Controlled mechanochemical synthesis and hydrogen desorption mechanisms of nanostructured Mg2CoH5. (21st January 2015)

• Record Type: Journal Article
• Authors: Zepon, G.; Leiva, D.R.; Kaufman, M.J.; Figueroa, S.J.A.; Floriano, R.; Lamas, D.G.; Asselli, A.A.C.; Botta, W.J.
• Is Part Of: International journal of hydrogen energy. Volume 40:Number 3(2015)
• Page Start: 1504
• Page End: 1515
• Publication Date: 2015-01-21
• Subjects: Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2014.11.085
• Languages: English
• ISSNs: 0360-3199

Abstract

<abstract xml:lang="en" abstract-type="author" id="abs0010"> <title id="sectitle0010">Abstract</title> <sec> <p id="abspara0010">Magnesium complex hydrides are attractive for hydrogen storage applications, mainly due to their high volumetric capacities and to their relatively low cost. In this work, nanocrystalline Mg₂CoH₅ was synthesized with very high yields (97%) by reactive milling cobalt and magnesium under relatively mild processing conditions (30 bar of H₂ pressure and 12 h of milling). The behavior of the milled Mg₂CoH₅ during heating was studied by a combination of several techniques including DSC, QMS, TGA and in-situ synchrotron XRD. It is shown for the first time that two different mechanisms of hydrogen desorption take place. At low temperatures (up to 325 °C), some hydrogen is released by a diffusional mechanism with no change in the crystalline structure of the high temperature γ-Mg₂CoH₅ phase. At higher temperatures, above 325 °C, the γ-Mg₂CoH₅ phase becomes unstable and the complex hydride decomposes into Mg, Co and H₂. This is the first work to report the diffusional hydrogen desorption mechanism for the Mg₂CoH₅ or any other complex hydride. Furthermore, a complete description of the allotropic β-Mg₂CoH₅ to γ-Mg₂CoH₅ phase transition is provided.</p> </sec> </abstract>