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Metal-free, polyether-mediated H_2-release from ammonia borane: roles of hydrogen bonding interactions in promoting dehydrogenation

Kim, Yongmin and Baek, Hyunjae and Lee, Jin Hee and Yeo, Shinyoung and Kim, Kibum and Hwang, Son-Jong and Eun, Bit and Nam, Suk Woo and Lim, Tae-Hoon and Yoon, Chang Won (2013) Metal-free, polyether-mediated H_2-release from ammonia borane: roles of hydrogen bonding interactions in promoting dehydrogenation. Physical Chemistry Chemical Physics, 15 (45). pp. 19584-19594. ISSN 1463-9076.

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Polyetheral additives were found to be efficient promoters to enhance the rate of H2-release from ammonia borane (AB) at various temperatures. In particular, tetraethylene glycol dimethyl ether (T4EGDE, 29 wt% relative to AB + T4EGDE) exhibited significantly improved activities for AB dehydrogenation, with the material-based hydrogen storage capacity of 10.3 wt% at 125 °C within 40 min. In situ FT-IR spectroscopy indicated the formation of B-(cyclodiborazanyl)amino-borohydride (BCDB), borazine, and μ-aminodiborane as gaseous byproducts. In addition, 11B nuclear magnetic resonance (NMR) spectroscopy further revealed that diammoniate of diborane (DADB) was initially formed to give polyaminoborane as liquid and/or solid spent-fuel, consistent with previous reports. Density Functional Theory (DFT) calculations suggested that hydrogen bonding interactions between AB and a polyetheral promoter initially played an important role in increasing the reactivity of B–H bonds of AB by transferring electron density from oxygen atoms of the promoter into B–H bonds of AB. These partially activated, hydridic B–H bonds were proposed to help promote the formation of diammoniate of diborane (DADB), which is considered as a reactive intermediate, eventually enhancing the rate of H2-release from AB. In addition, our in situ solid state 11B magic angle spinning (MAS) NMR measurements further confirmed that the rate of DADB formation from AB with a small quantity of T4EGDE was found to be much faster than that of pristine AB even at 50 °C. This metal-free method for H2-release from AB with an added, small quantity of polyethers would be helpful to develop feasible hydrogen storage systems for long-term fuel cell applications.

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Hwang, Son-Jong0000-0002-3210-466X
Additional Information:© 2013 Royal Society of Chemistry. Received 21st June 2013, Accepted 29th July 2013. First published online 05 Aug 2013. This research was supported by Korea Institute of Energy Technology Evaluation and Planning (KETEP) of the Ministry of Knowledge Economy (MEST) (the New Renewable Energy Program, No. 20113030040020). Part of this research was also supported by the National Research Foundation of Korea Grant funded by the Korean Government (MSIP) (2013, University-Institute cooperation program). The NMR facility at Caltech was supported by the National Science Foundation (NSF) under Grant Number 9724240 and partially supported by the MRSEC Program of the NSF under Award Number DMR-520565. We are grateful to Professor Larry Sneddon and Dr Tom Autrey for their valuable comments.
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Ministry of Knowledge Economy (Korea)20113030040020
National Research Foundation of KoreaUNSPECIFIED
Korean Government (MSIP)UNSPECIFIED
Issue or Number:45
Record Number:CaltechAUTHORS:20131205-131857710
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Official Citation:Metal-free, polyether-mediated H2-release from ammonia borane: roles of hydrogen bonding interactions in promoting dehydrogenation Yongmin Kim, Hyunjae Baek, Jin Hee Lee, Shinyoung Yeo, Kibum Kim, Son-Jong Hwang, Bit Eun, Suk Woo Nam, Tae-Hoon Lim and Chang Won Yoon Phys. Chem. Chem. Phys., 2013, 15, 19584-19594 DOI: 10.1039/C3CP52591K
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42860
Deposited By: Ruth Sustaita
Deposited On:05 Dec 2013 22:05
Last Modified:03 Oct 2019 06:02

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