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Materials 2015, 8(5), 2191-2203;

Revisiting the Hydrogen Storage Behavior of the Na-O-H System

WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK
Australian Synchrotron, Clayton, Victoria 3168, Australia
Author to whom correspondence should be addressed.
Academic Editor: Umit Demirci
Received: 19 February 2015 / Revised: 20 April 2015 / Accepted: 22 April 2015 / Published: 28 April 2015
(This article belongs to the Special Issue Hydrogen Storage Materials)
Full-Text   |   PDF [977 KB, uploaded 28 April 2015]   |  


Solid-state reactions between sodium hydride and sodium hydroxide are unusual among hydride-hydroxide systems since hydrogen can be stored reversibly. In order to understand the relationship between hydrogen uptake/release properties and phase/structure evolution, the dehydrogenation and hydrogenation behavior of the Na-O-H system has been investigated in detail both ex- and in-situ. Simultaneous thermogravimetric-differential thermal analysis coupled to mass spectrometry (TG-DTA-MS) experiments of NaH-NaOH composites reveal two principal features: Firstly, an H2 desorption event occurring between 240 and 380 °C and secondly an additional endothermic process at around 170 °C with no associated weight change. In-situ high-resolution synchrotron powder X-ray diffraction showed that NaOH appears to form a solid solution with NaH yielding a new cubic complex hydride phase below 200 °C. The Na-H-OH phase persists up to the maximum temperature of the in-situ diffraction experiment shortly before dehydrogenation occurs. The present work suggests that not only is the inter-phase synergic interaction of protic hydrogen (in NaOH) and hydridic hydrogen (in NaH) important in the dehydrogenation mechanism, but that also an intra-phase Hδ+… Hδ– interaction may be a crucial step in the desorption process. View Full-Text
Keywords: hydrogen storage; sodium oxide; sodium hydride; sodium hydroxide; in-situ synchrotron powder diffraction hydrogen storage; sodium oxide; sodium hydride; sodium hydroxide; in-situ synchrotron powder diffraction

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Mao, J.; Gu, Q.; Gregory, D.H. Revisiting the Hydrogen Storage Behavior of the Na-O-H System. Materials 2015, 8, 2191-2203.

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