The influence of LiH and TiH2 on hydrogen storage in MgB2 I: Promotion of bulk hydrogenation at reduced temperature

Snider, Jonathan L.; Liu, Y.-S.; Sawvel, April M.; Wan, Liwen F.; Stavila, Vitalie; Mattox, Tracy M.; Wijeratne, P.; Allendorf, Mark D.; Wood, Brandon C.; Klebanoff, Leonard E.

doi:10.1016/j.ijhydene.2021.09.169

Cited by 8 publications

(3 citation statements)

References 57 publications

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“…Both materials showed an improvement in hydrogenation compared to bulk MgB 2 , which highlights the importance of understanding nanoscale effects in 2D materials. We note here that prior studies of the MgB 2 system [59][60][61] using tungsten carbide (WC) milling hardware showed no prominent evidence for the NS observed here, although it is possible that such nanostructures were formed in small amounts. We attribute this to the shorter milling times used in these prior studies, and to the use of a different milling hardware.…”

Section: Discussioncontrasting

confidence: 66%

“…This confirms that solvent‐free mechanical exfoliation of MgB 2 can be achieved using HEBM with zirconia to produce ultrathin MgB 2 multilayers. We note here that several prior studies of the MgB 2 system either used no ball milling [ 30 ] or 1–2 h of ball milling with tungsten carbide vessel and balls, [ 59–61 ] with significant improvements observed in reactivity with hydrogen of ball‐milled products.…”

Section: Resultsmentioning

confidence: 99%

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Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers

Gunda

Ray

Klebanoff

et al. 2022

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meet those requirements and constitute promising long-term solutions that reduce greenhouse gas emissions. [2] Hydrogen has the highest gravimetric energy density of any fuel (121 MJ kg −1 ), [3] and is considered a viable solution for ground transportation, aircraft, and marine vessels. [3,4] On the other hand, hydrogen is outperformed by hydrocarbon fuels in terms of volumetric energy density, motivating the development of alternative, higher-density materials-based storage methods. [5] Solid-state storage technology offers potential safety advantages (due to low operational pressure), with the additional benefit of higher volumetric density. [6] Materials considered for reversible H 2 storage include interstitial [7] and complex metal hydrides, [8] metal-organic frameworks (MOFs), [9] and various nanomaterials. [10] Metal hydrides are considered leading candidates for applications and use cases requiring high volumetric densities. [10][11][12] Unfortunately, the reaction enthalpy ΔH required to release H 2 from metal hydrides is typically too large, leading to undesirable high dehydriding temperatures.Nanostructuring can improve both the thermodynamics and kinetics of metal hydrides [11,12] via increased surface area and altered nanointerfaces. [10,[13][14][15] The resulting improvements Metal boride nanostructures have shown significant promise for hydrogen storage applications. However, the synthesis of nanoscale metal boride particles is challenging because of their high surface energy, strong inter-and intraplanar bonding, and difficult-to-control surface termination. Here, it is demonstrated that mechanochemical exfoliation of magnesium diboride in zirconia produces 3-4 nm ultrathin MgB 2 nanosheets (multilayers) in high yield. High-pressure hydrogenation of these multilayers at 70 MPa and 330 °C followed by dehydrogenation at 390 °C reveals a hydrogen capacity of 5.1 wt%, which is ≈50 times larger than the capacity of bulk MgB 2 under the same conditions. This enhancement is attributed to the creation of defective sites by ball-milling and incomplete Mg surface coverage in MgB 2 multilayers, which disrupts the stable boron-boron ring structure. The density functional theory calculations indicate that the balance of Mg on the MgB 2 nanosheet surface changes as the material hydrogenates, as it is energetically favorable to trade a small number of Mg vacancies in Mg(BH 4 ) 2 for greater Mg coverage on the MgB 2 surface. The exfoliation and creation of ultrathin layers is a promising new direction for 2D metal boride/borohydride research with the potential to achieve high-capacity reversible hydrogen storage at more moderate pressures and temperatures.

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Section: Discussioncontrasting

confidence: 66%

Section: Resultsmentioning

confidence: 99%

Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers

Gunda

Ray

Klebanoff

et al. 2022

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“…Moreover, these multiple intermediate phases and chemical products can coexist, such that the actual solid-state reaction transpires at boundary and interphase regions with complex chemical speciation. Experiments have shown that the required pressure and temperature for hydrogenation can be moderately reduced through modifications introduced by ball milling, the use of additives, and nanosizing by confinement in host structures. ,,,− Although this offers hope for overcoming kinetic limitations, the mechanisms by which these modifications function have not been satisfactorily elucidated. Further rational improvement strategies require identifying the poorly understood individual chemical steps and materials changes that occur at the interfaces …”

Section: Introductionmentioning

confidence: 99%

Understanding Hydrogenation Chemistry at MgB₂Reactive Edges fromAb InitioMolecular Dynamics

Ray

Klebanoff

Stavila

et al. 2022

ACS Appl. Mater. Interfaces

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Solid-state hydrogen storage materials often operate via transient, multistep chemical reactions at complex interfaces that are difficult to capture. Here, we use direct ab initio molecular dynamics simulations at accelerated temperatures and hydrogen pressures to probe the hydrogenation chemistry of the candidate material MgB2 without a priori assumption of reaction pathways. Focusing on highly reactive (101̅0) edge planes where initial hydrogen attack is likely to occur, we track mechanistic steps toward the formation of hydrogen-saturated BH4 – units and key chemical intermediates, involving H2 dissociation, generation of functionalities and molecular complexes containing BH2 and BH3 motifs, and B–B bond breaking. The genesis of higher-order boron clustering is also observed. Different charge states and chemical environments at the B-rich and Mg-rich edge planes are found to produce different chemical pathways and preferred speciation, with implications for overall hydrogenation kinetics. The reaction processes rely on B–H bond polarization and fluctuations between ionic and covalent character, which are critically enabled by the presence of Mg2+ cations in the nearby interphase region. Our results provide guidance for devising kinetic improvement strategies for MgB2-based hydrogen storage materials, while also providing a template for exploring chemical pathways in other solid-state energy storage reactions.

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Mxene-supported NbVH nanoparticles as efficient catalysts for reversible hydrogen storage in magnesium borohydride

Xia,

Zheng,

Zhang

et al. 2024

Chemical Engineering Journal

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The influence of LiH and TiH2 on hydrogen storage in MgB2 I: Promotion of bulk hydrogenation at reduced temperature

Cited by 8 publications

References 57 publications

Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers

Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers

Understanding Hydrogenation Chemistry at MgB₂Reactive Edges fromAb InitioMolecular Dynamics

Mxene-supported NbVH nanoparticles as efficient catalysts for reversible hydrogen storage in magnesium borohydride

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The influence of LiH and TiH2 on hydrogen storage in MgB2 I: Promotion of bulk hydrogenation at reduced temperature

Cited by 8 publications

References 57 publications

Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers

Hydrogen Storage in Partially Exfoliated Magnesium Diboride Multilayers

Understanding Hydrogenation Chemistry at MgB2Reactive Edges fromAb InitioMolecular Dynamics

Mxene-supported NbVH nanoparticles as efficient catalysts for reversible hydrogen storage in magnesium borohydride

Contact Info

Product

Resources

About

Understanding Hydrogenation Chemistry at MgB₂Reactive Edges fromAb InitioMolecular Dynamics