共查询到20条相似文献,搜索用时 15 毫秒
1.
Xugang Zhang Zhinian LiFang Lv Hualing LiJing Mi Shumao WangXiaopeng Liu Lijun Jiang 《International Journal of Hydrogen Energy》2010
Significant improvements in the hydrogen absorption/desorption properties of the 2LiNH2–1.1MgH2–0.1LiBH4 composite have been achieved by adding 3wt% ZrCo hydride. The composite can absorb 5.3wt% hydrogen under 7.0 MPa hydrogen pressure in 10 min and desorb 3.75wt% hydrogen under 0.1 MPa H2 pressure in 60 min at 150 °C, compared with 2.75wt% and 1.67wt% hydrogen under the same hydrogenation/dehydrogenation conditions without the ZrCo hydride addition, respectively. TPD measurements showed that the dehydrogenation temperature of the ZrCo hydride-doped sample was decreased about 10 °C compared to that of the pristine sample. It is concluded that both the homogeneous distribution of ZrCo particles in the matrix observed by SEM and EDS and the destabilized N–H bonds detected by IR spectrum are the main reasons for the improvement of H-cycling kinetics of the 2LiNH2–1.1MgH2–0.1LiBH4 system. 相似文献
2.
Ashish Bhatnagar Sunita K. Pandey Viney Dixit Vivek Shukla Rohit R. Shahi M.A. Shaz O.N. Srivastava 《International Journal of Hydrogen Energy》2014
The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH2–NaAlH4 composite. De/rehydrogenation study reveals that MgH2–NaAlH4 composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH4 and MgH2. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH2–NaAlH4 composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH2–NaAlH4 catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH2–NaAlH4 is diminished to 0.45 wt.%. 相似文献
3.
Pei-Jun Wang Zhan-Zhao FangLai-Peng Ma Xiang-Dong KangPing Wang 《International Journal of Hydrogen Energy》2008
Single-walled carbon nanotubes (SWNTs) were mechanically milled with LiBH4/MgH2 mixture, and examined with respect to its effect on the reversible dehydrogenation properties of the Li–Mg–B–H system. Experimental results show that the addition of SWNTs results in an enhanced dehydriding rate and improved cyclic stability of the LiBH4/MgH2 composite. For example, the LiBH4/MgH2 composite with 10 wt% purified SWNTs additive can release nearly 10 wt% hydrogen within 20 min at 450 °C, with an average dehydriding rate over 2 times faster than that of the neat LiBH4/MgH2 sample. Based on the results of phase analysis and a series of designed experiments, the mechanism underlying the observed property improvement was discussed. 相似文献
4.
Jiasheng Wang Shumin Han Wei Zhang Dan Liang Yuan Li Xin Zhao Ruibing Wang 《International Journal of Hydrogen Energy》2013
A 2LiBH4–MgH2–MoS2 composite was prepared by solid-state ball milling, and the effects of MoS2 as an additive on the hydrogen storage properties of 2LiBH4–MgH2 system together with the corresponding mechanism were investigated. As shown in the TG–DSC and MS results, with the addition of 20 wt.% of MoS2, the onset dehydrogenation temperature is reduced to 206 °C, which is 113 °C lower than that of the pristine 2LiBH4–MgH2 system. Meanwhile, the total dehydrogenation amount can be increased from 9.26 wt.% to 10.47 wt.%, and no gas impurities such as B2H6 and H2S are released. Furthermore, MoS2 improves the dehydrogenation kinetics, and lowers the activation energy (Ea) 34.49 kJ mol−1 of the dehydrogenation reaction between Mg and LiBH4 to a value lower than that of the pristine 2LiBH4–MgH2 sample. According to the XRD test, Li2S and MoB2 are formed by the reaction between LiBH4 and MoS2, which act as catalysts and are responsible for the improved hydrogen storage properties of the 2LiBH4–MgH2 system. 相似文献
5.
In this paper, we report the hydrogen storage properties and reaction mechanism of NaAlH4–MgH2–LiBH4 (1:1:1) ternary-hydride system prepared by ball milling. It was found that during ball milling, the NaAlH4/MgH2/LiBH4 combination converted readily to the mixture of LiAlH4/MgH2/NaBH4 and there is a mutual destabilization among the hydrides. Three major dehydrogenation steps were observed in the system, which corresponds to the decomposition of LiAlH4, MgH2, and NaBH4, respectively. The onset dehydrogenation temperature of MgH2 in this system is observed at around 275 °C, which is over 55 °C lower from that of as-milled MgH2. Meanwhile, NaBH4-relevant decomposition showed significant improvement, starts to release hydrogen at 370 °C, which is reduced by about 110 °C compared to the as-milled NaBH4. The second and third steps decomposition enthalpy of the system were determined by differential scanning calorimetry measurements and the enthalpies were changed to be 61 and 100 kJ mol−1 H2 respectively, which are smaller than that of MgH2 and NaBH4 alone. From the Kissinger plot, the apparent activation energy, EA, for the decomposition of MgH2 and NaBH4 in the composite was reduced to 96.85 and 111.74 kJ mol−1 respectively. It is believed that the enhancement of the dehydrogenation properties was attributed to the formation of intermediate compounds, including Li–Mg, Mg–Al, and Mg–Al–B alloys, upon dehydrogenation, which change the thermodynamics of the reactions through altering the de/rehydrogenation pathway. 相似文献
6.
Xuezhang Xiao Shunkui WangGuoping Tu Liuting ZhangXiulin Fan Shouquan LiHongwei Ge Qidong WangLixin Chen 《International Journal of Hydrogen Energy》2014
2LiBH4 + MgH2 system is considered as an attractive candidate for reversible hydrogen storage with high capacity and favorable thermodynamics. However, its reaction kinetics has to be further improved for the practical application. In this work, we investigated the effect of NbCl5 additive on the de/hydrogenation kinetics and microstructure refinement in 2LiH–MgB2 composite systematically. The hydrogenation and dehydrogenation kinetics of 2LiH–MgB2 composite can be significantly enhanced with the increase of NbCl5 content. The 3 mol% NbCl5 doped 2LiH–MgB2 composite exhibits the superior reversible hydrogen storage performance, which requires 50 min to uptake 9.0 wt% H2 at 350 °C and release 8.5 wt% H2 at 400 °C, respectively. In contrast, the undoped 2LiH–MgB2 sample uptakes 6.2 wt% H2 and releases 3.1 wt% H2 under identical measurement conditions. Moreover, the 3 mol% NbCl5 doped 2LiH–MgB2 composite can release more than 9.0 wt% H2 within 300 min at 400 °C without obvious degradation of capacity over the first 10 cycles. Microstructure analyses clearly indicate that NbCl5 additive first reacts with LiH to form Nb and LiCl during ball-milling process, and then NbH is formed after the first hydrogenation and stabilized upon further de/hydrogenation cycling. The well-distributed NbH active species play an important role in the improvement of de/hydrogenation kinetics for Li–Mg–B–H system through facilitating hydrogen diffusion rapidly as well as prevent the particles from further growth in the subsequent hydrogenation and dehydrogenation processes. 相似文献
7.
Li Li Fangyuan QiuYijing Wang Yanan XuCuihua An Guang LiuLifang Jiao Huatang Yuan 《International Journal of Hydrogen Energy》2013
The hydrogen storage properties of LiAlH4 doped efficient TiN catalyst were systematically investigated. We observe that TiN catalyst enhances the dehydrogenation kinetics and decreases the dehydrogenation temperature of LiAlH4. The dehydrogenation behaviors of 2%TiN–LiAlH4 are investigated using temperature programmed desorption (TPD), differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR). Interestingly, the onset hydrogen desorption temperature of 2%TiN–LiAlH4 sample gets lowered from 151.0 °C to 90.0 °C with a faster kinetics, and the dehydrogenation rate reached a maximum value at 137.2 °C. By adding a small amount of as-prepared TiN, approximately 7.1 wt% of hydrogen can be released from the LiAlH4 at 130 °C. Interestingly, the result of the FTIR indicates that the 2%TiN–LiAlH4 maybe restore hydrogen under 5.5 MPa hydrogen. Moreover, 2%TiN–LiAlH4 displayed a substantially reduced activation energy for LiAlH4 dehydrogenation. 相似文献
8.
Kuikui Wang Xiangdong Kang Yujie Zhong Chaohao Hu Ping Wang 《International Journal of Hydrogen Energy》2014
The 2LiBH4–MgH2 reactive hydride composite is a promising hydrogen storage system due to the combined high hydrogen capacity and relatively moderate reaction enthalpy. However, the sluggish de/rehydrogenation kinetics severely impedes its practical applications. In this study, graphitic carbon nitride (C3N4) as a metal-free additive was added to the 2LiBH4–MgH2 composite and examined with respect to the promoting effect on the hydrogen storage properties of the composite. Our study found that mechanically milling with small amount of C3N4 additive can eliminate the incubation period between two dehydrogenation steps and thus markedly enhance the dehydrogenation kinetics of the LiBH4–MgH2 composite. Further cyclic study found that the composite with C3N4 additive exhibits improved cyclic dehydrogenation property although it also shows capacity loss upon cycling, particularly in the second cycle. Combined dehydrogenation property, phase analysis and a series of designed experiments suggested that the C3N4 additive could react with both LiBH4 and MgH2 in heating process, and the resulting products may improve the reversible dehydrogenation property of the composite system. 相似文献
9.
Michael U. Niemann Sesha S. Srinivasan Ashok Kumar Elias K. Stefanakos D. Yogi Goswami Kimberly McGrath 《International Journal of Hydrogen Energy》2009
In this article, we investigate the ternary LiNH2–MgH2–LiBH4 hydrogen storage system by adopting various processing reaction pathways. The stoichiometric ratio of LiNH2:MgH2:LiBH4 is kept constant with a 2:1:1 molar ratio. All samples are prepared using solid-state mechano-chemical synthesis with a constant rotational speed, but with varying milling duration. Furthermore, the order of addition of parent compounds as well as the crystallite size of MgH2 are varied before milling. All samples are intimate mixtures of Li–B–N–H quaternary hydride phase with MgH2, as evidenced by XRD and FTIR measurements. It is found that the samples with MgH2 crystallite sizes of approximately 10 nm exhibit lower initial hydrogen release at a temperature of 150 °C. Furthermore, it is observed that the crystallite size of Li–B–N–H has a significant effect on the amount of hydrogen release with an optimum size of 28 nm. The as-synthesized hydrides exhibit two main hydrogen release temperatures, one around 160 °C and the other around 300 °C. The main hydrogen release temperature is reduced from 310 °C to 270 °C, while hydrogen is first reversibly released at temperatures as low as 150 °C with a total hydrogen capacity of ∼6 wt.%. Detailed thermal, capacity, structural and microstructural properties are discussed and correlated with the activation energies of these materials. 相似文献
10.
The hydrogen storage performance of MgH2–10 wt.% TiC composite was investigated. The additive TiC nanoparticle led to a pronounced improvement in the de/hydrogenation kinetics of MgH2. The composite could dehydrogenate 6.3 wt.% at 573 K while the milled MgH2 only released 4.9 wt.% of hydrogen at the same condition. The improvement came from that the activation energy of dehydrogenation was decreased from 191.27 kJ mol−1 to 144.62 kJ mol−1 with the TiC additive. The MgH2–10 wt.% TiC composite also absorbed 6.01 wt.% (or 5.1 wt.%) of hydrogen under 1 MPa H2 at 573 K (or 473 K) in 3000 s. Even at 1 MPa H2 and 373 K, it could absorb 4.1 wt.% of hydrogen, but milled MgH2 could not absorb hydrogen at this condition. Additionally, the composite had good cycling stability, and its hydrogen capacity only decreased 3.3% of the first run after 10 de/hydrogenation cycles. The improved hydrogen storage properties were explained to the TiC particles embedded in the MgH2, which provided the pathways for the hydrogen diffusion into the MgH2–10 wt.% TiC composite. 相似文献
11.
Kuikui Wang Xiangdong Kang Junhong Luo Chaohao Hu Ping Wang 《International Journal of Hydrogen Energy》2013
In this study, activated carbon (AC) was added to the 2LiBH4–MgH2 composite and examined with respect to its effect on the hydrogen storage properties of the system. Our study found that AC is an effective additive for promoting the reversible dehydrogenation of the 2LiBH4–MgH2 composite. A series of control experiments were carried out to optimize the sample preparation method, milling time and addition amount of AC. In comparison with the neat LiBH4–MgH2 system, the LiBH4–MgH2–AC composite prepared under optimized conditions exhibits enhanced dehydrogenation kinetics, improved cyclic stability and particularly, eliminated incubation period between the two dehydrogenation stages. A combination of phase/microstructure/chemical state analyses has been conducted to gain insight into the promoting effect of AC on the reversible dehydrogenation of the 2LiBH4–MgH2 system. Our study found that AC exerts its promoting effect via tailoring nanophase structure of the 2LiBH4–MgH2 composite. 相似文献
12.
Rapee Gosalawit-Utke Chiara Milanese Payam Javadian Julian Jepsen Daniel Laipple Fahim Karmi Julián Puszkiel Torben R. Jensen Amedeo Marini Thomas Klassen Martin Dornheim 《International Journal of Hydrogen Energy》2013
Nanoconfinement of 2LiBH4–MgH2–TiCl3 in resorcinol–formaldehyde carbon aerogel scaffold (RF–CAS) for reversible hydrogen storage applications is proposed. RF–CAS is encapsulated with approximately 1.6 wt. % TiCl3 by solution impregnation technique, and it is further nanoconfined with bulk 2LiBH4–MgH2 via melt infiltration. Faster dehydrogenation kinetics is obtained after TiCl3 impregnation, for example, nanoconfined 2LiBH4–MgH2–TiCl3 requires ∼1 and 4.5 h, respectively, to release 95% of the total hydrogen content during the 1st and 2nd cycles, while nanoconfined 2LiBH4–MgH2 (∼2.5 and 7 h, respectively) and bulk material (∼23 and 22 h, respectively) take considerably longer. Moreover, 95–98.6% of the theoretical H2 storage capacity (3.6–3.75 wt. % H2) is reproduced after four hydrogen release and uptake cycles of the nanoconfined 2LiBH4–MgH2–TiCl3. The reversibility of this hydrogen storage material is confirmed by the formation of LiBH4 and MgH2 after rehydrogenation using FTIR and SR-PXD techniques, respectively. 相似文献
13.
Jinbao Gao Peter Ngene Monika Herrich Wei Xia Oliver Gutfleisch Martin Muhler Krijn P. de Jong Petra E. de Jongh 《International Journal of Hydrogen Energy》2014
For practical solid-state hydrogen storage, reversibility under mild conditions is crucial. Complex metal hydrides such as NaAlH4 and LiBH4 have attractive hydrogen contents. However, hydrogen release and especially uptake after desorption are sluggish and require high temperatures and pressures. Kinetics can be greatly enhanced by nanostructuring, for instance by confining metal hydrides in a porous carbon scaffold. We present for a detailed study of the impact of the nature of the carbon–metal hydride interface on the hydrogen storage properties. Nanostructures were prepared by melt infiltration of either NaAlH4 or LiBH4 into a carbon scaffold, of which the surface had been modified, varying from H-terminated to oxidized (up to 4.4 O/nm2). It has been suggested that the chemical and electronic properties of the carbon/metal hydride interface can have a large influence on hydrogen storage properties. However, no significant impact on the first H2 release temperatures was found. In contrast, the surface properties of the carbon played a major role in determining the reversible hydrogen storage capacity. Only a part of the oxygen-containing groups reacted with hydrides during melt infiltration, but further reaction during cycling led to significant losses, with reversible hydrogen storage capacity loss up to 40% for surface oxidized carbon. However, if the carbon surface had been hydrogen terminated, ∼6 wt% with respect to the NaAlH4 weight was released in the second cycle, corresponding to 95% reversibility. This clearly shows that control over the nature and amount of surface groups offers a strategy to achieve fully reversible hydrogen storage in complex metal hydride-carbon nanocomposites. 相似文献
14.
Huaqin Kou Ge Sang Zhiyong Huang Wenhua Luo Lixin Chen Xuezhang Xiao Changwen Hu Yuanlin Zhou 《International Journal of Hydrogen Energy》2014
In the present work, the role of NbF5 addition amount in affecting the comprehensive hydrogen storage properties (dehydrogenation, rehydrogenation, cycling performance, hydrogen capacity) of 2LiBH4–MgH2 system as well as the catalytic mechanism of NbF5 have been systematically studied. It is found that increasing the addition amount of NbF5 to the 2LiBH4–MgH2 system not only results in dehydrogenation temperature reduction and hydriding–dehydriding kinetics enhancement but also leads to the de/rehydrogenation capacity loss. Compared with other samples, 2LiBH4–MgH2 doping with NbF5 in weight ratios of 40:4 exhibits superior comprehensive hydrogen storage properties, which can stably release ∼8.31 wt.% hydrogen within 2.5 h under 4 bar H2 and absorb ∼8.79 wt.% hydrogen within 10 min under 65 bar H2 at 400 °C even up to 20 cycling. As far as we know, this is the first time that excellent reversibility as high as 20 cycles without obvious degradation tendency in both of hydrogen capacity and reaction rate has been achieved in the 2LiBH4–MgH2 system. The further experimental study reveals that the highly catalytic effects of NbF5 on the 2LiBH4–MgH2 system are derived from the reaction between NbF5 and LiBH4, which provides a fundamental insight into the catalytic mechanism of NbF5. 相似文献
15.
N.S. Mustafa F.A. Halim Yap M.S. Yahya M. Ismail 《International Journal of Hydrogen Energy》2018,43(24):11132-11140
The hydrogen storage properties and reaction mechanism of the combined NaAlH4 + Ca(BH4)2 (2:1) composite system was investigated in the present study. Analyses show that after 6 h of milling, the NaAlH4 + Ca(BH4)2 combination fully converted to the mixture of Ca(AlH4)2 + NaBH4, and a metathesis reaction occurred between the hydrides. Four major dehydrogenation stages were observed in the system, which corresponds to the decomposition of Ca(AlH4)2, CaAlH5, CaH2 and NaBH4, respectively. The onset desorption temperature of the composite system is reduced to 125 °C, which is much lower than a unary component of NaAlH4 and Ca(BH4)2. The de/rehydrogenation kinetics of the composite system had improve at a higher temperature. From the Kissinger plot, the apparent activation energies for the decomposition of CaAlH5 and NaBH4 in the composite system were reduced to 142.9 and 146.5 kJ/mol, respectively. It is believed that the formation of AlCa, AlB and CaB alloys during the dehydrogenation process is responsible for the distinct reduction in the onset desorption temperature and kinetics enhancement of the 2NaAlH4 + Ca(BH4)2 composite system. 相似文献
16.
Effective nanoconfinement of 2LiBH4–MgH2 via simply MgH2 premilling for reversible hydrogen storages
Rapee Gosalawit–Utke Sophida Thiangviriya Payam Javadian Daniel Laipple Claudio Pistidda Nils Bergemann Christian Horstmann Torben R. Jensen Thomas Klassen Martin Dornheim 《International Journal of Hydrogen Energy》2014
To improve nanoconfinement of LiBH4 and MgH2 in carbon aerogel scaffold (CAS), particle size reduction of MgH2 by premilling technique before melt infiltration is proposed. MgH2 is premilled for 5 h prior to milling with LiBH4 and nanoconfinement in CAS to obtained nanoconfined 2LiBH4–premilled MgH2. Significant confinement of both LiBH4 and MgH2 in CAS, confirmed by SEM–EDS–mapping results, is achieved due to MgH2 premilling. Due to effective nanoconfinement, enhancement of CAS:hydride composite weight ratio to 1:1, resulting in increase of hydrogen storage capacity, is possible. Nanoconfined 2LiBH4–premilled MgH2 reveals a single–step dehydrogenation at 345 °C with no B2H6 release, while dehydrogenation of nanoconfined sample without MgH2 premilling performs in multiple steps at elevated temperatures (up to 430 °C) together with considerable amount of B2H6 release. Activation energy (EA) for the main dehydrogenation of nanoconfined 2LiBH4–premilled MgH2 is considerably lower than those of LiBH4 and MgH2 of bulk 2LiBH4–MgH2 (ΔEA = 31.9 and 55.8 kJ/mol with respect to LiBH4 and MgH2, respectively). Approximately twice faster dehydrogenation rate are accomplished after MgH2 premilling. Three hydrogen release (T = 320 °C, P(H2) = 3–4 bar) and uptake (T = 320–325 °C, P(H2) = 84 bar) cycles of nanoconfined 2LiBH4–premilled MgH2 reveal up to 4.96 wt. % H2 (10 wt. % H2 with respect to hydride composite content), while the 1st desorption of nanoconfined sample without MgH2 premilling gives 4.30 wt. % of combined B2H6 and H2 gases. It should be remarked that not only kinetic improvement and B2H6 suppression are obtained by MgH2 premilling, but also the lowest dehydrogenation temperature (T = 320 °C) among other modified 2LiBH4–MgH2 systems is acquired. 相似文献
17.
Remarkable improvement of hydrogen sorption properties of Li–N–H system has been obtained by doping with a small amount of LiBH4. The starting and ending temperatures of hydrogen desorption shift to lower temperatures and the release of NH3 is obviously restrained by 10 mol% LiBH4 doping. The kinetics of hydrogen desorption and absorption of Li–N–H system became faster by the addition of LiBH4. About 4 wt.% H2 can be released within 30 min and ∼4.8 wt.% H2 can be reabsorbed within 2 min by LiBH4 doped sample at 250 °C, while only 1.44 wt.% H2 is released and 2.1 wt.% is reabsorbed for pure Li–N–H system. The quaternary hydride (LiNH2)x(LiBH4)(1−x) formed by the reaction between LiBH4 and LiNH2 may contribute to the enhancement of the hydrogen sorption performances by yielding a ionic liquid phase and transferring LiNH2 from solid state to molten state with a weakened N–H bond. 相似文献
18.
Supersaturated Mg(Al) solid solutions with reduced lattice constants were successfully prepared by ball milling Mg and Al powder mixtures. The microstructure and phase transition were investigated by XRD. The results indicated that disproportionation of supersaturated Mg(Al) solid solution to MgH2 and Al was caused by hydrogenation, then equilibrium Mg(Al) solid solution formed after dehydrogenation, while the intermetallic compound Mg17Al12 reversibly decomposed to MgH2 and intermediate phase Al3Mg2 which could further decompose to MgH2 and Al by hydriding. These reversible phase transitions make Mg–Al alloys show an observably lowered de/hydriding enthalpy and activation energy in comparison with pure Mg. 相似文献
19.
F.A. Halim Yap N.A. Ali N.H. Idris M. Ismail 《International Journal of Hydrogen Energy》2018,43(45):20882-20891
The effect of MgFe2O4 on the hydrogen storage properties of the composite Na3AlH64LiBH4 was studied for the first time, where it was found that MgFe2O4 addition decreased the onset desorption temperature of Na3AlH64LiBH4. Hydrogen (~9.5 wt%) was released in three stages and the dehydrogenation temperatures were reduced to 80 °C, 350 °C, and 430 °C for the first, second, and third stage, respectively. The absorption kinetics of Na3AlH64LiBH4 was also significantly improved due to the catalytic effect of MgFe2O4. Using Kissinger analysis, the apparent activation energies of decomposition of the Li3AlH6 and NaBH4 stages in Na3AlH64LiBH4-10 wt% MgFe2O4 were calculated to be 72 and 141 kJ/mol, respectively. These values were considerably lower than the corresponding values for the undoped composite. X-ray diffraction analysis revealed the formation of new products such as MgO and Fe during the heating process. Our results suggest that MgFe2O4 enhanced the hydrogen storage properties of Na3AlH64LiBH4 through the formation of active species, such as MgO and Fe. 相似文献
20.
Shu-Sheng Liu Li-Xian Sun Jian Zhang Yao Zhang Fen Xu Yong-Heng Xing Fen Li Jijun Zhao Yong Du Wang-Yu Hu Hui-Qiu Deng 《International Journal of Hydrogen Energy》2010
To improve the dehydrogenation properties of MgH2, a novel hydrogen storage system, MgH2–Li3AlH6, is prepared by mechanochemical milling. Three physical mixtures containing different mole ratios (1:4, 1:1 and 4:1) of MgH2 and Li3AlH6 are studied and there exists a mutual destabilization effect between the components. The last mixture shows a capacity of 6.5 wt% H2 with the lowest starting temperature of dehydrogenation (170 °C). First, Li3AlH6 decomposes into Al, LiH and H2, and then the as-formed Al can easily destabilize MgH2 to form the intermetallic compound Mg17Al12 at a temperature of 235 °C, which is about 180 °C lower than the decomposition temperature of pristine MgH2. Finally, the residual MgH2 undergoes a self-decomposition whose apparent activation energy has been reduced by about 22 kJ mol−1 compared with pristine MgH2. At a constant temperature of 250 °C, the mixture can dehydrogenate completely under an initial vacuum and rehydrogenate to form MgH2 under 2 MPa H2, showing good cycle stability after the first cycle with a capacity of 4.5 wt% H2. The comparison between 4 MgH2 + Li3AlH6 and 4 MgH2 + LiAlH4 mixtures is also investigated. 相似文献