Characterization of a New Phase of Ammonia Borane
An uncharacterized phase of ammonia borane (AB) was previously identified while investigating its thermal decomposition. This phase was identified as a key intermediate for the release of hydrogen from AB prompting the current characterization study. The new phase was investigated extensively using in situ solid state MAS NMR spectroscopy, including 11B, 15N and 1H NMR. Single-pulse excitation, cross polarization and T1 relaxation experiments collectively demonstrate a significant increase in mobility for the new phase when compared to the room temperature crystalline phase of AB. However, the data are not completely consistent with a liquid phase. The data are also not consistent with a solid phase, but are most consistent with a phase best described as “liquid-like”. This implies a disruption of the long-range order which is primarily stabilized by the extensive dihydrogen bonding network, allowing increased motional freedom. X-ray diffraction and Raman thermal decomposition data of neat AB provide support for a disordered phase, as does data of AB immobilized into a mesoporous scaffold. These observations suggest that a breakdown of the extensive hydrogen bonding network is necessary before hydrogen can be released and will be an important factor in the practical use of AB as a hydrogen storage material. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 984227
- Report Number(s):
- PNNL-SA-66903; ISSN 1754-5706; 25661; EB4202000; TRN: US201015%%883
- Journal Information:
- Energy & Environmental Science, 3(6):796-804, Vol. 3, Issue 6; ISSN 1754-5692
- Country of Publication:
- United States
- Language:
- English
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