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Stavila V, Li S, Dun C, Marple MAT, Mason HE, Snider JL, Reynolds JE, El Gabaly F, Sugar JD, Spataru CD, Zhou X, Dizdar B, Majzoub EH, Chatterjee R, Yano J, Schlomberg H, Lotsch BV, Urban JJ, Wood BC, Allendorf MD. Defying Thermodynamics: Stabilization of Alane Within Covalent Triazine Frameworks for Reversible Hydrogen Storage. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202107507] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Vitalie Stavila
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Sichi Li
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | - Chaochao Dun
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | | | - Harris E. Mason
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | | | | | - Farid El Gabaly
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Joshua D. Sugar
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | | | - Xiaowang Zhou
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Brennan Dizdar
- University of Missouri—St. Louis Department of Physics and Astronomy One University Blvd St. Louis MO 63121 USA
- University of Chicago Chicago IL 60637 USA
| | - Eric H. Majzoub
- University of Missouri—St. Louis Department of Physics and Astronomy One University Blvd St. Louis MO 63121 USA
| | - Ruchira Chatterjee
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Junko Yano
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Hendrik Schlomberg
- Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1 70569 Stuttgart Germany
- University of Munich (LMU) Department of Chemistry Butenandtstraße 5–13 81377 München Germany
| | - Bettina V. Lotsch
- Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1 70569 Stuttgart Germany
- University of Munich (LMU) Department of Chemistry Butenandtstraße 5–13 81377 München Germany
| | - Jeffrey J. Urban
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Brandon C. Wood
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | - Mark D. Allendorf
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
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Stavila V, Li S, Dun C, Marple MAT, Mason HE, Snider JL, Reynolds JE, El Gabaly F, Sugar JD, Spataru CD, Zhou X, Dizdar B, Majzoub EH, Chatterjee R, Yano J, Schlomberg H, Lotsch BV, Urban JJ, Wood BC, Allendorf MD. Rücktitelbild: Defying Thermodynamics: Stabilization of Alane Within Covalent Triazine Frameworks for Reversible Hydrogen Storage (Angew. Chem. 49/2021). Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202112490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Vitalie Stavila
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Sichi Li
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | - Chaochao Dun
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | | | - Harris E. Mason
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | | | | | - Farid El Gabaly
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Joshua D. Sugar
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | | | - Xiaowang Zhou
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Brennan Dizdar
- University of Missouri—St. Louis Department of Physics and Astronomy One University Blvd St. Louis MO 63121 USA
- University of Chicago Chicago IL 60637 USA
| | - Eric H. Majzoub
- University of Missouri—St. Louis Department of Physics and Astronomy One University Blvd St. Louis MO 63121 USA
| | - Ruchira Chatterjee
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Junko Yano
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Hendrik Schlomberg
- Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1 70569 Stuttgart Germany
- University of Munich (LMU) Department of Chemistry Butenandtstraße 5–13 81377 München Germany
| | - Bettina V. Lotsch
- Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1 70569 Stuttgart Germany
- University of Munich (LMU) Department of Chemistry Butenandtstraße 5–13 81377 München Germany
| | - Jeffrey J. Urban
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Brandon C. Wood
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | - Mark D. Allendorf
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
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Stavila V, Li S, Dun C, Marple MAT, Mason HE, Snider JL, Reynolds JE, El Gabaly F, Sugar JD, Spataru CD, Zhou X, Dizdar B, Majzoub EH, Chatterjee R, Yano J, Schlomberg H, Lotsch BV, Urban JJ, Wood BC, Allendorf MD. Defying Thermodynamics: Stabilization of Alane Within Covalent Triazine Frameworks for Reversible Hydrogen Storage. Angew Chem Int Ed Engl 2021; 60:25815-25824. [PMID: 34459093 DOI: 10.1002/anie.202107507] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2021] [Revised: 08/02/2021] [Indexed: 11/09/2022]
Abstract
The highly unfavorable thermodynamics of direct aluminum hydrogenation can be overcome by stabilizing alane within a nanoporous bipyridine-functionalized covalent triazine framework (AlH3 @CTF-bipyridine). This material and the counterpart AlH3 @CTF-biphenyl rapidly desorb H2 between 95 and 154 °C, with desorption complete at 250 °C. Sieverts measurements, 27 Al MAS NMR and 27 Al{1 H} REDOR experiments, and computational spectroscopy reveal that AlH3 @CTF-bipyridine dehydrogenation is reversible at 60 °C under 700 bar hydrogen, >10 times lower pressure than that required to hydrogenate bulk aluminum. DFT calculations and EPR measurements support an unconventional mechanism whereby strong AlH3 binding to bipyridine results in single-electron transfer to form AlH2 (AlH3 )n clusters. The resulting size-dependent charge redistribution alters the dehydrogenation/rehydrogenation thermochemistry, suggesting a novel strategy to enable reversibility in high-capacity metal hydrides.
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Affiliation(s)
- Vitalie Stavila
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
| | - Sichi Li
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550, USA
| | - Chaochao Dun
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA, 94720, USA
| | - Maxwell A T Marple
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550, USA
| | - Harris E Mason
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550, USA
| | - Jonathan L Snider
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
| | - Joseph E Reynolds
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
| | - Farid El Gabaly
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
| | - Joshua D Sugar
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
| | - Catalin D Spataru
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
| | - Xiaowang Zhou
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
| | - Brennan Dizdar
- University of Missouri-St. Louis, Department of Physics and Astronomy, One University Blvd, St. Louis, MO, 63121, USA.,University of Chicago, Chicago, IL, 60637, USA
| | - Eric H Majzoub
- University of Missouri-St. Louis, Department of Physics and Astronomy, One University Blvd, St. Louis, MO, 63121, USA
| | - Ruchira Chatterjee
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA, 94720, USA
| | - Junko Yano
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA, 94720, USA
| | - Hendrik Schlomberg
- Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569, Stuttgart, Germany.,University of Munich (LMU), Department of Chemistry, Butenandtstraße 5-13, 81377, München, Germany
| | - Bettina V Lotsch
- Max-Planck-Institut für Festkörperforschung, Heisenbergstraße 1, 70569, Stuttgart, Germany.,University of Munich (LMU), Department of Chemistry, Butenandtstraße 5-13, 81377, München, Germany
| | - Jeffrey J Urban
- Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, CA, 94720, USA
| | - Brandon C Wood
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, 94550, USA
| | - Mark D Allendorf
- Sandia National Laboratories, 7011 East Avenue, Livermore, CA, 94550, USA
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Stavila V, Li S, Dun C, Marple MAT, Mason HE, Snider JL, Reynolds JE, El Gabaly F, Sugar JD, Spataru CD, Zhou X, Dizdar B, Majzoub EH, Chatterjee R, Yano J, Schlomberg H, Lotsch BV, Urban JJ, Wood BC, Allendorf MD. Back Cover: Defying Thermodynamics: Stabilization of Alane Within Covalent Triazine Frameworks for Reversible Hydrogen Storage (Angew. Chem. Int. Ed. 49/2021). Angew Chem Int Ed Engl 2021. [DOI: 10.1002/anie.202112490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Vitalie Stavila
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Sichi Li
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | - Chaochao Dun
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | | | - Harris E. Mason
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | | | | | - Farid El Gabaly
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Joshua D. Sugar
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | | | - Xiaowang Zhou
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
| | - Brennan Dizdar
- University of Missouri—St. Louis Department of Physics and Astronomy One University Blvd St. Louis MO 63121 USA
- University of Chicago Chicago IL 60637 USA
| | - Eric H. Majzoub
- University of Missouri—St. Louis Department of Physics and Astronomy One University Blvd St. Louis MO 63121 USA
| | - Ruchira Chatterjee
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Junko Yano
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Hendrik Schlomberg
- Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1 70569 Stuttgart Germany
- University of Munich (LMU) Department of Chemistry Butenandtstraße 5–13 81377 München Germany
| | - Bettina V. Lotsch
- Max-Planck-Institut für Festkörperforschung Heisenbergstraße 1 70569 Stuttgart Germany
- University of Munich (LMU) Department of Chemistry Butenandtstraße 5–13 81377 München Germany
| | - Jeffrey J. Urban
- Lawrence Berkeley National Laboratory 1 Cyclotron Rd Berkeley CA 94720 USA
| | - Brandon C. Wood
- Lawrence Livermore National Laboratory 7000 East Avenue Livermore CA 94550 USA
| | - Mark D. Allendorf
- Sandia National Laboratories 7011 East Avenue Livermore CA 94550 USA
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Myung Y, Choi J, Wu F, Banerjee S, Majzoub EH, Jin J, Son SU, Braun PV, Banerjee P. Cationically Substituted Bi 0.7Fe 0.3OCl Nanosheets as Li Ion Battery Anodes. ACS Appl Mater Interfaces 2017; 9:14187-14196. [PMID: 28388093 DOI: 10.1021/acsami.6b16822] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Cation substitution of Bi3+ with Fe3+ in BiOCl leads to the formation of ionically layered Bi0.7Fe0.3OCl nanosheets. The synthesis follows a hydrolysis route using bismuth(III) nitrate and iron(III) chloride, followed by postannealing at 500 °C. Room temperature electrical conductivity improves from 6.11 × 10-8 S/m for BiOCl to 6.80 × 10-7 S/m for Bi0.7Fe0.3OCl. Correspondingly, the activation energy for electrical conduction reduces from 862 meV for pure BiOCl to 310 meV for Bi0.7Fe0.3OCl. These data suggest improved charge mobility in Bi0.7Fe0.3OCl nanosheets. Density functional theory calculations confirm this behavior by predicting a high density of states near the Fermi level for Bi0.7Fe0.3OCl. The improvement in electrical conductivity is exploited in the electrochemical performance of Bi0.7Fe0.3OCl nanosheets. The insertion capacity of Li+ ions shows an increase of 2.5×, from 215 mAh·.g-1 for undoped BiOCl to 542 mAh·g-1 for Bi0.7Fe0.3OCl after 50 cycles at a current density of 50 mA·g-1. Thus, the direct substitution of Bi3+ sites with Fe3+ in BiOCl results in nanosheets of an ionically layered ternary semiconductor compound which is attractive for Li ion battery anode applications.
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Affiliation(s)
- Yoon Myung
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis , St. Louis, Missouri 63130, United States
- Department of Nanotechnology and Advanced Materials Engineering, Sejong University , Seoul, 05006, Korea
| | - Jaewon Choi
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
- Department of Chemistry, Sungkyunkwan University , Suwon 16419, Korea
| | - Fei Wu
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis , St. Louis, Missouri 63130, United States
| | - Sriya Banerjee
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis , St. Louis, Missouri 63130, United States
| | - Eric H Majzoub
- Center for Nanoscience, Department of Physics and Astronomy, University of Missouri , St. Louis, Missouri 63121, United States
| | - Jaewon Jin
- Department of Chemistry, Sungkyunkwan University , Suwon 16419, Korea
| | - Seung Uk Son
- Department of Chemistry, Sungkyunkwan University , Suwon 16419, Korea
| | - Paul V Braun
- Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Parag Banerjee
- Department of Mechanical Engineering and Materials Science, Washington University in St. Louis , St. Louis, Missouri 63130, United States
- Institute of Materials Science and Engineering, Washington University in St. Louis , St. Louis, Missouri 63130, United States
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Stavila V, Bhakta RK, Alam TM, Majzoub EH, Allendorf MD. Reversible hydrogen storage by NaAlH4 confined within a titanium-functionalized MOF-74(Mg) nanoreactor. ACS Nano 2012; 6:9807-9817. [PMID: 23075161 DOI: 10.1021/nn304514c] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We demonstrate that NaAlH(4) confined within the nanopores of a titanium-functionalized metal-organic framework (MOF) template MOF-74(Mg) can reversibly store hydrogen with minimal loss of capacity. Hydride-infiltrated samples were synthesized by melt infiltration, achieving loadings up to 21 wt %. MOF-74(Mg) possesses one-dimensional, 12 Å channels lined with Mg atoms having open coordination sites, which can serve as sites for Ti catalyst stabilization. MOF-74(Mg) is stable under repeated hydrogen desorption and hydride regeneration cycles, allowing it to serve as a "nanoreactor". Confining NaAlH(4) within these pores alters the decomposition pathway by eliminating the stable intermediate Na(3)AlH(6) phase observed during bulk decomposition and proceeding directly to NaH, Al, and H(2), in agreement with theory. The onset of hydrogen desorption for both Ti-doped and undoped nano-NaAlH(4)@MOF-74(Mg) is ∼50 °C, nearly 100 °C lower than bulk NaAlH(4). However, the presence of titanium is not necessary for this increase in desorption kinetics but enables rehydriding to be almost fully reversible. Isothermal kinetic studies indicate that the activation energy for H(2) desorption is reduced from 79.5 kJ mol(-1) in bulk Ti-doped NaAlH(4) to 57.4 kJ mol(-1) for nanoconfined NaAlH(4). The structural properties of nano-NaAlH(4)@MOF-74(Mg) were probed using (23)Na and (27)Al solid-state MAS NMR, which indicates that the hydride is not decomposed during infiltration and that Al is present as tetrahedral AlH(4)(-) anions prior to desorption and as Al metal after desorption. Because of the highly ordered MOF structure and monodisperse pore dimensions, our results allow key template features to be identified to ensure reversible, low-temperature hydrogen storage.
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Affiliation(s)
- Vitalie Stavila
- Sandia National Laboratories, Livermore, California 94551-0969, United States.
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Duan Y, Zhang B, Sorescu DC, Karl Johnson J, Majzoub EH, Luebke DR. Density functional theory studies on the electronic, structural, phonon dynamical and thermo-stability properties of bicarbonates MHCO(3), M = Li, Na, K. J Phys Condens Matter 2012; 24:325501-16. [PMID: 22787158 DOI: 10.1088/0953-8984/24/32/325501] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The structural, electronic, phonon dispersion and thermodynamic properties of MHCO(3) (M = Li, Na, K) solids were investigated using density functional theory. The calculated bulk properties for both their ambient and the high-pressure phases are in good agreement with available experimental measurements. Solid phase LiHCO(3) has not yet been observed experimentally. We have predicted several possible crystal structures for LiHCO(3) using crystallographic database searching and prototype electrostatic ground state modeling. Our total energy and phonon free energy (F(PH)) calculations predict that LiHCO(3) will be stable under suitable conditions of temperature and partial pressures of CO(2) and H(2)O. Our calculations indicate that the [Formula: see text] groups in LiHCO(3) and NaHCO(3) form an infinite chain structure through O⋯H⋯O hydrogen bonds. In contrast, the [Formula: see text] anions form dimers, [Formula: see text], connected through double hydrogen bonds in all phases of KHCO(3). Based on density functional perturbation theory, the Born effective charge tensor of each atom type was obtained for all phases of the bicarbonates. Their phonon dispersions with the longitudinal optical-transverse optical splitting were also investigated. Based on lattice phonon dynamics study, the infrared spectra and the thermodynamic properties of these bicarbonates were obtained. Over the temperature range 0-900 K, the F(PH) and the entropies (S) of MHCO(3) (M =Li, Na, K) systems vary as F(PH)(LiHCO(3)) > F(PH)(NaHCO(3)) > F(PH)(KHCO(3)) and S(KHCO(3)) > S(NaHCO(3)) > S(LiHCO(3)), respectively, in agreement with the available experimental data. Analysis of the predicted thermodynamics of the CO(2) capture reactions indicates that the carbonate/bicarbonate transition reactions for Na and K could be used for CO(2) capture technology, in agreement with experiments.
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Affiliation(s)
- Yuhua Duan
- National Energy Technology Laboratory, United States Department of Energy, Pittsburgh, PA 15236, USA.
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Wagner LK, Majzoub EH, Allendorf MD, Grossman JC. Tuning metal hydride thermodynamics via size and composition: Li–H, Mg–H, Al–H, and Mg–Al–H nanoclusters for hydrogen storage. Phys Chem Chem Phys 2012; 14:6611-6. [DOI: 10.1039/c2cp24063g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Affiliation(s)
- Mitchell R. Anstey
- Sandia National Laboratories, P.O. Box 969, MS-9403, Livermore, California 94551
| | - Michael T. Corbett
- Sandia National Laboratories, P.O. Box 969, MS-9403, Livermore, California 94551
| | - Eric H. Majzoub
- Center for Nanoscience and Department of Physics and Astronomy, University of Missouri, St. Louis, Missouri 63121
| | - Joseph G. Cordaro
- Sandia National Laboratories, P.O. Box 969, MS-9403, Livermore, California 94551
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Ozolins V, Akbarzadeh AR, Gunaydin H, Michel K, Wolverton C, Majzoub EH. First-principles computational discovery of materials for hydrogen storage. ACTA ACUST UNITED AC 2009. [DOI: 10.1088/1742-6596/180/1/012076] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Ozolins V, Majzoub EH, Wolverton C. First-principles prediction of a ground state crystal structure of magnesium borohydride. Phys Rev Lett 2008; 100:135501. [PMID: 18517964 DOI: 10.1103/physrevlett.100.135501] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Indexed: 05/26/2023]
Abstract
Mg(BH(4))(2) contains a large amount of hydrogen by weight and by volume, but its promise as a candidate for hydrogen storage is dependent on the currently unknown thermodynamics of H2 release. Using first-principles density-functional theory calculations and a newly developed prototype electrostatic ground state search strategy, we predict a new T=0 K ground state of Mg(BH(4))(2) with I4[over ]m2 symmetry, which is 5 kJ/mol lower in energy than the recently proposed P6(1) structure. The calculated thermodynamics of H(2) release are within the range required for reversible storage.
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Affiliation(s)
- V Ozolins
- Department of Materials Science and Engineering, University of California, Los Angeles, California 90095-1595, USA
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Abstract
We demonstrate a new solid-state synthesis route to prepare calcium borohydride, Ca(BH4)2, by reacting a ball-milled mixture of CaB(6) and CaH(2) in a molar ratio of 1:2 at 700 bar of H2 pressure and 400-440 degrees C. Moreover, doping with catalysts was found to be crucial to enhance reaction kinetics. Thermogravimetric analysis and differential scanning calorimetry revealed a reversible low-temperature to high-temperature endothermic phase transition at 140 degrees C and another endothermic phase transition at 350-390 degrees C associated with hydrogen release upon formation of CaB(6) and CaH(2), as was evident from X-ray diffraction analysis. Thus, since Ca(BH(4))(2) here is shown to be prepared from its anticipated decomposition products, the conclusion is that it has potential to be utilized as a reversible hydrogen storage material. The theoretical reversible capacity was 9.6 wt % hydrogen.
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Abstract
A new bialkali alanate K2LiAlH6 was synthesized at 320-330 degrees C and 100-700 bar. It was structurally characterized by powder X-ray diffraction. It crystallizes in space group R3m (No. 166) with unit cell parameters a = 5.62068(8) and c = 27.3986(6) A. The Li and K cation sites are mutually exclusive, and Rietveld refinement finds no cation mixing. First-principles total energy calculations were performed for nine competing database structures of the stoichiometry A2BCX6, taken from fluoride and oxide compounds in the Inorganic Crystal Structure Database (ICSD). The relaxed structures were compared via their total energies and their agreement with experimental diffraction spectra. Two database structures K2LiAlF6 (R3m) and Cs2NaAlF6 (C2/m) were found to have the lowest total energies, but with the Rietveld method the K2LiAlF6 structure type was shown to be the most favorable. Ab initio total energy calculations support the validity of the structure determination. First-principles calculations also indicate that cation mixing is energetically unfavorable. Hydride properties such as plateau pressure are therefore more difficult to manipulate through alloying in this class of compounds.
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Affiliation(s)
- Ewa Rönnebro
- Sandia National Laboratories, 7011 East Avenue, Livermore, California 94551-0969, USA.
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