Synthesis and characterization of K8-x(H2) ySi46

Doinita Neiner; Norihiko L. Okamoto; Ping Yu; Sharon Leonard; Cathie L. Condron; Michael F. Toney; Quentin M. Ramasse; Nigel D. Browning; Susan M. Kauzlarich

doi:10.1021/ic9004592

Synthesis and characterization of K_8-x(H₂) _ySi₄₆

Doinita Neiner, Norihiko L. Okamoto, Ping Yu, Sharon Leonard, Cathie L. Condron, Michael F. Toney, Quentin M. Ramasse, Nigel D. Browning, Susan M. Kauzlarich

IMR - Materials Development Division

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Abstract

A hydrogen-containing inorganic clathrate with the nominal composition, K₇(H₂)₃Si₄₆, has been prepared in 98% yield by the reaction of K₄Si₄ with NH₄Br. Rietveld refinement of the powder X-ray diffraction data is consistent with the clathrate type I structure. Elemental analysis and ¹H MAS NMR confirmed the presence of hydrogen in this material. Type I clathrate structure is built up from a Si framework with two types of cages where the guest species, in this case K and H₂, can reside: a large cage composed of 24 Si, in which the guest resides in the-6d position, and a smaller one composed of 20 Si, in which the guest occupies the 2a position (cubic space group Pm3 n). Potassium occupancy was examined using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). The highangle annular dark-field (HAADF) STEM experimental and simulated images indicated that the K is deficient in both the 2a and the 6dsites. ¹H and ²⁹Si MAS NMR are consistent with the presence of H₂ in a restricted environment and the clathrate I structure, respectively. FTIR and ²⁹Si{¹H} CP MAS NMR results show no evidence for a Si-H bond, suggesting that hydrogen is present as H₂ in interstitial sites. Thermal gravimetry (TG) mass spectrometry (MS) provide additional confirmation of H₂ with hydrogen loss at ∼400 °C.

Original language	English
Pages (from-to)	815-822
Number of pages	8
Journal	Inorganic Chemistry
Volume	49
Issue number	3
DOIs	https://doi.org/10.1021/ic9004592
Publication status	Published - 2010 Feb 1

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title = "Synthesis and characterization of K8-x(H2) ySi46",

abstract = "A hydrogen-containing inorganic clathrate with the nominal composition, K7(H2)3Si46, has been prepared in 98% yield by the reaction of K4Si4 with NH4Br. Rietveld refinement of the powder X-ray diffraction data is consistent with the clathrate type I structure. Elemental analysis and 1H MAS NMR confirmed the presence of hydrogen in this material. Type I clathrate structure is built up from a Si framework with two types of cages where the guest species, in this case K and H2, can reside: a large cage composed of 24 Si, in which the guest resides in the-6d position, and a smaller one composed of 20 Si, in which the guest occupies the 2a position (cubic space group Pm3 n). Potassium occupancy was examined using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). The highangle annular dark-field (HAADF) STEM experimental and simulated images indicated that the K is deficient in both the 2a and the 6dsites. 1H and 29Si MAS NMR are consistent with the presence of H2 in a restricted environment and the clathrate I structure, respectively. FTIR and 29Si{1H} CP MAS NMR results show no evidence for a Si-H bond, suggesting that hydrogen is present as H2 in interstitial sites. Thermal gravimetry (TG) mass spectrometry (MS) provide additional confirmation of H2 with hydrogen loss at ∼400 °C.",

author = "Doinita Neiner and Okamoto, {Norihiko L.} and Ping Yu and Sharon Leonard and Condron, {Cathie L.} and Toney, {Michael F.} and Ramasse, {Quentin M.} and Browning, {Nigel D.} and Kauzlarich, {Susan M.}",

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AU - Neiner, Doinita

AU - Okamoto, Norihiko L.

AU - Yu, Ping

AU - Leonard, Sharon

AU - Condron, Cathie L.

AU - Toney, Michael F.

AU - Ramasse, Quentin M.

AU - Browning, Nigel D.

AU - Kauzlarich, Susan M.

PY - 2010/2/1

Y1 - 2010/2/1

N2 - A hydrogen-containing inorganic clathrate with the nominal composition, K7(H2)3Si46, has been prepared in 98% yield by the reaction of K4Si4 with NH4Br. Rietveld refinement of the powder X-ray diffraction data is consistent with the clathrate type I structure. Elemental analysis and 1H MAS NMR confirmed the presence of hydrogen in this material. Type I clathrate structure is built up from a Si framework with two types of cages where the guest species, in this case K and H2, can reside: a large cage composed of 24 Si, in which the guest resides in the-6d position, and a smaller one composed of 20 Si, in which the guest occupies the 2a position (cubic space group Pm3 n). Potassium occupancy was examined using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). The highangle annular dark-field (HAADF) STEM experimental and simulated images indicated that the K is deficient in both the 2a and the 6dsites. 1H and 29Si MAS NMR are consistent with the presence of H2 in a restricted environment and the clathrate I structure, respectively. FTIR and 29Si{1H} CP MAS NMR results show no evidence for a Si-H bond, suggesting that hydrogen is present as H2 in interstitial sites. Thermal gravimetry (TG) mass spectrometry (MS) provide additional confirmation of H2 with hydrogen loss at ∼400 °C.

AB - A hydrogen-containing inorganic clathrate with the nominal composition, K7(H2)3Si46, has been prepared in 98% yield by the reaction of K4Si4 with NH4Br. Rietveld refinement of the powder X-ray diffraction data is consistent with the clathrate type I structure. Elemental analysis and 1H MAS NMR confirmed the presence of hydrogen in this material. Type I clathrate structure is built up from a Si framework with two types of cages where the guest species, in this case K and H2, can reside: a large cage composed of 24 Si, in which the guest resides in the-6d position, and a smaller one composed of 20 Si, in which the guest occupies the 2a position (cubic space group Pm3 n). Potassium occupancy was examined using spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM). The highangle annular dark-field (HAADF) STEM experimental and simulated images indicated that the K is deficient in both the 2a and the 6dsites. 1H and 29Si MAS NMR are consistent with the presence of H2 in a restricted environment and the clathrate I structure, respectively. FTIR and 29Si{1H} CP MAS NMR results show no evidence for a Si-H bond, suggesting that hydrogen is present as H2 in interstitial sites. Thermal gravimetry (TG) mass spectrometry (MS) provide additional confirmation of H2 with hydrogen loss at ∼400 °C.

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Synthesis and characterization of K_8-x(H₂) _ySi₄₆

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