共查询到20条相似文献,搜索用时 31 毫秒
1.
Shuaishuai Deng Xuezhang XiaoLeyuan Han Yun LiShouquan Li Hongwei GeQidong Wang Lixin Chen 《International Journal of Hydrogen Energy》2012
The hydrogen storage properties of 5LiBH4 + Mg2FeH6 reactive hydride composites for reversible hydrogen storage were investigated by comparing with the 2LiBH4 + MgH2 composite in the present work. The dehydrogenation pathway and reaction mechanism of 5LiBH4 + Mg2FeH6 composite were also investigated and elucidated. The self-decomposition of Mg2FeH6 leads to the in situ formation of Mg and Fe particles on the surface of LiBH4, resulting in a well dispersion between different reacting phases. The formation of FeB is observed during the dehydrogenation of 5LiBH4 + Mg2FeH6 composite, which might supplies nucleation sites of MgB2 during the dehydrogenation process, but is not an ascendant catalyst for the self-decomposition of LiBH4. And FeB can also transform to the LiBH4 and Fe by reacting with LiH and H2 during the rehydrogenation process. The dehydrogenation capacity for 5LiBH4 + Mg2FeH6 composite still gets to 6.5 wt% even after four cycles. The X-ray diffraction analyses reveal the phase transitions during the hydriding and dehydriding cycle. The formed FeB in the composite maintains a nanostructure after four hydriding-dehydriding cycles. The loss of hydrogen storage capacity and de-/rehydrogenation kinetics can be attributed to the incomplete generation of Mg2FeH6 during the rehydrogenation process. 相似文献
2.
Henrietta W. Langmi G. Sean McGrady Rebecca Newhouse Ewa Rönnebro 《International Journal of Hydrogen Energy》2012
Two composite hydrogen storage materials based on Mg2FeH6 were investigated for the first time. The Mg2FeH6–LiBH4 composite of molar ratio 1:5 showed a hydrogen desorption capacity of 5.6 wt.% at 370 °C, and could be rehydrogenated to 3.6 wt.% with the formation of MgH2, as the material was heated to 445 °C and held at this temperature. The Mg2FeH6–LiNH2 composite of 3:10 molar ratio exhibited a hydrogen desorption capacity of 4.3 wt.% and released hydrogen at 100 °C lower then the Mg2FeH6–LiBH4 composite, but this mixture could not be rehydrogenated. Compared to neat Mg2FeH6, both composites show enhanced hydrogen storage properties in terms of desorption kinetics and capacity at these low temperatures. In particular, Mg2FeH6–LiNH2 exhibits a much lower desorption temperature than neat Mg2FeH6, but only Mg2FeH6–LiBH4 re-absorbs hydrogen. 相似文献
3.
MgH2 is a perspective hydrogen storage material whose main advantage is a relatively high hydrogen storage capacity (theoretically, 7.6 wt.% H2). This compound, however, shows poor hydrogen desorption kinetics. Much effort was devoted in the past to finding possible ways of enhancing hydrogen desorption rate from MgH2, which would bring this material closer to technical applications. One possible way is catalysis of hydrogen desorption. This paper investigates separate catalytic effects of Ni, Mg2Ni and Mg2NiH4 on the hydrogen desorption characteristics of MgH2. It was observed that the catalytic efficiency of Mg2NiH4 was considerably higher than that of pure Ni and non-hydrated intermetallic Mg2Ni. The Mg2NiH4 phase has two low-temperature modifications below 508 K: un-twinned phase LT1 and micro-twinned phase LT2. LT1 was observed to have significantly higher catalytic efficiency than LT2. 相似文献
4.
Myoung Youp Song Young Jun Kwak Hyung-Shik Shin Seong Ho Lee Byoung-Goan Kim 《International Journal of Hydrogen Energy》2013
In this work, differently from our previous work, MgH2 instead of Mg was used as a starting material. Ni, Ti, and LiBH4 with a high hydrogen-storage capacity of 18.4 wt% were added. A sample with a composition of MgH2–10Ni–2LiBH4–2Ti was prepared by reactive mechanical grinding. MgH2–10Ni–2LiBH4–2Ti after reactive mechanical grinding contained MgH2, Mg, Ni, TiH1.924, and MgO phases. The activation of MgH2–10Ni–2LiBH4–2Ti for hydriding and dehydriding reactions was not required. At the number of cycles, n = 2, MgH2–10Ni–2LiBH4–2Ti absorbed 4.09 wt% H for 5 min, 4.25 wt% H for 10 min, and 4.44 wt% H for 60 min at 573 K under 12 bar H2. At n = 1, MgH2–10Ni–2LiBH4–2Ti desorbed 0.13 wt% H for 10 min, 0.54 wt% H for 20 min, 1.07 wt% H for 30 min, and 1.97 wt% H for 60 min at 573 K under 1.0 bar H2. The PCT (Pressure–Composition–Temperature) curve at 593 K for MgH2–10Ni–2LiBH4–2Ti showed that its hydrogen-storage capacity was 5.10 wt%. The inverse dependence of the hydriding rate on temperature is partly due to a decrease in the pressure differential between the applied hydrogen pressure and the equilibrium plateau pressure with the increase in temperature. The rate-controlling step for the dehydriding reaction of the MgH2–10Ni–2LiBH4–2Ti at n = 1 was analyzed. 相似文献
5.
Mg–20 wt% Ni–Y composite was successfully prepared by reactive mechanical alloying (RMA). X-ray diffraction (XRD) measurement showed that both MgH2 and Mg2NiH4 co-exist in the milled composite. The composite exhibits excellent hydrogen sorption kinetics and does not need activation on the first hydrogen storage process. It can absorb 3.92 and 5.59 wt% hydrogen under 3.0 MPa hydrogen pressure at 293 and 473 K in 10 min, respectively, and desorb 4.67wt% hydrogen at 523 K in 30 min under 0.02 MPa hydrogen pressure. The equilibrium desorption pressure of the composite are 0.142, 0.051 and 0.025 MPa at 573, 543 and 523 K, respectively. The differential scanning calorimetry (DSC) measurement showed that dehydrogenation of Mg–20 wt% Ni–Y composite was depressed about 100 K comparing to that of milled pure MgH2. It is deduced that both the catalysis effect of Mg2Ni and YH3 distributed in Mg substrate and the crystal defects formed by RMA are the main reason for improving hydrogen sorption kinetics of the Mg–20 wt% Ni–Y composite. 相似文献
6.
F.C. Gennari L. Fernández Albanesi J.A. Puszkiel P. Arneodo Larochette 《International Journal of Hydrogen Energy》2011,36(1):563-570
Different destabilized LiBH4 systems with several interacting components are being explored for hydrogen storage applications. In this study, hydrogen sorption properties of as-milled 6LiBH4-MCl3 composites (M = Ce, Gd) are investigated by X-ray diffraction, differential scanning calorimetry and thermovolumetric measurements. The chemical interaction between metal halides and LiBH4 decreases the dehydrogenation temperature in comparison with as-milled LiBH4. Hydrogen release starts at 220 °C from the decomposition of M(BH4)3 formed during milling and proceeds through destabilization of LiBH4 by in-situ formed MH2. The dehydrogenation products CeB6-LiH and GdB4-LiH can be rehydrided under moderate conditions, i.e 400 °C and 6.0 MPa of hydrogen pressure for 2 h without catalyst. A new 6LiBH4-CeCl3-3LiH composite shows promissory hydrogen storage properties via the formation by milling of CeH2+x. Our study is the first work about reversible hydrogen storage in LiBH4-MCl3 composites destabilized by in-situ formed MH2. 相似文献
7.
Bin Hong Liu Bang Jie ZhangYing Jiang 《International Journal of Hydrogen Energy》2011,36(9):5418-5424
LiBH4+1/2MgH2 is a promising reactive hydride composite for hydrogen storage. In the present study, three Ce-based additives were used as catalysts to enhance the hydrogen storage performance of LiBH4+1/2MgH2 composites. The composites with Ce additives demonstrated significantly improved dehydrogenation kinetics and cyclic stability compared with the pure composite. X-ray diffraction and scanning electron microscopy analyses clearly revealed the phase transitions and morphological evolution during the hydriding-dehydriding cycling. The composites with Ce-based additives displayed stable nanostructures, in contrast to the rapid microstructural deterioration in the uncatalyzed composite. The CeB6 formed in the composites had a particle size of 10 nm after five cycles. It may act as the nucleus for MgB2 formation during dehydrogenation and thus account for the structural and performance stability of the composites upon cycling. 相似文献
8.
《International Journal of Hydrogen Energy》2020,45(52):28154-28162
Magnesium-based hydrogen storage materials (MgH2) are promising hydrogen carrier due to the high gravimetric hydrogen density; however, the undesirable thermodynamic stability and slow kinetics restrict its utilization. In this work, we assist the de/hydrogenation of MgH2 via in situ formed additives from the conversion of an MgNi2 alloy upon de/hydrogenation. The MgH2–16.7 wt%MgNi2 composite was synthesized by ball milling of Mg powder and MgNi2 alloy followed by a hydrogen combustion synthesis method, where most of the Mg converted to MgH2, and the others reacted with the MgNi2 generating Mg2NiH4, which produced in situ Mg2Ni during dehydrogenation. Results showed that the Mg2Ni and Mg2NiH4 could induce hydrogen absorption and desorption of the MgH2, that it absorbed 2.5 wt% H2 at 473 K, much higher than that of pure Mg, and the dehydrogenation capacity increased by 2.6 wt% at 573 K. Besides, the initial dehydrogenation temperature of the composite under the promotion of Mg2NiH4 decreased greatly by 100 K, whereas it is 623 K for MgH2. Furthermore, benefiting from the catalyst effect of Mg2NiH4 during dehydrogenation, the apparent activation energy of the composite reduced to 73.2 kJ mol−1 H2 from 129.5 kJ mol−1 H2. 相似文献
9.
In the present study, the synthesis of two different LiBH4–Y(BH4)3 and LiBH4–YH3 composites was performed by mechanochemical processing of the 4LiBH4–YCl3 mixture and as-milled 4LiBH4–YCl3 plus 3LiH. It was found that Y(BH4)3 and YH3 formed in situ during milling are effective to promote LiBH4 destabilization but differ substantially from each other in terms of the dehydrogenation pathway. During LiBH4–Y(BH4)3 dehydriding, Y(BH4)3 decomposes first generating in situ freshly YH3 and subsequently, it destabilizes LiBH4 with the formation of minor amounts of YB4. About 20% of the theoretical hydrogen storage was obtained via the rehydriding of YB4–4LiH–3LiCl at 400 °C and 6.5 MPa. As a novel result, a compound containing (B12H12)2− group was identified during dehydriding of Y(BH4)3. In the case of 4LiBH4–YH3 dehydrogenation, the increase of the hydrogen back pressure favors the formation of crystalline YB4, whereas a reduction to ≤0.1 MPa induces the formation of minor amounts of Li2B12H12. Although for hydrogen pressures ≤0.1 MPa direct LiBH4 decomposition can occur, the main dehydriding pathway of 4LiBH4–YH3 composite yields YB4 and LiH. The nanostructured composite obtained by mechanochemical processing gives good hydrogen storage reversibility (about 80%) regardless of the hydrogen back pressure. 相似文献
10.
Improved reversible dehydrogenation of LiBH4–MgH2 composite by the synergistic effects of Al and MgO
In this paper, we report a novel method of improving the reversible dehydrogenation properties of the 2LiBH4–MgH2 composite. Our study found that mechanically milling with small amount of Al powder can markedly shorten or even eliminate the problematic incubation period that interrupts the dehydrogenation steps of the 2LiBH4–MgH2 composite. But the resulting composite showed serious kinetics degradation upon cycling. In an effort to solve this problem, we found that combined usage of small amounts of Al and MgO enabled the 2LiBH4–MgH2 composite to rapidly and reversibly deliver around 9 wt% hydrogen at 400 °C under 0.3 MPa H2, which compares favorably with the dehydrogenation performance of the composites with transition-metal additives. A combination of phase/microstructural analyses and series of control experiments has been conducted to gain insight into the promoting effects of Al and MgO. It was found that Al and MgO additives act as precursor and promoter for the formation of AlB2 heterogeneous nucleation sites, respectively. 相似文献
11.
《International Journal of Hydrogen Energy》2019,44(55):29235-29248
A metal-organic framework based on Ni (II) as metal ion and trimasic acid (TMA) as organic linker was synthesized and introduced into MgH2 to prepare a Mg-(TMA-Ni MOF)-H composite through ball-milling. The microstructures, phase changes and hydrogen storage behaviors of the composite were systematically studied. It can be found that Ni ion in TMA-Ni MOF is attracted by Mg to form nano-sized Mg2Ni/Mg2NiH4 after de/rehydrogenation. The hydriding and dehydriding enthalpies of the Mg-MOF-H composite are evaluated to be −74.3 and 78.7 kJ mol−1 H2, respectively, which means that the thermodynamics of Mg remains unchanged. The absorption kinetics of the Mg-MOF-H composite is improved by showing an activation energy of 51.2 kJ mol−1 H2. The onset desorption temperature of the composite is 167.8 K lower than that of the pure MgH2 at the heating rate of 10 K/min. Such a significant enhancement on the sorption kinetic properties of the composite is attributed to the catalytic effects of the nanoscale Mg2Ni/Mg2NiH4 derived from TMA-Ni MOF by providing gateways for hydrogen diffusion during re/dehydrogenation processes. 相似文献
12.
Recent works showed that the addition of LiBH4 significantly improves the sorption kinetics of MgH2, and LiH decomposed from LiBH4 was supposed to play the catalytic effect on MgH2. In order to clarify this mechanism, the effect of LiH on the hydriding/dehydriding kinetics and thermodynamics of MgH2 was systematically investigated. The hydrogenation kinetics of LiH-doped samples, as well as the morphology after several cycles, was similar to those of pure MgH2, which indicate that Li+ had no catalytic effect on the hydrogenation of Mg. Moreover, the addition of LiH strongly retarded the hydrogen desorption of MgH2 doped with/without Nb2O5, and resulted in higher starting temperature of desorption, larger activation energy and larger pressure hysteresis of PCI curves of MgH2. H2, HD and D2 were observed in the desorption products of MgH2-2LiD, which confirms that H–H exchange indeed occurs between MgH2 and LiH, hence deteriorate desorption kinetics/thermodynamics of MgH2. The results implied that the additives containing H− could retard the hydrogen desorption of MgH2 by H–H exchange effect. 相似文献
13.
The effect of lithium borohydride (LiBH4) on the hydriding/dehydriding kinetics and thermodynamics of magnesium hydride (MgH2) was investigated. It was found that LiBH4 played both positive and negative effects on the hydrogen sorption of MgH2. With 10 mol.% LiBH4 content, MgH2–10 mol.% LiBH4 had superior hydrogen absorption/desorption properties, which could absorb 6.8 wt.% H within 1300 s at 200 °C under 3 MPa H2 and completed desorption within 740 s at 350 °C. However, with the increasing amount of LiBH4, the hydrogenation/dehydrogenation kinetics deteriorated, and the starting desorption temperature increased and the hysteresis of the pressure-composition isotherm (PCI) became larger. Our results showed that the positive effect of LiBH4 was mainly attributed to the more uniform powder mixture with smaller particle size, while the negative effect of LiBH4 might be caused by the H–H exchange between LiBH4 and MgH2. 相似文献
14.
Study on the synergistic catalytic effect of the SrTiO3 and Ni on the improvement of the hydrogen storage properties of the MgH2 system has been carried out. The composites have been prepared using ball milling method and comparisons on the hydrogen storage properties of the MgH2 – Ni and MgH2 – SrTiO3 composites have been presented. The MgH2 – 10 wt% SrTiO3 – 5 wt% Ni composite is found to has a decomposition temperature of 260 °C with a total decomposition capacity of 6 wt% of hydrogen. The composite is able to absorb 6.1 wt% of hydrogen in 1.3 min (320 °C, 27 atm of hydrogen). At 150 °C, the composite is able to absorb 2.9 wt% of hydrogen in 10 min under the pressure of 27 atm of hydrogen. The composite has successfully released 6.1 wt% of hydrogen in 13.1 min with a total dehydrogenation of 6.6 wt% of hydrogen (320 °C). The apparent activation energy, Ea, for decomposition of SrTiO3-doped MgH2 reduced from 109.0 kJ/mol to 98.6 kJ/mol after the addition of 5 wt% Ni. The formation of Mg2Ni and Mg2NiH4 as the active species help to boost the performance of the hydrogen storage properties of the MgH2 system. Observation of the scanning electron microscopy images suggested the catalytic role of the SrTiO3 additive is based on the modification of composite microstructure. 相似文献
15.
Yanli Zeng Ke FanXiaoyan Li Baoen XuXiaozhen Gao Lingpeng Meng 《International Journal of Hydrogen Energy》2010
The structures and properties of hydrogen storage alloy Mg2Ni, of aluminum and silver substituted alloys Mg2−xMxNi (M = Al and Ag, x = 0.16667), and of their hydrides Mg2NiH4, Mg2−xMxNiH4 (M = Al and Ag, x = 0.125) have been calculated from first-principles. Results show that the primitive cell sizes of the intermetallic alloys and hydrides were reduced by substitution of Mg with Al or Ag. Also, the interaction of Ni–Ni was weakened by the substitution. A strong covalent interaction between H and Ni atoms forms tetrahedral NiH4 units in Mg2NiH4. The NiH4 unit near the Al/Ag atom became tripod-like NiH3 in Mg2−xMxNiH4 (M = Al, Ag), indicating that the hydrogen storage capacity was decreased by the substitution. The calculated enthalpies of hydrogenation for Mg2Ni, Mg2−xAlxNi and Mg2−xAgxNi are −65.14, −51.56 and −53.63 kJ/mol H2, respectively, implying that the substitution destabilizes the hydrides. Therefore, the substitution is an effective technique for improving the thermodynamic behavior of hydrogenation/dehydrogenation in magnesium-based hydrogen storage materials. 相似文献
16.
F.C. Gennari 《Journal of power sources》2010,195(10):3266-3274
Mg50Ni-LiBH4 and Mg50Ni-LiBH4-CeCl3 composites have been prepared by short times of ball milling under argon atmosphere. Combination of HP-DSC and volumetric techniques show that Mg50Ni-LiBH4-CeCl3 composite not only uptakes hydrogen faster than Mg50Ni-LiBH4, but also releases hydrogen at a lower temperature (225 °C). The presence of CeCl3 has a catalytic role, but it does not modify the thermodynamic properties of the composite which corresponds to MgH2. Experimental studies on the hydriding/dehydriding mechanisms demonstrate that LiBH4 and Ni lead to the formation of MgNi3B2 in both composites. In addition, XRD/DSC analysis and thermodynamic calculations demonstrate that the addition of CeCl3 accounts for the enhancement of the hydrogen absorption/desorption kinetics through the interaction with LiBH4. The in situ formation and subsequent decomposition of Ce(BH4)3 provides a uniform distribution of nanosize CeB4 compound, which plays an important role in improving the kinetic properties of MgH2. 相似文献
17.
M. Polanski T.K. Nielsen I. Kunce M. Norek T. Płociński L.R. Jaroszewicz C. Gundlach T.R. Jensen J. Bystrzycki 《International Journal of Hydrogen Energy》2013
A ternary Mg2NiH4 hydride was synthesized using method that relies on a relatively short mechanical milling time (one hour) of a 2:1 MgH2–Ni powder mixture followed by sintering at a sufficiently high hydrogen pressure (>85 bar) and temperature (>400 °C). The ternary hydride forms in less than 2.5 h (including the milling time) with a yield of ∼90% as a mixture of two polymorphic forms. The mechanisms of formation and decomposition of ternary Mg2NiH4 under different hydrogen pressures were studied in detail using an in situ synchrotron radiation powder X-ray diffraction (SR-PXD) and high pressure DSC. The obtained experimental results are supported by morphological and microstructural investigations performed using SEM and high resolution STEM. Additionally, effects occurring during the desorption reaction were studied using DSC coupled with mass spectrometry. 相似文献
18.
LiBH4 is regarded as a promising hydrogen storage material due to its high hydrogen density. In this study, the dehydrogenation properties of LiBH4 were remarkably enhanced by doping hydrogenated Mg3RE compounds (RE denotes La, Ce, Nd rare earth metals), which are composed of nanostructured MgH2 and REH2+x (denoted as H − Mg3RE). For the LiBH4 + H − Mg3La mixture, the component LiBH4 desorbed 6 wt.% hydrogen even at a relatively low temperature of 340 °C, far lower than the desorption temperature of pure LiBH4 or the 2LiBH4 + MgH2 system. This kinetic improvement is attributed to the hydrogen exchange mechanism between the H − Mg3La and LiBH4, in the sense that the decomposition of MgH2 and LaH2+x catalyzed the dehydrogenation of LiBH4 through hydrogen exchange effect rather than mutual chemical reaction requiring higher temperature and hydrogen pressure. However, prior to fast hydrogen release, the hydrogen exchange effect suppressed the dehydriding of MgH2 and elevated its desorption temperature. It is expected to strengthen the hydrogen exchange effect by compositing the LiBH4 with other nanosized metal hydrides and to obtain better dehydrogenation properties. 相似文献
19.
《International Journal of Hydrogen Energy》2021,46(66):33186-33196
Additive doping is one of the effective methods to overcome the shortcomings of MgH2 on the aspect of relatively high operating temperatures and slow desorption kinetics. In this paper, hollow g-C3N4 (TCN) tubes with a diameter of 2 μm are synthesized through the hydrothermal and high-temperature pyrolysis methods, and then nickel is chemically reduced onto TCN to form Ni/TCN composite at 278 K. Ni/TCN is then introduced into the MgH2/Mg system by means of hydriding combustion and ball milling. The MgH2–Ni/TCN composite starts to release hydrogen at 535 K, which is 116 K lower than the as-milled MgH2 (651 K). The MgH2–Ni/TCN composite absorbs 5.24 wt% H2 within 3500 s at 423 K, and takes up 3.56 wt% H2 within 3500 s, even at a temperature as low as 373 K. The apparent activation energy (Ea) of the MgH2 decreases from 161.1 to 82.6 kJ/mol by the addition of Ni/TCN. Moreover, the MgH2–Ni/TCN sample shows excellent cycle stability, with a dehydrogenation capacity retention rate of 98.0% after 10 cycles. The carbon material enhances sorption kinetics by dispersing and stabilizating MgH2. Otherwise, the phase transformation between Mg2NiH4 and Mg2NiH0.3 accelerates the re/dehydrogenation reaction of the composite. 相似文献