High Hydrogen Mobility in an Amide–Borohydride Compound Studied by Quasielastic Neutron Scattering

Aslan, Neslihan; Gizer, Gökhan; Pistidda, Claudio; Dornheim, Martin; Müller, Martin; Busch, Sebastian; Lohstroh, Wiebke

Abstract

The hydrogen storage performance of reactive hydride composite Mg(NH₂)₂ + 2LiH can be significantly improved by the addition of LiBH₄ and the subsequent formation of an amide–borohydride compound Li 4 (BH₄)(NH₂)₃ during hydrogen release. Herein, an investigation into the structure and anion motions of Li4(BH₄)(NH2)₃ using synchrotron radiation powder X-ray diffraction (SR-PXD; 295–573 K) and quasi elastic neutron scattering (QENS; 297–514 K) is described. The highest temperature studied with QENS (514 K) is above the melting point of Li₄ (BH₄)(NH₂)₃. The neutron measurements confirm a long-range diffusive motion of hydrogen-containing species with the diffusion coefficient D≈10⁻⁶ cm² s⁻¹. Interestingly, this value is comparable to that of Li+ diffusion inferred from conductivity measurements. SR-PXD confirms the recrystallization of Li4 (BH₄)(NH₂)₃ from the melt into the α-phase upon cooling. At temperatures below 514 K, localized rotational motions are observed that are attributed to (BH₄)⁻ tetrahedra units mainly undergoing rotations around the C₃ axes. The activation energy for this thermally activated process is found to be Ea = 15.5 ± 0.9 and 17.4 ± 0.9 kJ mol⁻¹ respectively for the two instrumental resolutions utilized in the QENS measurements, corresponding to observation times of 55 and 14 ps.

Citation

Aslan, N., Gizer, G., Pistidda, C., Dornheim, M., Müller, M., Busch, S., & Lohstroh, W. (2021). High Hydrogen Mobility in an Amide–Borohydride Compound Studied by Quasielastic Neutron Scattering. Advanced Engineering Materials, 23(11), Article 2100620. https://doi.org/10.1002/adem.202100620

• Journal Article Type: Article
• Acceptance Date: Jul 21, 2021
• Online Publication Date: Aug 14, 2021
• Publication Date: 2021-11
• Deposit Date: Nov 14, 2024
• Publicly Available Date: Nov 20, 2024
• Journal: Advanced Engineering Materials
• Print ISSN: 1438-1656
• Electronic ISSN: 1527-2648
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 23
• Issue: 11
• Article Number: 2100620
• DOI: https://doi.org/10.1002/adem.202100620
• Public URL: https://nottingham-repository.worktribe.com/output/34872422
• Publisher URL: https://onlinelibrary.wiley.com/doi/10.1002/adem.202100620