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Revisiting the hydrogen storage behavior of the Na-O-H system

Journal Article


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 H��+... H��- interaction may be a crucial step in the desorption process.

Publication Date


  • 2015

Citation


  • Mao, J., Gu, Q., & Gregory, D. H. (2015). Revisiting the hydrogen storage behavior of the Na-O-H system. Materials, 8(5), 2191-2203. doi:10.3390/ma8052191

Scopus Eid


  • 2-s2.0-84930681170

Start Page


  • 2191

End Page


  • 2203

Volume


  • 8

Issue


  • 5

Place Of Publication


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 H��+... H��- interaction may be a crucial step in the desorption process.

Publication Date


  • 2015

Citation


  • Mao, J., Gu, Q., & Gregory, D. H. (2015). Revisiting the hydrogen storage behavior of the Na-O-H system. Materials, 8(5), 2191-2203. doi:10.3390/ma8052191

Scopus Eid


  • 2-s2.0-84930681170

Start Page


  • 2191

End Page


  • 2203

Volume


  • 8

Issue


  • 5

Place Of Publication