Phase boundary of pressure-induced I4mm to Cmc21 transition in ammonia borane at elevated temperature determined using Raman spectroscopy

The pressure-induced tetragonal (I4mm) to orthorhombic (Cmc21) phase transition in ammonia borane has been studied in a diamond anvil cell (DAC) using in situ Raman spectroscopy. At near ambient pressure in DAC, ammonia borane started decomposing as low as ∼88 °C, but at higher pressure, ammonia bor...

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Bibliographic Details
Published in:International journal of hydrogen energy 2014-05, Vol.39 (16), p.8293-8302
Main Authors: Sun, Yongzhou, Chen, Jiuhua, Drozd, Vadym, Durigin, Andriy, Najiba, Shah, Liu, Xiaoyang
Format: Article
Language:English
Subjects:
Alternative fuels. Production and utilization
Ammonia borane
Applied sciences
Clapeyron-slope
Energy
Exact sciences and technology
Fuels
Hydrogen
Hydrogen storage
Pressure-induced phase transition
Raman spectroscopy
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Summary:The pressure-induced tetragonal (I4mm) to orthorhombic (Cmc21) phase transition in ammonia borane has been studied in a diamond anvil cell (DAC) using in situ Raman spectroscopy. At near ambient pressure in DAC, ammonia borane started decomposing as low as ∼88 °C, but at higher pressure, ammonia borane is stable up to 100 °C above 0.5 GPa. In the pressure–temperature phase diagram, the boundary between tetragonal (I4mm) and orthorhombic (Cmc21) phase was determined by the characteristic change in Raman spectra during compression and decompression at 3 constant temperatures: 20, 60 and 100 °C, respectively. The result shows that the phase transition is reversible with a small hysteresis, while the phase boundary shifts towards higher pressure with increasing temperature and a positive Clapeyron-slope. The positive Clapeyron-slope indicates that the phase transition is exothermic and it is predicted that the rehydrogenation of the high pressure orthorhombic phase would be easier due to its lower enthalpy. •We determined the I4mm to Cmc21 phase transition boundary in ammonia borane.•The I4mm to Cmc21 phase transition is reversible with a small hysteresis.•The phase boundary has a positive Clapeyron-slope in pressure–temperature space.•The positive Clapeyron-slope indicates that the phase transition is endothermic.•Rehydrogenation may be easier for the Cmc21 phase than the I4mm phase.
ISSN:0360-3199
1879-3487
DOI:10.1016/j.ijhydene.2014.03.070