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

Journal Article · 10 January 2020 · ACS Nano

DOI: https://doi.org/10.1021/acsnano.9b07454 · OSTI ID:1604725

Jeong, Sohee ^[1]; Heo, Tae Wook  ^[2]; Oktawiec, Julia ^[3]; Shi, Rongpei ^[2]; Kang, ShinYoung ^[2]; White, James L. ^[4]; Schneemann, Andreas  ^[4]; Zaia, Edmond W. ^[1]; Wan, Liwen F.  ^[2]; Ray, Keith G. ^[2]; Liu, Yi-Sheng  ^[1]; Stavila, Vitalie  ^[4]; Guo, Jinghua  ^[5]; Long, Jeffrey R.  ^[3]; Wood, Brandon C.  ^[2]; Urban, Jeffrey J.  ^[1]

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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)

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.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). The Molecular Foundry (TMF) and Advanced Light Source (ALS); Sandia National Lab. (SNL-CA), Livermore, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Hydrogen Fuel Cell Technologies Office (HFTO); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Fuel Cell Technologies Office
• Grant/Contract Number: AC02-05CH11231; AC52-07NA27344; NA-0003525; NA0003525; AC04-94AL85000
• OSTI ID: 1604725
• Alternate ID(s): OSTI ID: 1782522; OSTI ID: 1810403
• Report Number(s): LLNL-JRNL-772956; SAND-2020-14102J; ark:/13030/qt3gt055vq
• Journal Information: ACS Nano, Vol. 14, Issue 2; ISSN 1936-0851
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
magnesium borohydride
hydrogen storage
phase evolution
thermodynamics
kinetic
reduced graphene oxide
36 MATERIALS SCIENCE
08 HYDROGEN
25 ENERGY STORAGE