Beyond Idealized Models of Nanoscale Metal Hydrides for Hydrogen Storage

Abstract

Metal hydrides are attractive for compact, lowpressure hydrogen storage, yet a foundational understanding of factors governing their thermodynamics and kinetics is still lacking. Predictive modeling from the atomic to the microstructural scale plays a critical role in addressing these gaps, particularly for nanoscale materials, which promise improved performance but are difficult to probe. Here, we summarize strategies being developed within the Hydrogen MaterialsAdvanced Research Consortium (HyMARC) for going beyond conventional models to incorporate more complex physics, more realistic structures, and better approximation of operation conditions in simulations of nanoscale metal hydrides. We highlight four beyond-ideal factors that influence predicted performance: (1) surface anharmonic dynamics, (2) interface and surface energy penalties, (3) mechanical stress under confinement, and (4) the presence of native surface oxide. Approaches for addressing these factors are demonstrated on model materials representative of high-capacity hydrogen storage systems, and implications for understanding performance under operating conditions are discussed.

Spontaneous dynamical disordering of borophenes in MgB2 and related metal borides

“…Under hydrogenation conditions, it is reasonable to assume that such sites could function as the predominant “scissors” for H 2 cleavage. As exothermic atomic H diffusion is expected to be facile, exemplified by low H diffusion barriers 35 in bulk MgB 2 and on the pristine Mg-terminated (0001) surfaces 36 , the resulting atomic H can then diffuse to other nearby favorable binding sites. However, one caveat is the lower density of sites with negative E H binding , which may prevent the disordered surface from attaining a high H coverage (assuming all B surface remain intact during hydrogenation).…”

A comprehensive review of hydrogen production and storage: A focus on the role of nanomaterials

“…A recent study by Wood et al [197] showed that mechanical stresses posed by an external confining medium could affect the thermodynamics and kinetics of phase transformations that occur during the de/rehydrogenation of some CMHs; they focused on incorporating more realistic effects in their models which are usually neglected in computations based on ideal conditions. Some unresolved challenges still plague the application of metal borohydrides for H2 storage.…”

Recent Development in Nanoconfined Hydrides for Energy Storage

“…After its first inclusion on the research outlook of scientists worldwide in 1996, nano-sized hydrides have known a wide expansion, mainly due to several important kinetic and thermodynamic improvements of nanoconfinement over their bulk counterparts [4,8,14,16,18,[21][22][23]27,28,. Over time, nanoconfinement has emerged as a reliable tool for tuning not only thermodynamic and kinetic behavior at nanoscale, but also for altering reaction pathways, lowering or even suppressing side-reactions and sideproducts, while also affording better size control of the particles over several hydrogen release/uptake cycles (Figure 2).…”

“…Nanoconfinement of active hydride species inside a porous host bears a number of physical and chemical implications [1,7,8,22,25,27,41,[52][53][54][55][56][59][60][61][62].…”

“…Among hydrogen storage materials, metal hydrides have gained increased popularity [5][6][7][8][22][23][24][25][26] and channeled many research groups to corroborate hydrogen sorption data to formulate general design principles for these materials [27,28], or to tackle the imminent need to expand current knowledge to production of large-scale hydrogen storage facilities [29]. While many advances have been made in the field of metal hydrides for hydrogen storage applications, the high thermal stability, sluggish kinetics and poor reversibility of hydrogen release/uptake have shifted researchers' attention towards nanoconfined hydrides that seem to alleviate some of these drawbacks, affording reversible, high gravimetric and volumetric hydrogen content at moderate temperatures [8,24,25].…”