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1

WestCHEM, School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ, UK

2

Australian Synchrotron, Clayton, Victoria 3168, Australia





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Author to whom correspondence should be addressed.



Academic Editor: Umit Demirci

Abstract 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





Autor: Jianfeng Mao 1, Qinfen Gu 2 and Duncan H. Gregory 1,*

Fuente: http://mdpi.com/



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