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Combined X-ray and Raman studies on the effect of cobalt additives on the decomposition of magnesium borohydride

Abstract

Magnesium borohydride (Mg(BH4)2) is one of the most promising hydrogen storage materials. Its kinetics of hydrogen desorption, reversibility, and complex reaction pathways during decomposition and rehydrogenation, however, present a challenge, which has been often addressed by using transition metal compounds as additives. In this work the decomposition of Mg(BH4)2 ball-milled with CoCl2 and CoF2 additives, was studied by means of a combination of several in-situ techniques. Synchrotron X-ray diffraction and Raman spectroscopy were used to follow the phase transitions and decomposition of Mg(BH4)2. By comparison with pure milled Mg(BH4)2, the temperature for the γ → ε phase transition in the samples with CoF2 or CoCl2 additives was reduced by 10–45 °C. In-situ Raman measurements showed the formation of a decomposition phase with vibrations at 2513, 2411 and 766 cm−1 in the sample with CoF2. Simultaneous X-ray absorption measurements at the Co K-edge revealed that the additives chemically transformed to other species. CoF2 slowly reacted upon heating till ~290 °C, whereas CoCl2 transformed drastically at ~180 °C.

Category

Academic article

Language

English

Author(s)

  • Olena Zavorotynska
  • Stefano Deledda
  • Jenny G. Vitillo
  • Ivan Saldan
  • Matylda Natalia Guzik
  • Marcello Baricco
  • John Walmsley
  • Jiri Muller
  • Bjørn Hauback

Affiliation

  • SINTEF Industry / Materials and Nanotechnology
  • University of Insubria, Varese
  • University of Turin
  • Lviv National University named after Ivan Franko
  • Institute for Energy Technology

Year

2015

Published in

Energies

Volume

8

Issue

9

Page(s)

9173 - 9190

View this publication at Norwegian Research Information Repository