (La/Y = 1/1) to 1.713 wt% (La/Y = 1/5) and the high-rate discharge (HRD1500) ability of the alloy electrodes increases gradually from 62.7% (La/Y = 1/1) to 88.6% (La/Y = 1/5). The hydrogen diffusion rate in the bulk of the alloy is the controlling step of hydriding/dehydriding kinetics. The Y element can effectively inhibit the hydrogen-induced amorphous (HIA) of La–Y–Ni alloys, but the poor stability of the Y element in alkaline KOH aqueous solution leads to a decrease in the electrochemical cyclic stability with increasing Y content.

Effect of element substitution and surface treatment on low temperature properties of AB3.42-type La–Y–Ni based hydrogen storage alloy

The low-temperature performance (LTP) of AB3.42-type La–Y–Ni hydrogen storage alloy was studied by methods of element substitution and surface treatment. The effect of Mn-additive on LTP of La1·3Ce0·5Y4·2Ni19.5-xMnxAl (x = 0, 0.2, 0.5) was systematically investigated. Electrochemical studies showed that Mn-additive deteriorated the LTP of the alloy by reducing platform pressure, deteriorating kinetic performance and forming more oxides on the alloy surface. RE-substitution and hot alkali-ultrasonic treatment of La1.3RE0.5Y4·2Ni19·5Al (RE = Ce, Sm, Nd) alloys were applied to further optimize the LTP. The maximum discharge capacity and capacity retention at the 100th cycle of La1·3Ce0·5Y4·2Ni19·5Al alloy were 252.1 mA h/g and 87.1% at 243 K, respectively. Furthermore, the LTP of RE-substitution alloys at 243 K was conspicuously improved by surface treatment, which were raised from 214.7 mA h/g to 301.1 mA h/g by Sm-substitute, from 220.9 mA h/g to 303.9 mA h/g by Nd-substitute and from 252.1 mA h/g to 254.8 mA h/g by Ce-substitute.

Phase evolution, thermodynamics and kinetics property of transition metal (TM = Zr, Ti, V) catalyzed Mg–Ce–Y–Ni hydrogen storage alloys

To improve hydrogen storage property of Mg-based alloy, the Mg–Ce–Y–Ni + 10 wt % M (M = Zr, Ti, V) composites were prepared by the combination of alloying and ball-milling, and their microstructure, phase evolution, as well as hydrogen storage thermodynamic and kinetic properties, were investigated by XRD, PCT, and DSC methods. The result shows that the hydrogenated samples are composed of MgH2, Mg2NiH4 and corresponding ZrH2, TiH2 and VH1.9 phases. In comparison, the |ΔH| value of M = Ti sample is larger than that of M = Zr and M = V samples, and the M = Ti sample has the highest the peak temperatures and lowest plateau pressure, which indicates that Zr and V elements are more efficient to reduce the thermodynamic stability of RE-Mg-Ni hydrogen storage alloys. Besides, the DSC curve of the M = V sample has another endothermic peak which corresponds to the decomposition reaction between VH1.9 and VH0.8, which has a contribution to desorption kinetic property for the M = V sample. The apparent activation energies (Ede) show an increasing trend in the following order: M = Zr (87.7 kJ/mol) < M = V (89.1 kJ/mol) < M = Ti (99.3 kJ/mol).

Structure and electrochemical hydrogen storage characteristics of nanocrystalline and amorphous MgNi-type alloy synthesized by mechanical milling

Both element substitution and surface modification were utilized to enhance the electrochemical performances of Mg–Ni-based alloys. Nanocrystalline and amorphous Mg1−xCexNi0.9Al0.1 (x = 0–0.08) + 50 wt.% Ni hydrogen storage alloys were synthesized through mechanical milling. The sample alloys show excellent activation property and have good electrochemical hydrogenation and dehydrogenation property at normal temperature. The discharge capacity has a peak value with Ce content varying which is 461.6 mAh/g for 10-h milled alloy, while that of Ce0.04 alloy augments from 352.6 to 536.9 mAh/g with milling time extending from 5 to 30 h. Cycle stability is conspicuously improved with Ce content and milling duration augment. To be specific, when cycle number is fixed at 100, the capacity retention rate augments from 41% to 72% after Ce dosage rising from 0 to 0.08 for the 10-h milled alloy and from 58% to 76% after milling duration extending from 5 to 30 h for Ce0.06 alloy. Additionally, the electrochemical kinetics of the alloys own peak values with Ce proportion varying; however, they always rise with milling duration extending.

Structure and Electrochemical Hydrogen Storage Properties of as-Milled Mg–Ce–Ni–Al-Based Alloys

At room temperature, crystalline Mg-based alloys, including Mg2Ni, MgNi, REMg12 and La2Mg17, have been proved with weak electrochemical hydrogen storage performances. For improving their electrochemical property, the Mg is partially substituted by Ce in Mg–Ni-based alloys and the surface modification treatment is performed by mechanical coating Ni. Mechanical milling is utilized to synthesize the amorphous and nanocrystalline Mg1−xCexNi0.9Al0.1 (x = 0, 0.02, 0.04, 0.06, 0.08) + 50 wt%Ni hydrogen storage alloys. The effects made by Ce substitution and mechanical milling on the electrochemical hydrogen storage property and structure have been analyzed. It shows that the as-milled alloys electrochemically absorb and desorb hydrogen well at room temperature. The as-milled alloys, without any activation, can reach their maximal discharge capacities during first cycling. The maximal value of the 30-h-milled alloy depending on Ce content is 578.4 mAh/g, while that of the x = 0.08 alloy always grows when prolonging milling duration. The maximal discharge capacity augments from 337.4 to 521.2 mAh/g when milling duration grows from 5 to 30 h. The cycle stability grows with increasing Ce content and milling duration. Concretely, the S100 value augments from 55 to 82% for the alloy milled for 30 h with Ce content rising from 0 to 0.08 and from 66 to 82% when milling the x = 0.08 alloy mechanically from 5 to 30 h. The alloys’ electrochemical dynamics parameters were measured as well which have maximum values depending on Ce content and keep growing up with milling duration extending.

Improved electrochemical performance of Ti1.4V0.6Ni hydrogen storage alloy in its composite with LiAlH4

Ti1.4V0.6Ni + xLiAlH4 (x = 0.5, 1, 1.5, 2, 2.5, wt.%) composites were prepared by ball-milling, and the effects of LiAlH4 content on structure and electrochemical properties of the composites were investigated systematically. The addition of LiAlH4 to the Ti1.4V0.6Ni alloy significantly affected the morphology and size of the composite particles. The electrochemical cycling stability and rate dischargeability of the composite electrodes benefitted from adding some LiAlH4 (x = 1), which however deteriorated when the LiAlH4 content increased further. The positive effect of LiAlH4 on the electrochemical performance of the studied alloy was caused by suppression of the dissolution of active components of the Ti1.4V0.6Ni hydrogen storage alloy.

Elaboration and electrochemical characterization of Mg–Ni hydrogen storage alloy electrodes for Ni/MH batteries

Mg–Ni hydrogen storage alloy electrodes with composition of Mg–33, 50, 67 Ni at. % in amorphous phase were prepared by means of mechanical alloying (MA) process using a planetary ball mill. The electrochemical hydrogen storage characteristics and mechanisms of these electrodes were investigated by electrochemical measurements, X–ray diffraction (XRD) and scanning electron microscope (SEM) analyses. The relationship between alloy composition and electrochemical properties was evaluated. In addition, optimum milling time and composition of Mg–Ni hydrogen storage alloy with acceptable electrochemical performance were determined. XRD results show that the alloys exhibit dominatingly amorphous structures after milling of 20 h. The electrochemical measurements revealed that the discharge capacity of Mg33Ni67 and Mg67Ni33 alloy electrodes reached a maximum when alloys were prepared after 20 h of milling time (260 and 381 mAhg−1, respectively). The maximum discharge capacity of Mg50Ni50 alloy was observable after 40 h milling (525 mAhg−1). It was also found that the cyclic stability of the alloys increased with increasing Ni content. Among these alloys, the amorphous Mg50Ni50 alloy presents the best overall electrochemical performance. In this paper, electrode process kinetics of Mg50Ni50 alloy electrode was also studied by means of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The impedance spectra of electrodes were measured at different depths of discharge (DODs). The observed spectra were fit well with the equivalent circuit model used in the paper. The electrochemical parameters calculated from electrochemical impedance were also compared. The electrochemical discharge and cyclic performance of 20, 40 and 60 h milled Mg50Ni50 alloy electrodes were demonstrated by the fitted charge transfer resistance and Warburg impedance obtained at various DODs. It was further observed that the controlling-step of the discharge process changed from a mixed rate-determining process at lower DODs to a mass-transfer controlled process at higher DODs. The fitted results demonstrated that charge–transfer resistance (Rct) increased with DOD. The Rct of 40 h milled Mg50Ni50 alloy (29.27 Ω) was lower than that of 20 h (41.89 Ω) and 60 h milled alloys (92.43 Ω) at fully discharge state.

A novel method to prepare Ti1.4V0.6Ni alloy covered with carbon and nanostructured Co3O4, and its good electrochemical hydrogen storage properties as negative electrode material for Ni-MH battery

We describe our recent progress on a novel method to prepare Ti1.4V0.6Ni hydrogen storage alloy covered with nanostructured Co3O4 by utilizing zelolitic imidazolate framework 67 (ZIF-67) as the template. Ti1.4V0.6Ni@C@Co3O4 composite is prepared through a dopamine self-polymerization and a facile precipitation reaction with the subsequent thermal treatment. This specific composite structure combines the high conductivity of carbon together with the promising catalytic property of nanostructured Co3O4, therefore the enhanced electrochemical activity and stability are realized. As a result, Ti1.4V0.6Ni@C@Co3O4 composite electrode possesses a capacity conservation rate of 56.1% after 300 charging/discharging cycles, remarkably larger than that of Ti1.4V0.6Ni (25.3%). Moreover, a study of the kinetics demonstrates that nanostructured Co3O4 coating accelerates the charge-transfer reaction of the electrode. These results prove that coating with carbon and nanostructured Co3O4 is a potential method for enhancing electrochemical hydrogen storage properties of hydrogen storage alloys.

Hydrogen Storage Thermodynamics and Dynamics of Nd–Mg–Ni-Based NdMg12-Type Alloys Synthesized by Mechanical Milling

Nanocrystalline and amorphous NdMg12-type NdMg11Ni + x wt% Ni (x = 100, 200) hydrogen storage alloys were synthesized by mechanical milling. The effects of Ni content and milling time on hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The gaseous hydrogen absorption and desorption properties were investigated by Sieverts apparatus and differential scanning calorimeter connected with a H2 detector. Results show that increasing Ni content significantly improves hydrogen absorption and desorption kinetics of the alloys. Furthermore, varying milling time has an obvious effect on the hydrogen storage properties of the alloys. Hydrogen absorption saturation ratio (\(R_{ 1 0}^{\text{a}}\); a ratio of the hydrogen absorption capacity in 10 min to the saturated hydrogen absorption capacity) of the alloys obtains the maximum value with varying milling time. Hydrogen desorption ratio (\(R_{ 2 0}^{\text{d}}\), a ratio of the hydrogen desorption capacity in 20 min to the saturated hydrogen absorption capacity) of the alloys always increases with extending milling time. The improved hydrogen desorption kinetics of the alloys are considered to be ascribed to the decreased hydrogen desorption activation energy caused by increasing Ni content and milling time.

Microstructures and electrochemical performances of Mm(NiCoMnAl) 5 -Mg 2 Ni hydrogen storage alloys prepared by casting and rapid quenching

Microstructures and electrochemical performances of Mm(NiCoMnAl) 5 -Mg 2 Ni hydrogen storage alloys prepared by casting and rapid quenching

Study on solid solubility of Mg in Pr3−xMgxNi9 and electrochemical properties of PuNi3-type single-phase RE–Mg–Ni (RE = La, Pr, Nd) hydrogen storage alloys

In this paper, via adjusting Mg content in Pr3−xMgxNi9 (x=0.45−1.2) alloys, a PuNi3-type single-phase Pr2MgNi9 alloy was obtained by powder-sintering method. The solid solubility of Mg in PuNi3-type phase and phase transformation of Pr3−xMgxNi9 (x=0.45−1.2) alloys at 1173K sintering temperature, as well as hydrogen storage properties of single-phase RE2MgNi9 (RE=La, Pr, Nd) alloys were subsequently studied. We found that when x increased from 0.45 to 1.0, entrance of Mg into Pr2 sites of PuNi3-type phase resulted in a phase transformation from Gd2Co7-type to PuNi3-type, reaching the maximum solid solubility at x=1.0 with a PuNi3-type single phase at 1173K. As x further increased to 1.2, an MgCu4Sn-type secondary phase formed. That was the phase transformation occurs to increase the super-stacking phase possessing more [A2B4] slabs with increase of Mg content. Electrochemical results showed that single-phase alloy had good discharge capacity and superior cycling stability. Comparing with PuNi3-type single-phase La2MgNi9 and Nd2MgNi9 alloys, PuNi3-type single-phase Pr2MgNi9 alloy also exhibited preferable cycling stability and high rate dischargeability (HRD), which were 86.3% (at 100 cycles) and 56.7% (at a current density of 1500mAg−1), respectively.

Hydrogen storage performances of LaMg11Ni + x wt% Ni (x = 100, 200) alloys prepared by mechanical milling

In order to improve the hydrogen storage performances of Mg-based materials, LaMg11Ni alloy was prepared by vacuum induction melting. Then the nanocrystalline/amorphous LaMg11Ni+xwt% Ni (x=100, 200) hydrogen storage alloys were synthesized by ball milling technology. The structure characterizations of the alloys were carried out by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical hydrogen storage characteristics were tested by using programmed control battery testing system. The electrochemical impedance spectra (EIS), potentiodynamic polarization curves and potential-step curves were also plotted by an electrochemical workstation (PARSTAT 2273). The results indicate that the as-milled alloys exhibit a nanocrystalline and amorphous structure, and the amorphization degree of the alloys visibly increases with extending milling time. Prolonging the milling duration markedly enhances the electrochemical discharge capacity and cyclic stability of the alloys. The electrochemical kinetics, including high rate discharge ability (HRD), charge transfer rate, limiting current density (IL), hydrogen diffusion coefficient (D), monotonously decrease with milling time prolonging.

Kinetic properties of La2Mg17–x wt.% Ni (x = 0–200) hydrogen storage alloys prepared by ball milling

The as-cast La2Mg17 with different amount of Ni powders were mixed through ball milling to produce a new type of La2Mg17–x wt.% Ni (x = 50, 100, 150, 200) alloy. The microstructures of the alloys were characterized by XRD technique, the results show that the crystal structure transfers to amorphous one with the increasing amount of Ni powders. La2Mg17–50 wt.% Ni alloy reaches the highest hydrogen absorption capacity of 5.13 wt.% at 300 °C under 2 MPa hydrogen pressure due to its amorphous structure. Furthermore, La2Mg17–50 wt.% Ni alloy expresses fast hydriding kinetics and absorbs 4.99 wt.% hydrogen gas in 200 s. The hydrogen desorption ability described as discharge capacity during electrochemical reaction is fade next to La2Mg17–200 wt.% Ni alloy, attributed to the less Mg2NiH4 with lower enthalpies and easier to release H2. The maximum discharge capacity of La2Mg17–200 wt.% Ni alloy reaches to exciting 980.90 mAh/g, while the La2Mg17 alloy is only 18.10 mAh/g with inconspicuous improvement of cycle stability. These dramatic difference in electrochemical performance reflect the consequence of sluggish dehydriding process of La2Mg17–50 and 100 wt.% Ni alloys again. Whereas La2Mg17–200 wt.% Ni alloy has lower resistance both on alloy surface and in the bulk.

Mechanism of Cancer Cell Death Induced by Hydrogen Discharged from Palladium Base Hydrogen Storage Alloy

The mechanism of cancer cell death induced by hydrogen discharged from Pd-5at.% Ni hydrogen storage alloy has been investigated. Cancer cell (HeLa : cervical cancer cell) death was observed in the limited region within ~ 3 mm from the sample. The measurement of surviving fraction of cells revealed that almost all the cancer cells in the well of 96-well multi plate, 6.2 mm in diameter were extinct (p &lt; 0.01), while no detectable influence was observed in the normal cells. From the fluorescent imaging experiment, it was indicated that the cell death induced by discharged hydrogen was due to the “Apoptosis” and hydrogen peroxide was detected in both intracellular and extracellular regions. Furthermore, the generation of hydrogen radical and hydroxyl radical was observed in the ESR measurement. From the results obtained, the mechanism of cancer cell death is proposed.

Designs for miniaturization of bending actuator utilizing hydrogen storage alloy

Bending behavior of a miniature actuator utilizing Pd–Ni hydrogen storage alloy (HSA) has been investigated on hydriding and dehydriding process. The actuator has a bimorph structure consisting of the HSA thin sheet and copper plating on one side of the sheet. Palladium sputtering on the back surface of the HSA significantly improves bending characteristics due to the catalytic action of palladium. The maximum bending velocity is obtained in the HSA with 10μm thick Cu-plating. The bending actuators having the same aspect ratio (length to width) and different dimensions show the same bending velocity and the critical aspect ratio of the actuator free from the constraint by deformation in width direction is around five. The bending behavior can be controlled by adjusting the surrounding hydrogen pressure.

First-Principles Studies on the Structures and Properties of Ti- and Zn-Substituted Mg&lt;sub&gt;2&lt;/sub&gt;Ni Hydrogen Storage Alloys and their Hydrides

In order to study the improvement mechanism of transition metal elements on Mg-based hydrogen storage alloys, especially for the structures and properties of hydrogen storage alloy Mg2Ni, Ti and Zn substituted alloys Mg2-mMmNi,Mg2Ni1-nMn (M=Ti and Zn, m, n=0.1667), and their hydrides Mg2NiH4,Mg2-mMmNiH4,Mg2Ni1-nMnH4(M=Ti and Zn, m , n=0.125) have been investigated by first-principles. Through analyzing the results of the crystal structure, electron density distribution and density of states, the changes of structures and properties resulting from the adding of transition metal elements Ti and V of intermetallic Mg2Ni and its hydride Mg2NiH4 were investigated. The results showed that the addition of transition metal elements can reduce the stability of the Mg2Ni system to varying degrees and improve the dehydrogenation dynamics performance. Therefore, it may be considered that the substitution by transition metal elements in Mg-based hydrogen storage alloys is an effective technique to improve the thermodynamic behavior of hydrogenation/dehydrogenation in Mg-based hydrogen storage alloys (HSAs).

Effect of ball milling time on microstructure and electrochemical properties of CeMg12+100%Ni hydrogen storage alloy

In order to improve hydrogen storage performances of CeMg12 type alloys, ball milling technology was used for preparing nanocrystalline/amorphous CeMg12+100%Ni composite hydrogen storage alloys. The microstructures and morphologies of alloy samples were characterised by X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. The electrochemical hydrogen storage characteristics of as milled alloys were tested by an automatic galvanostatic system. The electrochemical impedance spectra were plotted by an electrochemical workstation (PARSTAT2273). The hydrogen diffusion coefficients D in the alloys were calculated by virtue of potential step method. The results show that the amount of nanocrystalline/amorphous Mg2Ni phase and Ni phase within alloy samples increase with prolonging milling time. Prolonging of ball milled duration markedly improves the electrochemical discharge properties and cyclic stability of alloy samples. The amorphisation degree of the milling alloys increases with rising milling duration. Furthermore, the high rate dischargeability, electrochemical impedance spectra and potential step measurement all indicate that electrochemical kinetics of alloy electrodes first increases and then decreases with increasing ball milling.

Electrochemical hydrogen storage properties of Mg2−xAlxNi (x = 0, 0.3, 0.5, 0.7) prepared by hydriding combustion synthesis and mechanical milling

Abstract Mg 2− x Al x Ni ( x = 0, 0.3, 0.5, 0.7) hydrogen storage alloys used as the negative electrode in a nickel–metal hydride (Ni–MH) battery were successfully prepared by means of hydriding combustion synthesis (HCS) and the selected alloy Mg 1.5 Al 0.5 Ni was further modified by mechanical milling (MM). The structural and electrochemical hydrogen storage properties of Mg 2− x Al x Ni alloys have been investigated in detail. XRD results show that a new phase Mg 3 AlNi 2 that possesses an excellent cycling stability is observed with the substitution of Al for Mg. A short-time mechanical milling has a significant effect on improving the discharge capacity of the HCS product of Mg 1.5 Al 0.5 Ni. The maximum discharge capacity of Mg 1.5 Al 0.5 Ni ascends with increasing mechanical milling time and reaches the maximum 245.5 mAh/g when milled for 10 h. The alloy milled for 5 h shows the best electrochemical kinetics, which is due to its smaller mean particle size and uniform distribution of the particles. Further increasing in mechanical milling time could not bring about better electrochemical kinetics, which might be attributed to the agglomeration of the alloy particles and thus the charge-transfer reaction and hydrogen diffusion are restrained. It is suggested that the novel method of HCS + MM is promising to prepare ternary Mg-based intermetallic compound for electrochemical hydrogen storage.