Synthesis, structure and NH3 sorption properties of mixed Mg1-xMnx(NH3)6Cl2 ammines

Perizat Berdiyeva, Anastasiia Karabanova, Jakob B. Grinderslev, Rune E. Johnsen, Didier Blanchard, Bjørn C. Hauback, Stefano Deledda*

*Corresponding author for this work

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Abstract

This paper describes the synthesis, crystal structure, and NH3 sorption properties of Mg1- xMnx(NH3)6Cl2 (x = 0-1) mixed metal halide ammines, with reversible NH3 storage capacity in the temperature range 20-350 °C. The stoichiometry (x) dependent NH3 desorption temperatures were monitored using in situ synchrotron radiation powder X-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. The thermal analyses reveal that the NH3 release temperatures decrease in the mixed metal halide ammines in comparison to pure Mg(NH3)6Cl2, approaching the values of Mn(NH3)6Cl2. Desorption occurs in three steps of four, one and one NH3 moles, with the corresponding activation energies of 54.8 kJ∙mol-1, 73.2 kJ∙mol-1 and 91.0 kJ∙mol-1 in Mg0.5Mn0.5(NH3)6Cl2, which is significantly lower than the NH3 release activation energies of Mg(NH3)6Cl2 (Ea = 60.8 kJ∙mol-1, 74.8 kJ∙mol-1 and 91.8 kJ∙mol-1). This work shows that Mg1- xMnx(NH3)yCl2 (x = 0 to 1, y = 0 to 6) is stable within the investigated temperature range (20-350 °C) and also upon NH3 cycling.

Original languageEnglish
Article number2746
JournalEnergies
Volume13
Issue number11
ISSN1996-1073
DOIs
Publication statusPublished - 2020

Keywords

  • Ammonia storage
  • In situ powder X-ray diffraction
  • Metal chlorides
  • Mixed hexammines
  • Solid solution

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