Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub>
Many Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites formed by alkali or alkaline earth metals and/or bind covalently to the polyanions. The latter is the case for polyanionic hydrides like Sr<i>Tr</i><sub>2</sub>H<sub>2</sub...
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MDPI AG
2019-04-01
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| Series: | Crystals |
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| Online Access: | https://www.mdpi.com/2073-4352/9/4/193 |
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| author | Anton Werwein Christopher Benndorf Marko Bertmer Alexandra Franz Oliver Oeckler Holger Kohlmann |
| author_facet | Anton Werwein Christopher Benndorf Marko Bertmer Alexandra Franz Oliver Oeckler Holger Kohlmann |
| author_sort | Anton Werwein |
| collection | DOAJ |
| description | Many Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites formed by alkali or alkaline earth metals and/or bind covalently to the polyanions. The latter is the case for polyanionic hydrides like Sr<i>Tr</i><sub>2</sub>H<sub>2</sub> (<i>Tr</i> = Al, Ga) with slightly puckered honeycomb-like polyanions decorated with hydrogen atoms. This study addresses the hydrogenation behavior of <i>LnTr</i><sub>2</sub>, where the lanthanide metals <i>Ln</i> introduce one additional valence electron. Hydrogenation reactions were performed in autoclaves and followed by thermal analysis up to 5.0 MPa hydrogen gas pressure. Products were analyzed by powder X-ray and neutron diffraction, transmission electron microscopy, and NMR spectroscopy. Phases <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb) decompose into binary hydrides and aluminium-rich intermetallics upon hydrogenation, while LaGa<sub>2</sub> forms a ternary hydride LaGa<sub>2</sub>H<sub>0.71(2)</sub>. Hydrogen atoms are statistically distributed over two kinds of trigonal-bipyramidal La<sub>3</sub>Ga<sub>2</sub> interstitials with 67% and 4% occupancy, respectively. Ga-H distances (2.4992(2) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. <sup>2</sup>H solid-state NMR spectroscopy and theoretical calculations on Density Functional Theory (DFT) level confirm that LaGa<sub>2</sub>H<sub>0.7</sub> is a typical interstitial metallic hydride. |
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| language | English |
| last_indexed | 2024-04-14T00:51:17Z |
| publishDate | 2019-04-01 |
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| series | Crystals |
| spelling | doaj.art-f24219780ff54d9ba3a9e9599afd32682022-12-22T02:21:47ZengMDPI AGCrystals2073-43522019-04-019419310.3390/cryst9040193cryst9040193Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub>Anton Werwein0Christopher Benndorf1Marko Bertmer2Alexandra Franz3Oliver Oeckler4Holger Kohlmann5Leipzig University, Institute of Inorganic Chemistry, Johannisallee 29, 04103 Leipzig, GermanyLeipzig University; Institute of Mineralogy, Crystallography and Materials Science, Scharnhorststraße 20, 04275 Leipzig, GermanyLeipzig University, Felix Bloch Institute for Solid State Physics, Linnéstraße 5, 04103 Leipzig, GermanyHelmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, GermanyLeipzig University; Institute of Mineralogy, Crystallography and Materials Science, Scharnhorststraße 20, 04275 Leipzig, GermanyLeipzig University, Institute of Inorganic Chemistry, Johannisallee 29, 04103 Leipzig, GermanyMany Zintl phases take up hydrogen and form hydrides. Hydrogen atoms occupy interstitial sites formed by alkali or alkaline earth metals and/or bind covalently to the polyanions. The latter is the case for polyanionic hydrides like Sr<i>Tr</i><sub>2</sub>H<sub>2</sub> (<i>Tr</i> = Al, Ga) with slightly puckered honeycomb-like polyanions decorated with hydrogen atoms. This study addresses the hydrogenation behavior of <i>LnTr</i><sub>2</sub>, where the lanthanide metals <i>Ln</i> introduce one additional valence electron. Hydrogenation reactions were performed in autoclaves and followed by thermal analysis up to 5.0 MPa hydrogen gas pressure. Products were analyzed by powder X-ray and neutron diffraction, transmission electron microscopy, and NMR spectroscopy. Phases <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb) decompose into binary hydrides and aluminium-rich intermetallics upon hydrogenation, while LaGa<sub>2</sub> forms a ternary hydride LaGa<sub>2</sub>H<sub>0.71(2)</sub>. Hydrogen atoms are statistically distributed over two kinds of trigonal-bipyramidal La<sub>3</sub>Ga<sub>2</sub> interstitials with 67% and 4% occupancy, respectively. Ga-H distances (2.4992(2) Å) are considerably longer than in polyanionic hydrides and not indicative of covalent bonding. <sup>2</sup>H solid-state NMR spectroscopy and theoretical calculations on Density Functional Theory (DFT) level confirm that LaGa<sub>2</sub>H<sub>0.7</sub> is a typical interstitial metallic hydride.https://www.mdpi.com/2073-4352/9/4/193Zintl phasesmetal hydridesinterstitial hydridesZintl phase hydrideslanthanidespowder diffractionneutron diffractiondeuteridesthermal analysissolid-state NMR |
| spellingShingle | Anton Werwein Christopher Benndorf Marko Bertmer Alexandra Franz Oliver Oeckler Holger Kohlmann Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub> Crystals Zintl phases metal hydrides interstitial hydrides Zintl phase hydrides lanthanides powder diffraction neutron diffraction deuterides thermal analysis solid-state NMR |
| title | Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub> |
| title_full | Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub> |
| title_fullStr | Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub> |
| title_full_unstemmed | Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub> |
| title_short | Hydrogenation Properties of <i>Ln</i>Al<sub>2</sub> (<i>Ln</i> = La, Eu, Yb), LaGa<sub>2</sub>, LaSi<sub>2</sub> and the Crystal Structure of LaGa<sub>2</sub>H<sub>0.71(2)</sub> |
| title_sort | hydrogenation properties of i ln i al sub 2 sub i ln i la eu yb laga sub 2 sub lasi sub 2 sub and the crystal structure of laga sub 2 sub h sub 0 71 2 sub |
| topic | Zintl phases metal hydrides interstitial hydrides Zintl phase hydrides lanthanides powder diffraction neutron diffraction deuterides thermal analysis solid-state NMR |
| url | https://www.mdpi.com/2073-4352/9/4/193 |
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