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

Jianfeng Mao, Qinfen Gu, Duncan H. Gregory

Research output: Contribution to journalArticlepeer-review

17 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)2191-2203
Number of pages13
Issue number5
Publication statusPublished - 2015
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Materials Science(all)


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