Neutron vibrational spectroscopic evidence for short H∙∙∙H contacts in the RNiInH_{1.4; 1.6} (R = Ce, La) metal hydride

Journal Article · Mon Feb 14 23:00:00 EST 2022 · Journal of Alloys and Compounds

DOI:https://doi.org/10.1016/j.jallcom.2021.162381· OSTI ID:1832230

Klein, Ryan A. ^[1]; Balderas-Xicohténcatl, Rafael ^[2]; Maehlen, Jan Petter ^[3]; Udovic, Terrence J. ^[4]; Brown, Craig M. ^[5]; Delaplane, Robert ^[3]; Cheng, Yongqiang ^[2]; Denys, Roman V. ^[3]; Ramirez-Cuesta, Anibal J. ^[2]; Yartys, Volodymyr A. ^[3]

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1. National Renewable Energy Lab. (NREL), Golden, CO (United States); National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
3. Institute for Energy Technology, Kjeller (Norway)
4. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States); Univ. of Maryland, College Park, MD (United States)
5. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States)

Intermetallic metal hydrides are critical materials for hydrogen storage applications, however, metal hydrides with greater storage capacities are still needed. Within metal hydrides, the volumetric storage capacities are limited by the number of hydrogen-accommodating interstitial sites which can be simultaneously occupied given a minimum hydride nearest-neighbor distance of ~2.1 A, according to the Switendick-Westlake criterion. To date, violations of this criterion are rare. Perhaps the most well studied compounds violating this criterion are the RNiInHx compounds (R = Ce, La, Nd). Previous neutron diffraction studies on the deuterated species revealed the presence of Ni-D∙∙∙D-Ni-D∙∙∙D-Ni chains with anomalously close D∙∙∙D contacts of ~1.6 A. Yet there are no neutron vibrational spectroscopic investigations reported for these atypical hydrides. Here we use neutron vibrational spectroscopy (NVS) measurements to probe the hydrogen dynamics in LaNiInHx (x = 0.67, 1.6) and CeNiInH_1.4. For x > 0.67, the presence of close H...H contacts yields two related features in the vibrational spectrum centered near ~90 meV corresponding to the oscillations of paired H atoms simultaneously occupying neighboring R₃Ni tetrahedra. Notably, these features are energetically distinct from comparable vibrational motions for "unpaired" H atoms when x = 0.67. To compare, we also present powder neutron diffraction and NVS measurements for the newly characterized, chemically similar Sn compounds CeNiSnH, CeNiSnH₂, and CeNiSnD₂. These compounds also contain R₃Ni tetrahedra, however, the H-occupied tetrahedra are well separated from each other with the closest H∙∙∙H distances exceeding 2.1 A, and the Switendick-Westlake criterion is not violated. Consequently, the spectral signature of the close H∙∙∙H contacts is absent in these hydrides.

• Research Organization: National Renewable Energy Laboratory (NREL), Golden, CO (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE), Hydrogen and Fuel Cell Technologies Office
• Grant/Contract Number: AC36-08GO28308; AC05-00OR22725
• OSTI ID: 1832230
• Alternate ID(s): OSTI ID: 1845759
• Report Number(s): NREL/JA--5900-81026; MainId:79802; UUID:07081dee-8ecc-43ca-828e-2d6ab76bf2e5; MainAdminID:63310
• Journal Information: Journal of Alloys and Compounds, Journal Name: Journal of Alloys and Compounds Vol. 894; ISSN 0925-8388
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

08 HYDROGEN
Switendick-Westlake criterion
density functional theory
hydrogen storage
inelastic neutron scattering
metal hydride
neutron vibrational spectroscopy
powder neutron diffraction