Hydrogen storage properties of 3Mg(NH 2) 2-2Li 3AlH 6

Dongan Liu, Andrea Sudik, Jun Yang*, Patrick Ferro, Chris Wolverton

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Recent efforts have been made to develop high-capacity complex hydride composites by combining alanates and amides. The hydrogen storage mechanisms in those composites are not unambiguously clarified because of chemical reactions during the sample preparation process. In this Article, we have studied the effects of sample preparation conditions on the phase stability of a mixture of 3Mg(NH 2) 2-2Li 3AlH 6 and identified that unlike high-energy ball-milling light mixing generates a physical mixture of the reactants without decomposition. Subsequently, the hydrogen storage properties, the desorption pathway, and the reversible reaction mechanism of the composite were investigated through a combination of kinetic measurements and phase and microstructure analyses. The results reveal that the first step of hydrogen release (initiated at 170 °C) involves decomposition of Li 3AlH 6 to LiH and Al. The second step of hydrogen release occurs as the temperature increases (to 230 °C) when Mg(NH 2) 2 reacts with LiH to form Li 2Mg(NH) 2. If desorption of the 3Mg(NH 2) 2-2Li 3AlH 6 mixture is limited to a temperature of 400 °C, then the reversible reaction takes place between Li 2Mg(NH) 2 (plus H 2) and LiH and Mg(NH 2) 2. We find that the Al generated from the first hydrogen release step does not participate in the reversible hydrogen storage process and instead inhibits mass transfer that results in higher desorption temperatures (and low desorption rates) and lowers the overall reversible capacity (2.7 wt %) as compared with the neat reaction (i.e., ∼4.3 wt % without the presence of Al).

Original languageEnglish (US)
Pages (from-to)1485-1492
Number of pages8
JournalJournal of Physical Chemistry C
Volume116
Issue number1
DOIs
StatePublished - Jan 12 2012

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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