In situ characterization of the decomposition behavior of Mg(BH4)(2) by X-ray Raman scattering spectroscopy

Christoph J. Sahle (1, 2) , Simon Kujawski (3) , Arndt Remhof (4) , Yigang Yan (4) , Nicholas P. Stadie (4) , Ali Al-Zein (2) , Metin Tolan (3) , Simo Huotari (1) , Michael Krisch (2) , Christian Sternemann (3)

1 Helsingin yliopisto = Helsingfors universitet = University of Helsinki
2 ESRF - European Synchrotron Radiation Facility
3 TU - Technische Universität Dortmund [Dortmund]
4 EMPA Materials for Energy Conversion

We present an in situ study of the thermal decomposition of Mg(BH4)(2) in a hydrogen atmosphere of up to 4 bar and up to 500 degrees C using X-ray Raman scattering spectroscopy at the boron K-edge and the magnesium L2,3-edges. The combination of the fingerprinting analysis of both edges yields detailed quantitative information on the reaction products during decomposition, an issue of crucial importance in determining whether Mg(BH4)(2) can be used as a next-generation hydrogen storage material. This work reveals the formation of reaction intermediate(s) at 300 degrees C, accompanied by a significant hydrogen release without the occurrence of stable boron compounds such as amorphous boron or MgB12H12. At temperatures between 300 degrees C and 400 degrees C, further hydrogen release proceeds via the formation of higher boranes and crystalline MgH2. Above 400 degrees C, decomposition into the constituting elements takes place. Therefore, at moderate temperatures, Mg(BH4)(2) is shown to be a promising high-density hydrogen storage material with great potential for reversible energy storage applications

Domaines: Chimie

Christoph J. Sahle, Simon Kujawski, Arndt Remhof, Yigang Yan, Nicholas P. Stadie, et al.. In situ characterization of the decomposition behavior of Mg(BH4)(2) by X-ray Raman scattering spectroscopy. Physical Chemistry Chemical Physics, 2016, 18 (7), pp.5397-5403. ⟨10.1039/c5cp06571b⟩. ⟨hal-01572901⟩