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Title: A Mechanistic Analysis of Phase Evolution and Hydrogen Storage Behavior in Nanocrystalline Mg(BH4)2 within Reduced Graphene Oxide

Abstract

Magnesium borohydride (Mg(BH4)2, abbreviated here MBH) has received tremendous attention as a promising onboard hydrogen storage medium due to its excellent gravimetric and volumetric hydrogen storage capacities. While the polymorphs of MBH-alpha (α), beta (β), and gamma (γ)-have distinct properties, their synthetic homogeneity can be difficult to control, mainly due to their structural complexity and similar thermodynamic properties. In this work, we describe an effective approach for obtaining pure polymorphic phases of MBH nanomaterials within a reduced graphene oxide support (abbreviated MBHg) under mild conditions (60-190 °C under mild vacuum, 2 Torr), starting from two distinct samples initially dried under Ar and vacuum. Specifically, we selectively synthesize the thermodynamically stable α phase and metastable β phase from the γ-phase within the temperature range of 150-180 °C. The relevant underlying phase evolution mechanism is elucidated by theoretical thermodynamics and kinetic nucleation modeling. Finally, the resulting MBHg composites exhibit structural stability, resistance to oxidation, and partially reversible formation of diverse [BH4]- species during de- and rehydrogenation processes, rendering them intriguing candidates for further optimization toward hydrogen storage applications.

Authors:
 [1]; ORCiD logo [2];  [3];  [2];  [2];  [4]; ORCiD logo [4];  [1]; ORCiD logo [2];  [2]; ORCiD logo [1]; ORCiD logo [4]; ORCiD logo [5]; ORCiD logo [3]; ORCiD logo [2]; ORCiD logo [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  4. Sandia National Lab. (SNL-CA), Livermore, CA (United States)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Santa Cruz, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
OSTI Identifier:
1604725
Grant/Contract Number:  
AC02-05CH11231; AC52-07NA27344; NA-0003525
Resource Type:
Accepted Manuscript
Journal Name:
ACS Nano
Additional Journal Information:
Journal Volume: 14; Journal Issue: 2; Journal ID: ISSN 1936-0851
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; magnesium borohydride; hydrogen storage; phase evolution; thermodynamics; kinetic; reduced graphene oxide

Citation Formats

Jeong, Sohee, Heo, Tae Wook, Oktawiec, Julia, Shi, Rongpei, Kang, ShinYoung, White, James L., Schneemann, Andreas, Zaia, Edmond W., Wan, Liwen F., Ray, Keith G., Liu, Yi-Sheng, Stavila, Vitalie, Guo, Jinghua, Long, Jeffrey R., Wood, Brandon C., and Urban, Jeffrey J. A Mechanistic Analysis of Phase Evolution and Hydrogen Storage Behavior in Nanocrystalline Mg(BH4)2 within Reduced Graphene Oxide. United States: N. p., 2020. Web. https://doi.org/10.1021/acsnano.9b07454.
Jeong, Sohee, Heo, Tae Wook, Oktawiec, Julia, Shi, Rongpei, Kang, ShinYoung, White, James L., Schneemann, Andreas, Zaia, Edmond W., Wan, Liwen F., Ray, Keith G., Liu, Yi-Sheng, Stavila, Vitalie, Guo, Jinghua, Long, Jeffrey R., Wood, Brandon C., & Urban, Jeffrey J. A Mechanistic Analysis of Phase Evolution and Hydrogen Storage Behavior in Nanocrystalline Mg(BH4)2 within Reduced Graphene Oxide. United States. https://doi.org/10.1021/acsnano.9b07454
Jeong, Sohee, Heo, Tae Wook, Oktawiec, Julia, Shi, Rongpei, Kang, ShinYoung, White, James L., Schneemann, Andreas, Zaia, Edmond W., Wan, Liwen F., Ray, Keith G., Liu, Yi-Sheng, Stavila, Vitalie, Guo, Jinghua, Long, Jeffrey R., Wood, Brandon C., and Urban, Jeffrey J. Fri . "A Mechanistic Analysis of Phase Evolution and Hydrogen Storage Behavior in Nanocrystalline Mg(BH4)2 within Reduced Graphene Oxide". United States. https://doi.org/10.1021/acsnano.9b07454. https://www.osti.gov/servlets/purl/1604725.
@article{osti_1604725,
title = {A Mechanistic Analysis of Phase Evolution and Hydrogen Storage Behavior in Nanocrystalline Mg(BH4)2 within Reduced Graphene Oxide},
author = {Jeong, Sohee and Heo, Tae Wook and Oktawiec, Julia and Shi, Rongpei and Kang, ShinYoung and White, James L. and Schneemann, Andreas and Zaia, Edmond W. and Wan, Liwen F. and Ray, Keith G. and Liu, Yi-Sheng and Stavila, Vitalie and Guo, Jinghua and Long, Jeffrey R. and Wood, Brandon C. and Urban, Jeffrey J.},
abstractNote = {Magnesium borohydride (Mg(BH4)2, abbreviated here MBH) has received tremendous attention as a promising onboard hydrogen storage medium due to its excellent gravimetric and volumetric hydrogen storage capacities. While the polymorphs of MBH-alpha (α), beta (β), and gamma (γ)-have distinct properties, their synthetic homogeneity can be difficult to control, mainly due to their structural complexity and similar thermodynamic properties. In this work, we describe an effective approach for obtaining pure polymorphic phases of MBH nanomaterials within a reduced graphene oxide support (abbreviated MBHg) under mild conditions (60-190 °C under mild vacuum, 2 Torr), starting from two distinct samples initially dried under Ar and vacuum. Specifically, we selectively synthesize the thermodynamically stable α phase and metastable β phase from the γ-phase within the temperature range of 150-180 °C. The relevant underlying phase evolution mechanism is elucidated by theoretical thermodynamics and kinetic nucleation modeling. Finally, the resulting MBHg composites exhibit structural stability, resistance to oxidation, and partially reversible formation of diverse [BH4]- species during de- and rehydrogenation processes, rendering them intriguing candidates for further optimization toward hydrogen storage applications.},
doi = {10.1021/acsnano.9b07454},
journal = {ACS Nano},
number = 2,
volume = 14,
place = {United States},
year = {2020},
month = {1}
}

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