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Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 8 ) 1 e7
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Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition Hao Sun, Dianchen Feng, Yanghuan Zhang*, Huiping Ren** School of Material and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, Inner Mongolia, PR China
article info
abstract
Article history:
Mg24Ni10Cu2 and Mg22Y2Ni10Cu2 alloys were prepared via vacuum induction melting, and
Received 23 July 2018
the nanocrystalline/amorphous Mg24Ni10Cu2 and Mg24Ni10Cu2 þ 100 wt% Ni alloys were
Received in revised form
synthesized through ball milling method. Microstructure and hydrogen storage properties
15 August 2018
of the alloys were investigated and compared as well. The results suggest that adding Ni in
Accepted 21 August 2018
the milling process significantly promotes formation of amorphous and nanocrystalline
Available online xxx
structure. For these four alloys, the as-milled Mg24Ni10Cu2 with 100 wt% Ni shows the best hydrogen storage performances that 2.03 wt% hydrogen content can be absorbed just in
Keywords:
1 min, and the electrochemical capacity reaches to 899.2 mAh/g. Furthermore, ball milling
Mg2Ni-type alloy
with Ni promotes the charge transfer reaction and hydrogen diffusion ability which is
Ball milling
advantageous to the high rate discharge ability.
Partial substitution
© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Gas absorption Electrochemical performance
Introduction Hydrogen energy is deemed as one of the significant directions for energy development in the future because of its environmental protection, safety and efficiency [1e5]. Nevertheless, storage and transportation of hydrogen are the biggest obstacle to use of hydrogen energy at present. Mg2Nibased alloys are extremely potential alloys for hydrogen storage on account of the advantages including greater capacity, safety, low cost and light weight [6e10]. However, several immanent shortcomings, such as the elevated temperature for hydrogen absorption, slow kinetics of hydrogen desorption, high stability of thermodynamics and poor
electrochemical cycle stability [11e13], restrict the practical application of Mg-based alloys [14]. Among the Mg-base alloys, Mg2Ni alloy is the most promising candidate for hydrogen storage which attributes to the fast charge/discharge kinetics and moderate hydrogen content. Usually, three methods are widely used to develop performance of Mg-base alloys i.e. adding alternative metal elements, optimizing the preparing method and using catalysts. Partial replacement of rare earth or alkaline earth on Mg-site and the transition metals on Ni-site have been significantly discussed in the a legion of reports [15]. Elemental substitutions have been reported to be effect for elevation of hydrogen storage performance (the
* Corresponding author. 7# Areding Street, Kun Disrict, Baotou, 014010, PR China. ** Corresponding author. E-mail addresses: [email protected] (Y. Zhang), [email protected] (H. Ren). https://doi.org/10.1016/j.ijhydene.2018.08.156 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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electrochemical, gas hydrogen absorption and desorption) of Mg-based samples [15e17]. Meanwhile, performances of the Mg2Ni-type alloys can be significantly enhanced by using different preparation methods, which mainly includes mechanical alloying (MA) [18], cold working [19], hydrogen burning method [20], vapor deposition [21] and melt-spinning [22e24]. In addition, adding catalysts such as graphene [25], halogenide [26], transition metal oxides [27] and other hydrides [6] is reported to obviously promote the hydrogen absorption kinetics and ability. In this paper, four Mg2Ni-type alloys with different content Y substitution were synthesized using casting and ball milling. Influences of preparation method and element substitution on the properties of gaseous and electrochemical for the experimental alloys were studied.
Experimental Mg24Ni10Cu2 and Mg22Y2Ni10Cu2 ingots were first melted in a high vacuum inducting melting furnace under 0.04 MPa helium, the purity of Mg, Ni, Cu and Y are 99.5%, 99.9%, 99.9% and 99.8%, respectively, and then grinded into powder (particle size < 50 mm). The part of as-cast Mg24Ni10Cu2 alloy was mixed with Ni (particle size < 48 mm) both in powder form in a ratio of 1:1 (wt%). Following, we milled the mixture via a planetary-type mill with stainless steel vials in an argon atmosphere for 20 h. The mass ratio of the powder and ball is 1:40 and the milling speed is 350 rpm. For convenience, the as-cast Mg24Ni10Cu2, as-cast Mg22Y2Ni10Cu2, as-milled Mg24Ni10Cu2 and as-milled Mg24Ni10Cu2þ100 wt% Ni alloys are mentioned as following: 1#, 2#, 3# and 4#. We employed X-ray diffractometer (XRD, Philips X'pert pro with Cu-ka radiation, scanned in the 2q range of 15-95 at room temperature) to investigate the crystalline structure and phase constitutions of the experimental samples. Microstructure of the alloys was taken with scanning electron microscope (SEM, FEI QUANTA 400) and transmission electron microscopy (TEM, JEM-2100, 200 kV). Hydrogen absorption kinetic was gauged by a PCT apparatus (Sieverts-type) with the parameters of 623 K and 5 MPa hydrogen pressure. The electrochemical performances of alloys were gauged with the parameters of 303 K by the battery testing facilities (LAND 2100) and an electrochemical workstation (PARSTAT 2273) with an open tri-electrode electrolysis cell, which comprises one negative electrode, one positive electrode and plus a reference electrode. Before test, electrode pellet with about 1 g and 10 mm in diameter were made by the mixed sample power and carbonyl nickel powder in a weight ratio of 1:4 at 25 MPa, and then soaked in KOH electrolyte for 24 h. For every cycle, we first charged the electrode by using 60 mA/g constant current for 20 h, then wait for 15 min, and followed by discharging process with 60 mA/g to a cut-off voltage of 0.500 V (vs. Hg/HgO). For the case of measuring the electrochemical impedance spectra (EIS) and Tafel polarization curves, the charging process was completed and right away by a calm of 120 min to stabilize the potential. Subsequently, the EIS were performed with frequency range of 10 kHze5 mHz, at this point the
electrode has to release 50% of the electricity. Additionally, to evaluate the corrosion resistance of the working electrodes in electrolyte, the Tafel polarization curves were employed with parameters of a potential range of 1.2 V ~ þ1.0 V and a scanning rate of 5 mV/s. As to the potentiostatic discharge, firstly, the alloys were fully charged, and then discharged with 500 mV potential steps for 4500 s on the electrochemical workstation using CorrWare.
Results and discussion Microstructure characteristics XRD patterns of the four alloys are presented in Fig. 1. From XRD it able to show that the original Mg24Ni10Cu2 contains two phases, where Mg2(Ni,Cu) is account for the majority and Mg as a secondary phase. With increasing of the addition of Y, the diffraction peaks for MgYNi4 are also observed. No other phases were detected in the as-cast alloys, suggesting that Cu element is completely dissolved in other phases. It is clear that diffraction peaks of the 3# alloy contributes slightly broaden, demonstrating formation of nanocrystalline or amorphous structure. At the same time, Ni adding in asmilled alloy leads to obviously broadening of the diffraction peaks and more lower intensity. And the diffraction peaks of Mg2Ni and Mg nearly disappear, which indicates that Ni adding facilitates to formation of amorphous or nanocrystalline during the milling process. This is mainly because the nickel powder is harder than the alloy powder. In the process of high-speed ball milling, Ni powder has a certain cutting effect on the alloy and accelerates the amorphous/nanocrystallization of the alloy. In Figs. 2 and 3, we present the SEM images and EDS profiles of the original Mg24Ni10Cu2 and Mg22Y2Ni10Cu2 alloy. One can find typical cast morphology that dendritic structure of two alloys. It is very obvious that two or three structures exist
Fig. 1 e XRD patterns of the as-cast Mg24Ni10Cu2(1#), Mg22Y2Ni10Cu2(2#),as-milled Mg24Ni10Cu2(3#) and Mg24Ni10Cu2 þ100 wt% Ni (4#).
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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Fig. 2 e SEM images (a) together with typical EDS spectra (b) and (c) of the as-cast Mg24Ni10Cu2 alloy.
Fig. 3 e SEM images (a) together with typical EDS spectra (b), (c) and (d) of the as-cast Mg22Y2Ni10Cu2 alloy.
in the as-cast alloys. Mg24Ni10Cu2 sample is composed of almost gray strip-like phase with a small amount of black structure. EDS analysis shows that the strip a phases are Mg2(Ni, Cu) and black structures are Mg-rich phases. Mg22Y2Ni10Cu2 alloy has exact the same phase constitution except MgYNi4 presents white contrast. Fig. 4 shows the TEM images of as-milled alloys. It can be found that the electron diffraction (ED) pattern of 3# alloy displays multi-haloes, meaning crystal structure characters. While, 4# alloy has a typical nanocrystalline/amorphous structure identified by the broad and dull halo electron diffraction patterns, demonstrating existence of large number of grain boundaries and internal energy. The result also explains that Ni adding facilitates formation of the nanocrystalline or amorphous structure of the alloy, which conforms well from the XRD results.
cast 1# alloy possesses the slowest hydriding rate. Hydrogen absorption capacities of the 1#, 2#, 3# and 4# alloys are 0.847 wt%, 1.329 wt%, 1.043 wt% and 2.03 wt% within 600 s, respectively. The result indicates that ball milling process for Ni is effective to inhance the hydrogenation properties of alloy. The improved hydriding rate by adding Ni attributes to formation of amorphous and nanocrystalline originate from the fact that the hydrogen diffusivity in a glass matrix is faster than that in a crystalline structure [11,24,28]. Furthermore, Ni adding is helpful to the catalytic effect for the hydrogen reactions [29]. The hydriding rate improved by substitution Y for Mg of the alloys is due to the secondary phase (MgYNi4) which provides more channel for the hydrogen diffusion and significantly catalytic effect [30,31].
Electrochemical hydrogen storage performances Gaseous hydrogen activation properties Electrochemical discharging capacity In Fig. 5, we present the activation performance of the four sample alloys prepared by different methods. Clearly, the as-
The electrochemical activation ability is an important performance of Ni-MH battery, which can be estimated through
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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Fig. 4 e TEM images and ED patterns of as-milling alloys: (a) Mg24Ni10Cu2 and (b) Mg24Ni10Cu2þ100 wt%Ni.
Fig. 5 e Variations of the first hydrogen desorption capacity of the four alloys with time varying.
the cycles times of charging and discharging to the make the discharge capacity to its maximum. Changes of the discharge capacities for the four samples vs. the cycle number are illustrated in Fig. 6. It shows. that the samples reach to the max discharge capacities happened in the 1st cycle, indicating the alloys possess activation properties. The maximum discharge capacities of four alloys are 74.9, 67.9, 156.8 and 899.7 mAh/g, respectively. The 1# and 2# alloys have extremely poor reversibility which can only discharge less than 10% percent of the largest discharge (999 mAh/g) capacity. It also suggests that discharge capacity cannot be improved by addition of rare-earth element Y. Discharge capacity of as-milled 3# alloy is still very low, but it is over two times of that as-cast. This is mainly due to the more grain boundary produced through grain refinement and the nanocrystalline structure through ball milling. One can observe that due to addition of a large amount of nickel, the maximum discharge of 4# is much greater than any other three samples. The active effect of Ni addition on the discharge capacity is originated from three reasons [32]. Firstly, as a hard particle, Ni cuts the alloy during the ball milling process to encourage the formation of nanocrystalline or amorphous alloy [33].
Fig. 6 e Evolution of discharge capacity of the four alloys with cycle number.
Secondly, adding Ni to the alloy helps improving the corrosion resistance of Mg-based alloy in alkali solution of KOH, which is advantageous to the cycle stability and the discharge capacity. Thirdly, Ni weakens the binding force between H and Mg atoms, and thus can dramatically decreases stability of the metal hydride therefore improves the kinetics of hydrogen absorption.
Electrochemical cycle stability The repeated charging performance of the battery originate from the cycling stability of the negative electrode material, one can be described by capacity retention (Sn). Sn can be calculated by Cn/Cmax 100% [33], in which Cmax represents the maximum discharge content, and Cn denotes the discharge capacity at the nth cycles. From the results shown in Fig. 7, it shows that the Sn decrease with increasing of the cycle time. while, the decline extent is obviously different for four alloys. The 1# alloy presents the best cycling stability, which is mainlydue to poor discharge capacity (Cmax ¼ 74.9 mAh/g). 3# and 4# also have quite low cycling stability, demonstrating that fine grain is useless to the cyclic stability [34]. Contrarily, increased surface area by fine grains increases contacting
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 8 ) 1 e7
Fig. 7 e Evolution of Sn values of the four alloys with cycle number.
between the alloy and electrolyte, and accelerated the corrosion rate of the sample.
Electrochemical kinetics For power batteries, it is necessary that they have the high current density discharge performances. However, it is known to all that the elevation of discharge current scale leads to the decreasing of discharge capacity of the electrode. This property can be characterized by the high rate discharge ability (HRD) of the sample samples [35]. HRD can be obtained by HRD ¼ Ci/(Ci þ C60) 100%, in which Ci denotes the largest discharge capacity of the cathode by using i mA/g current density, then the alloy electrode resumes discharge at the current densities of 60 mA/g by a rest of 10 min, the maximum discharge capacity is defined as C60. Changes of HRD of the four samples are showed in Fig. 8. Based on the test results at the current density of 300 mA/g, effects of production methods on HRD can be demonstrated, as inserted in Fig. 8. The HRD of 1#, 2#, 3# and 4# alloys are 69.5%, 70.5%, 57.7% and 80.1%, respectively. From the figures given above, the 3# alloys is the lowest
Fig. 8 e Evolution of HRD values of the four alloys with discharge current density.
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values, it also shows that Y substitution has insignificant influence on HRD. The 3# alloy has the lowest HRD, while the 4# alloy has the best performance, which indicates that the Ni adding contributes to improving the high rate discharge ability. Zhang et al. [20,36] reported that HRD of the electrode is generally affected by the charge-transfer rate and hydrogen diffusivity. To comprehend further, we use EIS qualitatively evaluate the charge transfer capability. The EIS result of the four alloys is showed in Fig. 9. It shows that every EIS is composed of two semicircular arcs at the high and middle frequencies separately and a line at the low frequency. Among them, the radius of the semicircle in the middle frequency represents the charge transfer resistance. The 3# and 4# alloys have the smaller radius of the semicircle, shows ball milling and Ni adding is advantageous to the charge transfer reaction, which agrees well with the HRD results. In the study of electrochemical properties of samples, the limiting current density (IL) is a significant parameter for characterization of the electrochemical kinetic performance. For this case, Tafel polarization curve I can characterize this property, as shown in Fig. 10. We can see that each anodic polarization curve possesses an obvious inflexion, meaning the presence of critical value. The values of IL of 4# and 3# alloys are 2.24 A/g and 0.44 A/g, manifesting that ball milling with Ni is helpful for the diffusion of hydrogen. The hydrogen diffusion coefficient is evaluated by the semilogarithmic curves of ratio of the anodic current and working duration, as shown in Fig. 11. According to the White's model [32,37], every electrode material particle is assumed to be a perfect sphere, the hydrogen diffusion coefficient could be gained by the slope of the linear area of the corresponding plots as followings: lgi ¼ lg ± 6FDðC0 Cs Þ= da2 p2 Dt= 2:303a2
(1)
D ¼ 2:303a2 ½dðlgiÞ=dðlgtÞ =p2
(2)
where i denotes the diffusion current density (mA/g), F denotes the Faraday constant, D represents the diffusion coefficient of hydrogen, a denotes the radius of alloy particles
Fig. 9 e Electrochemical impedance spectra (EIS) of the four alloys.
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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Fig. 10 e Tafel polarization curves of the four alloys.
exists in Mg22Y2Ni10Cu2 alloy with the additive of Y, Cu element is completely dissolved in other phases. The nanocrystalline or amorphous structure in the alloy powder can be produced by ball milling, and adding Ni makes that dramatically speed-up. Based on the first H2 absorption capacity for the four alloys, the as-cast Mg22Y2Ni10Cu2 and as-milled Mg24Ni10Cu2 þ 100 wt %Ni are 1.329% and 2.03% with in 600 s. The discharge capability measurement of the alloy implies that the as-milled alloys have excellent performance, namely the capability of Mg24Ni10Cu2 þ 100 wt% Ni reaching 899.7 mAh/g, while the performance of the cycling stability is still bad. Furthermore, electrochemical kinetics of Mg24Ni10Cu2 þ 100 wt% Ni is the best of four alloys, and HRD of the 4# alloy is 80.1% at 300 mA/g, and IL and D are 2.24 A/g and 4.35 1011 cm2/s, respectively, which show that ball milling and composite nickel contribute to the diffusivity of the hydrogen and charge-transfer rate.
Acknowledgments This study was financially supported by the Natural Science Foundation of Inner Mongolia, China (2015MS0558, 2018LH05003) and the Science Research Project of the Colleges and Universities of the Inner Mongolia(NJZZ18142).
references
Fig. 11 e Semi-logarithmic curves of anodic current vs. time responses of the four alloys.
(1.5 103 cm), C0 is the original hydrogen concentration in matrix, Cs denotes the hydrogen content on the surface of the electrode material particles, d denotes the density of the electrodes, t denotes the discharge time, respectively. The evolutions of the D of the alloys derived from Eq. (2) with different manufacturing methods are also inserted in Fig. 11. The results demonstrate that D of the as-casted alloy is smaller but that of the as-milled alloys are larger. D of the 4# alloy is maximum (4.35 1011 cm2/s), meaning that ball milling and Ni adding contributes to the diffusivity of the hydrogen atoms. The result may be ascribed to the factor that amorphous could effectively slow down the oxidation of alloy [38].
Conclusions In this study, we investigated the gaseous and electrochemical properties of Mg2Ni-based hydrogen storage material prepared by various ways. The results are as follows: the as-cast Mg24Ni10Cu2 alloy is composed of two phases, Mg2Ni and Mg, where the former accounts for the majority. MgYNi4 phase
[1] Zou JX, Long S, Chen X, Zeng XQ, Ding WJ. Preparation and hydrogen sorption properties of a Ni decorated Mg based Mg@Ni nano-composite. Int J Hydrogen Energy 2015;40:1820e8. [2] Zhai TT, Yang T, Yuan ZM, Xu S, Bu WG, Qi Y, et al. Influences of hydrogen-induced amorphization and annealing treatment on gaseous hydrogen storage properties of La1xPrxMgNi3.6Co0.4 (x¼0e0.4) alloys. J Alloy Comp 2015;639:15e20. [3] Kumar Sanjay, Miyaoka H, Ichikawa T, Dey GK, Kojima Y. Micro-alloyed Mg2Ni for better performance as negative electrode of Ni-MH battery and hydrogen storage. Int J Hydrogen Energy 2017;42:5220e6. [4] Lv YJ, Zhang B, Wu Y. Effect of Ni content on microstructural evolution and hydrogen storage properties of MgexNie3La (x¼5,10,15,20 at.%) alloys. J Alloy Comp 2015;641:176e80. [5] Li Y, Gu QF, Li Q, Zhang TF. In-situ synchrotron X-ray diffraction investigation on hydrogen-induced decomposition of long period stacking ordered structure in MgeNieY system. Scripta Mater 2017;127:102e7. [6] Zhao X, Han SM, Zhu XL, Liu BZ, Chen XC, Liu YQ, et al. Effect of LaH3eTiH2 composite additive on the hydrogen storage properties of Mg2Ni alloys. J Alloy Comp 2013;581:270e4. [7] Junko M, Naoki U, Kanai T, Kazumi H, Akiba E. Effect of Mg/Ni ratio on microstructure of Mg-Ni films deposited by magnetron sputtering. J Alloy Comp 2014;617:47e51. [8] Ohara R, Chao-Ho L, Chii-Shyang H. Electrochemical and structural characterization of electroless nickel coating on Mg2Ni hydrogen storage alloy. J Alloy Comp 2013;580:s368e72. [9] Cho YH, Aminorroaya S, Liu HK, Dahle AK. The effect of transition metals on hydrogen migration and catalysis in cast MgeNi alloysInt. J Hydrogen Energy 2011;36:4984e92.
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 8 ) 1 e7
[10] Fu H, Wu WS, Dou Y, Liu BZ, Li HN, Peng QM. Hydrogen diffusion kinetics and structural integrity of superhigh pressure Mg-5 wt%Ni alloys with dendrite interface. J Power Sources 2016;320:212e21. [11] Yuan ZM, Yang T, Bu WG, Shang HW, Qi Y, Zhang YH. Structure, hydrogen storage kinetics and thermodynamics of Mg-based Sm5Mg41 alloy. Int J Hydrogen Energy 2016;41:5994e6003. [12] Wang PS, Liu SH, Du Y. Experimental investigation and thermodynamic calculation of the MgeMneNi system. Calphad 2015;49:41e9. a m R, Marcell G, Erhard S, Marco C, Luca PJ. [13] Ad Dehydrogenation-hydrogenation characteristics of nanocrystalline Mg2Ni powders compacted by high-pressure torsion. Alloy Comp 2017;702:84e91. [14] Tran XQ, Mcdonald SD, Gu QF, Nogita K. In-situ synchrotron X-ray diffraction investigation of the hydriding and dehydriding properties of a cast MgeNi alloy. J Alloy Comp 2015;636:249e56. [15] Zhou WH, Zhu D, Tang ZY, Wu CL, Huang LW, Ma ZW, et al. Improvement in low-temperature and instantaneous highrate output performance of Al-free AB5-type hydrogen storage alloy for negative electrode in Ni/MH battery: effect of thermodynamic and kinetic regulation via partial Mn substituting. J Power Sources 2017;343:11e21. [16] Si TZ, Ma Y, Li YT, Liu DM. Solid solution of Cu in Mg2NiH4 and its destabilized effect on hydrogen desorption Mater. Chem Phys 2017;193:1e6. [17] Shao HY, Li XG. Effect of nanostructure and partial substitution on gas absorption and electrochemical properties in Mg2Ni-based alloys. J Alloy Comp 2016;667:191e7. [18] Zadorozhnyy VY, Menjo M, Zadogozhnyy MY, Kaloshkin SD, Louzguine-luzgin DV. Hydrogen sorption properties of nanostructured bulk Mg2Ni intermetallic compound. J Alloy Comp 2014;586(Suppl 1):S400e4. Gajdics M, Varga LK, Kra ve sz A, llics G, Pe ter L, Spassov T. [19] Re Hydrogen storage of nanocrystalline MgeNi alloy processed by equal-channel angular pressing and cold rolling. Int J Hydrogen Energy 2014;39:9911e7. [20] Zhu YF, Yang C, Zhu JY, Li LQ. Structural and electrochemical hydrogen storage properties of Mg2Ni-based alloys. J Alloy Comp 2011;509:5309e14. us D. Exploring the [21] Wirth E, Milcius D, Filiou C, Nore hydrogen sorption capacity of MgeNi powders produced by the vapour deposition technique. Int J Hydrogen Energy 2008;33:3122e7. [22] Zhang YH, Wang HT, Zhai TT, Yang T, Qi Y, Zhao DL. Hydrogen storage characteristics of the nanocrystalline and amorphous MgeNdeNieCu-based alloys prepared by melt spinning. Int J Hydrogen Energy 2014;39:3790e8. [23] Zhang TB, Song WJ, Kou HC, Li JS. Surface valence transformation during thermal activation and hydrogenation thermodynamics of MgeNieY melt-spun ribbons. Appl Surf Sci 2016;371:35e43. [24] Hongo T, Kaveh E, Makoto A, Junko M, Akiba E, Horita Z. Significance of grain boundaries and stacking faults on
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
7
hydrogen storage properties of Mg2Ni intermetallics processed by high-pressure torsion. Acta Mater 2015;92:46e54. Huang LW, Elkedim O, Nowak M, Jurczyk M, Chassagnon R, Meng DW. Synergistic effects of multiwalled carbon nanotubes and Al on the electrochemical hydrogen storage properties of Mg2Ni-type alloy prepared by mechanical alloying. Int J Hydrogen Energy 2012;37:1538e45. Liu LH, Min M, Liu F, Yin H, Zhang YS, Qiu GH. Influence of vanadium doping on the supercapacitance performance of hexagonal birnessite. J Power Sources 2015;277:26e35. Song JZ, Han SM, Fu RD. Effect of La2O3-CaO composite additive on the hydrogen storage properties of Mg2Ni alloy. Mater Sci Eng B 2014;188:114e8. Zhang QA, Zhang LX, Wang QQ. Crystallization behavior and hydrogen storage kinetics of amorphous Mg11Y2Ni2 alloy. J Alloy Comp 2013;551:376e81. Fujimoto T, Ogawa S, Kanai T, Naoki U, Yoshida T, Shinya Y. Hydrogen storage property of materials composed of Mg nanoparticles and Ni nanoparticles fabricated by gas evaporation method. Int J Hydrogen Energy 2015;40:11890e4. Song WJ, Li JS, Zhang TB, Kou HC, Xue XY. Microstructure and tailoring hydrogenation performance of Y-doped Mg2Ni alloys. J Power Sources 2014;245:808e15. ChitsazKhoyi L, Raygan Sh, Pourabdoli M. Mechanical milling of Mg, Ni and Y powder mixture and investigating the effects of produced nanostructured MgNi4Y on hydrogen desorption properties of MgH2. Int J Hydrogen Energy 2013;38:6687e93. Zhang YH, Wang HT, Zhai TT, Yang T, Yuan ZM, Zhao DL. Hydrogen storage performances of LaMg11Niþxwt% Ni (x¼100, 200) alloys prepared by mechanical milling. J Alloy Comp 2015;645:S438e45. Tian X, Yun GH, Wang HY, Shang T, Yao ZQ, Wei W, et al. Preparation and electrochemical properties of LaeMgeNibased La0.75Mg0.25Ni3.3Co0.5 multiphase hydrogen storage alloy as negative material of Ni/MH battery. Int J Hydrogen Energy 2014;39:8474e81. Hou XJ, Hu R, Zhang TB, Kou HC, Song WJ, Li JS. Microstructure and electrochemical hydrogenation/ dehydrogenation performance of melt-spun La-doped Mg2Ni alloys. Mater Char 2015;106:163e74. Liu JJ, Han SM, Li Y, Zhao X, Yang SQ, Zhao YM. Cooperative effects of Sm and Mg on electrochemical performance of LaeMgeNi-based alloys with A2B7 and A5B19etype super-stacking structure. Int J Hydrogen Energy 2015;40:1116e27. Kuriyama N, Sakai T, Miyamura H, Uehara I, Ishikawa H. Electrochemical impedance and deterioration behavior of metal hydride electrodes. J Alloy Comp 1993;202:193. Zheng G, Popov BN, White RE. Electrochemical determination of the diffusion coefficient of hydrogen through an LaNi4.25Al0.75 electrode in alkaline aqueous solution. J Electrochem Soc 1995;142:2695e8. Liu ZP, Yang SQ, Li Y, Ma MZ, Han SM. Improved electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys with lanthanum partially substituted by yttrium. J Rare Earths 2015;33:397e402.
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
Available online at www.sciencedirect.com
ScienceDirect journal homepage: www.elsevier.com/locate/he
Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition Hao Sun, Dianchen Feng, Yanghuan Zhang*, Huiping Ren** School of Material and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, Inner Mongolia, PR China
article info
abstract
Article history:
Mg24Ni10Cu2 and Mg22Y2Ni10Cu2 alloys were prepared via vacuum induction melting, and
Received 23 July 2018
the nanocrystalline/amorphous Mg24Ni10Cu2 and Mg24Ni10Cu2 þ 100 wt% Ni alloys were
Received in revised form
synthesized through ball milling method. Microstructure and hydrogen storage properties
15 August 2018
of the alloys were investigated and compared as well. The results suggest that adding Ni in
Accepted 21 August 2018
the milling process significantly promotes formation of amorphous and nanocrystalline
Available online xxx
structure. For these four alloys, the as-milled Mg24Ni10Cu2 with 100 wt% Ni shows the best hydrogen storage performances that 2.03 wt% hydrogen content can be absorbed just in
Keywords:
1 min, and the electrochemical capacity reaches to 899.2 mAh/g. Furthermore, ball milling
Mg2Ni-type alloy
with Ni promotes the charge transfer reaction and hydrogen diffusion ability which is
Ball milling
advantageous to the high rate discharge ability.
Partial substitution
© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Gas absorption Electrochemical performance
Introduction Hydrogen energy is deemed as one of the significant directions for energy development in the future because of its environmental protection, safety and efficiency [1e5]. Nevertheless, storage and transportation of hydrogen are the biggest obstacle to use of hydrogen energy at present. Mg2Nibased alloys are extremely potential alloys for hydrogen storage on account of the advantages including greater capacity, safety, low cost and light weight [6e10]. However, several immanent shortcomings, such as the elevated temperature for hydrogen absorption, slow kinetics of hydrogen desorption, high stability of thermodynamics and poor
electrochemical cycle stability [11e13], restrict the practical application of Mg-based alloys [14]. Among the Mg-base alloys, Mg2Ni alloy is the most promising candidate for hydrogen storage which attributes to the fast charge/discharge kinetics and moderate hydrogen content. Usually, three methods are widely used to develop performance of Mg-base alloys i.e. adding alternative metal elements, optimizing the preparing method and using catalysts. Partial replacement of rare earth or alkaline earth on Mg-site and the transition metals on Ni-site have been significantly discussed in the a legion of reports [15]. Elemental substitutions have been reported to be effect for elevation of hydrogen storage performance (the
* Corresponding author. 7# Areding Street, Kun Disrict, Baotou, 014010, PR China. ** Corresponding author. E-mail addresses: [email protected] (Y. Zhang), [email protected] (H. Ren). https://doi.org/10.1016/j.ijhydene.2018.08.156 0360-3199/© 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved. Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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electrochemical, gas hydrogen absorption and desorption) of Mg-based samples [15e17]. Meanwhile, performances of the Mg2Ni-type alloys can be significantly enhanced by using different preparation methods, which mainly includes mechanical alloying (MA) [18], cold working [19], hydrogen burning method [20], vapor deposition [21] and melt-spinning [22e24]. In addition, adding catalysts such as graphene [25], halogenide [26], transition metal oxides [27] and other hydrides [6] is reported to obviously promote the hydrogen absorption kinetics and ability. In this paper, four Mg2Ni-type alloys with different content Y substitution were synthesized using casting and ball milling. Influences of preparation method and element substitution on the properties of gaseous and electrochemical for the experimental alloys were studied.
Experimental Mg24Ni10Cu2 and Mg22Y2Ni10Cu2 ingots were first melted in a high vacuum inducting melting furnace under 0.04 MPa helium, the purity of Mg, Ni, Cu and Y are 99.5%, 99.9%, 99.9% and 99.8%, respectively, and then grinded into powder (particle size < 50 mm). The part of as-cast Mg24Ni10Cu2 alloy was mixed with Ni (particle size < 48 mm) both in powder form in a ratio of 1:1 (wt%). Following, we milled the mixture via a planetary-type mill with stainless steel vials in an argon atmosphere for 20 h. The mass ratio of the powder and ball is 1:40 and the milling speed is 350 rpm. For convenience, the as-cast Mg24Ni10Cu2, as-cast Mg22Y2Ni10Cu2, as-milled Mg24Ni10Cu2 and as-milled Mg24Ni10Cu2þ100 wt% Ni alloys are mentioned as following: 1#, 2#, 3# and 4#. We employed X-ray diffractometer (XRD, Philips X'pert pro with Cu-ka radiation, scanned in the 2q range of 15-95 at room temperature) to investigate the crystalline structure and phase constitutions of the experimental samples. Microstructure of the alloys was taken with scanning electron microscope (SEM, FEI QUANTA 400) and transmission electron microscopy (TEM, JEM-2100, 200 kV). Hydrogen absorption kinetic was gauged by a PCT apparatus (Sieverts-type) with the parameters of 623 K and 5 MPa hydrogen pressure. The electrochemical performances of alloys were gauged with the parameters of 303 K by the battery testing facilities (LAND 2100) and an electrochemical workstation (PARSTAT 2273) with an open tri-electrode electrolysis cell, which comprises one negative electrode, one positive electrode and plus a reference electrode. Before test, electrode pellet with about 1 g and 10 mm in diameter were made by the mixed sample power and carbonyl nickel powder in a weight ratio of 1:4 at 25 MPa, and then soaked in KOH electrolyte for 24 h. For every cycle, we first charged the electrode by using 60 mA/g constant current for 20 h, then wait for 15 min, and followed by discharging process with 60 mA/g to a cut-off voltage of 0.500 V (vs. Hg/HgO). For the case of measuring the electrochemical impedance spectra (EIS) and Tafel polarization curves, the charging process was completed and right away by a calm of 120 min to stabilize the potential. Subsequently, the EIS were performed with frequency range of 10 kHze5 mHz, at this point the
electrode has to release 50% of the electricity. Additionally, to evaluate the corrosion resistance of the working electrodes in electrolyte, the Tafel polarization curves were employed with parameters of a potential range of 1.2 V ~ þ1.0 V and a scanning rate of 5 mV/s. As to the potentiostatic discharge, firstly, the alloys were fully charged, and then discharged with 500 mV potential steps for 4500 s on the electrochemical workstation using CorrWare.
Results and discussion Microstructure characteristics XRD patterns of the four alloys are presented in Fig. 1. From XRD it able to show that the original Mg24Ni10Cu2 contains two phases, where Mg2(Ni,Cu) is account for the majority and Mg as a secondary phase. With increasing of the addition of Y, the diffraction peaks for MgYNi4 are also observed. No other phases were detected in the as-cast alloys, suggesting that Cu element is completely dissolved in other phases. It is clear that diffraction peaks of the 3# alloy contributes slightly broaden, demonstrating formation of nanocrystalline or amorphous structure. At the same time, Ni adding in asmilled alloy leads to obviously broadening of the diffraction peaks and more lower intensity. And the diffraction peaks of Mg2Ni and Mg nearly disappear, which indicates that Ni adding facilitates to formation of amorphous or nanocrystalline during the milling process. This is mainly because the nickel powder is harder than the alloy powder. In the process of high-speed ball milling, Ni powder has a certain cutting effect on the alloy and accelerates the amorphous/nanocrystallization of the alloy. In Figs. 2 and 3, we present the SEM images and EDS profiles of the original Mg24Ni10Cu2 and Mg22Y2Ni10Cu2 alloy. One can find typical cast morphology that dendritic structure of two alloys. It is very obvious that two or three structures exist
Fig. 1 e XRD patterns of the as-cast Mg24Ni10Cu2(1#), Mg22Y2Ni10Cu2(2#),as-milled Mg24Ni10Cu2(3#) and Mg24Ni10Cu2 þ100 wt% Ni (4#).
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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Fig. 2 e SEM images (a) together with typical EDS spectra (b) and (c) of the as-cast Mg24Ni10Cu2 alloy.
Fig. 3 e SEM images (a) together with typical EDS spectra (b), (c) and (d) of the as-cast Mg22Y2Ni10Cu2 alloy.
in the as-cast alloys. Mg24Ni10Cu2 sample is composed of almost gray strip-like phase with a small amount of black structure. EDS analysis shows that the strip a phases are Mg2(Ni, Cu) and black structures are Mg-rich phases. Mg22Y2Ni10Cu2 alloy has exact the same phase constitution except MgYNi4 presents white contrast. Fig. 4 shows the TEM images of as-milled alloys. It can be found that the electron diffraction (ED) pattern of 3# alloy displays multi-haloes, meaning crystal structure characters. While, 4# alloy has a typical nanocrystalline/amorphous structure identified by the broad and dull halo electron diffraction patterns, demonstrating existence of large number of grain boundaries and internal energy. The result also explains that Ni adding facilitates formation of the nanocrystalline or amorphous structure of the alloy, which conforms well from the XRD results.
cast 1# alloy possesses the slowest hydriding rate. Hydrogen absorption capacities of the 1#, 2#, 3# and 4# alloys are 0.847 wt%, 1.329 wt%, 1.043 wt% and 2.03 wt% within 600 s, respectively. The result indicates that ball milling process for Ni is effective to inhance the hydrogenation properties of alloy. The improved hydriding rate by adding Ni attributes to formation of amorphous and nanocrystalline originate from the fact that the hydrogen diffusivity in a glass matrix is faster than that in a crystalline structure [11,24,28]. Furthermore, Ni adding is helpful to the catalytic effect for the hydrogen reactions [29]. The hydriding rate improved by substitution Y for Mg of the alloys is due to the secondary phase (MgYNi4) which provides more channel for the hydrogen diffusion and significantly catalytic effect [30,31].
Electrochemical hydrogen storage performances Gaseous hydrogen activation properties Electrochemical discharging capacity In Fig. 5, we present the activation performance of the four sample alloys prepared by different methods. Clearly, the as-
The electrochemical activation ability is an important performance of Ni-MH battery, which can be estimated through
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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Fig. 4 e TEM images and ED patterns of as-milling alloys: (a) Mg24Ni10Cu2 and (b) Mg24Ni10Cu2þ100 wt%Ni.
Fig. 5 e Variations of the first hydrogen desorption capacity of the four alloys with time varying.
the cycles times of charging and discharging to the make the discharge capacity to its maximum. Changes of the discharge capacities for the four samples vs. the cycle number are illustrated in Fig. 6. It shows. that the samples reach to the max discharge capacities happened in the 1st cycle, indicating the alloys possess activation properties. The maximum discharge capacities of four alloys are 74.9, 67.9, 156.8 and 899.7 mAh/g, respectively. The 1# and 2# alloys have extremely poor reversibility which can only discharge less than 10% percent of the largest discharge (999 mAh/g) capacity. It also suggests that discharge capacity cannot be improved by addition of rare-earth element Y. Discharge capacity of as-milled 3# alloy is still very low, but it is over two times of that as-cast. This is mainly due to the more grain boundary produced through grain refinement and the nanocrystalline structure through ball milling. One can observe that due to addition of a large amount of nickel, the maximum discharge of 4# is much greater than any other three samples. The active effect of Ni addition on the discharge capacity is originated from three reasons [32]. Firstly, as a hard particle, Ni cuts the alloy during the ball milling process to encourage the formation of nanocrystalline or amorphous alloy [33].
Fig. 6 e Evolution of discharge capacity of the four alloys with cycle number.
Secondly, adding Ni to the alloy helps improving the corrosion resistance of Mg-based alloy in alkali solution of KOH, which is advantageous to the cycle stability and the discharge capacity. Thirdly, Ni weakens the binding force between H and Mg atoms, and thus can dramatically decreases stability of the metal hydride therefore improves the kinetics of hydrogen absorption.
Electrochemical cycle stability The repeated charging performance of the battery originate from the cycling stability of the negative electrode material, one can be described by capacity retention (Sn). Sn can be calculated by Cn/Cmax 100% [33], in which Cmax represents the maximum discharge content, and Cn denotes the discharge capacity at the nth cycles. From the results shown in Fig. 7, it shows that the Sn decrease with increasing of the cycle time. while, the decline extent is obviously different for four alloys. The 1# alloy presents the best cycling stability, which is mainlydue to poor discharge capacity (Cmax ¼ 74.9 mAh/g). 3# and 4# also have quite low cycling stability, demonstrating that fine grain is useless to the cyclic stability [34]. Contrarily, increased surface area by fine grains increases contacting
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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Fig. 7 e Evolution of Sn values of the four alloys with cycle number.
between the alloy and electrolyte, and accelerated the corrosion rate of the sample.
Electrochemical kinetics For power batteries, it is necessary that they have the high current density discharge performances. However, it is known to all that the elevation of discharge current scale leads to the decreasing of discharge capacity of the electrode. This property can be characterized by the high rate discharge ability (HRD) of the sample samples [35]. HRD can be obtained by HRD ¼ Ci/(Ci þ C60) 100%, in which Ci denotes the largest discharge capacity of the cathode by using i mA/g current density, then the alloy electrode resumes discharge at the current densities of 60 mA/g by a rest of 10 min, the maximum discharge capacity is defined as C60. Changes of HRD of the four samples are showed in Fig. 8. Based on the test results at the current density of 300 mA/g, effects of production methods on HRD can be demonstrated, as inserted in Fig. 8. The HRD of 1#, 2#, 3# and 4# alloys are 69.5%, 70.5%, 57.7% and 80.1%, respectively. From the figures given above, the 3# alloys is the lowest
Fig. 8 e Evolution of HRD values of the four alloys with discharge current density.
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values, it also shows that Y substitution has insignificant influence on HRD. The 3# alloy has the lowest HRD, while the 4# alloy has the best performance, which indicates that the Ni adding contributes to improving the high rate discharge ability. Zhang et al. [20,36] reported that HRD of the electrode is generally affected by the charge-transfer rate and hydrogen diffusivity. To comprehend further, we use EIS qualitatively evaluate the charge transfer capability. The EIS result of the four alloys is showed in Fig. 9. It shows that every EIS is composed of two semicircular arcs at the high and middle frequencies separately and a line at the low frequency. Among them, the radius of the semicircle in the middle frequency represents the charge transfer resistance. The 3# and 4# alloys have the smaller radius of the semicircle, shows ball milling and Ni adding is advantageous to the charge transfer reaction, which agrees well with the HRD results. In the study of electrochemical properties of samples, the limiting current density (IL) is a significant parameter for characterization of the electrochemical kinetic performance. For this case, Tafel polarization curve I can characterize this property, as shown in Fig. 10. We can see that each anodic polarization curve possesses an obvious inflexion, meaning the presence of critical value. The values of IL of 4# and 3# alloys are 2.24 A/g and 0.44 A/g, manifesting that ball milling with Ni is helpful for the diffusion of hydrogen. The hydrogen diffusion coefficient is evaluated by the semilogarithmic curves of ratio of the anodic current and working duration, as shown in Fig. 11. According to the White's model [32,37], every electrode material particle is assumed to be a perfect sphere, the hydrogen diffusion coefficient could be gained by the slope of the linear area of the corresponding plots as followings: lgi ¼ lg ± 6FDðC0 Cs Þ= da2 p2 Dt= 2:303a2
(1)
D ¼ 2:303a2 ½dðlgiÞ=dðlgtÞ =p2
(2)
where i denotes the diffusion current density (mA/g), F denotes the Faraday constant, D represents the diffusion coefficient of hydrogen, a denotes the radius of alloy particles
Fig. 9 e Electrochemical impedance spectra (EIS) of the four alloys.
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
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Fig. 10 e Tafel polarization curves of the four alloys.
exists in Mg22Y2Ni10Cu2 alloy with the additive of Y, Cu element is completely dissolved in other phases. The nanocrystalline or amorphous structure in the alloy powder can be produced by ball milling, and adding Ni makes that dramatically speed-up. Based on the first H2 absorption capacity for the four alloys, the as-cast Mg22Y2Ni10Cu2 and as-milled Mg24Ni10Cu2 þ 100 wt %Ni are 1.329% and 2.03% with in 600 s. The discharge capability measurement of the alloy implies that the as-milled alloys have excellent performance, namely the capability of Mg24Ni10Cu2 þ 100 wt% Ni reaching 899.7 mAh/g, while the performance of the cycling stability is still bad. Furthermore, electrochemical kinetics of Mg24Ni10Cu2 þ 100 wt% Ni is the best of four alloys, and HRD of the 4# alloy is 80.1% at 300 mA/g, and IL and D are 2.24 A/g and 4.35 1011 cm2/s, respectively, which show that ball milling and composite nickel contribute to the diffusivity of the hydrogen and charge-transfer rate.
Acknowledgments This study was financially supported by the Natural Science Foundation of Inner Mongolia, China (2015MS0558, 2018LH05003) and the Science Research Project of the Colleges and Universities of the Inner Mongolia(NJZZ18142).
references
Fig. 11 e Semi-logarithmic curves of anodic current vs. time responses of the four alloys.
(1.5 103 cm), C0 is the original hydrogen concentration in matrix, Cs denotes the hydrogen content on the surface of the electrode material particles, d denotes the density of the electrodes, t denotes the discharge time, respectively. The evolutions of the D of the alloys derived from Eq. (2) with different manufacturing methods are also inserted in Fig. 11. The results demonstrate that D of the as-casted alloy is smaller but that of the as-milled alloys are larger. D of the 4# alloy is maximum (4.35 1011 cm2/s), meaning that ball milling and Ni adding contributes to the diffusivity of the hydrogen atoms. The result may be ascribed to the factor that amorphous could effectively slow down the oxidation of alloy [38].
Conclusions In this study, we investigated the gaseous and electrochemical properties of Mg2Ni-based hydrogen storage material prepared by various ways. The results are as follows: the as-cast Mg24Ni10Cu2 alloy is composed of two phases, Mg2Ni and Mg, where the former accounts for the majority. MgYNi4 phase
[1] Zou JX, Long S, Chen X, Zeng XQ, Ding WJ. Preparation and hydrogen sorption properties of a Ni decorated Mg based Mg@Ni nano-composite. Int J Hydrogen Energy 2015;40:1820e8. [2] Zhai TT, Yang T, Yuan ZM, Xu S, Bu WG, Qi Y, et al. Influences of hydrogen-induced amorphization and annealing treatment on gaseous hydrogen storage properties of La1xPrxMgNi3.6Co0.4 (x¼0e0.4) alloys. J Alloy Comp 2015;639:15e20. [3] Kumar Sanjay, Miyaoka H, Ichikawa T, Dey GK, Kojima Y. Micro-alloyed Mg2Ni for better performance as negative electrode of Ni-MH battery and hydrogen storage. Int J Hydrogen Energy 2017;42:5220e6. [4] Lv YJ, Zhang B, Wu Y. Effect of Ni content on microstructural evolution and hydrogen storage properties of MgexNie3La (x¼5,10,15,20 at.%) alloys. J Alloy Comp 2015;641:176e80. [5] Li Y, Gu QF, Li Q, Zhang TF. In-situ synchrotron X-ray diffraction investigation on hydrogen-induced decomposition of long period stacking ordered structure in MgeNieY system. Scripta Mater 2017;127:102e7. [6] Zhao X, Han SM, Zhu XL, Liu BZ, Chen XC, Liu YQ, et al. Effect of LaH3eTiH2 composite additive on the hydrogen storage properties of Mg2Ni alloys. J Alloy Comp 2013;581:270e4. [7] Junko M, Naoki U, Kanai T, Kazumi H, Akiba E. Effect of Mg/Ni ratio on microstructure of Mg-Ni films deposited by magnetron sputtering. J Alloy Comp 2014;617:47e51. [8] Ohara R, Chao-Ho L, Chii-Shyang H. Electrochemical and structural characterization of electroless nickel coating on Mg2Ni hydrogen storage alloy. J Alloy Comp 2013;580:s368e72. [9] Cho YH, Aminorroaya S, Liu HK, Dahle AK. The effect of transition metals on hydrogen migration and catalysis in cast MgeNi alloysInt. J Hydrogen Energy 2011;36:4984e92.
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156
i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 8 ) 1 e7
[10] Fu H, Wu WS, Dou Y, Liu BZ, Li HN, Peng QM. Hydrogen diffusion kinetics and structural integrity of superhigh pressure Mg-5 wt%Ni alloys with dendrite interface. J Power Sources 2016;320:212e21. [11] Yuan ZM, Yang T, Bu WG, Shang HW, Qi Y, Zhang YH. Structure, hydrogen storage kinetics and thermodynamics of Mg-based Sm5Mg41 alloy. Int J Hydrogen Energy 2016;41:5994e6003. [12] Wang PS, Liu SH, Du Y. Experimental investigation and thermodynamic calculation of the MgeMneNi system. Calphad 2015;49:41e9. a m R, Marcell G, Erhard S, Marco C, Luca PJ. [13] Ad Dehydrogenation-hydrogenation characteristics of nanocrystalline Mg2Ni powders compacted by high-pressure torsion. Alloy Comp 2017;702:84e91. [14] Tran XQ, Mcdonald SD, Gu QF, Nogita K. In-situ synchrotron X-ray diffraction investigation of the hydriding and dehydriding properties of a cast MgeNi alloy. J Alloy Comp 2015;636:249e56. [15] Zhou WH, Zhu D, Tang ZY, Wu CL, Huang LW, Ma ZW, et al. Improvement in low-temperature and instantaneous highrate output performance of Al-free AB5-type hydrogen storage alloy for negative electrode in Ni/MH battery: effect of thermodynamic and kinetic regulation via partial Mn substituting. J Power Sources 2017;343:11e21. [16] Si TZ, Ma Y, Li YT, Liu DM. Solid solution of Cu in Mg2NiH4 and its destabilized effect on hydrogen desorption Mater. Chem Phys 2017;193:1e6. [17] Shao HY, Li XG. Effect of nanostructure and partial substitution on gas absorption and electrochemical properties in Mg2Ni-based alloys. J Alloy Comp 2016;667:191e7. [18] Zadorozhnyy VY, Menjo M, Zadogozhnyy MY, Kaloshkin SD, Louzguine-luzgin DV. Hydrogen sorption properties of nanostructured bulk Mg2Ni intermetallic compound. J Alloy Comp 2014;586(Suppl 1):S400e4. Gajdics M, Varga LK, Kra ve sz A, llics G, Pe ter L, Spassov T. [19] Re Hydrogen storage of nanocrystalline MgeNi alloy processed by equal-channel angular pressing and cold rolling. Int J Hydrogen Energy 2014;39:9911e7. [20] Zhu YF, Yang C, Zhu JY, Li LQ. Structural and electrochemical hydrogen storage properties of Mg2Ni-based alloys. J Alloy Comp 2011;509:5309e14. us D. Exploring the [21] Wirth E, Milcius D, Filiou C, Nore hydrogen sorption capacity of MgeNi powders produced by the vapour deposition technique. Int J Hydrogen Energy 2008;33:3122e7. [22] Zhang YH, Wang HT, Zhai TT, Yang T, Qi Y, Zhao DL. Hydrogen storage characteristics of the nanocrystalline and amorphous MgeNdeNieCu-based alloys prepared by melt spinning. Int J Hydrogen Energy 2014;39:3790e8. [23] Zhang TB, Song WJ, Kou HC, Li JS. Surface valence transformation during thermal activation and hydrogenation thermodynamics of MgeNieY melt-spun ribbons. Appl Surf Sci 2016;371:35e43. [24] Hongo T, Kaveh E, Makoto A, Junko M, Akiba E, Horita Z. Significance of grain boundaries and stacking faults on
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
7
hydrogen storage properties of Mg2Ni intermetallics processed by high-pressure torsion. Acta Mater 2015;92:46e54. Huang LW, Elkedim O, Nowak M, Jurczyk M, Chassagnon R, Meng DW. Synergistic effects of multiwalled carbon nanotubes and Al on the electrochemical hydrogen storage properties of Mg2Ni-type alloy prepared by mechanical alloying. Int J Hydrogen Energy 2012;37:1538e45. Liu LH, Min M, Liu F, Yin H, Zhang YS, Qiu GH. Influence of vanadium doping on the supercapacitance performance of hexagonal birnessite. J Power Sources 2015;277:26e35. Song JZ, Han SM, Fu RD. Effect of La2O3-CaO composite additive on the hydrogen storage properties of Mg2Ni alloy. Mater Sci Eng B 2014;188:114e8. Zhang QA, Zhang LX, Wang QQ. Crystallization behavior and hydrogen storage kinetics of amorphous Mg11Y2Ni2 alloy. J Alloy Comp 2013;551:376e81. Fujimoto T, Ogawa S, Kanai T, Naoki U, Yoshida T, Shinya Y. Hydrogen storage property of materials composed of Mg nanoparticles and Ni nanoparticles fabricated by gas evaporation method. Int J Hydrogen Energy 2015;40:11890e4. Song WJ, Li JS, Zhang TB, Kou HC, Xue XY. Microstructure and tailoring hydrogenation performance of Y-doped Mg2Ni alloys. J Power Sources 2014;245:808e15. ChitsazKhoyi L, Raygan Sh, Pourabdoli M. Mechanical milling of Mg, Ni and Y powder mixture and investigating the effects of produced nanostructured MgNi4Y on hydrogen desorption properties of MgH2. Int J Hydrogen Energy 2013;38:6687e93. Zhang YH, Wang HT, Zhai TT, Yang T, Yuan ZM, Zhao DL. Hydrogen storage performances of LaMg11Niþxwt% Ni (x¼100, 200) alloys prepared by mechanical milling. J Alloy Comp 2015;645:S438e45. Tian X, Yun GH, Wang HY, Shang T, Yao ZQ, Wei W, et al. Preparation and electrochemical properties of LaeMgeNibased La0.75Mg0.25Ni3.3Co0.5 multiphase hydrogen storage alloy as negative material of Ni/MH battery. Int J Hydrogen Energy 2014;39:8474e81. Hou XJ, Hu R, Zhang TB, Kou HC, Song WJ, Li JS. Microstructure and electrochemical hydrogenation/ dehydrogenation performance of melt-spun La-doped Mg2Ni alloys. Mater Char 2015;106:163e74. Liu JJ, Han SM, Li Y, Zhao X, Yang SQ, Zhao YM. Cooperative effects of Sm and Mg on electrochemical performance of LaeMgeNi-based alloys with A2B7 and A5B19etype super-stacking structure. Int J Hydrogen Energy 2015;40:1116e27. Kuriyama N, Sakai T, Miyamura H, Uehara I, Ishikawa H. Electrochemical impedance and deterioration behavior of metal hydride electrodes. J Alloy Comp 1993;202:193. Zheng G, Popov BN, White RE. Electrochemical determination of the diffusion coefficient of hydrogen through an LaNi4.25Al0.75 electrode in alkaline aqueous solution. J Electrochem Soc 1995;142:2695e8. Liu ZP, Yang SQ, Li Y, Ma MZ, Han SM. Improved electrochemical kinetic performances of La-Mg-Ni-based hydrogen storage alloys with lanthanum partially substituted by yttrium. J Rare Earths 2015;33:397e402.
Please cite this article in press as: Sun H, et al., Gas hydrogen absorption and electrochemical properties of Mg24Ni10Cu2 alloys improved by Y substitution, ball milling and Ni addition, International Journal of Hydrogen Energy (2018), https://doi.org/10.1016/ j.ijhydene.2018.08.156