2018 Fiscal Year Annual Research Report
ＬｉとＮａバッテリーのための新規酸水素化物電極の合成と解析
| Project/Area Number |
17F17341
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| Research Institution | Kyoto University |
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Principal Investigator |
陰山 洋 京都大学, 工学研究科, 教授 (40302640)
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| Co-Investigator(Kenkyū-buntansha) |
BROUX THIBAULT 京都大学, 工学(系)研究科(研究院), 外国人特別研究員
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| Project Period (FY) |
2017-11-10 – 2020-03-31
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| Keywords | high pressure synthesis / oxyhydride |
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| Outline of Annual Research Achievements |
During the last year, 6 new oxyhydrides compounds have been prepared: LnHO with Ln = Sm, Gd, Tb, Dy, Ho, and Er. Their conductivities and the ammonia synthesis catalytic activity have also been estimated. Two novel high-pressure polymorphs of lanthanum oxyhydride have been successfully predicted and stabilized under pressure. High-pressure synthesis offers an access to new compounds that exhibit novel chemical and physical functions. When reacted at 3 GPa, the fluorite structure of LaHO with anion-centered tetrahedral (HLa4/OLa4) geometry is transformed to the PbCl2-type structure involving coordination number increase of H- to five (HLa5 square pyramids). Upon further application of pressure to 5 GPa, LaHO changed into the anti Fe2P-type structure. This fact underlines the role of multiple anions with distinct compressibility for the realization of unique anion-coordination reversal.
So far, two papers have been submitted and accepted in the Journal of American Chemical Society.
T. Broux, et al., Chemical pressure-induced anion order-disorder transition in LnHO enabled by hydride size flexibility, J. Am. Chem. Soc. 2018, 140, 11170-11173
T. Broux, et al., High-pressure Polymorphs of LaHO with Anion Coordination Reversal
J. Am. Chem. Soc. 2019, accepted
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Thanks to JSPS funding we have been able to supply rapidly and efficiently the studies with required precursors and high pressure spare parts in order to go as far as we could in the search for new materials. Thanks to unique Kageyama-sensei laboratory facilities, we have been able to make progression in the search for new materials.
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| Strategy for Future Research Activity |
In the future, we want to extend the anionic composition of these materials and search for high-pressure polymorphs to divalent cations such Ca, Ba, etc… We believe that this study can be extended to other oxyhydrides and more generally hydride-fluorides and hydride-nitrides. Since high pressure phases of CaF2 have been theoretically predicted to be excellent ionic conductors, 23,32 α-LaHO, γ-LaHO and δ-LaHO may also be a potential candidate for hydride conductors, possibly after introduction of appropriate anion vacancy by aliovalent cation substitution. Higher-pressure study is also of great interest. AIRSS searches on LaHO up to 100 GPa has predicted a further transition to a hexagonal (P63/mmc) structure with HLa5 bipyramidal and OLa6 octahedral coordination
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