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1.
To improve the hydrogen storage property of LiBH4, the LiBH4/Ca(AlH4)2 reactive systems with various ratios were constructed, and their de-/hydrogenation properties as well as the reaction mechanisms were investigated experimentally. It was found that the sample with the LiBH4 to Ca(AlH4)2 molar ratio of 6:1 exhibits the best comprehensive hydrogen storage properties, desorbing hydrogen completely (8.2 wt.%) within 35 min at 450 °C and reversibly absorbing 4.5 wt.% of hydrogen at 450 °C under a hydrogen pressure as low as 4.0 MPa. During the first dehydrogenation process of the LiBH4/Ca(AlH4)2 systems, the CaH2 and Al particles were in situ precipitated via the self-decomposition of Ca(AlH4)2, and then reacted with LiBH4 to form CaB6, AlB2 and LiH. Whereafter, the sample can cycle between LiBH4 + Ca(BH4)2 + Al in the hydrogenated state and CaB6 + AlB2 + LiH in the dehydrogenated state. 相似文献
2.
Jianjun Jiang Jia WeiHaiyan Leng Qian LiKuo-Chih Chou 《International Journal of Hydrogen Energy》2013
The various Mg–B–Al–H systems composed of Mg(BH4)2 and different Al-sources (metallic Al, LiAlH4 and its decomposition products) have been investigated as potential hydrogen storage materials. The role of Al was studied on the dehydrogenation and the rehydrogenation of the systems. The results indicate that the different Al-sources exhibit a similar improving effect on the dehydrogenation properties of Mg(BH4)2. Taking the Mg(BH4)2 + LiAlH4 system as an example, at first LiAlH4 rapidly decomposes into LiH and Al, then Mg(BH4)2 decomposes into MgH2 and B, finally the MgH2 reacts with Al, LiH and B, which forms Mg3Al2 and MgAlB4. The system starts to desorb H2 at 140 °C and desorbs 3.6 wt.% H2 below 300 °C, while individual Mg(BH4)2 starts to desorb H2 at 250 °C and desorbs only 1.3 wt.% H2 below 300 °C. The isothermal desorption kinetics of the Mg–B–Al–H systems is about 40% faster than that of Mg(BH4)2 at the hydrogen desorption ratio of 90%. In addition, the Mg–B–Al–H systems show partial reversibility at moderate temperature and pressure. For Al-added system, the product of rehydrogenation is MgH2, while for LiAlH4-added system the product is composed of LiBH4 and MgH2. 相似文献
3.
Borohydrides such as Mg(BH4)2 and Ca(BH4)2 continue to attract attention as potential hydrogen storage materials because of their high hydrogen content. In this study the desorption kinetics of Mg(BH4)2, Ca(BH4)2 and a 5Mg(BH4)2/Ca(BH4)2 mixture of the two were compared in the two-phase region at the same temperature and at a constant pressure thermodynamic driving force. The rate of hydrogen desorption from the two-phase region in the 5Mg(BH4)2/Ca(BH4)2 mixture was faster than that from either of the constituents. This indicated that Ca(BH4)2 was able to serve as a destabilizing agent for Mg(BH4)2. The results also showed that the desorption rates from the two-phase region were much faster than those from the single phase region. Modeling studies showed that the rate of hydrogen release from Mg(BH4)2, during the first 80% of the reaction, is diffusion controlled while in Ca(BH4)2 the reaction rate is phase boundary controlled. In the mixture the rate appears to be under the mixed control of both processes. 相似文献
4.
C. Rongeat I. LindemannA. Borgschulte L. SchultzO. Gutfleisch 《International Journal of Hydrogen Energy》2011,36(1):247-253
Calcium borohydride is one of the most interesting compounds for solid-state hydrogen storage, in particular because of its high hydrogen capacity. In this paper, the synthesis of Ca(BH4)2 by metathesis reaction via ball milling of a mixture of LiBH4 and CaCl2 is described. The effectiveness of this synthesis technique and the possible substitution of Cl ions in the borohydride phases is analysed depending on the back-pressure used for milling. When performed by ball milling under Ar, the metathesis reaction is not successful. A large quantity of a solid solution Li(BH4)1−xClx remains in the sample and CaHCl is formed rather than Ca(BH4)2. In contrast, the use of H2 back-pressure during milling favours the borohydride phases rather than CaHCl and leads to the formation of a solid solution Ca(BH4)2-yCly where [BH4]− groups are partially substituted by Cl ions. This compound has a similar structure as β-Ca(BH4)2 but with smaller lattice parameters. It is present in the as-milled sample together with LiCl and Li(BH4)1−xClx. The decomposition of the mixture occurs at lower temperature than for pure LiBH4 but higher than for pure Ca(BH4)2. The presence of chlorides in the structure of borohydride compounds changes dramatically the thermal properties of the material prepared and should be considered each time a metathesis reaction is used for synthesis. 相似文献
5.
Yanjing Yang Mingxia Gao Yongfeng Liu Jianhui Wang Jian Gu Hongge Pan Zhengxiao Guo 《International Journal of Hydrogen Energy》2012
A two-step ball-milling method has been provided to synthesize Mg(BH4)2 using NaBH4 and MgCl2 as starting materials. The method offers high yield and high purity (96%) of the compound. The as-synthesized Mg(BH4)2 is then combined with LiAlH4 by ball-milling in order to form new multi-hydride systems with high hydrogen storage properties. The structure, the dehydrogenation and the reversibility of the combined systems are studied. Analyses show that a metathesis reaction takes place between Mg(BH4)2 and LiAlH4 during milling, forming Mg(AlH4)2 and LiBH4. Mg(BH4)2 is excessive and remains in the ball-milled product when the molar ratio of Mg(BH4)2 to LiAlH4 is over 0.5. The onset dehydrogenation temperature of the combined systems is lowered to ca. 120 °C, which is much lower than that of either Mg(BH4)2 or LiAlH4. The dehydrogenation capacities of the combined systems below 300 °C are all higher than that of both Mg(BH4)2 and LiAlH4. The combined systems are reversible for hydrogen storage at moderate hydrogenation condition, and rapid hydrogenation occurred within the initial 30 min. Moreover, the remained Mg(BH4)2 in the combined systems is found also partially reversible. The mechanism of the enhancement of the hydrogen storage properties and the dehydrogenation/hydrogenation process of the combined systems were discussed. 相似文献
6.
R.A. Varin L. Zbroniec M. Polanski Y. Filinchuk R. Černý 《International Journal of Hydrogen Energy》2012
Manganese borohydride (Mn(BH4)2) was successfully synthesized by a mechano-chemical activation synthesis (MCAS) from lithium borohydride (LiBH4) and manganese chloride (MnCl2) by applying high energy ball milling for 30 min. For the first time a wide range of molar ratios n = 1, 2, 3, 5, 9 and 23 in the (nLiBH4 + MnCl2) mixture was investigated. During ball milling for 30 min the mixtures release only a very small quantity of H2 that increases with the molar ratio n but does not exceed ∼0.2 wt.% for n = 23. However, longer milling duration leads to more H2 released. For the equimolar ratio n = 1 the principal phases synthesized are Li2MnCl4, an inverse cubic spinel phase, and the Mn(BH4)2 borohydride. For n = 2 a LiCl salt is formed which coexists with Mn(BH4)2. With the n increasing from 3 to 23 LiBH4 is not completely reacted and its increasing amount is retained in the microstructure coexisting with LiCl and Mn(BH4)2. Gas mass spectrometry during Temperature Programmed Desorption (TPD) up to 450 °C shows the release of hydrogen as a principal gas with a maximum intensity around 130–150 °C accompanied by a miniscule quantity of borane B2H6. The intensity of the B2H6 peak is 200–600 times smaller than the intensity of the corresponding H2 peak. In situ heating experiments using a continuous monitoring during heating show no evidence of melting of Mn(BH4)2 up to about 270–280 °C. At 100 °C under 1 bar H2 pressure the ball milled n = 2 and 3 mixtures are capable of desorbing quite rapidly ∼4 wt.% H2 which is a very large amount of H2 considering that the mixture also contains 2 mol of LiCl salt. The H2 quantities experimentally desorbed at 100 and 200 °C do not exceed the maximum theoretical quantities of H2 expected to be desorbed from Mn(BH4)2 for various molar ratios n. It clearly confirms that the contribution from B2H6 evolved is negligibly small (if any) when desorption occurs isothermally in the practical temperature range 100–200 °C. It is found that the ball milled mixture with the molar ratio n = 3 exhibits the highest rate constant k and the lowest apparent activation energy for dehydrogenation, EA ∼ 102 kJ/mol. Decreasing or increasing the molar ratio n below or above 3 increases the apparent activation energy. Ball milled mixtures with the molar ratio n = 2 and 3 discharge slowly H2 during storage at room temperature and 40 °C. The addition of 5 wt.% nano-Ni with a specific surface area of 60.5 m2/g substantially enhances the rate of discharge at 40 °C. 相似文献
7.
Grigorii L. Soloveichik Matthew Andrus Yan GaoJ.-C. Zhao Sergei Kniajanski 《International Journal of Hydrogen Energy》2009
Different methods for preparation of unsolvated magnesium borohydride, a promising material for hydrogen storage, based on exchange reaction of MgCl2 with lithium and sodium borohydride in different solvents have been evaluated. A convenient scalable method for synthesis of pure Mg(BH4)2 by ball milling a mixture of MgCl2 and NaBH4 in diethyl ether has been developed. Crystalline stable low and high temperature phases, as well as a new metastable phase of unsolvated magnesium borohydride have been prepared. 相似文献
8.
Cheng-Hong Liu Yi-Chia Kuo Bing-Hung Chen Chan-Li Hsueh Kuo-Jen Hwang Jie-Ren Ku Fanghei Tsau Ming-Shan Jeng 《International Journal of Hydrogen Energy》2010
Solid-state composites of NaBH4 and Co-based catalyst have been fabricated for hydrogen generation via a novel mechanochemical technique, i.e. the high-energy ball milling, in which the gravimetric storage capacity of hydrogen has reached 6.7 wt%, meeting the 2010 target of at least 0.06 kg H2/kg set by the U.S. Department of Energy (DOE). The active catalysts used in the hydrolysis reaction of sodium borohydride for hydrogen generation are mainly cobalt oxides. Controlled addition of water, namely water used as a limiting agent, to the solid composites of NaBH4 and Co-based catalyst greatly improves the H2 storage capacity and resolved the issues of low gravimetric H2 storage in conventional aqueous system of sodium borohydride. Factors influencing the performance of hydrogen production such as amounts of H2O added, catalyst loadings and durations of ball-milling processes are investigated. Moreover the hydrolyzed products of NaBH4 and spent catalysts are analyzed as well. 相似文献
9.
Mg(BH4)2·2NH3 is a relatively new compound considered for hydrogen storage. The fundamental properties of the compound were comprehensively studied using first-principles calculations, such as crystal structure and electronic structure, reaction Gibbs free energy and possible reaction pathway. The calculated crystal structure is in good agreement with the experimental and other theoretical results. Results from electronic density of states (DOS) and electron localization function (ELF) show the covalent characteristics of the N–H and the B–H bonds, and the weak ionic interactions between the Mg atom and the NH3 ligands or the (BH4)− ligands. The reaction Gibbs free energies of several possible decomposition reactions were calculated between 0 and 700 K. All the reactions are exothermic. The most likely reaction pathway of the dehydrogenation reaction was clarified to show five distinct steps. 相似文献
10.
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
11.
Prior investigations have proposed, and successfully implemented, a stand-alone supply of aqueous hydrogen peroxide for use in fuel cells. An apparent obstacle for considering the use of aqueous hydrogen peroxide as an energy storage compound is the corrosive nature of the nominally required 50 wt.% maximum concentration. Here we propose storage of concentrated hydrogen peroxide in a high weight percent solid slurry, namely the equilibrium system of CaO2·2H2O2(s)/H2O2(aq), that mitigates much of the risk associated with the storage of such high concentrations. We have prepared and studied surrogate slurries of calcium hydroxide/water that are assumed to resemble the peroxo compound slurries. These slurries have the consistency of a paste rather than a distinct two-phase (liquid plus solid) system. This paste-like property of the prepared surrogates enable them to be contained within a 200 lines-per-inch. (LPI) nickel mesh screen (33.6% open area) with no solids leakage, and only liquid transport driven by an adsorbent material is placed in physical contact on the exterior of the screen. This hydrogen peroxide slurry approach suggests a convenient and safe mechanism of storing hydrogen peroxide for use in, say, vehicle applications. This is because fuel cell design requires only aqueous hydrogen peroxide use, that can be achieved using the separation approach utilizing the screen material here. This proposed method of storage should mitigate hazards associated with unintentional spills and leakage issues arising from aqueous solution use. 相似文献
12.
Mg(AlH4)2 and CaAlH5 were synthesized by direct ball milling of AlH3 and MgH2 or AlH3 and CaH2 hydrides. The XRD profiles indicated crystalline compounds. Several ball-milling conditions were studied and the optimum parameters were found. Among these, the key parameter is the pause used to cool down the milling device, which allows reducing the temperature rise during milling. Thus, the maximum yield of complex hydrides was obtained by minimizing the desorbed alane amount. The decomposition properties were studied and were in agreement with those reported for different synthesis methods. Mg(AlH4)2 with a good hydrogen capacity and a decomposition reaction enthalpy close to 0 kJ/mol H2 can be a candidate for one-way storage systems. As for CaAlH5, it might be suitable for reversible hydrogen storage thanks to its dehydrogenation reaction enthalpy (26 kJ/mol H2). However, rather high activation energy values were evaluated for both compounds (119 and 161 kJ/mol, respectively). 相似文献
13.
The hydrogen storage properties and mechanisms of the Ca(BH4)2-added 2LiNH2–MgH2 system were systematically investigated. The results showed that the addition of Ca(BH4)2 pronouncedly improved hydrogen storage properties of the 2LiNH2–MgH2 system. The onset temperature for dehydrogenation of the 2LiNH2–MgH2–0.3Ca(BH4)2 sample is only 80 °C, a ca. 40 °C decline with respect to the pristine sample. Further hydrogenation examination indicated that the dehydrogenated 2LiNH2–MgH2–0.1Ca(BH4)2 sample could absorb ca. 4.7 wt% of hydrogen at 160 °C and 100 atm while only 0.8 wt% of hydrogen was recharged into the dehydrogenated pristine sample under the same conditions. Structural analyses revealed that during ball milling, a metathesis reaction between Ca(BH4)2 and LiNH2 firstly occurred to convert to Ca(NH2)2 and LiBH4, and then, the newly developed LiBH4 reacted with LiNH2 to form Li4(BH4)(NH2)3. Upon heating, the in situ formed Ca(NH2)2 and Li4(BH4)(NH2)3 work together to significantly decrease the operating temperatures for hydrogen storage in the Ca(BH4)2-added 2LiNH2–MgH2 system. 相似文献
14.
In this work, a mixed-cation borohydride (K2Mn(BH4)4) with P21/n structure was successfully synthesized by mechanochemical milling of the 2KBH4–MnCl2 sample under argon. The structural and thermal decomposition properties of the borohydride compounds were investigated using XRD, Raman spectroscopy, FTIR, TGA-MS and DSC. Apart from K2Mn(BH4)4, the KMnCl3 and unreacted KBH4 compounds were present in the milled 2KBH4–MnCl2. The two mass loss regions were observed for the milled sample: one was from 100 to 160 °C with a 1.6 ± 0.1 wt% loss (a release of majority hydrogen and trace diborane), which was associated with the decomposition of K2Mn(BH4)4 to form KBH4, boron, and finely dispersed manganese; the other was from 165 to 260 °C with a 1.9 ± 0.1 wt% loss (only hydrogen release), which was due to the reaction of KBH4 with KMnCl3 to give KCl, boron, finely dispersed manganese. Simultaneously, the formed KCl could dissolve in KBH4 to yield a K(BH4)xCl1−x solid solution, and also react with KMnCl3 to form a new compound K4MnCl6. 相似文献
15.
Kiho Park Hyun-Sook Lee Arndt Remhof Young-Su Lee Yigang Yan Min-Young Kim Sun Jin Kim Andreas Züttel Young Whan Cho 《International Journal of Hydrogen Energy》2013
Y(BH4)3 is one of the candidates for solid-state hydrogen storage, which contains 9.06 wt% of hydrogen. In this study, the thermal properties of Y(BH4)3 synthesized via two different methods are extensively examined. One method relies on the solid–solid metathesis reaction between LiBH4 and YCl3, and the other method is the gas–solid reaction between B2H6 and YH3. The two samples are studied by differential scanning calorimetry, thermogravimetry, and X-ray diffraction. They exhibit distinctly different polymorphic phase transformation and melting. It turns out that the side product LiCl in the metathesis reaction, which has been regarded as being inert, shifts the melting point and promotes the formation of YB4 during decomposition. Differential scanning calorimetry and in situ X-ray diffraction data indicate that the addition of LiBH4 to Y(BH4)3 induces co-melting as is found in the cases of LiBH4–Ca(BH4)2 or LiBH4–Mg(BH4)2. Melt infiltration of Y(BH4)3 into mesoporous carbon cage confirms such melting behavior. 相似文献
16.
Sesha Srinivasan Diego Escobar Yogi Goswami Elias Stefanakos 《International Journal of Hydrogen Energy》2008,33(9):2268-2272
Transition metal complex borohydrides, Zn(BH4)2 have been synthesized by solid-state mechanochemical process. Various catalysts such as TiCl3, TiF3, nanoNi, nanoFe, Ti, nanoTi, and Zn were used to dope the borohydride in order to lower the decomposition temperature in the range of , without a significant reduction in the hydrogen content per total weight of the sample. In addition, the structural, bonding and thermal characteristics of undoped and catalysts doped Zn(BH4)2 were compared and analyzed to find out the optimum catalyst and dopant concentration. Among the different catalysts, 1.5 mol% of nanoNi obtained from Quantum Sphere Inc. was found to possess the optimum behavior in terms of fast kinetics and lowering the melting and decomposition temperature of Zn(BH4)2. 相似文献
17.
Yongfeng Liu Ni Jian Zhuanghe Ren Jianjiang Hu Fang Du Mingxia Gao Hongge Pan 《International Journal of Hydrogen Energy》2018,43(30):13981-13989
A novel dual-cation/anion complex hydride (Li2Mg(BH4)2(NH2)2), which contains a theoretical hydrogen capacity of 12.1 wt%, is successfully synthesized for the first time by ball milling a mixture consisting of MgBH4NH2 and Li2BH4NH2. The prepared Li2Mg(BH4)2(NH2)2 crystallizes in a triclinic structure, and the [NH2] and [BH4] groups remain intact within the structure. Upon heating, the prepared Li2Mg(BH4)2(NH2)2 decomposes to release approximately 8.7 wt% hydrogen in a three-step reaction at 100–450 °C. In addition, a small amount of ammonia is evolved during the first and second thermal decomposition steps as a side product. This ammonia is responsible for the lower experimental dehydrogenation amount compared to the theoretical hydrogen capacity. The XRD and FTIR results reveal that Li2Mg(BH4)2(NH2)2 first decomposes to LiMgBN2, LiBH4, BN, LiH and MgBNH8 at 100–250 °C, and then, the newly formed MgBNH8 reacts with LiH to form Mg, LiBH4 and BN at 250–340 °C. Finally, the decomposition of LiBH4 releases hydrogen and generates LiH and B at 340–450 °C. 相似文献
18.
Juner Chen Yao ZhangZhitao Xiong Guotao WuHailiang Chu Teng HePing Chen 《International Journal of Hydrogen Energy》2012
Co-based catalyst can significantly improve the dehydrogenation kinetics of the eutectic composite of LiBH4–Mg(BH4)2 (1/1 M ratio). The onset hydrogen desorption temperature of the composite is at about 155 °C, which is ca. 245, 110 or 27 °C lower than that of LiBH4, Mg(BH4)2 or pristine LiBH4–Mg(BH4)2, respectively. Upon holding the samples at 270 °C, the Co catalyzed composite can release hydrogen at a rate 1.6 times faster than that of the pristine one. Electron Paramagnetic Resonance (EPR) characterization evidenced that Co was in a reduced state of Co+ which may serve as the functional species in catalyzing the dehydrogenation of the composite. 相似文献
19.
A novel lithium amidoborane borohydride complex, Li2(NH2BH3)(BH4), was synthesized using mechanochemical method and its crystal structure was successfully determined by a combination of X-ray diffraction (XRD) analysis and first-principles calculations. Interestingly, this compound does not exist as a pure phase, but requires almost equivalent amount of amorphous LiAB as a stabilizing agent. In this paper, we report a careful study of the structure, property, and dehydrogenation mechanism of the 1:1 Li2(NH2BH3)(BH4)/LiAB composite. This composite can release ∼8 wt% H2 at 100 °C via a two-step dehydrogenation process, with dehydrogenation kinetics better than the parenting phases. The composite and its dehydrogenation products were characterized by the combined XRD, Fourier transformation infrared (FTIR) spectroscopy, and solid-state 11B MAS NMR techniques. Selective deuterium labeling was performed to elucidate a reaction sequence for the hydrogen release by analyzing the released gases. 相似文献
20.
In order to investigate the catalytic effect of TiN, TiMn2 and LaNi5 on the hydrogen storage capacity of LiAlH4, 2 mol% of the catalyst was milled with LiH/Al and then hydrogenated in Me2O. Doping with TiN, TiMn2 or LaNi5 led to substantial hydrogenation of LiH/Al in accordance with the formation of LiAlH4. In each case the amount of hydrogen absorbed was dependent on the catalyst and the ball-to-powder ratio used during milling. A high ball-to-powder ratio results in an improvement in the hydrogen storage capacity of LiAlH4. For each ball-to-powder ratio the highest hydrogen storage capacity was recorded for the TiN-catalyzed sample; hydrogen storage capacity increased from 3.2 to 4.8 to 6.0 wt.% H as the ball to-powder ratio increased from 10:1 to 20:1 to 40:1. The high levels of hydrogenation of LiH/Al catalyzed with TiN, TiMn2 and LaNi5 are remarkable because for the LiAlH4 system only a TiCl3 catalyst has previously been shown to result in rehydrogenation of the dehydrogenated products to LiAlH4. 相似文献