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dc.contributor.authorTortoza, Mariana
dc.contributor.authorHumphries, Terry
dc.contributor.authorSheppard, Drew
dc.contributor.authorPaskevicius, Mark
dc.contributor.authorRowles, Matthew
dc.contributor.authorSofianos, M. Veronica
dc.contributor.authorAguey-Zinsou, K
dc.contributor.authorBuckley, Craig
dc.identifier.citationTortoza, M. and Humphries, T. and Sheppard, D. and Paskevicius, M. and Rowles, M. and Sofianos, M. and Aguey-Zinsou, K. et al. 2018. Thermodynamics and performance of the Mg-H-F system for thermochemical energy storage applications. Physical Chemistry Chemical Physics. 20 (4): pp. 2274-2283.

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Magnesium hydride (MgH 2 ) is a hydrogen storage material that operates at temperatures above 300 °C. Unfortunately, magnesium sintering occurs above 420 °C, inhibiting its application as a thermal energy storage material. In this study, the substitution of fluorine for hydrogen in MgH 2 to form a range of Mg(H x F 1-x ) 2 (x = 1, 0.95, 0.85, 0.70, 0.50, 0) composites has been utilised to thermodynamically stabilise the material, so it can be used as a thermochemical energy storage material that can replace molten salts in concentrating solar thermal plants. These materials have been studied by in situ synchrotron X-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, temperature-programmed-desorption mass spectrometry and Pressure-Composition-Isothermal (PCI) analysis. Thermal analysis has determined that the thermal stability of Mg-H-F solid solutions increases proportionally with fluorine content, with Mg(H 0.85 F 0.15 ) 2 having a maximum rate of H 2 desorption at 434 °C, with a practical hydrogen capacity of 4.6 ± 0.2 wt% H 2 (theoretical 5.4 wt% H 2 ). An extremely stable Mg(H 0.43 F 0.57 ) 2 phase is formed upon the decomposition of each Mg-H-F composition of which the remaining H 2 is not released until above 505 °C. PCI measurements of Mg(H 0.85 F 0.15 ) 2 have determined the enthalpy (?H des ) to be 73.6 ± 0.2 kJ mol -1 H 2 and entropy (?S des ) to be 131.2 ± 0.2 J K -1 mol -1 H 2 , which is slightly lower than MgH 2 with ?H des of 74.06 kJ mol -1 H 2 and ?S des = 133.4 J K -1 mol -1 H 2 . Cycling studies of Mg(H 0.85 F 0.15 ) 2 over six absorption/desorption cycles between 425 and 480 °C show an increased usable cycling temperature of ~80 °C compared to bulk MgH 2 , increasing the thermal operating temperatures for technological applications.

dc.publisherR S C Publications
dc.titleThermodynamics and performance of the Mg-H-F system for thermochemical energy storage applications
dc.typeJournal Article
dcterms.source.titlePhysical Chemistry Chemical Physics
curtin.departmentSchool of Electrical Engineering, Computing and Mathematical Science (EECMS)
curtin.accessStatusOpen access
curtin.contributor.orcidSofianos, M. Veronica [0000-0002-9654-1463]
curtin.contributor.orcidRowles, Matthew [0000-0002-7448-6774]
curtin.contributor.orcidPaskevicius, Mark [0000-0003-2677-3434]
curtin.contributor.orcidHumphries, Terry [0000-0003-2677-3434]
curtin.contributor.orcidTortoza, Mariana [0000-0003-2677-3434]
curtin.contributor.orcidBuckley, Craig [0000-0002-3075-1863]

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