A Sr-Ga Oxy-Hydroxide with High Thermal Stability: Unraveling Its Characteristic Hydrogen-Bond Network

Yusuke Asai, Yuto Nishihara, Yoko Kokubo, Kenji Arai, Kosaku Ohishi, Satoshi Ogawa, Miwa Saito, Yusuke Nambu, Maxim Avdeev, Koji Kimoto, Zi Lang Goo, Kunihisa Sugimoto, Miki Inada, Katsuro Hayashi, Teruki Motohashi

Oxy-hydroxides represent potential proton carriers for solid acid catalysts and proton conductors owing to their hydroxide-rich compositions. However, their applications in high-temperature environments are limited due to thermal instability associated with dehydration at moderate to high temperatures. Therefore, the development of oxy-hydroxides with enhanced thermal stability is of critical importance. Herein, we report the discovery of a strontium–gallium oxy-hydroxide, Sr2Ga3O6(OH), with exceptional thermal stability. The Sr–Ga oxy-hydroxide was successfully synthesized via an unconventional synthesis route, “vapor hydroxidation”, involving high-temperature heat treatment in highly concentrated water vapor. Structural characterization employing X-ray diffraction, neutron diffraction, and transmission electron microscopy revealed that the Sr–Ga oxy-hydroxide crystallizes in a trigonal structure (R3̅ space group) with lattice parameters a = 18.1904(2) Å and c = 7.2693(1) Å. Notably, OH– anions are nonuniformly distributed within the crystal structure and are confined to a narrow space between two strontium sites. Thermogravimetry combined with desorption gas analysis indicated that OH– anions are retained in the crystal structure up to approximately 850 °C. In situ infrared spectroscopy upon heating demonstrated proton redistribution via multilinked hydrogen bonds at elevated temperatures, which likely contributes to the excellent thermal stability.

Inorg. Chem. 2025, 64, 36, 18294-18303. (DOI: 10.1039/ acs.inorgchem.5c02586)

プレスリリース（神奈川大学）