Hydrogen Storage Properties of Magnesium Hydride with V-Based

Article pubs.acs.org/JPCC

Hydrogen Storage Properties of Magnesium Hydride with V‑Based Additives Chai Ren,† Z. Zak Fang,*,† Chengshang Zhou,† Jun Lu,‡ Yang Ren,§ and Xiaoyi Zhang§ †

Department of Metallurgical Engineering, University of Utah, 135 South 1460 East, Room 412, Salt Lake City, Utah 84112-0114, United States ‡ Chemical Science and Engineering Division, and §Advanced Photon Source, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States ABSTRACT: Magnesium hydride is one of the most promising candidates for solid-state hydrogen storage and thermal energy storage applications. The effects of V-based solid solution alloys on the hydrogenation and dehydrogenation behavior of magnesium hydride are studied. Significant reduction of the dehydrogenation temperature and improvements of the kinetics of both absorption and desorption reactions were observed for MgH2 with V-based additives. Those observations were made using thermogravimetric analysis (TGA) and pressure−composition−temperature (PCT) techniques. In situ synchrotron X-ray diffraction (XRD) measurements suggest that the additives functioned as catalysts during the reactions. The comparison of the characteristics of different additives suggested that the hydrogen equilibrium pressures of those additives themselves have a significant bearing on their effects on the kinetic behaviors of MgH2. The lower is the stability of an additive as a hydride, the more effective it would be as a catalyst.

1. INTRODUCTION

Another effective method is using additives to improve the kinetics of the dehydrogenation and hydrogenation reactions of MgH2, including lowering the dehydrogenation temperature. In general, a small amount of additives that do not react with Mg/ MgH2 and do not participate in the dehydrogenation or hydrogenation processes may be considered as “catalysts”. A list of materials including transition metals,12−14 transition metal oxides,15−18 and intermetallic compounds19−24 has been reported as effective catalysts. For example, Nb2O5 was reported effective for room-temperature hydrogenation and low-temperature dehydrogenation.25 Lu et al. reported significant improvements in both the hydrogenation and the dehydrogenation behavior of MgH2 by preparing it using an ultra high energy high pressure planetary mill with TiH2 additives.26,27 The current authors found that the hydrogen storage properties of MgH2 with TiH2 additive can be further improved by using other Ti-based intermetallic compounds as well, such as TiMn2.28 However, when a large amount of an additive is used, this additive may no longer be considered as a catalyst, but alloyed with MgH2. Examples include the following systems: Mg−LaNi5,21 Mg−FeTi1.2,19 Mg−(Fe0.8Mn0.2)Ti,29 Mg−TiMn1.5,30 and Mg−Ti0.4Cr0.15Mn0.15V0.3.31 Although the low temperature dehydrogenation and hydrogenation behavior

Magnesium hydride (MgH2) is considered one of the most promising candidates for solid-state hydrogen storage due to its high theoretical hydrogen capacity (7.6 wt %), good reversibility, and relatively low cost. MgH2 is also considered for thermal energy storage applications. However, two factors have impeded MgH2 from meeting the criteria for practical applications: (1) the thermodynamic stability of MgH2 leads to its dehydrogenation temperature being as high as 350−400 °C; and (2) the kinetic rates of both dehydrogenation and hydrogenation reactions of Mg are usually poor and require high temperature conditions.1,2 Extensive works have been reported on improving the hydrogen storage properties of the MgH2-based systems. Among various types of techniques, using mechanical method to reduce MgH2 particle sizes into nanoscale has been demonstrated as an effective approach.3 Wagemans et al. predicted that the decomposition enthalpy can be decreased by reducing MgH2 particle size to 0.9 nm.4 Recently, this prediction has been proved by several researchers who synthesized MgH2 with nanoscale structures or highly deformed with high dislocation density structures.5−11 However, the size of the nanosized MgH2 crystals will inevitably grow during the cyclic dehydrogenation and hydrogenation reactions, which would cause degradation of the material’s properties. © 2014 American Chemical Society

Received: May 14, 2014 Revised: September 2, 2014 Published: September 3, 2014 21778

dx.doi.org/10.1021/jp504766b | J. Phys. Chem. C 2014, 118, 21778−21784

The Journal of Physical Chemistry C

Article

ments were performed using a Philips X’Pert PW3040 X-ray diffractometer with Cu Kα1 radiation. Powders were mixed inside the glovebox with a batch size of 3 g and a 95:5 MgH2 to additive molar ratio. A custom-made ultra-high-energy-high-pressure (UHEHP) planetary milling machine was used for the milling process of the samples. Each sample was loaded into a custom-made milling canister with a ball-to-powder ratio of 20:1 by volume and milled under 50 bar hydrogen pressure for 4 h. Nanosized MgH2 powders with homogeneously distributed additives were obtained from this process. The crystalline size of as-milled powder ranged from 5 to 10 nm based on calculation using the XRD line broadening technique and the Williamson−Hall method.56 2.2. Sample Characterization. The dehydrogenation behaviors of the samples were characterized using a thermal gravimetric analyzer (Shimadzu, TGA50) inside the argon atmosphere glovebox. About 15 mg of each sample was heated under 50 mL/min flowing argon up to 400 °C with a heating rate of 20, 10, 5, 2, and 1 °C/min, respectively. The hydrogenation and dehydrogenation behaviors and the equilibrium pressures of the samples were measured using a commercial Sieverts-type apparatus (Hy-Energy, PCTPro2000). About 0.15 g of powder of each sample was sealed inside a stainless-steel PCT sample holder. A Teledyne Taber model 206 piezoelectric transducer with a range from 0 to 200 bar and 10−3 bar resolution was used for the pressure measurements. The temperature control of sample holders was completed by the PID controller (Watlow, PID Controller SD). The amount of hydrogen uptake/release was calculated on the basis of the pressure change inside the calibrated volume.57,58 To characterize the phase transformations during dehydrogenation, in situ XRD experiment of MgH2−5 mol % V75Ti5Cr20 was performed on the 11-ID-D beamline at the Advanced Photon Source (APS), Argonne National Laboratory (ANL). The high energy high brightness synchrotron X-ray and silicon (220) monochromator provide a 16.202 keV X-ray beam (wavelength 0.765334 Å) with a relative bandwidth Δλ = 1.77 × 10−4 Å and a flux of about 1 × 1012 photons/s. XRD patterns with up to 40° diffraction angle were collected by a Pilatus 2 M detector at a sample-to-detector distance of 177 mm. A Linkam THMS600 microscope heating stage was used for the in situ XRD experiment. The sample was heated to 230 °C with a heating rate of 3 °C/min under the argon flow of 4 mL/min. The XRD patterns were collected at a frequency of 10 scans/min.

of MgH2 can be improved significantly by using a larger quantity of additives, the improvements are achieved at a significant cost of decreasing the hydrogen storage capacity. Deposition of Mg-based binary and ternary metal thin films was also reported as an effective approach for improving the kinetics. Various transition metals (Ti, Cr, V, and Fe) as well as some nontransition metal (Al, Si) were experimented as additives to Mg during deposition process.32−36 V and V-based alloys have been shown as an effective additive for improving MgH2’s desorption as well as absorption kinetics. Studies on mechanical milled MgH2−V powder, Mg− V−Nb thin films, and Mg−V−Cr thin films showed remarkably rapid low-temperature hydrogenation kinetics and good hightemperature cycle stability.36−41 However, different preparation methods of the samples limit the comparability of the results. Therefore, a systematic study of the catalysis effect of V-based alloys on the hydrogenation and dehydrogenation properties of MgH2 is highly desired. Vanadium by itself is also one of the most studied hydrogen storage materials. V−H reactions have rapid reaction kinetics, and V has up to 2.3 wt % reversible hydrogen capacity.42,43 There are several research reports available in literature that deal with V-based bcc binary and ternary alloys regarding their stability and hydrogen capacity.44−48 A study reported by Yukawa on the effects of alloying on hydrogen storage behavior of V showed that the stability of V-based hydride varies with alloying elements. Among the alloying elements, Ti stabilizes Vbased hydride and improves its hydrogen capacity. Cr could destabilize V hydride; however, it decreases its hydrogen capacity.49,50 Built on the basis of those results, ternary V−Ti− Cr systems were developed, enabling a wide adjustable range of plateau pressures.51−55 It seems that all of those V−Ti−Cr alloys could be used as catalytic additives for improving the properties MgH2. A logical question that arises from those prior research results is if there is a correlation between one alloy’s hydrogen storage properties and its potential effects as a catalyst. Therefore, the present research focuses on studying the catalysis effect of V and V-based alloys on the hydrogenation and dehydrogenation behaviors of MgH2 and the possible correlation between the stability of a V-base hydride and its catalytic effects on MgH2.

2. EXPERIMENTAL PROCEDURE 2.1. Sample Preparation. The information on raw materials for this work is shown in Table 1. All handling of raw materials was carried out inside an argon circulating glovebox with less than 1 ppm controlled oxygen and water level. The V-based alloys were in their solid solution states with a body-center-cubic crystal structure. To identify the phase composition of the raw materials, X-ray diffraction measure-

3. RESULTS 3.1. Dehydrogenation Properties. The dehydrogenation of high energy ball milled MgH2 with V-based additives was characterized by conducting a series of thermal gravimetric analysis (TGA) at five different heating rates (1, 2, 5, 10, and 20 °C/min). Figure 1 shows the comparison of the TGA curves of as-milled MgH2 and MgH2 with various kinds of V-based additives with a heating rate of 5 °C/min. The dehydrogenation temperatures were determined at the 40% conversion point, and the values are 333 °C for pure MgH2, 217 °C for MgH2−5 mol % V75Ti5Cr20, 229 °C for MgH2−5 mol % V80Ti8Cr12, 220 °C for MgH2−5 mol % V, 233 °C for MgH2−5 mol % V80Ti20, and 227 °C for MgH2−5 mol % V80Cr20. The dehydrogenation temperatures of MgH2 with V-based additive are within the range of 217−233 °C, which is approximately 100 °C lower than that of pure MgH2. Such a significant difference clearly

Table 1. Raw Material Information material

composition

supplier

MgH2 V V75Ti5Cr20 V80Ti8Cr12 VTi VCr

>98% >99.5% V75Ti5Cr20 V80Ti8Cr12 V80Ti20 V80Cr20

Sigma-Aldrich Sigma-Aldrich Ames Lab Ames Lab Sophisticated Alloys Sophisticated Alloys 21779



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plausible partially because the quantity of the sample is very small; thus the heat dissipation by the sample holder was fast. Further, a detailed report on overheating and maintaining isothermal conditions during hydrogenation is provided in ref 59. Figure 3 shows the comparison of room-temperature

Figure 1. TGA curves of as-milled MgH2 and MgH2 with V75Ti5Cr20, V80Ti8Cr12, V, VCr, and VTi additives.

demonstrates the improvements in the dehydrogenation property of MgH2 by adding the V-based additives. Among the V-based additives, V 75Ti5 Cr20 provides the lowest dehydrogenation temperature of 217 °C, which is comparable to other additives that were reported to be very effective for MgH2 including the more recent report on TiMn2 additive by the present authors.28 To further investigate the dehydrogenation kinetics, isothermal dehydrogenation tests were performed at 240 °C on MgH2 with all five additives with a back pressure of 0.01 bar. The isothermal dehydrogenation curves are shown in Figure 2.

Figure 3. PCT hydrogenation kinetics of MgH2 with V75Ti5Cr20, V80Ti8Cr12, V, VCr, and VTi additives under room temperature and 1 bar hydrogen pressure.

hydrogenation kinetic curves of MgH2 with V75Ti5Cr20, V80Ti8Cr12, V, V80Ti20, and V80Cr20 additives. On the basis of the figure, the sample of MgH2−5 mol % V75Ti5Cr20 showed a rapid hydrogenation step at the beginning with 1.5 wt % hydrogen absorbed within the first 10 min. The hydrogen uptake of this sample increased with time and reached 3.5 wt % hydrogen absorbed in 200 min. By comparing the different kinds of V-based additives, it can be seen that the effectiveness of the additives on improving hydrogenation kinetics follows an order of V75Ti5Cr20, V, V80Ti8Cr12, V80Cr20, and V80Ti20 from highest to lowest. The significant hydrogen absorption of MgH2 with V-based additives at such a moderate condition (1 bar hydrogen pressure and room temperature) suggests a strong effect of V-based additives on the hydrogenation of Mg. 3.3. PCI Measurement. The thermodynamic behavior of MgH2 with V75Ti5Cr20 was studied by performing the pressure−composition−isothermal (PCI) measurements using the Sivert-type PCT system. Figure 4 compares the PCI curves of pure MgH2 and the MgH2−5% V75Ti5Cr20 samples measured at 300 °C. No significant differences in the equilibrium pressures can be observed between the MgH2 with and without V75Ti5Cr20 additive. In other words, the Vbased additives have strong effects on the kinetics of hydrogenation and dehydrogenation; they do not affect the

Figure 2. PCT dehydrogenation kinetics of MgH2 with V75Ti5Cr20, V80Ti8Cr12, V, VCr, and VTi additives.

All of the samples were able to fully dehydrogenate within 10 min, and the samples with V75Ti5Cr20, V80Ti8Cr12, and pure V as additives were able to complete dehydrogenation within about 6 min. As compared to the pure MgH2 sample, which did not dehydrogenate at all at this low temperature, these results demonstrate a significant improvement in the kinetics of dehydrogenation of MgH2with V-based alloys additives. 3.2. Hydrogenation Properties. The ability of Mg with Ti-based additives to uptake a significant amount of hydrogen at relatively low hydrogen pressure and room temperature has been reported previously.28 To characterize the effect of Vbased additives on the hydrogenation kinetics of Mg, a series of hydrogenation experiments were performed using the PCT under 1 bar hydrogen pressure and at room temperature. The experiments were designed and conducted under isothermal conditions. The real-time temperature was monitored using a K-type thermocouple that is placed in contact with the wall of the sample vial. No significant temperature change was observed during the hydrogenation experiment. This is

Figure 4. PCI hydriding measurements of as-milled MgH2 and MgH2−5% V75Ti5Cr20 at 300 °C. 21780



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solid solutions are located at 20.93° and 29.31°. The data were processed using the commercial program X’Pert HighScore Plus. The background was described by a polynomial function, and the peak profile was expressed by a pseudo-Voigt function. The lattice parameter of V75Ti5Cr20 was determined to be 2.98 Å at room temperature. This value is consistent with the range of VTiCr alloy lattice parameters reported by Miraglia et al.60 During the dehydrogenation of MgH2, a 1.3% lattice expansion was observed, which may be related to the hydrogen transfer process from desorbing MgH2, similar to the “hydrogen exchange” reported previously by Laversenne et al.41 However, the lattice parameter decreased to its original value after the dehydrogenation, and no other significant changes were observed. Therefore, the in situ XRD result shows that no phase transformation of V75Ti5Cr20 is involved in the dehydrogenation process of MgH2. It appears that the addition of V-based solid solution alloy has a catalytic effect on the dehydrogenation of MgH2, similar to that of TiH2 and TiMn2.26−28 The fundamental understanding of such a catalytic effect is, however, still lacking.

thermodynamic stability of magnesium hydride. This is an important data point for understanding the effects of additives. 3.4. In Situ XRD Measurement. To understand the effect of V-based additives on the behavior of MgH2, in situ synchrotron XRD measurements were carried out to study the sequence of phase transformations of MgH2 with additives during its dehydrogenation process. Specifically, the MgH2−5 mol % V75Ti5Cr20 sample was studied. As described in the section on experimental procedures, the as-milled MgH2−5 mol % V75Ti5Cr20 was heated to 230 °C with a rate of 3 °C/ min under 4 mL/min of flowing argon. The XRD patterns were collected in situ during the heating and dehydrogenation process with a scan frequency of 10 scans/min. Figure 5a shows

4. DISCUSSION The activation energies of the dehydrogenation of MgH2 with different V-based additives were calculated on the basis of the nonisothermal TGA analysis using the Ozawa−Flynn−Wall method.61−63 The OFW method is based on the rate equation: ⎛ −E ⎞ dα = Af (α) exp⎜ a ⎟ ⎝ RT ⎠ dt

where α is the fractional conversion, t is the reaction time, A is the pre-exponential factor, f(α) is the mechanism related kinetic function, and R is the gas constant. Integrate the rate equation under a constant heating rate β: log β = −

Figure 5. In situ XRD data for ball milled MgH2−5 mol % V75Ti5Cr20. (a) Grayscale contour plot of XRD patterns as a function of time. (b) Temperature profile of the experimental heating procedure.

⎛ R 0.457Ea − 2.315 − log⎜ RT ⎝ AEa

∫0

a

dα ⎞ ⎟ f (α ) ⎠

where temperature T is defined as T = T0 + βt (T0 is the starting temperature.). The activation energy Ea can be calculated from the slope of log β versus 1/T plot at a given α value. The TGA measurements were performed for the MgH2 with each type of V-based additives at five different heating rates (1, 2, 5, 10, and 20 °C/min). The dehydrogenation temperatures were determined by the 40% conversion point, and the results are summarized in Table 2. The activation energies were calculated on the basis of the slopes of log β versus 1000/T

the gray scale contour plot of the XRD intensity of the ball milled MgH2−10 mol % V75Ti5Cr20 during the heating process. Figure 5b is the temperature profile corresponding to the in situ XRD measurement. The as-milled sample contained β-MgH2, γ-MgH2, and the additive VTiCr phases. The dehydrogenation of MgH2 started at about 170 °C, and a small amount of βMgH2 remained until the end of the experiment at 230 °C. Two diffraction peaks for the metallic V phase with Ti and Cr Table 2. Activation Energy of MgH2 with V-Based Additives

dehydrogenation temp, °C sample

1 °C/min

2 °C/min

3 °C/min

4 °C/min

5 °C/min

QA of dehydrogenation, kJ/mol·H2

MgH2−V75Ti5Cr20 MgH2−V80Ti8Cr12 MgH2−V MgH2−VTi MgH2−VCr MgH2 MgH2−TiMn2 MgH2−TiH2

181.66 186.60 187.61 199.66 188.28

201.42 200.86 197.12 212.19 203.80

218.17 230.33 226.96 238.27 224.66

246.15 248.29 240.9 261.72 249.78

261.32 271.2 259.13 284.31 271.51

71.20 68.86 77.33 71.77 70.79 96.0064 74.2228 67.2428

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lines where β is the heating rate and T is the dehydrogenation temperature. The results are also presented in Table 2. On the basis of the results, the addition of V-based alloys in MgH2 significantly decreases the activation energy of dehydrogenation. The MgH2 with V80Ti8Cr12 additive shows the lowest activation energy of 68.86 mJ/mol H2, and the MgH2 with pure V additive has the highest activation energy of 77.33 mJ/mol H2. The activation energies of V-based additives are about the same as Ti-based additives, which explains the similar dehydrogenation behavior of these two systems. As discussed in the Results, no significant phase transformation of V-based additives was observed during the dehydrogenation of MgH2. Considering that the V-based additives do enhance the kinetic rate of dehydrogenation, this result suggests that the V-based solid solution alloy has a catalyst-like effect on the dehydrogenation of MgH2. Similar in situ XRD measurements were also performed on high energy ball milled MgH2 with TiH2 and TiMn2 additives by the current authors.65 During dehydrogenation processes, both TiH2 and TiMn2 additives remained stable as well. Therefore, all three transition metal alloy additives have similar catalytic effects on MgH2. However, the effectiveness of these additives varies considerably. Even for different V-based alloys as reported in this study with different solid solution elements, their effectiveness on improving the kinetics of MgH2 differs considerably; it is thus important to find the factors that determine the effectiveness of those different additives. One of the common characteristics of all of these additives is that they are all hydrogen storage materials in and of themselves. It is thus hypothesized that the hydrogen storage properties of these materials may have a relation to their effects on MgH2. As mentioned in the Introduction, V-based alloy is one of the wellstudied systems for hydrogen storage with a wide range of adjustable properties by changing the alloy compositions. The unique properties of vanadium alloys provide a good system for studying the correlations between the hydrogenation storage properties of the additives and their effects on MgH2. In contrast, the structure of TiMn2 alloy is very complex, and it would be difficult to study using it as a model material. To that end, we examined the hydrogen storage properties of V-based alloys themselves. Figure 6 shows the measured PCI

36.7 bar for V75Ti5Cr20 and 3.3 bar for V80Ti8Cr12, respectively. For the other additives, the room-temperature plateau pressure was reported as 4.8 bar for pure V by Yukawa et al.49 and 2 bar for V80Ti20 by Ono et al.48 Another additive of interest is V−Cr alloy. A systemic study on V−Cr alloys by Lynch et al. showed a dramatic change of the hydrogen solubility by increasing the Cr composition, and the V80.4Cr19.6 alloy does not form a dihydride even at the extreme condition of 60.8 bar and −78 °C.47 Now we try to correlate the hydrogen storage properties of V-based alloys with their effectiveness as additives to Mg and MgH2. Specifically, we can correlate the plateau pressures of the V-based alloys with their effects as additives on the roomtemperature hydrogenation kinetics of MgH2. As shown in Table 3, it can be seen that there seems to be a general trend. Table 3. Correlation between Additive’s Improvement in Hydrogenation Kinetics and Additive’s Plateau Pressure time to reach 1.5 wt % hydrogenation (min) additive’s room temp plateau pressure (bar)

V75Ti5Cr20

V

10.8

18.3

V80Ti8Cr12 V80Cr20 35.1

36.7

4.8

3.3

42.7

V80Ti20 109.5 2

The higher is the plateau pressure, the better is the kinetics of MgH2 with V-based additives. In other words, the less stable transition metal hydrides seem to have better effects on the hydrogenation and dehydrogenation of Mg. This result may help in understanding the role of those additives during hydrogenation and dehydrogenation. The only exception is V80Cr20, which can be explained by its poor solubility for hydrogen that may have limited its functions as a hydrogen storage material. Regarding the kinetics of magnesium hydrogenation, a list of possible rate-limiting kinetic steps was summarized by Bloch et al.:66 (1) the diffusion of hydrogen in Mg hydride and metal phases,67−69 (2) the diffusion of hydrogen along the hydride− metal interface,70 (3) surface passivation caused by oxygen or sulfur,66 and (4) the required activation energy for hydrogen dissociation and reassociation on the surface.71 A widely accepted hypothesis is that the transition metal additives can help step (4) by lowering the activation energies. Transition metals may also help other steps by enhancing coefficients of hydrogen diffusion. Previous studies suggested that the V additive may function as a catalyst and help transport proton due to the fast rate of diffusion of hydrogen in V.38,39,41 For Vbased alloys, Matumura et al. reported that the alloying elements may affect the chemical interactions between V−H atoms and modify equilibrium pressure of V-based bcc solid solution alloys.72 The alloying of V with Ti stabilizes the Vbased hydrides and the alloying with Cr destabilizes the hydrides as indicated by the increase and decrease of plateau pressures, respectively. If the V-based additive is to function as a path for hydrogen diffusion, a stable hydride phase of V may not be a desired property. A stable hydride would limit the amount of active sites for hydrogen diffusion and prevent the additive from aiding the transport of H in the system. This viewpoint is supported by the results in Table 3. The only exception is V80Cr20, which can be explained by its poor solubility for hydrogen that may have limited its functions as a hydrogen storage material. To further extrapolate on the basis of the published literature and the current results, an ideal

Figure 6. PCI hydriding measurements of V75Ti5Cr20 and V80Ti8Cr12 at room temperature.

plots of absorption isothermal at room temperature for the V80Ti8Cr12 and V75Ti5Cr20 alloys. Similar to other V-based alloys, a slope can be observed for both VTiCr alloys, indicating a gradual change of the absorption pressure during the β2 to γ phase transformation. By taking the middle point of the plateau, the plateau pressure of these two alloys can be determined as 21782



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via Accumulative Roll-Bonding (ARB). Int. J. Hydrogen Energy 2011, 36, 3022−3036. (11) Lang, J.; Huot, J. A New Approach to the Processing of Metal Hydrides. J. Alloys Compd. 2011, 509, L18−L22. (12) Liang, G.; Huot, J.; Boily, S.; Van Neste, A.; Schulz, R. Catalytic Effect of Transition Metals on Hydrogen Sorption in Nanocrystalline Ball Milled MgH2-Tm (Tm = Ti, V, Mn, Fe and Ni) Systems. J. Alloys Compd. 1999, 292, 247−252. (13) Hanada, N.; Ichikawa, T.; Fujii, H. Catalytic Effect of Nanoparticle 3d-Transition Metals on Hydrogen Storage Properties in Magnesium Hydride MgH2 Prepared by Mechanical Milling. J. Phys. Chem. B 2005, 109, 7188−7194. (14) Shang, C. X.; Bououdina, M.; Song, Y.; Guo, Z. X. Mechanical Alloying and Electronic Simulations of (MgH2−M) Systems (M = Al, Ti, Fe, Ni, Cu and Nb) for Hydrogen Storage. Int. J. Hydrogen Energy 2004, 29, 73−80. (15) Song, M.; Bobet, J. L.; Darriet, B. Improvement in Hydrogen Sorption Properties of Mg by Reactive Mechanical Grinding with Cr2O3, Al2O3 and CeO2. J. Alloys Compd. 2002, 340, 256−262. (16) Friedrichs, O.; Aguey-Zinsou, F.; Ares Fernández, J. R.; SánchezLópez, J. C.; Justo, A.; Klassen, T.; Bormann, R.; Fernández, A. MgH2 with Nb2O5 as Additive for Hydrogen Storage: Chemical, Structural and Kinetic Behavior with Heating. Acta Mater. 2006, 54, 105−110. (17) Wang, P.; Wang, A.; Zhang, H.; Ding, B.; Hu, Z. Hydrogenation Characteristics of Mg-TiO2 (rutile) Composite. J. Alloys Compd. 2000, 313, 218−223. (18) Milošević, S.; Rašković-Lovre, Ž .; Kurko, S.; Vujasin, R.; Cvjetićanin, N.; Matović, L.; Grbović Novaković, J. Influence of VO2 Nanostructured Ceramics on Hydrogen Desorption Properties from Magnesium Hydride. Ceram. Int. 2013, 39, 51−56. (19) Liang, G. X.; Wang, E.; Fang, S. S. Hydrogen Absorption and Desorption Characteristics of Mechanically Milled Mg − 35 wt.% FeTi1.2 Powders. J. Alloys Compd. 1995, 223, 111−114. (20) Orimo, S.; Fujii, H.; Horie, S. Investigations of Interfacial Materials Designed the Effect of Interface Microstructures in ZrCr1.8Cu0.3/Mg on MgH2 Formation as a Result of Hydrogen Interdiffusion. J. Alloys Compd. 1995, 231, 766−772. (21) Liang, G.; Boily, S.; Huot, J.; Van Neste, A.; Schulz, R. Hydrogen Absorption Properties of a Mechanically Milled Mg - 50 wt. % LaNi5 Composite. J. Alloys Compd. 1998, 268, 302−7. (22) Terzieva, M.; Khrussanova, M.; Peshev, P. Hydriding and Dehydriding Characteristics of Mg-LaNi5 Composite Materials Prepared by Mechanical Alloying. J. Alloys Compd. 1998, 267, 235− 239. (23) Wang, P.; Wang, A.; Zhang, H.; Ding, B.; Hu, Z. Hydriding Properties of a Mechanically Milled Mg-50 wt.% ZrFe 1.4Cr 0.6 Composite. J. Alloys Compd. 2000, 297, 240−245. (24) Fernández, J. F.; Bodega, J.; Sánchez, C. R. Hydriding/ Dehydriding Properties of Magnesium-ZrCr2 Composites. J. Alloys Compd. 2003, 356−357, 343−347. (25) Hanada, N.; Ichikawa, T.; Hino, S.; Fujii, H. Remarkable Improvement of Hydrogen Sorption Kinetics in Magnesium Catalyzed with Nb2O5. J. Alloys Compd. 2006, 420, 46−49. (26) Lu, J.; Choi, Y. J.; Fang, Z. Z.; Sohn, H. Y.; Rönnebro, E. Hydrogenation of Nanocrystalline Mg at Room Temperature in the Presence of TiH2. J. Am. Chem. Soc. 2010, 132, 6616−6617. (27) Lu, J.; Choi, Y. J.; Fang, Z. Z.; Sohn, H. Y.; Rönnebro, E. Hydrogen Storage Properties of Nanosized MgH2-0.1TiH2 Prepared by Ultrahigh-Energy-High-Pressure Milling. J. Am. Chem. Soc. 2009, 131, 15843−15852. (28) Zhou, C.; Fang, Z. Z.; Ren, C.; Li, J.; Lu, J. Effect of Ti Intermetallic Catalysts on Hydrogen Storage Properties of Magnesium Hydride. J. Phys. Chem. C 2013, 117, 12973−12980. (29) Reule, H.; Hirscher, M.; Weißhardt, A.; Kronmüller, H. Hydrogen Desorption Properties of Mechanically Alloyed MgH2 Composite Materials. J. Alloys Compd. 2000, 305, 246−252. (30) Hu, Y. Q.; Zhang, H. F.; Wang, A. M.; Ding, B. Z.; Hu, Z. Q. Preparation and Hydriding/Dehydriding Properties of Mechanically

additive for MgH2 should be a material with reasonable hydrogen capacity, excellent hydrogen diffusion dynamics, and very unstable hydride phase.

5. CONCLUSION The addition of V-based solid solution alloys can lead to significant improvements of the hydrogenation and dehydrogenation kinetics of magnesium hydride. In situ synchrotron XRD results indicated that the additive does not participate in the Mg−H reactions; rather it functioned similarly as a catalyst. Further analysis of the additive materials plateau pressure revealed that the less stable V-based hydrides provide better enhancement of the hydrogenation reaction of Mg.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This research was supported by the U.S. Department of Energy (DOE) under contract number DE-AR0000173 and the National Science Foundation (Grant no. 0933778). Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under Contract no. DE-AC02-06CH11357. We also appreciate the support of Beamline staffs of 11-ID-D and 11ID-C, which made the experiments possible. We are grateful to Dr. J Vajo for providing VTiCr alloys and for his very helpful suggestions.

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REFERENCES

(1) Jain, I. P.; La, C.; Jain, A. Hydrogen Storage in Mg: A Most Promising Material. Int. J. Hydrogen Energy 2010, 35, 5133−5144. (2) Stampfer, J. F.; Holley, C. E.; Suttle, J. F. The MagnesiumHydrogen System 1−3. J. Am. Chem. Soc. 1960, 82, 3504−3508. (3) Sakintuna, B.; Lamari-Darkrim, F.; Hirscher, M. Metal Hydride Materials for Solid Hydrogen Storage: A Review. Int. J. Hydrogen Energy 2007, 32, 1121−1140. (4) Wagemans, R. W. P.; van Lenthe, J. H.; de Jongh, P. E.; van Dillen, A. J.; de Jong, K. P. Hydrogen Storage in Magnesium Clusters: Quantum Chemical Study. J. Am. Chem. Soc. 2005, 127, 16675−16680. (5) Jeon, K. J.; Moon, H. R.; Ruminski, A. M.; Jiang, B.; Kisielowski, C.; Bardhan, R.; Urban, J. J. Air-Stable Magnesium Nanocomposites Provide Rapid and High-Capacity Hydrogen Storage without Using Heavy-Metal Catalysts. Nat. Mater. 2011, 10, 286−290. (6) Kalisvaart, W. P.; Kubis, A.; Danaie, M.; Amirkhiz, B. S.; Mitlin, D. Microstructural Evolution During Hydrogen Sorption Cycling of Mg-FeTi Nanolayered Composites. Acta Mater. 2011, 59, 2083−2095. (7) Vons, V. A.; Anastasopol, A.; Legerstee, W. J.; Mulder, F. M.; Eijt, S. W. H.; Schmidt-Ott, A. Low-Temperature Hydrogen Desorption and the Structural Properties of Spark Discharge Generated Mg Nanoparticles. Acta Mater. 2011, 59, 3070−3080. (8) Liu, Y.; Wang, G. C. Air Stability of Low-Temperature Dehydrogenation of Pd-Decorated Mg Blades. Nanotechnology 2012, 23, 025401. (9) Anastasopol, A.; Pfeiffer, T. V.; Schmidt-Ott, A.; Mulder, F. M.; Eijt, S. W. H. Fractal Disperse Hydrogen Sorption Kinetics in Spark Discharge Generated Mg/NbOx and Mg/Pd Nanocomposites. Appl. Phys. Lett. 2011, 99, 194103. (10) Danaie, M.; Mauer, C.; Mitlin, D.; Huot, J. Hydrogen Storage in Bulk Mg-Ti and Mg-Stainless Steel Multilayer Composites Synthesized 21783



Article

Milled Mg−30 wt% TiMn1.5 Composite. J. Alloys Compd. 2003, 354, 296−302. (31) Yu, X. B.; Guo, Y. H.; Yang, H.; Wu, Z.; Grant, D. M.; Walker, G. S. Improved Hydrogen Storage in Magnesium Hydride Catalyzed by Nanosized Ti0.4Cr0.15Mn0.15V0.3 Alloy. J. Phys. Chem. C 2009, 113, 5324−5328. (32) Niessen, R. A. H.; Notten, P. H. L. Electrochemical Hydrogen Storage Characteristics of Thin Film MgX (X = Sc, Ti, V, Cr) Compounds. Electrochem. Solid-State Lett. 2005, 8, A534−A538. (33) Zahiri, B.; Amirkhiz, B. S.; Mitlin, D. Hydrogen Storage Cycling of MgH2 Thin Film Nanocomposites Catalyzed by Bimetallic Cr Ti. Appl. Phys. Lett. 2010, 97, 083106−3. (34) Kalisvaart, W. P.; Kubis, A.; Danaie, M.; Amirkhiz, B. S.; Mitlin, D. Microstructural Evolution During Hydrogen Sorption Cycling of Mg−FeTi Nanolayered Composites. Acta Mater. 2011, 59, 2083− 2095. (35) Zahiri, R.; Zahiri, B.; Kubis, A.; Kalisvaart, P.; Shalchi Amirkhiz, B.; Mitlin, D. Microstructural Evolution During Low Temperature Sorption Cycling of Mg-AlTi Multilayer Nanocomposites. Int. J. Hydrogen Energy 2012, 37, 4215−4226. (36) Zahiri, B.; Danaie, M.; Tan, X. H.; Amirkhiz, B. S.; Botton, G. A.; Mitlin, D. Stable Hydrogen Storage Cycling in Magnesium Hydride, in the Range of Room Temperature to 300 C, Achieved Using a New Bimetallic Cr-V Nanoscale Catalyst. J. Phys. Chem. C 2012, 116, 3188−3199. (37) Liang, G.; Huot, J.; Boily, S.; Van Neste, A.; Schulz, R. Hydrogen Storage Properties of the Mechanically Milled MgH2 −V Nanocomposite. J. Alloys Compd. 1999, 291, 295−299. (38) Schimmel, H. G.; Huot, J.; Chapon, L. C.; Tichelaar, F. D.; Mulder, F. M. Hydrogen cycling of Niobium and Vanadium Catalyzed Nanostructured Magnesium. J. Am. Chem. Soc. 2005, 127, 14348− 14354. (39) Charbonnier, J.; de Rango, P.; Fruchart, D.; Miraglia, S.; Pontonnier, L.; Rivoirard, S.; Skryabina, N.; Vulliet, P. Hydrogenation of Transition Element Additives (Ti, V) During Ball Milling of Magnesium Hydride. J. Alloys Compd. 2004, 383, 205−208. (40) Tan, X. H.; Zahiri, B.; Holt, C. M. B.; Kubis, A.; Mitlin, D. A TEM Based Study of the Microstructure During Room Temperature and Low Temperature Hydrogen Storage Cycling in MgH2 Promoted by Nb−V. Acta Mater. 2012, 60, 5646−5661. (41) Laversenne, L.; Andrieux, J.; Plante, D. In Operando Study of TiVCr Additive in MgH2 Composites. Int. J. Hydrogen Energy 2013, 38, 11937−11945. (42) Pesch, W.; Schober, T. Z.; Wenzl, H. A TEM Study of the Phase Diagrams VH and VD. Scr. Metall. 1982, 16, 307. (43) Reilly, J. J.; Wiswall, R. H. BNL Rep. 1972, 16546. (44) Maeland, A. J.; Libowitz, G. G.; Lynch, J. F. Hydride Formation Rates of Titanium-Based b.c.c. Solid Solution Alloys. J. Less-Common Met. 1984, 104, 361−364. (45) Maeland, A. J.; Libowitz, G. G.; Lynch, J. F.; Rak, G. Hydride Formation Rates of B.C.C. Group V Metals. J. Less-Common Met. 1984, 104, 133−139. (46) Lynch, J. F.; Maeland, A. J.; Libowitz, G. G. Lattice Parameter Variation and Thermodynamics of Dihydride Formation in the Vanadium-Rich Vanadium−Titanium−Iron/Hydrogen System. Z. Phys. Chem., Neue Folge 1985, 145, 51−59. (47) Lynch, J. F.; Reilly, J. J.; Millot, F. The Absorption of Hydrogen by Binary Vanadium-Chromium Alloys. J. Phys. Chem. Solids 1978, 39, 883−890. (48) Ono, S.; Nomura, K.; Ikeda, Y. The Reaction of Hydrogen with Alloys of Vanadium and Titanium. J. Less-Common Met. 1980, 72, 159−165. (49) Yukawa, H.; Takagi, M.; Teshima, A.; Morinaga, M. Alloying Effects on the Stability of Vanadium Hydrides. J. Alloys Compd. 2002, 330−332, 105−109. (50) Yukawa, H.; Yamashita, D.; Ito, S.; Morinaga, M.; Yamaguchi, S. Compositional Dependence of Hydriding Properties of Vanadium Alloys at Low Hydrogen Pressures. J. Alloys Compd. 2003, 356−357, 45−49.

(51) Yu, X. B.; Chen, J. Z.; Wu, Z.; Xia, B. J.; Xu, N. X. Effect of Cr Content on Hydrogen Storage Properties for Ti-V-Based BCC-Phase Alloys. Int. J. Hydrogen Energy 2004, 29, 1377−1381. (52) Itoh, H.; Arashima, H.; Kubo, K.; Kabutomori, T. The Influence of Microstructure on Hydrogen Absorption Properties of Ti−Cr−V Alloys. J. Alloys Compd. 2002, 330−332, 287−291. (53) Arashima, H.; Takahashi, F.; Ebisawa, T.; Itoh, H.; Kabutomori, T. Correlation Between Hydrogen Absorption Properties and homogeneity of Ti−Cr−V Alloys. J. Alloys Compd. 2003, 356−357, 405−408. (54) Pan, H.; Li, R.; Gao, M.; Liu, Y.; Wang, Q. Effects of Cr on the Structural and Electrochemical Properties of TiV-Based Two-Phase Hydrogen Storage Alloys. J. Alloys Compd. 2005, 404−406, 669−674. (55) Cho, S. W.; Han, C. S.; Park, C. N.; Akiba, E. The Hydrogen Storage Characteristics of Ti−Cr−V Alloys. J. Alloys Compd. 1999, 288, 294−298. (56) Williamson, G. K.; Hall, W. H. X-ray Line Broadening From Filed Aluminum and Wolfram. Acta Metall. 1963, 1, 22−31. (57) Checchetto, R.; Trettel, G.; Miotello, A. Sievert-Type Apparatus for the Study of Hydrogen Storage in Solids. Meas. Sci. Technol. 2004, 15, 127−130. (58) Lee, Y. W.; Clemens, B. M.; Gross, K. J. Novel Sieverts’ Type Volumetric Measurements of Hydrogen Storage Properties for Very Small Sample Quantities. J. Alloys Compd. 2008, 452, 410−413. (59) Li, J.; Fan, P.; Fang, Z. Z.; Zhou, C. Kinetics of isothermal hydrogenation of magnesium with TiH2 additive. Int. J. Hydrogen Energy 2014, 39, 7373−7381. (60) Miraglia, S.; de Rango, P.; Rivoirard, S.; Fruchart, D.; Charbonnier, J.; Skryabina, N. Hydrogen Sorption Properties of Compounds Based on BCC Ti1−xV1−yCr1+x+y Alloys. J. Alloys Compd. 2012, 536, 1−6. (61) Flynn, J. H.; Wall, L. A. A Quick, Direct Method for the Determination of Activation Energy from Thermogravimetric Data. J. Polym. Sci., Part B: Polym. Lett. 1966, 4, 323−328. (62) Ozawa, T. Kinetic Analysis of Derivative Curves in Thermal Analysis. J. Therm. Anal. 1970, 2, 301−324. (63) Li, C. R.; Tang, T. Isoconversion Method for Kinetic Analysis of Solid-State Reactions from Dynamic Thermoanalytical data. J. Mater. Sci. 1999, 34, 3467−3470. (64) Choi, Y. J.; Lu, J.; Sohn, H. Y.; Fang, Z. Z. Hydrogen Storage Properties of the Mg−Ti−H System Prepared by High-Energy-HighPressure Reactive Milling. J. Power Sources 2008, 180, 491−497. (65) Ren, C.; Fang, Z. Z.; Zhou, C.; Lu, J.; Ren, Y.; Zhang, X.; Luo, X. In situ X-ray Diffraction Study of Dehydrogenation of MgH2 with Ti-based Additives. Int. J. Hydrogen Energy 2014, 39, 5868−5873. (66) Bloch, J.; Mintz, M. H. Kinetics and Mechanisms of Metal Hydrides Formation - A review. J. Alloys Compd. 1997, 253−254, 529−541. (67) Rudman, P. S. Hydrogen-Diffusion-Rate-Limited Hydriding and Dehydriding Kinetics. J. Appl. Phys. 1979, 50, 7195−7199. (68) Barkhordarian, G.; Klassen, T.; Bormann, R. Kinetic Investigation of the Effect of Milling Time on the Hydrogen Sorption Reaction of Magnesium Catalyzed with Different Nb2O5 Contents. J. Alloys Compd. 2006, 407, 249−255. (69) Fernandez, J. F.; Sanchez, C. R. Rate Determining Step in the Absorption and Desorption of Hydrogen by Magnesium. J. Alloys Compd. 2002, 340, 189−198. (70) Schober, T. The Magnesium-Hydrogen System: Transmission Electron Microscopy. Metall. Trans. A 1981, 12, 951−957. (71) Du, A. J.; Smith, S. C.; Lu, G. Q. First-Principle Studies of the Formation and Diffusion of Hydrogen Vacancies in Magnesium Hydride. J. Phys. Chem. C 2007, 111, 8360−8365. (72) Matumura, T.; Yukawa, H.; Morinaga, M. Alloying Effects on the Electronic Structures of VH and V H. J. Alloys Compd. 1999, 284, 82−88.

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