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Desolvation and Dehydrogenation of Solvated Magnesium Salts of Dodecahydrododecaborate: Relationship between Structure and Thermal Decomposition

Chen, Xuenian and Liu, Yi-Hsin and Alexander, Anne-Marie and Gallucci, Judith C. and Hwang, Son-Jong and Lingam, Hima Kumar and Huang, Zhenguo and Wang, Cong and Li, Huizhen and Zhao, Qianyi and Ozkan, Umit S. and Shore, Sheldon G. and Zhao, Ji-Cheng (2014) Desolvation and Dehydrogenation of Solvated Magnesium Salts of Dodecahydrododecaborate: Relationship between Structure and Thermal Decomposition. Chemistry: a European Journal, 20 (24). pp. 7325-7333. ISSN 0947-6539. http://resolver.caltech.edu/CaltechAUTHORS:20140717-091003293

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Abstract

Attempts to synthesize solvent-free MgB_(12)H_(12) by heating various solvated forms (H_2O, NH_3, and CH_3OH) of the salt failed because of the competition between desolvation and dehydrogenation. This competition has been studied by thermogravimetric analysis (TGA) and temperature-programmed desorption (TPD). Products were characterized by IR, solution- and solid-state NMR spectroscopy, elemental analysis, and single-crystal or powder X-ray diffraction analysis. For hydrated salts, thermal decomposition proceeded in three stages, loss of water to form first hexahydrated then trihydrated, and finally loss of water and hydrogen to form polyhydroxylated complexes. For partially ammoniated salts, two stages of thermal decomposition were observed as ammonia and hydrogen were released with weight loss first of 14 % and then 5.5 %. Thermal decomposition of methanolated salts proceeded through a single step with a total weight loss of 32 % with the release of methanol, methane, and hydrogen. All the gaseous products of thermal decomposition were characterized by using mass spectrometry. Residual solid materials were characterized by solid-state 11B magic-angle spinning (MAS) NMR spectroscopy and X-ray powder diffraction analysis by which the molecular structures of hexahydrated and trihydrated complexes were solved. Both hydrogen and dihydrogen bonds were observed in structures of [Mg(H_2O_6B_(12)H_(12)]⋅6 H_2O and [Mg(CH_3OH)_(6)B_(12)H_(12)]⋅6 CH_3OH, which were determined by single-crystal X-ray diffraction analysis. The structural factors influencing thermal decomposition behavior are identified and discussed. The dependence of dehydrogenation on the formation of dihydrogen bonds may be an important consideration in the design of solid-state hydrogen storage materials.


Item Type:Article
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http://dx.doi.org/10.1002/chem.201303842DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/chem.201303842/abstractPublisherArticle
ORCID:
AuthorORCID
Hwang, Son-Jong0000-0002-3210-466X
Additional Information:© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Received: October 1, 2013; Revised: February 20, 2014; Published online on April 30, 2014. The authors from HNU thank the financial support from the National Natural Science Foundation of China (NSFC) under Grant Number 21371051. The work in OSU was supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, under Contract No. DE-FC3605GO15062 and Office of Science, Office of Basic Energy Sciences, under Contract No. DE-FG02–07ER15896. The NMR facility at Caltech was supported by the U.S. Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, through the Hydrogen, Fuel Cells & Infrastructure Technologies Program under contract numbers DE-AI-01–05EE11105, the National Science Foundation (NSF) under Grant Number 9724240, and partially supported by the MRSEC Program of the NSF under Award Number DMR-520565. The authors declare no competing financial interest.
Funders:
Funding AgencyGrant Number
National Natural Science Foundation of China21371051
Department of Energy (DOE)DE-FC3605GO15062
Department of Energy (DOE)DE-FG02–07ER15896
NSFDMR-9724240
NSFDMR-520565
Record Number:CaltechAUTHORS:20140717-091003293
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20140717-091003293
Official Citation:Chen, X., Liu, Y.-H., Alexander, A.-M., Gallucci, J. C., Hwang, S.-J., Lingam, H. K., Huang, Z., Wang, C., Li, H., Zhao, Q., Ozkan, U. S., Shore, S. G. and Zhao, J.-C. (2014), Desolvation and Dehydrogenation of Solvated Magnesium Salts of Dodecahydrododecaborate: Relationship between Structure and Thermal Decomposition. Chem. Eur. J., 20: 7325–7333. doi: 10.1002/chem.201303842
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:47286
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:17 Jul 2014 23:56
Last Modified:26 Apr 2017 22:20

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