Isotopic Exchange in Porous and Dense Magnesium Borohydride

Olena Zavorotynska, Stefano Deledda, Guanqiao Li, Motoaki Matsuo, Shin Ichi Orimo, Bjørn C. Hauback

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Magnesium borohydride (Mg(BH4)2) is one of the most promising complex hydrides presently studied for energy-related applications. Many of its properties depend on the stability of the BH4- anion. The BH4- stability was investigated with respect to H→D exchange. In'situ Raman measurements on high-surface-area porous Mg(BH4)2 in 0.3'MPa D2 have shown that the isotopic exchange at appreciable rates occurs already at 373'K. This is the lowest exchange temperature observed in stable borohydrides. Gas-solid isotopic exchange follows the BH4-+D.→BH3D-+H. mechanism at least at the initial reaction steps. Ex'situ deuteration of porous Mg(BH4)2 and its dense-phase polymorph indicates that the intrinsic porosity of the hydride is the key behind the high isotopic exchange rates. It implies that the solid-state H(D) diffusion is considerably slower than the gas-solid H→D exchange reaction at the surface and it is a rate-limiting steps for hydrogen desorption and absorption in Mg(BH4)2. The H-to-D exchange in high-surface-area complex ionic hydride Mg(BH4)2 exhibits exceptionally high rates at low temperature and pressure. The gas-solid H→D exchange at the surface is thus significantly faster than the solid-state H(D) diffusion in the bulk. The latter can be regarded as the rate-limiting step for hydrogen desorption and absorption in Mg(BH4)2.

Original languageEnglish
Pages (from-to)10592-10595
Number of pages4
JournalAngewandte Chemie - International Edition
Volume54
Issue number36
DOIs
Publication statusPublished - 2015 Sep 1

Keywords

  • Raman spectroscopy
  • gas-solid exchange
  • hydrogen isotope exchange
  • magnesium borohydride

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)

Fingerprint Dive into the research topics of 'Isotopic Exchange in Porous and Dense Magnesium Borohydride'. Together they form a unique fingerprint.

Cite this